Effects of urbanization on
avian diversity and human-

nature interactions in
tropical environments

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Tesis doctoral
Adewale Gboyega Awoyemi



 

  



EFFECTS OF URBANIZATION ON AVIAN 

DIVERSITY AND HUMAN-NATURE 

INTERACTIONS IN TROPICAL ENVIRONMENTS 

EFECTOS DE LA URBANIZACIÓN EN LA DIVERSIDAD 

DE AVES Y LAS INTERACCIONES HUMANO-

NATURALEZA EN AMBIENTES TROPICALES 

 

By  

Adewale Gboyega Awoyemi 

 

Programa de Doctorado Biología Fundamental y de Sistemas 

DOCTORAL THESIS 

Granada, March 2025 

 



 

 

 

 

 

 

 

 

 

Printed in Granada (Spain), January 2025 

Cover illustration: Andrés Aguayo Padial 

Interior illustration: Adewale Gboyega Awoyemi 

Photo credit: International Institute of Tropical Agriculture 

 

This Doctoral Thesis has been presented under the modality of Thesis by 

publications. 

 

 

 

To be cited as: 

 Awoyemi, A.G. (2025) Effects of urbanization on avian diversity and human-

nature interactions in tropical environments. Doctoral thesis, University of 

Granada, Granada, Spain. 



Effects of urbanization on avian diversity and 

human-nature interactions in tropical 

environments 

 

 

 

 

Doctoral Thesis Presented by Mr. Adewale Gboyega Awoyemi to qualify for a 

Doctorate Degree from the University of Granada, Spain 

Memoria de Tesis Doctoral Presentada por el Licenciado D. Adewale Gboyega 

Awoyemi para optar al grado de Doctor por la Universidad de Granada, Spain 

 

 

 

 

Supervised by: 

 

 

 

 

Prof. Juan Diego Ibáñez-Álamo       

 



The doctoral student Adewale Gboyega Awoyemi, and his Thesis Director Prof. 

Juan Diego Ibáñez-Álamo, guarantee by signing this Thesis, that the doctoral 

student performed the presented work under Prof. Ibáñez-Álamo’s direction. They 

both confirm, to the best of their knowledge, that the rights of other authors to be 

cited have been respected when their results or publications have been used. 

 

In Granada, 20 January 2025. 

 

Thesis Director 

 

 

 

Signed: Prof. Juan Diego Ibáñez-Álamo 

 

Doctorate student 

 

Signed: Adewale Gboyega Awoyemi 

 



 

 

 

 

 

 

 

 

 

 

 

 

The A.G. Leventis Foundation and A.P. Leventis Ornithological Research Institute 

(APLORI) financed this doctoral project, which was developed in the Animal 

Ecology in Urban Areas Group of the Department of Zoology, University of 

Granada, Spain. 



 

 

 

 

 

 

 

 

To Omobamidele, Adetomi, Adetola, Adeshina and Adeola Awoyemi 

 

 

 

 

 

 



 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

“Africa’s urbanization is a double-edged sword: it can 

bring economic growth, but also devastating 

environmental costs.” 

Dr. Jane Goodall, 

Reason for Hope: A Spiritual Journey, 1999 



 

 

Contents 

 
 

Summary ................................................................................................................... 1 

Resumen .................................................................................................................... 4 

General introduction ............................................................................................... 7 

Urbanization’s impacts on socio-ecological systems ............................................. 7 

Thesis aims........................................................................................................... 11 

Thesis objectives .................................................................................................. 11 

Objetivos de la tesis ............................................................................................. 12 

General methodology ............................................................................................. 13 

Study area............................................................................................................. 13 

General field procedure ........................................................................................ 13 

Chapter 1:   Status of urban ecology in Africa: A systematic review ................ 18 

Abstract ................................................................................................................ 18 

Introduction .......................................................................................................... 19 

Methods ............................................................................................................... 21 

Bibliographic search and paper screening........................................................ 21 

Data extraction and categorization ................................................................... 22 

Statistical analyses ........................................................................................... 24 

Results .................................................................................................................. 25 

Discussion ............................................................................................................ 31 

Spatio-temporal patterns in knowledge ............................................................ 31 

Gaps in knowledge according to taxonomy and scientific fields ..................... 37 

Conclusions .......................................................................................................... 40 

Recommendations ................................................................................................ 41 

Supporting Materials ............................................................................................ 42 

Acknowledgements .............................................................................................. 42 

References……………………………………………………………………….....42



ii 

Chapter 2:  Associations between urbanization and avian communities in the 

Afrotropics: Evidence from taxonomic, functional and phylogenetic diversity 

 ................................................................................................................................. 58 

Abstract ................................................................................................................ 58 

Introduction .......................................................................................................... 59 

Methods ............................................................................................................... 61 

Study area and site description ......................................................................... 61 

Estimation of site characteristics and bird data collection ............................... 63 

Avian diversity and community metrics .......................................................... 63 

Statistical analyses ........................................................................................... 64 

Results .................................................................................................................. 66 

Avian biodiversity during the dry season ........................................................ 67 

Avian biodiversity during the wet season ........................................................ 69 

Discussion ............................................................................................................ 71 

Variations in avian diversity across urbanization, seasons, and vegetation zones

 ......................................................................................................................... 71 

Effects of local influential features on avian diversity across urbanization, 

seasons, and vegetation zones .......................................................................... 73 

Conclusions and recommendations ...................................................................... 75 

Supporting Materials ............................................................................................ 75 

Acknowledgements .............................................................................................. 76 

References…………………………………………………………………………. 76 

Chapter 3:   Remotely sensed spectral indicators of bird taxonomic, functional 

and phylogenetic diversity across Afrotropical urban and non-urban 

habitats .................................................................................................................... 86 

Abstract ................................................................................................................ 86 

Introduction .......................................................................................................... 87 

Materials and methods ......................................................................................... 89 

Study area ......................................................................................................... 89 

Site selection and bird enumeration ................................................................. 90 

Avian diversity and community metrics .......................................................... 91 

Extraction of multispectral indices .................................................................. 92 

Statistical analyses ........................................................................................... 92 

Results .................................................................................................................. 95 

Ranking of multispectral predictors of avian diversity metrics ....................... 96 

Relationships between avian diversity metrics and the mean of spectral indices 

across habitats .................................................................................................. 96 

Relationships between avian diversity metrics and the standard deviation of 

spectral indices across habitats ........................................................................ 98



iii 

Discussion .......................................................................................................... 100 

Predictive power of spectral indices across multifaceted avian diversity ...... 101 

Relationships between spectral indices and multifaceted avian diversity across 

habitats ........................................................................................................... 102 

Conclusions ........................................................................................................ 104 

Supporting Materials .......................................................................................... 105 

Acknowledgements ............................................................................................ 105 

References………………………………………………………………… ……...106 

Chapter 4:   Urban-associated changes in avian-mediated regulating ecosystem 

services in the Afrotropics ................................................................................... 119 

Abstract .............................................................................................................. 119 

Introduction ........................................................................................................ 120 

Methods ............................................................................................................. 123 

Study areas ..................................................................................................... 123 

Estimation of site characteristics and bird censuses ...................................... 123 

Estimation of ecosystem services .................................................................. 124 

Statistical analyses ......................................................................................... 125 

Results ................................................................................................................ 126 

Discussions ........................................................................................................ 128 

Differences in avian-mediated regulating ecosystem services across 

Afrotropical environments ............................................................................. 128 

Effects of local habitat attributes on avian-mediated regulating ecosystem 

services ........................................................................................................... 130 

Conclusions and recommendations .................................................................... 131 

Supplementary Material ..................................................................................... 132 

Acknowledgements ............................................................................................ 132 

References………………………………………………………………………...133 

Chapter 5:   Human-nature interactions in the Afrotropics: Experiential and 

cognitive connections among urban residents in southern Nigeria ................. 146 

Abstract .............................................................................................................. 146 

Introduction ........................................................................................................ 147 

Methods ............................................................................................................. 150 

Study area and design .................................................................................... 150 

Structured questionnaire and variables .......................................................... 153 

Current experience of nature .......................................................................... 153 

Previous experiences and setting ................................................................... 154 

Nature connectedness ..................................................................................... 155 

Perception of nature ....................................................................................... 155



iv 

Measured indicators of nature (vegetation and birds) .................................... 155 

Safety perception ........................................................................................... 156 

Socioeconomic characteristics ....................................................................... 156 

Methods of data analysis ................................................................................ 156 

Latent class analysis ....................................................................................... 156 

Regression analysis ........................................................................................ 157 

Results ................................................................................................................ 158 

Description of the sample .............................................................................. 158 

Latent class membership: patterns of nature experience ................................ 160 

Cognitive connection to nature ...................................................................... 163 

Discussion .......................................................................................................... 166 

Relationships between experiential connection to nature and socioeconomic 

and demographic variables............................................................................. 166 

Factors influencing cognitive connection to nature ....................................... 168 

Reasons for infrequent nature visitation ........................................................ 170 

Study limitations and future research directions ............................................ 171 

Conclusions ........................................................................................................ 172 

Supporting Materials .......................................................................................... 172 

Acknowledgements ............................................................................................ 172 

References………………………………………………………………...............173 

General discussion ............................................................................................... 187 

Conclusions ........................................................................................................... 193 

Conclusiones ......................................................................................................... 196 

List of publications ............................................................................................... 199 

Publications from the thesis ............................................................................... 199 

General references ............................................................................................... 200 

Acknowledgements .............................................................................................. 208 

 

 



 
 

 

 

Summary 

 

Urbanization is a rapidly expanding global phenomenon that poses significant threats 

to biodiversity. Despite its importance, the impacts of urbanization on biodiversity in 

certain regions remain understudied. Recent studies have highlighted the need for more 

research on the topic, particularly in Africa, where unprecedented urbanization overlaps 

with vast biodiversity. Thus, this thesis investigated the impacts of urbanization on 

socioecological systems in the Afrotropics, providing data useful in achieving 

sustainable urban development in line with SDG Goal 11 (Sustainable Cities and 

Communities) in the region.  

