Bird article

Four in five bird species can’t tolerate human pressure

Most of the terrestrial world has been modified by human actions, either through urbanisation or air pollution and climate change, which can impact animal and plant populations and ecological communities.

Habitat loss and fragmentation are a common result of intense land use in the forms of built infrastructure (e.g. urban areas and roads) and agriculture (e.g. areas utilised for crops). All of which influence population dynamics, dispersal and ecological interactions, and the distribution and abundance of wildlife across space and time.

Some species thrive in human-dominated environments, while others are highly sensitive to all human pressures. Indeed, new research from the University of Helsinki in Finland and Aarhus University in Denmark has shown that the majority of the world’s bird species are unable to thrive in human-dominated environments.

The team quantified human pressure tolerances of over 6000 bird species on six continents between 2013 and 2021 and the Human Footprint Index, which holds data on built environments, human population density, light pollution, agriculture and road infrastructure provided the tolerance values and uncertainty estimates.

After quantifying tolerance to breeding in human-dominated environments, the study found that 78% of the world’s bird species struggle in those habitats with significant human pressure. These species are also more likely to have declining populations.

According to the paper, published in Global Ecology and Biogeography, a higher proportion of species in Europe and North America are tolerant of human activities than in Latin America, Asia and Africa. This may partly be explained by Europe having been altered by humans for millennia, meaning some species will have already vanished while others had a long time to adapt to slower pre-industrial changes to habitats.

Some species fare better than others and can survive even in urban environments. For example, Common Swifts are an example of such species that can be found breeding in urban areas around the world. Whereas the Great Snipe is especially sensitive to human presence and requires a pristine habitat to breed successfully.

The UN finalised the Kunming-Montreal Global Biodiversity Framework in December 2022, an agreement aiming to protect 30% of the Earth’s land for conservation. This study therefore enables us to identify species that are particularly sensitive to human activity and need more protected habitats to thrive in the future.

Although the quantification of species’ tolerance to human pressures is unprecedented at both spatial and taxonomic levels, further attempts to understand the underlying mechanisms are needed. Most importantly, future studies and conservation planning could investigate species’ tolerances to specific human pressure to gain a more detailed understanding of which human pressures each species can tolerate. The associated precision values can subsequently be applied to scientific research and conservation.

Reference: Marjakangas, E-L, Johnston, A, Santangeli, A, and Lehikoinen, A. 2024. Bird species’ tolerance to human pressures and associations with population change. Global Ecology and Biogeography, DOI: 10.1111/geb.13816.


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