As urbanization reshapes global landscapes, ecological balance is increasingly at risk, especially in Africa. The primary drivers are rapid development and expanding human settlements, often without proper environmental considerations, posing a serious threat to birds and biodiversity and weakening ecological resilience. These changes create opportunities for invasive species to thrive, further threatening native bird populations and the essential roles they play in ecosystems. Without strategic environmental planning, urban expansion will continue to erode biodiversity, altering species interactions, ecosystem functions, and threatening species survival.

I recently led a study published in Frontiers in Conservation Science revealing how urban growth in Kenya and Nigeria degrades bird communities, undermining both species diversity and their ecological roles. With more than half of the global population already in urban areas — a figure projected to reach about 70% by 2050 — the pressures on biodiversity are mounting. In Africa, urban land cover is expected to triple by 2030, and the potential impact on birds and biodiversity is particularly alarming.

Birds are key indicators of environmental health, making them crucial for assessing human impacts on ecosystems. Although urbanization contributes to habitat loss, fragmentation, and the spread of invasive species, its effects on birds’ ecological roles in Africa remain understudied, despite the region’s rich but vulnerable ecosystems.

“Urbanization is fundamentally reshaping African landscapes, and its impacts on avian biodiversity are often overlooked,” said one of my co-authors, Peggy Ngila. “Our research sheds light on how this process is changing the composition of bird communities and their vital ecosystem services, such as seed dispersal, pollination, and pest control.”

The study utilized citizen science data from Kenyan and Nigerian bird-mapping projects. These national projects are part of the African Bird Atlas Project aimed at monitoring birds across the continent with the help of citizen scientists (members of the public passionate about birds and nature). Analyzing the presence and ecological roles of bird species in various urbanization categories — from cities to rural and mostly uninhabited areas — provides insights on how urbanization affects birds, their diversity and ecological functions.

As urbanization has intensified, the variety of bird species and their roles in the ecosystem shrinks, resulting in more uniform communities with generalist species. On the other hand, rural and less-developed areas, like sparsely populated and mostly uninhabited areas, continue to support a greater diversity of bird species and functions. This indicates that urbanization is driving out specialized species (those with specific habitat or dietary requirements), though these species are essential for maintaining a healthy and balanced environment.

Functional richness and diversity are critical for understanding how ecosystems operate and ensuring species survival. “When urbanization erodes functional richness, it not only disrupts essential ecosystem services like pest control, seed dispersal, and nutrient cycling but also weakens species’ ability to adapt and persist in changing environments,” said one of my other co-authors, Iniunam Iniunam. “As specialized species disappear, ecosystems become dominated by generalists, reducing ecological resilience and increasing the risk of biodiversity collapse. This loss threatens not just individual species but the overall stability of ecosystems that support both wildlife and human communities.”

Ogunpa Forest Reserve in Oyo state, Nigeria, exemplifies how urban expansion threatens critical bird habitats. Once a thriving green space within the city of Ibadan, the forest has been drastically reduced due to infrastructure projects, like the construction of the Baywood luxury estate. Hectares of old-growth trees were cleared without a comprehensive environmental impact assessment (EIA), raising concerns of environmental injustice among conservationists. The Ogunpa case highlights a growing crisis across Africa, where rapid urbanization encroaches upon ecologically significant landscapes, diminishing biodiversity and disrupting essential ecosystem services.

Urbanization and the spread of invasive species

The Indian house crow (Corvus splendens), a species introduced to Kenya from the Indian subcontinent in 1891, has become another pressing threat. With the crow population now approaching 1 million, these invasive birds prey on native bird species, including their nests, eggs and young. Efforts such as using starlicides (a chemical used to poison birds like crows) to control its population have been implemented to protect native birds from this invasion.

The proliferation of these invasive crows shows how urbanization is not only reshaping habitats but also enabling the spread of nonnative species that further strain local ecosystems. “The species is clearly benefiting amidst urban sprawl, with the main highway connecting Mombasa and Nairobi serving as a key corridor for its spread,” says Anthony Kuria, Kenya’s head of the African office of the Tropical Biology Association and another co-author of the paper. “The species has firmly established itself in Mombasa and other coastal towns. Further fueled by warming climates and an abundance of food in growing towns along the highway, the risk of unchecked population growth upcountry poses serious challenges. It threatens native bird species in rural areas and disrupts agriculture and animal husbandry, causing significant losses. Additionally, its presence brings noise pollution and aggressive scavenging, which could affect tourism by disturbing guests in restaurants,” he told me.

Balancing urban and sustainable development

“The loss of biodiversity in urbanizing regions is not just an environmental issue — it’s also a public health issue,” Pantong Mark, a citizen scientist and medical doctor at Jos University Teaching Hospital, Nigeria, told me. “By decreasing the diversity of birds, we are undermining the very systems that help regulate diseases, control pests, and promote overall ecosystem health.”

There is an urgent need for action to integrate biodiversity conservation into urban planning. Protecting wildlife habitats and promoting green spaces in urban areas are essential for preserving species, habitats and ecosystem that sustain human life.

As cities continue to expand, the challenge lies in balancing development with conservation — a pressing necessity for safeguarding Africa’s biodiversity and ensuring a sustainable future for the planet.

Bello Adamu Danmallam is a researcher at the A.P. Leventis Ornithological Research Institute Center of Excellence in Nigeria, and coordinates the IUCN Species Survival Commission Center for Species Survival Nigeria.

Banner image: Red-throated bee-eaters (Merops bulocki) are in decline in some areas due to urbanization. Image by Yves Bas via iNaturalist (CC BY 4.0).

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Citations:

Danmallam, B. A., Ngila, P. M., Iniunam, I. A., Kuria, A., Tende, T., Ngugi, S., … Trevelyan, R. (2024). Ecological consequences of urbanization in Afrotropical bird communities: Present and future prospects. Frontiers in Conservation Science, 5. doi:10.3389/fcosc.2024.1503408

Seto, K. C., Güneralp, B., & Hutyra, L. R. (2012). Global forecasts of urban expansion to 2030 and direct impacts on biodiversity and carbon pools. Proceedings of the National Academy of Sciences, 109(40), 16083-16088. doi:10.1073/pnas.1211658109