This thesis began with a comprehensive systematic literature review to assess 

the current state of urban ecology in Africa (Chapter 1). The review revealed a striking 

knowledge gap, with only 795 relevant papers published in the last century (1920—

2020), much less than those from other continents. Notably, a disproportionate number 

of these studies (40%) were conducted in South Africa, indicating a significant 

geographical bias in our current knowledge on the topic. This review found that 

research efforts are driven by economic wealth (GDP) and the importance of 

conservation in African urban ecology. However, the review also exposed a surprising 

oversight: the Afrotropics, which is the most urbanized and biodiverse-rich African 

region, is not a primary focus of study. Furthermore, most urban ecology studies in 

Africa were conducted in a single city (55%), with substantial knowledge gaps 

persisting across taxonomic groups, scientific fields, and ecoregions. To partially 

address these important gaps, this thesis focused on investigating different research 

questions in multiple cities in Nigeria (Chapters 2—5), a typical Afrotropical country 

experiencing rapid urbanization. These additional chapters investigated the impacts of 

urbanization on bird taxonomic, functional and phylogenetic diversity (Chapters 2—

3), avian-mediated regulating ecosystem services, including pest control, seed 

dispersal, pollination, and scavenging (Chapter 4), and human-nature interactions 

(Chapter 5).



2 

 

The results of these studies unequivocally demonstrated that urbanization has 

profound negative impacts on bird diversity and ecosystem services in the Afrotropics. 

Compared to non-urban areas, urban areas exhibited significantly lower bird taxonomic 

diversity (Chapter 2) and reduced provisioning of essential ecosystem services provided 

by wildlife, including pest control, seed dispersal and pollination (Chapter 4). 

Scavenging was the only bird-mediated ecosystem service enhanced by urban 

development (wet season). Furthermore, certain urban attributes, such as the presence 

of vehicles and pedestrians, were found to compromise bird phylogenetic divergence 

and ecosystem service provision, particularly pollination and seed dispersal. However, 

the results also highlight the potential for targeted conservation efforts to mitigate these 

negative impacts. Notably, the presence of water bodies and specific vegetation types, 

such as canopy and bush cover, can significantly enhance multiple components of bird 

diversity and crucial bird-mediated regulating ecosystem services (Chapters 2 and 4). 

By preserving and restoring these key habitat features, it may be possible to reverse the 

decline of bird diversity and the associated regulating ecosystem services in 

Afrotropical cities, particularly seed dispersal and pollination.  

Chapter 3 presents a novel application of machine learning and remote sensing 

techniques in estimating local habitat variables influencing bird diversity components 

across urban and non-urban areas. This study revealed that the Modified Chlorophyll 

Absorption Ratio Index (MCARI) is the most effective indicator of taxonomic and 

phylogenetic bird diversity in the Afrotropics. In contrast, the Normalized Difference 

Water Index 2 (NDWI2) and Soil Adjusted Total Vegetation Index (SATVI) were 

found to be the best predictors of functional diversity and phylogenetic divergence, 

respectively. Interestingly, the Normalized Difference Vegetation Index (NDVI), a 

commonly used predictor across regions and topics, ranked relatively low (25th 

percentile) in most cases. These results recommended the use of these alternative 

predictors (MCARI, NDWI2 and SATVI) rather than the NDVI in predicting bird 

biodiversity in urban and non-urban areas of the Afrotropics. This is likely due to 

NDVI's limitations, including scaling issues, saturation in high-biomass areas, and 

sensitivity to soil brightness, which can compromise its accuracy in diverse 

Afrotropical environments. The remote sensing approach employed in this study offers 

a potentially more efficient and cost-effective method for estimating local habitat 

variables compared to traditional manual estimation techniques. By leveraging machine 

learning algorithms and remotely sensed data, this approach can help reduce the labor, 

expense, and investigator error associated with manual data collection. 

In addition to the ecological impacts, urbanization also has significant social 

implications. By investigating the extinction of experience concept among urban 

dwellers in Nigeria, Chapter 5 found that most citizens had little or no contact with 



3 

 

nature. The main reasons cited for this disconnection were lack of time, money, and 

nearby natural areas. The study also found that respondents with higher nature contact 

were more connected to nature, and that the perception of neighborhood safety was an 

important factor promoting nature contact. Furthermore, the study also found that 

respondents living in Lagos, and those with lower levels of income and education, 

showed greater dissociation from nature. These findings could be useful to fight against 

the worrying extinction of experience in the region, providing potential factors to 

consider and implement in future urban development plans in the Afrotropics.  

Overall, the Chapters of this thesis highlight the need for more research on the 

impacts of urbanization on biodiversity and ecosystem services in the Afrotropics. They 

also emphasize the importance of promoting nature contact and experience among 

urban dwellers, particularly in regions with rapid urbanization such as the study area 

(i.e. Nigeria). By addressing these knowledge gaps and promoting nature experience, 

we can work towards creating more sustainable and resilient urban ecosystems that will 

benefit both people and the environment.



 
 

 

 

Resumen 

 

La urbanización es un fenómeno global en rápida expansión que plantea importantes 

amenazas a la biodiversidad. A pesar de su importancia, los impactos de la urbanización 

sobre la biodiversidad aún no se han estudiado lo suficiente en ciertas regiones. 

Estudios recientes destacan la necesidad de realizar más investigaciones sobre el tema, 

particularmente en África, donde una urbanización sin precedentes se solapa con una 

gran biodiversidad. Esta tesis, por tanto, se centra en el estudio de los impactos de la 

urbanización en los sistemas socio-ecológicos del África tropical, proporcionando 

datos útiles para lograr un desarrollo urbano sostenible en línea con el Objetivo de 

Desarrollo Sostenible 11 (Ciudades y Comunidades Sostenibles) en la región. 

 Esta tesis comienza con una exhaustiva revisión sistemática de la literatura para 

evaluar el estado actual de la ecología urbana en África (Capítulo 1). La revisión reveló 

una sorprendente falta de información sobre el tema, con solo 795 artículos publicados 

en el último siglo (1920-2020), muchos menos que en otros continentes. Además, un 

gran número de estos estudios (40%) se realizó en Sudáfrica, lo que indica un 

importante sesgo geográfico en nuestro conocimiento actual sobre el tema. Esta 

revisión encontró también que los esfuerzos de investigación sobre ecología urbana en 

África están asociados con la riqueza económica (PIB) y el estado de conservación de 

los ecosistemas. Sorprendentemente, la revisión también expuso que el Afrotrópico, la 

región africana más urbanizada y rica en biodiversidad, no está prácticamente 

estudiada. Además, este primer capítulo identificó que la mayoría (55%) de los estudios 

de ecología urbana en África se realizaron en una sola ciudad, y que existen importantes 

lagunas de conocimiento con respecto a ciertos grupos taxonómicos, campos científicos 

y ecorregiones. Para abordar parcialmente estas importantes lagunas, esta tesis se centró 

en investigar algunas de las principales preguntas sobre el tema a través del estudio de 

múltiples ciudades de Nigeria (capítulos 2 a 5), un típico país afrotropical que 

experimenta una rápida urbanización. De manera muy resumida, estos capítulos 

investigaron los impactos de la  urbanización en la diversidad taxonómica, funcional y 

filogenética de las aves (Capítulos 2 y 3), los servicios ecosistémicos reguladores 

mediados por las aves, incluido el control de plagas, la dispersión de semillas, la 



5 

 

polinización y el consumo de carroña (Capítulo 4), y las interacciones entre humanos y 

naturaleza (Capítulo 5). 

 Los resultados de estos estudios demostraron inequívocamente que la 

urbanización tiene profundos impactos negativos en la diversidad de aves y los 

servicios ecosistémicos en el Afrotrópico. En comparación con las áreas no urbanas, 

las áreas urbanas exhibieron una diversidad taxonómica de aves significativamente 

menor (Capítulo 2) y mostraron menores niveles de servicios ecosistémicos esenciales 

proporcionados por los organismos silvestres, incluido el control de plagas, la 

dispersión de semillas y la polinización (Capítulo 4). El consumo de carroña fue el 

único servicio ecosistémico mediado por las aves que mejoró en relación al desarrollo 

urbano (estación lluviosa). Además, se identificaron ciertas características urbanas, 

como la presencia de vehículos y peatones, que afectan negativamente a la diversidad 

filogenética de las aves y la prestación de servicios ecosistémicos, en particular la 

polinización y la dispersión de semillas. Sin embargo, los resultados también resaltan 

el potencial que pueden tener ciertas actividades de conservación para mitigar estos 

impactos negativos. En particular, la presencia de masas de agua y algunos tipos de 

vegetación específicos, como la cobertura arbórea y arbustiva, pueden mejorar 

significativamente múltiples componentes de la diversidad de aves así como varios de 

los servicios ecosistémicos de regulación que proporcionan (Capítulos 2 y 4). Al 

preservar y restaurar estas características clave del hábitat en las ciudades del África 

tropical, se podría revertir la reducción en la diversidad de aves y los servicios 

ecosistémicos reguladores en la zona, en particular la dispersión de semillas y la 

polinización. 

 El Capítulo 3 presenta una aplicación novedosa de técnicas de aprendizaje 

automático y teledetección para estimar las variables del hábitat local que influyen en 

los distintos componentes de la diversidad de aves en áreas urbanas y no urbanas. Este 

estudio reveló que el índice de absorción de clorofila modificado (MCARI) es el 

indicador más eficaz de la diversidad taxonómica y filogenética de aves en el 

Afrotrópico. Por el contrario, se encontró que el Índice de Diferencia Normalizada de 

Agua 2 (NDWI2) y el Índice de Vegetación Total Ajustado del Suelo (SATVI) eran los 

mejores predictores de la diversidad funcional y la divergencia filogenética, 

respectivamente. Curiosamente, el Índice de Diferencia Normalizada de Vegetación

(NDVI), un predictor comúnmente utilizado en todas las regiones y temas, obtuvo una 

clasificación de idoneidad relativamente baja (percentil 25) en la mayoría de los casos. 

