The devastating impact of humans on biodiversity

Studies from around the world, including from the Ume River, have been compared to map human impacts on plant and animal life.

ImageMattias Pettersson

Biological diversity is under threat. More and more plant and animal species are disappearing worldwide. Humans are responsible for this. Until now, however, there has been no synthesis of the severity of human interventions in nature and whether the effects can be found everywhere in the world and in all groups of organisms.

In order to close these research gaps, a team lead from the aquatic research institute Eawag and the University of Zurich has now conducted one of the largest syntheses studies ever of the effects of humans on biodiversity. One of the co-authors of the study, which has just been published in the journal “Nature”, is Eric Capo, Assistant Professor in the Department of Ecology and Environmental Science at Umeå University.

Covers all groups of organisms

The researchers collaborated to compile data from around 2,100 studies that compared biodiversity at almost 50,000 sites affected by humans with almost 50,000 reference sites that were unaffected. Several of the studies were conducted in Sweden.

The studies cover terrestrial, freshwater and marine habitats around the world, and all groups of organisms, from microbes and fungi to plants and invertebrates, fish, birds and mammals. Among the included studies are, for example, comparisons of habitat changes in the Ume River and the effect of pollution on aquatic life in Swedish lakes.

“This kind of meta-analysis project may soon be replaced by AI tools, but digging into papers – published across different decades and by different research groups – still requires scientific expertise and a human eye. For example, to identify which images show samples taken before and after a perturbation, or which represent control versus experimental groups,” says Eric Capo.

Striking results

The findings of the study are unequivocal and leave no doubt as to the devastating impact humans are having on biodiversity worldwide.

“We have analysed the effect of the five main human impacts on biodiversity: habitat changes, direct exploitation such as hunting or fishing, climate change, pollution and invasive species. Our findings show that all five factors have a strong impact on biodiversity worldwide, in all groups of organisms and all ecosystems,” says François Keck, the lead author of the study.

According to the study, environmental pollution, such as from the spraying of pesticides, and habitat changes have a particularly negative impact on the number of species and the composition of species communities.

ImagePixabay

On average, the number of species at impacted sites was almost twenty percent lower than at unaffected sites. Particularly severe species losses across all biogeographic regions are found in vertebrates such as reptiles, amphibians and mammals. Their populations are usually much smaller than those of the invertebrates; this increases the probability of extinction.

“This study illustrates why the biological monitoring of ecosystems is important, both in non-impacted and human polluted areas. Without data from before human impact, it is more difficult to fully understand how – and to what extent – ecosystems and their services are altered by human societies,” says Eric Capo.

Text:Sara-Lena Brännström (Umeå University) / Simon Koechlin (Eawag)