Estos resultados apoyan el uso de estos predictores alternativos (MCARI, NDWI2 y 

SATVI) en lugar del NDVI para predecir la diversidad de aves en áreas urbanas y no 

urbanas del África tropical. Es probable que esto se deba a las limitaciones del NDVI, 



6 
 

incluidos problemas de escala, saturación en áreas de alta biomasa y sensibilidad al 

brillo del suelo, que pueden comprometer su precisión en diversos ambientes del 

Afrotrópico. El uso de la teledetección en este estudio ofrece un método potencialmente 

más eficiente y rentable para estimar las variables del hábitat local en comparación con 

las técnicas tradicionales de estimación manual en campo. Al aprovechar los algoritmos 

de aprendizaje automático y los datos de detección remota, este enfoque puede ayudar 

a reducir el esfuerzo de trabajo de campo, los gastos y los errores de los investigadores 

asociados con la recopilación manual de datos. 

 Además de los impactos ecológicos, la urbanización también tiene importantes 

implicaciones sociales. Al investigar el concepto de extinción de la experiencia entre 

los habitantes urbanos de Nigeria, el Capítulo 5 encontró que la mayoría de los 

ciudadanos de esta región tenían poco o ningún contacto con la naturaleza. Los 

principales motivos citados para esta desconexión fueron la falta de tiempo, dinero y 

espacios naturales cercanos. El estudio también encontró que los encuestados con 

mayor contacto con la naturaleza estaban más conectados con la naturaleza y que la 

percepción de seguridad del vecindario era un factor importante que promovía el 

contacto con la naturaleza. Además, el estudio también encontró que los encuestados 

que vivían en Lagos y aquellos con niveles más bajos de ingresos y educación 

mostraban una mayor disociación con la naturaleza. Estos hallazgos podrían ser útiles 

para luchar contra la preocupante extinción de la experiencia en la región, 

proporcionando elementos adicionales a considerar e implementar en futuros planes de 

desarrollo urbano en el Afrotrópico. 

 En general, los capítulos de esta tesis destacan la necesidad de realizar más 

investigaciones sobre los impactos de la urbanización en la biodiversidad y los servicios 

ecosistémicos en el África tropical. También enfatizan la importancia de promover el 

contacto y la experiencia con la naturaleza entre los habitantes urbanos, particularmente 

en regiones con rápida urbanización como es el área de estudio (Nigeria). Al abordar 

estas lagunas de conocimiento y promover la experiencia en la naturaleza, podemos 

ayudar a crear ecosistemas urbanos más sostenibles y resilientes que beneficiarán tanto 

a las personas como al medio ambiente.

 



 
 

 

 

General introduction 

 

Urbanization’s impacts on socioecological systems 

Urbanization, the conversion of natural areas into built environments, is one of the 

greatest global environmental challenges of recent decades (Seto et al., 2012; United 

Nations, 2016). This human-induced landscape change is tightly linked with 

humanity’s rapidly increasing population and rural-urban migration (Oyeleye, 2013; 

United Nations, 2019). For instance, approximately 50 % of the global human 

population (i.e., 6.2 billion) lived in urban areas at the start of the 21st century (Grimm 

et al., 2008; United Nations, 2024). It is also predicted that urban areas will continue to 

expand in the near future, with grave consequences for socioecological systems (Angel 

et al., 2011; Seto et al., 2012; United Nations, 2018). 

Broadly speaking, an urban area is a contiguous patch of built-up land greater 

than 1 km2, and dominated by human-constructed features like buildings (>10 

buildings/ha), high human density (>1600 inhabitants/km2), roads, and vehicles 

(Marzluff et al., 2001; Niemelä, 1999; Nilon et al., 2003; Schneider et al., 2010). In 

contrast, non-urban habitats consist of extensive wilderness and vegetation cover, 

interspersed with agricultural landscapes (MacGregor-Fors, 2011; Marzluff et al., 

2001). Thus, the burgeoning field of urban ecology investigates the “interaction of 

organisms, built structures and the physical environment where people are 

concentrated” (Forman, 2014). This scientific field tests overarching hypotheses at the 

interface of urbanization and socioecological systems, particularly investigating drivers 

of biodiversity, human-nature interactions and the ecosystem services provided by 

urban nature (e.g., Arjona et al., 2023; Cox & Gaston, 2015; Ibáñez-Álamo et al., 2020; 

Reynolds & Howes, 2023; Soga et al., 2015). This holistic approach is necessary given 

that actions targeted at minimizing human footprints while conserving urban nature still 

need the support of urban dwellers (Miller & Hobbs, 2002). The field of urban ecology 

will ultimately enhance the achievement of inclusive, safe and sustainable urban 

development in line with SDG Goal11 (United Nations, 2015).



General introduction 

8 

 

To start with, the interrogation of urbanization’s impacts on biodiversity has 

received considerable attention relative to other socioecological systems such as 

human-nature interactions and ecosystem service provisioning (Hagen et al., 2017; 

Ibáñez-Álamo et al., 2017; Lin & Grimm, 2015; Magle et al., 2012; Wu, 2014). These 

studies also show how research effort favor certain taxa, regions and biodiversity 

components (i.e., taxonomic, functional or phylogenetic diversity). Regarding taxa, 

urban ecology research effort expended on biodiversity focused more on higher plants 

and animals than microorganisms (Donaldson et al., 2017; Shwartz et al., 2014) despite 

their relevance in stabilizing ecosystems (Epp Schmidt et al., 2019; Thompson et al., 

2017). 

In relation with geography, most urban ecology studies are concentrated in 

Global North regions (e.g.; Europe and North America) relative to those in the Global 

South, particularly Africa and Asia (e.g., Marzluff, 2016; Shackleton et al., 2021). This 

implies a significant mismatch worthy of scientific attention given that the Global South 

is the most impacted by urban development while simultaneously holding the greater 

proportion of the Earth’s biological diversity (Gatti et al., 2015; Seto et al., 2012). The 

need for more urban ecology studies from the Global South is not far-fetched. This 

region consists of underdeveloped and developing countries mainly located in Africa, 

Latin America, Asia, and Oceania (Dados & Connell, 2012; Shackleton et al., 2021). 

The Global South has peculiar biophysical and socioeconomic characteristics (e.g., 

high rate of urbanization, unemployment, and poverty, and issues of security, 

governance and health) compared to the Global North (World Cities Report, 2020). 

Thus, urban ecology theories from the Global North do not always fit the Global South, 

and several authors have advocated for more Global South urban ecological studies 

(e.g., Okpala, 1978; Shackleton et al., 2021).  

Perhaps, the Afrotropics remains the most understudied Global South region 

regarding urban ecology (Shackleton et al., 2021). For instance, while investigating 

drivers of urban taxonomic diversity is not uncommon in the Afrotropics (Adegbola et 

al., 2024; Afrifa et al., 2022), comparing taxonomic diversity between urban and 

adjacent non-urban habitats are scarce despite the capability of such an approach to 

provide nuanced understanding of urbanization’s impacts on biodiversity (Chamberlain 

et al., 2017). From an applied perspective, citizens’ interactions with nature are also 

low in urban environments of this region (Lee et al., 2022), and an understanding of the 

reasons for this disconnect is crucial to develop mitigating interventions (Shackleton et 

al., 2021). This need for applied urban ecology studies from the Afrotropics also 

extends to regulating ecosystem services. The few (< 50) papers published on the topic 

for the whole African continent focused on South Africa and few ecosystem services



General introduction 

9 

 

(i.e., pollination and regulation of water flow and runoff) (du Toit et al., 2018; Reynolds 

& Howes, 2023), highlighting the need for additional studies overcoming this important 

lack of knowledge. 

In relation with biodiversity components, there is a scientific consensus 

showing that urbanization generally reduces taxonomic diversity, the presence of 

species in an area (Magurran, 2004), through a process known as the biotic 

homogenization (Aronson et al., 2014; McKinney, 2006, 2008). However, much less is 

known with respect to functional and phylogenetic diversity despite its potential 

relevance for conservation decisions (Cadotte et al., 2011, 2012; Tucker et al., 2017). 

The former focus on how the functional traits of species influence ecosystem services 

and functioning (Mouchet et al., 2010; Reynolds & Howes, 2023) while the later 

provides information on the evolutionary richness or divergence of all species in a given 

community assemblage (Faith, 1992; Helmus et al., 2007). This bias is even more 

crucial in cities where urbanization exerts differing impacts on the various components 

of biodiversity (Dylewski et al., 2023; Ibáñez-Álamo et al., 2020; Leveau et al., 2020). 

Some key research questions here are: (1.) How will urban planners and 

conservationists simultaneously conserve the various components of biodiversity in 

urban centers? (2.) What are the local influential variables that could enhance the 

various components of urban biodiversity? Answering these questions is key to 

proposing tailored interventions that could mitigate the loss of biodiversity due to urban 

development in general, and particularly on the African continent. Moreover, the 

impact of urbanization on functional and phylogenetic diversity is poorly understood 

in the Afrotropics (Hagen et al., 2017; Ibáñez-Álamo et al., 2017) and, thus, demanding 

additional investigations. 

From a more applied point of view, several studies report how local attributes 

(e.g., impervious surfaces, numbers of vehicles and pedestrians, tree canopy, and the 

coverage of bush, grass, water) affect biodiversity in urban areas worldwide (e.g., 

Adegbola et al., 2024; Ibáñez-Álamo et al., 2020; Wood & Esaian, 2020). These local 

urban attributes could not only help to understand the patterns and processes of urban 

ecosystems but also allow specific recommendations for city planners and conservation 

practitioners (Arjona et al., 2023; Aronson et al., 2014; Shackleton et al., 2021). In this 

same context, recent advances show that employing remotely sensed spectral indices 

(e.g., NDVI and EVI) is more comprehensive and less laborious in capturing how site 

characteristics influence biodiversity than the field-based estimation of those local 

influential variables (Benedetti et al., 2023; Leveau et al., 2020). This remote sensing 

approach could be important in Africa, where socio-economic constraints limit urban 

ecology studies (see Shackleton et al., 2021).



General introduction 

10 

 

Urbanization-induced biodiversity loss has far-reaching consequences for both 

the environment and human well-being (Liang et al., 2019; Moore et al., 2003). One of 

such negative effects corresponds with the alteration of ecosystem services provided by 

organisms (e.g., wildlife, vegetation); known as the tangible (e.g., food, water) and 

intangible (e.g., climate regulation, pest control) benefits people derive from nature 

(Pinho et al. 2017). Regulating ecosystem services (RES) are disproportionately 

impacted, with urbanization favoring scavenging over other essential services like seed 

dispersal, pollination, and pest control (Chamberlain et al., 2017; Fattorini, 2011; 

Schneiberg et al., 2020; Wenzel et al., 2020). Despite these findings, research on this 

topic is largely skewed towards Global North countries, with a striking knowledge gap 

in African regions (Shackleton et al., 2021). To date, fewer than 50 studies have 

investigated this issue on the entire African continent (du Toit et al., 2018), highlighting 

the need for more comprehensive and inclusive research. 

The disruption of ecosystem services not only compromises human well-being 

but also exacerbates the disconnection between people and nature. Urbanization's 

potential to limit natural areas and excursion opportunities can lead to the "extinction 

of experience" (Pyle, 1993), where people become increasingly disconnected from 

nature. While research has investigated the components and mechanisms driving this 

phenomenon, it is heavily biased towards Global North countries (Barragan-Jason et 

al., 2022; Bashan et al., 2021; Pett et al., 2016), leaving important knowledge gaps in 

our understanding of human-nature interactions in regions of the Global South. This 

knowledge gap is concerning, as it leaves us with a limited understanding of human-

nature interactions in Global South regions like the Afrotropics. 

This thesis employed different scientific approaches to bridge some of the most 

relevant knowledge gaps regarding Afrotropical urban ecology. To start with, Chapter 

1 incorporated the systematic literature review to determine the state of African urban 

ecology and identify critical knowledge gaps in the last century (1920–2020). The 

remaining four chapters tested how urbanization shapes various socioecological 

systems in the Afrotropics using Nigeria, the most populous African country that is 

rapidly urbanizing (Seto et al., 2012; World Bank, 2021), as the study area. 

Accordingly, Chapter 2 delved into how urbanization affects avian taxonomic, 

functional and phylogenetic diversity across habitats (i.e., urban vs. non-urban), seasons 

(i.e., dry vs. wet), and vegetation zones (i.e., rainforest vs. savannah), and tested the 

effects of local influential variables (e.g., impervious surfaces, numbers of vehicles and 

pedestrians, tree canopy, and the coverage of bush, grass, water) estimated in the field. 

Chapter 3 complemented Chapter 2 by using satellite data (i.e., remotely sensed 

multispectral indices like NDVI, EVI) to predict how urbanization affects avian 



General introduction 

11 

 

taxonomic, functional and phylogenetic diversity across the habitats and vegetation 

zones. This approach is necessary given social unrest that hamper biodiversity 

monitoring in some Afrotropical areas (Ojukwu, 2011; Otu et al., 2018). In addition, 

this remote sensing approach provides more accurate data, and is less laborious, 

expensive and prone to investigators' errors compared to the manual or field-based 

estimation of local influential variables (Ghosh et al., 1995; Gorrod & Keith, 2009; 

Morrison, 2016). From an applied perspective, Chapter 4 interrogated variations in 

bird-mediated regulating ecosystem services (i.e., pest control, fruit dispersal, 

pollination and scavenging) across the seasons, habitats, and vegetation zones. Lastly, 

Chapter 5 examined human-nature interactions in Afrotropical urban areas. Birds were 

the focal species used to investigate Chapters 2—5 because their composition changes 

between seasons and vegetation zones (e.g., Brown et al., 1982; Morelli et al., 2021), 

and have a well-validated phylogeny (e.g., Jetz et al., 2012). Birds are also commonly 

used in human dimension studies investigating drivers of human-nature interactions 

and ecosystem services in urban areas (e.g. Cox & Gaston, 2015; Reynolds & Howes, 

2023). 

Overall, this thesis will identify critical knowledge gaps in African urban 

ecology and expand our understanding on how urbanization shapes different 

biodiversity components, human-nature interactions and regulating ecosystem services 

(Fig. 1). Thus, it can provide very much needed data for sustainable urban development 

in the region and beyond. 

Thesis aims 

To identify knowledge gaps in African urban ecology and investigate how urbanization 

affects socioecological systems across Afrotropical environments and seasons. 

Thesis objectives 

1. To determine the status of African urban ecology in the last century (1920–

2020).  

2. To study the effects of urbanization on bird taxonomic, functional and 

phylogenetic diversity across Afrotropical habitats, vegetation zones and 

seasons. 

3. To examine how remotely sensed multispectral indices predict urbanization’s 

impacts on bird taxonomic, functional and phylogenetic diversity across 

Afrotropical habitats and vegetation zones.



General introduction 

12 

 

4. To study how urbanization influences avian-mediated regulating ecosystem 

services (pest control, fruit dispersal, pollination and scavenging) across 

Afrotropical habitats, vegetation zones and seasons. 

5. To investigate drivers of human-nature interactions in Afrotropical urban 

habitats. 

Objetivos de la tesis 

1. Determinar el estado de la ecología urbana africana en el último siglo (1920-

2020).  

2. Estudiar los efectos de la urbanización en la diversidad taxonómica, funcional 

y filogenética de las aves en distintos hábitats, zonas de vegetación y estaciones 

del trópico africano. 

3. Examinar cómo los índices multiespectrales basado en datos satelitales 

predicen los impactos de la urbanización en la diversidad taxonómica, 

funcional y filogenética de las aves en los hábitats y zonas de vegetación del 

trópico africano. 

4. Estudiar cómo la urbanización influye en los servicios ecosistémicos 

reguladores mediados por las aves (control de plagas, dispersión de frutos, 

polinización y consumo de carroña) en hábitats, zonas de vegetación y 

estaciones del Afrotrópico. 

5. Investigar los determinantes de las interacciones entre los humanos y la 

naturaleza en los hábitats urbanos del África tropical. 

 

Figure 1: An overview of the thesis objectives. 



 

 

General methodology 

Study area 

Chapter 1 is a systematic literature review that covered 58 countries making up the 

entire African continent (United Nations, 2024; World Cities Report, 2020). The 

literature search, covering 1920—2020, was performed in Web of Science, Google 

Scholar, and Scopus on 8 March 2021. The resulting papers were screened with Rayyan 

(https://www.rayyan.ai/), a web-based semi-automation App (Olofsson et al. 2017; 

Ouzzani et al., 2016), and followed the highly recommended Preferred Reporting Items 

for Systematic Reviews and meta-analyses (PRISMA Statement) (Abreha, 2019; 

Moher et al. 2009) indicated in Figure 1 of Chapter 1. Additional data were collected 

from different global databases, including the Global Biodiversity Information Facility 

(GBIF, 2021; accessed May 2022), World Wildlife Fund for Nature (WWF: Olson et 

al., 2001), Africapolis for urbanization intensity (OECD/SWAC, 2020; accessed 9th 

June 2021) and the United Nations for socio-demographic details (United Nations, 

2018).  

Data for the remaining Chapters were taken from Nigeria. This country is 

situated in the Afrotropical belt, experiencing the distinct climatic variations of wet 

(April—September) and dry (October—March) seasons (Ezealor, 2001; 

OECD/SWAC, 2020). In Nigeria, annual rainfall intensity (4,000 mm—600 mm) and 

duration decrease northwards from the southern coast compared with the mean annual 

temperature (8◦C—40◦C) (Ezealor, 2001). These climatic variations shape Nigeria’s 

vegetation physiognomy and bird composition (Barshep et al., 2022; Elgood et al., 

1994). Thus, the southern Nigerian sites visited for this study support dense evergreen 

forests of tall trees with thick undergrowth (termed “rainforest”) in comparison with 

the northern sites dominated by grasses interspersed by small-medium sized trees 

(termed “savannah”) (Ezealor, 2001). 

General field procedure 

Data were collected from paired urban and non-urban habitats of eight Nigerian cities 

evenly distributed across the rainforest (Auchi, Calabar, Ibadan, Lagos) and savannah 

(Birnin Kebbi, Dutse, Gombe, Jos) vegetation zones (see Fig. 1 of Chapter 2). In 

https://www.rayyan.ai/


General methodology 

14 

general, each urban area (e.g., Fig. 2) consisted of a contiguous patch of built-up land 

greater than 1 km2, and dominated by human-constructed features like buildings (>10 

buildings/ha), high human density (>1600 inhabitants/km2), roads, and vehicles 

(Marzluff et al., 2001; Niemelä, 1999; Nilon et al., 2003; Schneider et al., 2010). The 

paired non-urban habitat (e.g., Fig. 3), always situated in an adjacent area, was 

characterized by extensive wilderness/vegetation cover interspersed with agricultural 

matrix and sparsely settled villages (MacGregor-Fors, 2011; Marzluff et al., 2001). Any 

urban or non-urban site in this study was located at least 20 km away from each other 

to grant the independence of their avian communities (Liker et al. 2008). 

 
Figure 2: Drone shot of Ibadan, a typical urban center where data were collected  

in Nigeria. Credit: IITA Communications Office. 

Fieldwork for Chapters 2—4 was carried out in paired urban and non-urban 

habitats of either all or some of the eight Nigerian cities (depending on the Chapter) 

distributed across the rainforest (Ado, Auchi, Calabar, Ibadan, Lagos) and savannah 

(Birnin Kebbi, Dutse, Gombe, Jos) vegetation zones (Fig. 1). This mainly involved the 

use of the point count method (Bibby et al., 2000; Sanllorente et al., 2023) for recording 

birds and local influential variables estimated manually in the field (i.e., impervious 

surfaces, numbers of vehicles and pedestrians, tree canopy, and the coverage of bush, 

grass, water) or via remote sensing (e.g., 29 variables including NDVI, EVI etc.). 



General methodology 

15 

 
Figure 3: Drone shot of the Olokemeji Forest Reserve, a typical non-urban  

habitat where data were collected in Nigeria. Credit: IITA 

Communications Office. 

This methodology has been previously used by multiple studies (Benedetti et 

al., 2023; Leveau et al., 2020; Reynolds & Howes, 2023; Sanllorente et al., 2023). For 

Chapters 2—4, fifty points (i.e., 25 urban vs 25 non-urban) were randomly selected 

(Møller et al., 2012) in each of the eight cities, equally distributed across the rainforest 

(Auchi, Calabar, Ibadan, Lagos) and savannah (Birnin Kebbi, Dutse, Gombe, Jos). Each 

point was marked with a GPS to ensure data collection was from the same location 

throughout the entire study. Data for Chapters 2 and 4 were collected across the dry 

(November 2020—January 2021) and wet (August—September 2021) seasons, while 

Chapter 3 utilized only the cloudless data from the dry season (November 2020—

January 2021). Data collection for Chapter 5 was restricted to the southern rainforest 

sites (i.e., Auchi, Calabar, Ibadan, Lagos) due to important security issues (kidnapping 

and banditry) in northern Nigeria at the time. During the wet season (August—

September 2021), the four southern sites were visited for data collection for Chapter 5. 

The same field data, comprising bird counts, formed the basis for Chapters 2—5. 

Meanwhile, additional data were integrated into each chapter. The local influential 

variables (e.g., number of vehicles, canopy cover….) were incorporated to 

contextualize the bird count data for Chapter 2. To investigate Chapter 3, remotely 

sensed spectral indices (e.g., NDVI, EVI…) were added to the bird count data. For 

Chapter 4, diet information was extracted from Savitraits, serving as a proxy for 

ecosystem service provisioning by the sampled birds. Finally, structured questionnaires 

were administered to 600 respondents (300 women and 300 men), offering a socio-

ecological perspective, were added to the bird count data and local influential variables.



General methodology 

16 

 
Figure 3: Distribution of study sites across the savannah and rainforest  

vegetation zones in Nigeria. At each city, data were collected in paired 

urban and non-urban sites.



 

 

 



 

 

 

Chapter 1 

 

Status of urban ecology in Africa: A systematic review 

 

Adewale G. Awoyemi1,2,3 and Juan Diego Ibáñez-Álamo1 

 

1Department of Zoology, Faculty of Sciences, University of Granada, Granada, Spain 

2Forest Center, International Institute of Tropical Agriculture, Ibadan, Nigeria 

3A.P. Leventis Ornithological Research Institute, Jos, Nigeria 

 

 

Published in Landscape and Urban Planning (2023), 233: 104707, 1–16. 

https://doi.org/10.1016/j.landurbplan.2023.104707  

 

Abstract 

Urbanization is an extreme human activity and is expanding worldwide, consequently 

increasing the attention of scientists across research areas of urban ecology. Recent 

studies have warned of the lack of information from certain regions, particularly Africa, 

which is rapidly urbanizing. Thus, we did a detailed literature search to determine the 

state of knowledge in African urban ecology in the last century. We found 795 relevant 

papers from where data were collected and tested to understand geographic and 

ecological mismatches in research effort, allowing us to identify important knowledge 

gaps (e.g., taxonomy and scientific fields). We also tested the effect of current and 

future urbanization intensity, human population density, size and conservation status of 

https://doi.org/10.1016/j.landurbplan.2023.104707


Chapter 1 

19 

ecoregions and Gross Domestic Product (GDP) on research effort. Our results suggest 

a low turnout of papers and a dearth of knowledge about African urban ecology. Studies 

were conducted in 72% of African countries, with South Africa alone accounting for 

almost 40% of all published papers. The studies were either conducted at the city (55%) 

or local/country (34%) level, suggesting the lack of transnational research 

collaboration. Interestingly, only country GDP and the size and conservation status of 

ecoregions significantly predicted the number of publications, suggesting that research 

effort is driven by economic reasons and the relevance of conservation in African urban 

ecology. We need to account for these biases to advance our understanding of the 

impacts of urbanization on African biodiversity.  

Introduction 

Rapidly expanding urbanization is a major threat to nature worldwide, leading to the 

reduction of biodiversity and alteration of species interactions and ecosystem services 

(Gaston, 2010; Mcdonald et al., 2008; McKinney, 2006; United Nations, 2016). The 

impacts of urbanization could be even worse in the near future due to the geometric 

progression of human population. According to the United Nations (2019), the global 

human population density will increase from 60 humans/km2 in 2020 to 78 humans/km2 

in 2050, while the global urban land cover will increase from 824,200 km2 to 1,145,698 

km2 during the same period (Angel et al., 2011). Thus, research on urban ecology is 

imperative to achieve sustainable development, allowing for the understanding of 

ecological processes in urban areas and providing necessary data for urban planning, 

landscape design, policy formulation and biodiversity conservation (Corbyn, 2010; 

Moragues-Faus & Carroll, 2018).  

Given the availability of various definitions of urban ecology, we follow the 

scientific proposition that incorporates the ‘interaction of organisms, built structures 

and the physical environment where people of urbanization, the concept of social and 

ecological integration (inclusiveness) has been proposed to enhance biodiversity in 

urban areas (e.g., Haase et al., 2017). For instance, Ferketic et al., (2010) demonstrated 

the usefulness of inclusiveness in promoting conservation justice in Cape Town (South 

Africa), thereby influencing the ecology of the city, and an understanding of such a 

nexus is useful to design resilient and sustainable urban areas (Childers et al., 2015; 

Grimm et al., 2008). 

The globally recognized multi-disciplinary fields and the embedded scientific 

topics in urban ecology have attracted increasing attention from researchers (e.g., 

Anderson et al., 2013; Cilliers et al., 2013; Girma et al., 2019). However, several papers 

have highlighted important knowledge gaps across regions, taxa and scientific topics 

(e.g., Magle et al., 2012; Tóth et al., 2020; van der Walt et al., 2015). Probably, one of 



Review of African urban ecology 

20 

the most important mismatches between urban ecology research effort and the 

urbanization process is the lack of knowledge on the topic from the most rapidly 

urbanizing continents of South America, Asia and Africa (Ibáñez-Álamo et al., 2017; 

Seto et al., 2012; Shackleton et al., 2021). As identified in these studies, geographic 

biases impede the full comprehension of the real impacts of urbanization on nature. 

Future studies conducted in appropriate areas will therefore be useful to determine 

ameliorative strategies needed to promote the co-existence of humans with nature, 

thereby enhancing urban habitats and the associated biodiversity, which is in line with 

the 11th Sustainable Development Goal of the United Nations (2021). 

Literature reviews provide an opportunity for summarizing the state of 

evidence-based knowledge applied in many fields (e.g., Ibáñez-Álamo et al., 2017; 

Magle et al., 2012). Broadly, this involves the incorporation of published literature in 

any given field (Garousi et al., 2019). However, the generalization and application of 

findings from literature reviews in decision-making have been a subject for debate, 

mainly due to transparency, objectivity, repeatability and credibility (Sánchez-Tójar et 

al., 2020). Since traditional approaches to literature reviews are prone to errors (Grant 

& Booth, 2009), rigorous methodological approaches have been developed and applied 

more recently in the field of urban ecology (e.g., Cilliers et al., 2018; Kendal et al., 

2020; Ibáñez-Álamo et al., 2017), allowing for an important advancement in our 

understanding of the effect of urban areas on organisms.  

In the present study, we conducted a systematic literature review to determine 

trends in urban ecological research conducted in Africa. Relative to other regions such 

as Asia, Europe and North America (Forman, 2016; Lin & Grimm, 2015; Magle et al., 

2012; Wu et al., 2014), there have been few attempts aimed at synthesizing the state of 

knowledge in African urban ecology (e.g., Cilliers et al., 2013; Shackleton et al., 2017; 

Lindley et al., 2018; du Toit et al., 2018). Our aims were to (i) analyze the current status 

of research effort on urban ecology in this continent, (ii) identify research gaps 

(geographic, taxonomic and ecological) and (iii) provide recommendations and insights 

on future prospects. Additionally, (iv) we investigated the potential association of urban 

ecology research effort with some factors previously associated with the number of 

scientific publications. On the one hand, we tested whether the number of publications 

in the field (i.e., urban  ecology) per country could be influenced by human population 

density, economic wealth, as well as the current or future urbanization prospects. Given 

the positive association between human  population density and the degree of 

urbanization (e.g., Gao & O’Neill, 2021; Qizhi et al., 2016), we would expect that 

countries with high human population density would hold the majority of studies in 

urban ecology. Furthermore, if urban ecology research effort is driven by the intensity 

of urbanization, based on the scientific reasoning of geographic focus areas of particular 



Chapter 1 

21 

interest, we could predict a positive association of the number of publications on this 

topic in those countries currently more urbanized or with the highest rate of urban 

expansion (i.e., future urbanization). Although the relationship between urbanization 

and economic growth is often contested (e.g., Chen et al., 2014; Moomaw & Shatter, 

1996), we would expect that wealthier countries (i.e., higher Gross Domestic Product 

–GDP–) are those concentrating the majority of urban ecological studies as increased 

funding positively influences publication rates (Man et al., 2004). On the other hand, 

we also tested whether the number of publications in the field could be influenced by 

the conservation status and size of African ecoregions. Previous reviews have pointed 

out the positive association between the conservation status of study sites and research 

effort (e.g., de Lima et al., 2011). Thus, if research effort is based on conservation 

oriented reasons, we would expect that threatened ecoregions will be more studied. In 

addition, since smaller areas generally support lower species richness (see Rantalainen 

et al., 2005), we would expect that larger ecoregions will provide more study 

opportunities for researchers specializing in different species and scientific topics, and 

will therefore be more studied. Considering the marked differences between Global 

North and Global South urban settings (Shackleton et al., 2021), we acknowledge that 

there could be other factors (e.g., climate severity, colonial history or high diversity in 

human-nature interactions) shaping the urban ecology research effort in Africa, which 

is considered part of the Global South. However, we did not include them because of 

the difficulty of extracting such information and to avoid overparameterization of 

models. Findings of this study will provide additional information about African urban 

landscapes that should generate interest among researchers, conservation practitioners 

and policymakers. 

Methods 

Bibliographic search and paper screening 

We performed a literature search in Web of Science, Google Scholar and Scopus on 8 

March 2021 using different combinations of 89 relevant keywords within the article 

titles, abstracts and keywords, covering the period 1920–2020. The search string 

containing research focus (23 keywords; e.g., ecology, biodiversity and wellbeing) and 

urban terms (5 keywords; e.g., urban, city and town) were matched with region (Africa 

and country name). We performed independent searches for each of the 58 countries 

and autonomous territories in the continent. A detailed description of these search 

terms, and the relevant Web of Science categories (41) and Scopus study fields (10) 

selected can be found in Table S1. The relevance of the use of such comprehensive 

keywords has been demonstrated by previous studies (e.g., Raji & Downs, 2021; Roy 

et al., 2012; Tan & bin Abdul Hamid, 2014).



Review of African urban ecology 

22 

We then uploaded all detected papers on Rayyan (https://www.rayyan.ai/) for 

screening. Rayyan is a web-based App that uses a semi automation process to screen 

paper’s preliminary pages with a high degree of precision (Olofsson et al., 2017; 

Ouzzani et al., 2016). Its adaptability and many functions allow the detection of 

duplicates, verification, collaboration and decisions in systematic reviews (Abreha, 

2019; de Keijzer et al., 2016). In the present study, both authors independently 

performed the paper selection process by activating the “blind function” in Rayyan and 

reached a consensus thereafter. Our selection process followed the Preferred Reporting 

Items for Systematic Reviews and meta-analyses (PRISMA Statement) (Abreha, 2019; 

Moher et al., 2009), which is presented in Fig. 1. Based on article titles and abstracts, 

we first excluded duplicates, non-African studies and investigations carried out outside 

urban settings. We also excluded papers on human diseases, climate change, pollution 

and agriculture when they were exclusively focused on clear different disciplines, such 

as malaria studies exclusively focused on the medical science (e.g., Kigozi et al., 2020) 

or agricultural papers investigating different crop varieties without any socio-

ecological, biodiversity or human dimensions focus (e.g., Kent et al., 2001). Several 

systematic reviews already exist on these disciplines (e.g., Fayiga et al., 2018; Hulme 

et al., 2001; Orsini et al., 2013). The remaining articles were then screened and those 

that met the following criteria were retained for data extraction: (1) urban landscape, 

ecological and  sociological studies, (2) journal articles published in English, (3) peer-

reviewed as a first step towards quality control (Beninde et al., 2015; Raji & Downs, 

2021), and (4) biodiversity conservation studies (including pet animals and introduced 

species). 

Data extraction and categorization 

We extracted the following data from each included paper: title, year of publication, 

journal, country of study and study sites. We then classified each paper based on type 

(field study, review or perspective) and scale, which included city (conducted in a 

single city), local (involving more than one city in a country), regional (involving more 

than one African country) and global (involving more than the African continent). 

Further, we followed the classification of Magle et al. (2012) to allocate each paper to 

one of the following scientific fields, including animal behavior, community ecology, 

conservation, human dimensions, human-wildlife conflict, landscape ecology, 

population ecology, wildlife disease and wildlife management. For taxonomic studies, 

we extracted information on the kingdoms and classes of focal species based on the 

classification of the Global Biodiversity Information Facility (GBIF) (GBIF, 2021; 

accessed May 2022).



Chapter 1 

23 

 

Figure 1. PRISMA flow diagram for determining the state of urban ecology in  

Africa using the Rayyan Software. 

With the exception of reviews and perspectives, we obtained the coordinates of all 1405 

African study sites included in the selected papers by using Google Earth. This ensured 

conformity and completion given that the coordinates of some sites were either not 

originally provided in the papers or were presented in different formats. We then 

obtained information on all terrestrial ecoregions found in Africa from the World 

Wildlife Fund for Nature (WWF: Olson et al., 2001). Further data on the ecoregions, 

including size, conservation status and the biome they are located in, were also 

collected (Burgess et al., 2004). In addition, we obtained data on urbanization intensity 

and urban land cover (2015) across the continent, as well as the total population (2015) 

and total land area of each studied country from Africapolis (OECD/SWAC, 2020; 

accessed 9th June 2021). Urban land cover was used as a proxy for country urbanization 

intensity, while the total population was divided by the total land area to obtain the 

population density of each country. We then overlaid the study sites across ecoregions 

and urbanization intensity, as well as urbanization intensity across ecoregions, using 

QGIS (version 3.24 Tisler). Africapolis is the single most important and comprehensive 

geospatial database on cities and urbanization dynamics in Africa, which incorporates 

data on demography, satellite and aerial imagery and other cartographic sources 

(OECD/SWAC, 2020). To investigate urbanization prospect based on the urban land 

cover, data on the average annual rate of change of the percentage urban expansion by 

country (2015–2050) were integrated (United Nations, 2018). The Gross Domestic 

Product (GDP 2020; US$) of each studied country was also extracted from the National 

Accounts Section of the United Nations Statistics Division (accessed 6th May 2022).



Review of African urban ecology 

24 

Statistical analyses 

All analyses were carried out using R Version 1.4.1717 (R Core Team, 2016). We 

performed descriptive statistics using the number of published urban ecological studies 

to determine temporal and spatial trends in urban ecological knowledge across years, 

countries, study scales, scientific fields, journals, and taxonomic kingdoms and classes. 

We first used the number of published urban ecological studies (hereafter: 

research effort) per country as the response variable to test the effect of urbanization 

intensity, urbanization prospect, human population density and GDP using general 

linear models (LM). We used the “performance” package to check for multi-collinearity 

among the independent variables (Bernat-Ponce et al., 2021; Lüdeck et al., 2021) and 

tested the normality (Shapiro & Wilk, 1965) of the dependent variable (p < 0.05). The 

independent variables had low correlation (Variance Inflation Factor < 5) and, 

consequently, were all included in the models, but research effort was log-transformed 

to obtain reasonably normally distributed residuals from final models, and models that 

did not violate LM assumptions when examined visually as diagnostic plots (Crawley, 

2013). Using the stepwise backward selection method (Crawley, 2013), variables with 

the highest p values were removed and the procedure repeated until the best model was 

selected as the one with the lowest Akaike Information Criterion value (Burnham & 

Anderson, 2002). Statistical significance was set at p value < 0.05. We also conducted 

a sensitivity analysis (Moher et al., 2009) due to the disproportionate weight of South 

African studies in our database, causing outliers. Of the overall 710 field studies that 

mentioned the 42 African countries represented here, 313 (44 %) were from South 

Africa. The second model therefore incorporated the same variables as the first but 

without South African papers. 

Secondly, we tested for mismatches in the distribution of research effort across 

ecoregions. Note that this information could not be combined with the one collected at 

the country level and thus requires for an additional model to be tested. Given that 

research effort was not normally distributed (p < 0.05) even after log-transformation, 

we built a separate model using Poisson Logistic Regression to test if the size and 

conservation status of ecoregions (factor: Critical, Endangered, Vulnerable, Relatively 

Stable or Relatively Intact) influence research effort. We then conducted a Tukey post-

hoc test for a pairwise comparison across the different categories of conservation status 

using the package “emmeans” (Manley et al., 2015; Yvoz et al., 2020).



Chapter 1 

25 

Results 

Our search string detected a total of 60,355 papers out of which 17,793 duplicates were 

removed. The output of the remaining processes of Rayyan screening led to the 

retention of 795 papers considered in this review (Fig. 1). Out of them, 691 (87 %) were 

field studies, 90 (11 %) reviews and 14 (2 %) perspectives, all of which were published 

in 377 journals (Table S2). The first urban ecology studies focused on Africa date back 

from the 1970s (Okpala, 1978; Hugo, 1979), but the publication rate on the topic was 

slow (<10 papers/year) until 2006 when an exponential growth started, culminating in 

126 papers published in 2020 (Fig. 2). From a geographical point of view, we found 

studies from 72 % of the countries that make up the African continent (42 out of 58 

countries and autonomous territories; Fig. 3).  

 

Figure 2. Urban ecology research effort (number of urban ecological studies)  

across years. 

However, a single country (South Africa) published 4 out of every 10 papers on the 

topic (N = 313), with the highly-urbanized and biodiversity-rich countries of tropical 

regions of the continent recording little (<40 papers; e.g., Democratic Republic of the 

Congo and Kenya) or even no urban studies (e.g., Angola and Liberia; Figs. 3 and 4) 

for the period of study (1920–2020). Furthermore, papers found in our literature search 

showed that most urban ecological research in Africa (89 %) was performed within 

countries, either focused on a single city (N = 434; 55 %) or conducted locally (N = 

270; 34 %). We identified very few international research as only 4 % of the studies 



Review of African urban ecology 

26 

were carried out regionally (i.e., including more than one African country; N = 29) and 

only 8 % were coordinated at a global scale (i.e., including data from other continents 

too; N = 62).  

The result of the LM analysis for all countries shows that research effort 

significantly increased with higher GDP, but not according to any other predictors 

(Table 2; Fig. 5). Contrary to our expectation, countries with higher human density and 

current or future urbanization prospects (up to 2050) have not been more studied (Table 

1). In contrast, wealthier African countries have significantly investigated more on 

urban ecology (Table 1; Fig. 5). The same significant pattern was found for the 

sensitivity analysis (i.e., when South Africa was removed; Table S3). 

Table 1: Results of a GLM exploring the predictors of the number of urban  

ecological studies published across all countries. The number of urban 

studies + 1 was log-transformed to achieve a normal distribution of 

residuals. The last model (F40 = 51.9, P < 0.001; AIC=100.57) incorporated 

only the significant variable and had an adjusted R2 = 0.55. 
 Estimate SE t-value p-value 

Intercept 1.41E+00 1.38E-01 10.22 <0.001 

Gross Domestic Product 9.88E-12 1.37E-12 7.203 <0.001 

    

Rejected variables    

Urbanization intensity 1.07E-01 1.20E-01 0.892 0.378 

Human population density -9.24E-04 9.68E-04 -0.955 0.346 

Urbanization prospect 5.19E-02 3.69E-02 1.4 0.167 

Regarding ecoregions, we found information from 75 out of the 119 

ecologically relevant regions in Africa (Fig. 6a-b; Table S4). This implies 37 % of 

ecoregions without a single urban ecology study. The research effort at this respect is 

not homogeneously distributed and varies considerably depending on the biome (Table 

2). Furthermore, 22 out of the 44 African ecoregions without urban ecology studies are 

classified as threatened (Table S4) (Burgess et al., 2004). The Poisson Logistic 

Regression shows that research effort significantly increased in larger and more 

threatened ecoregions (Table 3). Urban areas in critical, endangered and vulnerable 

ecoregions have been more intensively studied (Fig. 7). 

Our review also showed important taxonomic biases in the study of urban 

ecology in Africa. We found information on studies focusing on seven kingdoms, with 

Animalia and Plantae being the most studied so far (Fig. 8). This result also highlights 

our limited understanding of other organisms, including Archaea, Bacteria, Chromista, 

Fungi and Protozoa, which when combined accounted only for 5 % of the studies. The



Chapter 1 

27 

number of studied classes was considerably higher in Animalia (27) than Plantae (9), 

with Aves (N = 138; 34 %) and Mammalia (N = 95; 23 %) accounting for the majority 

of studied animal groups (Fig. 9). Regarding plants, the most commonly studied classes 

were Magnoliopsida (N = 253; 66 %) and Liliopsida (N = 94; 24 %).  

Table 2: Urban ecology research effort (i.e., studied ecoregion/total ecoregion %)  

across African biomes and ecoregions. 

Biome 

Total 

ecoregio

n 

Studied 

ecoregion 

Research 

effort (%) 

Temperate Coniferous Forests 1 1 100 

Mangroves 5 4 80 

Tropical and Subtropical Moist Broadleaf 

Forests 
30 23 77 

Mediterranean Forests, Woodlands, and 

Scrub 
7 5 71 

Tropical and Subtropical Grasslands, 

Savannas, Shrublands, and Woodlands 
24 16 67 

Montane Grasslands and Shrublands 16 10 63 

Flooded Grasslands and Savannas 10 6 60 

Deserts and Xeric Shrublands 23 9 39 

Tropical and Subtropical Dry Broadleaf 

Forests 
3 1 33 

From a more conceptual point of view, we found variation in research effort among 

scientific fields (Fig. 10). The main focus of urban ecology in Africa seems to be 

applied studies given that conservation and human dimensions studies were the two 

most commonly investigated fields, with 41 % of all papers falling into these two 

categories. The scientific fields of wildlife management, wildlife disease and human-

wildlife conflict were the least studied, accounting for merely 6 % of the total 

publications represented in this review. Our data showed that pattern approaches (e.g., 

Population, Community or Landscape Ecology) are more common than mechanistic 

studies (e.g., Animal Behavior) in Africa (Fig. 10). The first animal behaviour studies 

were published in the early 1990s, investigating insects (Paillette et al., 1993) and birds 

(Van Zyl, 1994). But the focus on this discipline has considerably increased since 2015, 

with 64 % of all Africa urban ecology studies on animal behavior published after this 

year (Table S2). Despite this increasing interest, there is still an important taxonomic 

bias, and only 44 % of the 27 animal classes were represented in animal behaviour 

studies, including Mammalia (38), Aves (47), Reptilia (7), Amphibia (6), Insecta (5),



Review of African urban ecology 

28 

Gastropoda (2), Actinopterygii (2), Arachnida (1), Clitellata (1), Entognatha (1), 

Malacostraca (1) and Sarcopterygii (1). 

 

Figure 3. The distribution of urban ecological studies across African countries. 

 

 

 



Chapter 1 

29 

Table 3: Results of a Poisson Logistic Regression exploring the relationship  

between the number of published urban studies and the conservation 

status and size of ecoregions. Conservation status is a factor with 5 levels 

(Critical, Endangered, Relatively Intact, Relatively Stable, Vulnerable) 

and size is a continuous variable. Critical has been set as the intercept in 

the model. 

 Estimate SE z-value p-value 

Intercept 2.99E+00 4.50E-02 66.467 <0.001 

Endangered 2.44E-01 6.46E-02 3.782 <0.001 

Relatively Intact -2.33E+00 2.13E-01 -10.971 <0.001 

Relatively Stable -1.13E+00 9.02E-02 -12.524 <0.001 

Vulnerable -2.62E-02 1.10E-01 -0.239 0.811 

Size 5.45E-07 4.69E-08 11.609 <0.001 

 

Figure 4. The distribution of urban ecological study sites superimposed on  

urbanization intensity.



Review of African urban ecology 

30 

 

Figure 5. Relationship between urban ecology research effort (number of urban  

ecological studies) across all countries and Gross Domestic Products 

(USD). Note that the y-axis is on a logarithmic scale and that there are several 

overlapping point. 

 

 

Figure 6. Map of the African terrestrial ecoregions showing the distribution of  

urban ecological study sites (a) and urbanization intensity (b). The maps 

were simplified to facilitate interpretation. Thus, we retain outlines of relatively 

large ecoregions >10,000 km2 and those including study sites. However, the 

names of all ecoregions, their corresponding numbers in the map and additional 

details (e.g., size) are included in Table S4.



Chapter 1 

31 

 
Figure 7. Urban ecology research effort (number of urban ecology studies) across  

the conservation categories of ecoregions. Box-plots show median, quartiles, 

5- and 95- percentiles and extreme values. Different letters indicate significant 

differences (P < 0.01) between conservation status according to Tukey post-

hoc tests using the package “emmeans” (Manley et al., 2015; Yvoz et al., 2020). 

 

Discussion 

Spatio-temporal patterns in knowledge 

Our literature search shows almost 800 urban ecology papers for the entire African 

continent. According to a recent review investigating the top 20 countries publishing 

on urban ecology (Shackleton et al., 2021), this number is lower than the number of 

publications from medium-sized European countries, such as Germany (2,479) or Spain 

(1,864), and much lower than the research effort identified for the United States 

(12,728), China (6,655) or Australia (2,900). This suggests that urban ecology research 

in Africa is still considerably low compared to other regions of the World (e.g., Europe, 

North America, Asia or Australia), matching previous findings that already indicated 

the African continent was the least studied regarding urban ecology (e.g., Magle et al., 

2012 stated that Africa accounted for 2.8 % of published papers on urban wildlife 

ecology in 2010). It is interesting to note that despite the exponential growth in research 

effort during the last 15 years, mimicking the global trend on the topic (Lin & Grimm, 

2015), Africa has not increased its relative contribution to the field like other regions 

(e.g., Asia) that were also underrepresented a decade ago (Magle et al., 2012; Wu et al., 

2014; Shackleton et al., 2021). The overall 



Review of African urban ecology 

32 

number of urban ecology papers in Africa does not seem to be associated with a delayed 

start in the discipline. Our review shows that African urban ecology started at the end 

of 1970s around the same time that this discipline started in other regions of the World 

(McDonnel, 2011; Wu, Xiang, & Zhao, 2014). We cannot be completely sure that there 

have not been earlier publications in non-English languages, but probably the first 

African paper explicitly mentioning the concept of urban ecology corresponded to 

Okpala’s study (1978). This pioneering investigation focused on socio-economic 

aspects from Lagos (Nigeria), already highlighting the potential conflict of trying to 

apply European or American urban ecology theory to the African case, an argument 

that is still valid within the Global North and Global South framework (Shackleton et 

al., 2021). The current underrepresentation of African urban ecology is particularly 

worrying as most African urban settings are considered as clear representatives of the 

Global South urban settings, integrating particular biophysical and socio-economic 

contexts (Shackleton et al., 2021). 

 
Figure 8. Urban ecology research effort (number of urban ecological studies)  

across taxonomic kingdoms.



Chapter 1 

33 

Thus, the lack of knowledge at this respect impedes us to complement our 

understanding of urban ecology, which is based on the more traditional Global North 

perspective. There could be other different reasons explaining the low number of 

publications from Africa. The lack of local capacity/experts in the field is one of them. 

This factor has been previously highlighted as a key difference between the Global 

North and Global South urban settings that could influence the lower level of urban 

ecology research effort in the latter (Shackleton et al., 2021). According to the 

UNESCO’s database for the period 2015–2020 (UNESCO, 2020; accessed 30 Oct 

2022), the number of researchers per million of inhabitants in Northern (732.4) and, 

particularly, Sub-Saharan Africa (97.4), is considerably lower than in other egions of 

the planet, such as North America (4,544.8), Europe (3,010.4) or Oceania (3,510.5). 

This low ratio of skilled people has been demonstrated to influence research 

effort in Africa regarding other fields such as ornithology (Cresswell, 2018). Therefore, 

we encourage funding bodies to finance the education of local urban ecologists and 

researchers to overcome this potential restriction. Another potential reason explaining 

the low research effort is partially linked to the previous one: the lack of investment in 

Research and Development (R&D) in Africa compared to other continents. Despite the 

African Union aims at reaching to the 1 % of GDP invested in R&D (United Nations. 

Economic Commission for Africa 2018), current data indicate that it is 0.64 % and 0.34 

% for northern and sub-Saharan Africa, respectively. This is quite far from the values 

of North American, European or Eastern Asian countries that reached a mean of 2.6 % 

in 2020. Matching the target proposed by the African Union will certainly help to 

increase the focus on multiple topics, including urban ecology. However, there are ways 

to improve knowledge on urban ecology in Africa even without the need of large 

economic investments. For example, the use of available databases, such as the various 

atlas projects, which have been successfully implemented in the continent (Botts et al., 

2011; Lee & Nel, 2020). Other repositories, such as the Global Biodiversity 

Information Facility, laboratories, herbaria and museums in and outside of Africa are 

also useful tools to advance our understanding of the ecology of African urban areas 

and biodiversity as some recent studies have already shown (e.g., Cohen et al., 2021; 

Fishpool & Collar, 2018). This approach could also be implemented in collaboration 

with inhabitants of African urban areas through citizen science projects (e.g., iNaturalist 

or the Southern African Bird Atlas Project) that can serve to improve information on 

certain urban questions (e.g., animal distribution) as well as promote the connection 

between citizens and nature (Reynolds et al., 2021). Engaging citizens could also be 

instrumental to help increase the urban governance in the Global South, including 

Africa (Shackleton et al., 2021), and ultimately promote additional support for urban 

ecology studies in this continent.



Review of African urban ecology 

34 

 Our review also shows that research effort is not homogeneously distributed 

within the African continent. From a political point of view, there is an important 

variation among African countries in their urban ecology research effort. One single 

country (South Africa) stands out as it is responsible for almost 40 % of published 

papers on the topic. This is so despite only representing 4 % of African territory and 

1.02 % of all urban areas in the region (OECD/SWAC, 2020). This high rate of urban 

ecology publications matches previous information indicating that South Africa is very 

active in the field at the global level (Shackleton et al., 2021). This does not seem to 

depend on its number of researchers per million of inhabitants (411.6) or its R&D 

investment (0.62 % of GDP), which is lower than the mean for Northern Africa 

(UNESCO, 2020), an area that not even combining all its countries reaches half the 

number of papers published in South Africa. This country started publishing urban 

ecology papers at the earliest stages in Africa (Hugo, 1979), so it is possible that this 

long-term publication period is behind its uniqueness. Another possibility could be that 

several South African cities (e.g., Cape Town and Durban) are located in biodiversity 

hotspots of global importance (Cilliers & Siebert, 2012). Alternatively, given that 

Global North urban principles do not always apply to Global South urban areas 

(Okpala, 1978; Shackleton et al., 2021), there could be a special interest by funders 

and/or researchers from this country to acquire first-hand knowledge of direct 

application to South-African urban settings. For instance, some universities from this 

country (e.g., Witwatersrand) have strategically focused on global change research, 

including urban ecology (Scholes et al., 2013) or have developed specific institutes for 

the study of ‘urbanism from an African perspective’ (e. g., The African Centre for 

Cities, from the University of Cape Town in South Africa; 

<https://www.africancentreforcities.net/about/acc-at-uct/>). Independently of the 

reasons for this important outlier, urban ecology research effort varies considerably 

within African countries. We identified that 28 % of these countries did not publish a 

single urban ecology study and thus, they completely depend on urban knowledge 

obtained elsewhere that sometimes might not be really useful for their local situations. 

 Our analyses show that the number of publications per country on the topic is 

not associated with current or future urbanization. This result contradicts our initial 

prediction; however, it could be well understood from a Global South perspective. 

African countries, like other countries from this group, have several particularities 

compared to those from the Global North (Shackleton et al., 2021). One of them is the 

extremely high urbanization rate. Africa is the continent of the World with the most 

intense urbanization (Cohen, 2006; Seto et al., 2012), with many African countries 

experiencing urbanization rates above 4 % (e.g., Mali, Nigeria, Angola or 

Mozambique), an order of magnitude higher than those from other regions of the planet 

(World Bank, 2021). This factor leads to unplanned urbanization (Zhang, 2016) and



Chapter 1 

35 

compromises sustainable urban development in the continent by impeding the 

implementation of ecologically-sound practices (Cohen, 2006) and hence potentially 

explaining the mismatch between urbanization and urban ecology research effort. 

 Furthermore, we found that the human population density of a country was not 

significantly associated with the number of publications on urban ecology either. The 

reasons for this lack of association could be the same as explained before for the current 

and future urbanization prospects as these are positively correlated with human 

population density (e.g., Gao & O’Neill, 2021; Qizhi et al., 2016). However, this 

predictor could also be associated with other potential factors that might prevent 

investing resources and effort in investigating about urban ecology. For example, there 

is an increase in people living in extreme poverty in Africa, with more than half of the 

urban population living in slums and informal settlements (World Cities Report, 2016). 

Highly populated areas also require a higher infrastructure investment, which is 

particularly needed in Africa (Zhang, 2016). Thus, socio-economic priorities combined 

with an insufficient capacity of urban governance (Zhang, 2016; Shackleton et al., 

2021) could prevent finding the initially expected effect of human population density. 

Considering all these results and factors, particularly the uncoupled distribution 

between urban ecology knowledge and future urban prospects, we would recommend 

local authorities, funding bodies and researchers to make an effort in the study of the 

areas that soon will be transformed into urban landscapes. This is particularly important 

in the tropical African belt given that it will concentrate the greatest urban expansion 

in the future (Seto et al., 2012), but also holds the largest biodiversity of the continent 

(Cazzolla Gatti et al., 2015). 

 Interestingly, our results indicate that the number of published urban ecological 

studies depended on economic factors (i.e., GDP). This association has been found in 

other cross-sectional (e.g., Doi & Takahara, 2016; Fisher et al., 2011) and longitudinal 

studies (Vinkler, 2008). This economic indicator is in addition significantly associated 

with a higher rate of influential publications within their subject area (Bornmann et al., 

2014). However, other investigations showed that R&D investment rather than per 

capita GDP is positively associated with research productivity in different continents 

(Meo et al., 2013, 2014). It is possible that GDP is a better predictor of R&D in Africa 

than in other regions, thus potentially explaining the obtained finding. This influence 

of economic factors on urban ecology research effort is crucial given the link between 

cities and economic wealth (Zhang, 2016), which could lead us to think that as 

urbanization progresses in Africa, the better their economies will be and consequently 

more research on urban ecology could be made. This scenario seems unlikely as this 

association between economic and urban growth is decoupled in the African continent 

(Cohen, 2004), which does not warranty this increasing research effort in the future. 



Review of African urban ecology 

36 

Other factors not considered in our analyses could also explain the country-wide 

variation in urban ecology research. For example, political instability could play an 

important role for the lack of studies on the topic in certain countries such as Western 

Sahara, South Sudan or Libya. The fact that the majority of published studies were 

conducted locally within a single city or country (e.g., Koricho et al., 2020; Lindley et 

al., 2018; Muleya & Campbell, 2020) suggests the need for investigation of 

local/national cases for the application of specific solutions. However, it also highlights 

the lack of transnational collaboration among African countries. This low level of 

international research both within Africa and with countries from other continents is 

particularly important considering that: (1) it impedes the generalization of findings at 

the continental and global scale, and (2) reduces the number of substantive 

contributions to scientific progress (Bornmann et al., 2014). Therefore, we recommend 

funders and researchers alike to strengthen or promote the creation of new international 

networks or institutes on African urban ecology as well as encourage urban ecologists 

of the continent to participate in other global actions, networks (e.g., the Urban 

Biodiversity Research Coordination Network) or societies (e.g., Society for Urban 

Ecology) that are already running. 

 The geographic variation in research effort could also be linked to conservation 

aspects. Conservation research in Africa is particularly relevant and prolific in the 

global context (Doi & Takahara, 2016). There are still some controversies on whether 

conservation status is significantly and positively associated with research effort at the 

species level (e.g., Brooke et al., 2014; Ducatez & Lefebvre, 2014; Ibáñez-Álamo et 

al., 2017), but countries with a higher level of environmental protection activity 

investigate more in ecology (Doi & Takahara, 2016). Our results match this finding 

given that urban ecology research effort is significantly associated with the 

conservation status of African ecoregions. The ecologically relevant regions belonging 

to the most threatened categories (Critical, Endangered and Vulnerable) showed the 

highest number of publications on the topic. This is logical considering the previously 

described restricted R&D investment in Africa that would divert the current available 

resources towards areas of conservation concern. Despite this, we found that about half 

(50 %) of African ecoregions without a single published study on the topic are classified 

as threatened, and urbanization is considered a leading threat in the area (Burgess et al., 

2004), suggesting the need for additional studies to determine the ecological effects of 

urbanization and propose suitable conservation actions. On the other side, the 

significant effect of ecoregion size fitted our initial expectations as larger ecoregions 

would support higher biodiversity levels (Rantalainen et al., 2005) and consequently a 

higher likelihood of being investigated. As larger and more threatened ecoregions were 

significantly more studied in the continent, there is a need to expend greater research 

effort on smaller and relatively stable ecoregions (e.g., East African Montane 



Chapter 1 

37 

Moorlands and Lake Chad Flooded Savanna), which are more likely to suffer unnoticed 

fragmentation from urbanization and other anthropogenic land use changes as also 

indicated by previous studies (e.g., Beyer, Venter, Grantham, & Watson, 2020; 

Burgess, Hales, Ricketts, & Dinerstein, 2006; McDonald et al., 2008). Particularly 

surprising is the lack of studies from the majority (77 %) of ecoregions from the 

Tropical and Subtropical Dry Broadleaf Forests biome. These ecoregions mainly 

correspond with large areas of Madagascar, a megadiverse country 

(<https://www.biodiversitya-z.org/content/megadiverse-countries> accessed 30 

October 2022) with the lowest percentage of urban land cover in the whole continent 

(0.04 %; OECD/SWAC, 2020). In contrast, other forested biomes are quite well 

represented, which makes sense considering that forests, especially those from Western 

Africa, support higher biodiversity and endangered species, thus promoting a more 

intense ecological research effort (Doi & Takahara, 2016). 

Gaps in knowledge according to taxonomy and scientific fields 

Our review also offers interesting information on the current methodological and 

conceptual orientation of urban ecological research in Africa. From a methodological 

point of view, we found an important taxonomic bias in the study of urban ecology in 

Africa similar to those previously reported (e.g., Callaghan et al., 2020; Shwartz et al., 

2014). This taxonomic bias has a strong effect in our urban ecology knowledge given 

that the impact of urbanization varies considerably depending on the type of organisms 

considered (McKinney 2008; Paul & Meyer, 2001). Our literature search offered 

studies focused on organisms belonging to seven kingdoms, although the majority of 

urban ecology research used either animals or plants as model systems. This result 

highlights our limited understanding of other organisms in the African urban context, 

including Archaea, Bacteria, Chromista, Fungi and Protozoa, which should be 

prioritized for future studies. This is justified by current literature highlighting their 

relevance in natural environments (e.g., Epp Schmidt et al., 2019; Kartzinel et al., 2019; 

Thompson et al., 2017). The uneven distribution of urban ecology research effort went 

down to lower taxonomic levels (e.g., classes). Among animals, birds and mammals 

were the two most studied groups. The publication bias towards these two classes in 

urban ecology is not restricted to Africa alone (Donaldson et al., 2017; Shwartz et al., 

2014), and has also been identified in other study fields such as conservation biology  

(Lawler et al., 2006) and invasion ecology (Pyšek et al., 2008). Several reasons have 

been proposed to explain this bias for birds and mammals, such as body size (Brodie 

2009) or conservation status of focal species (Donaldson et al., 2017). Regarding plants, 

flowering plants (Magnoliopsida and Liliopsida) dominate urban ecology research 

effort in Africa, replicating the patterns found by other research effort studies on plants 

(Richardson & Rejmanek, 2011; Stranga & Katsanevakis, 



Review of African urban ecology 

38 

2021). In contrast with plants, with the richly diverse Magnoliopsida (Tracheophyta) 

relatively well studied (Cilliers & Bredenkampl, 1999; Moussa et al., 2020; van der 

Walt et al., 2015), the most diverse animal group of Arthropoda is clearly 

und