Our Impact on Plants and Animals Worse than Feared

The impact of humans on plants and animals is much more extensive than previously thought. Vertebrates in particular are showing a significant loss of diversity, according to an international study.

This is the first time a comprehensive assessment has been made of the severity of human interference in nature and whether it affects all organisms.

– When species disappear, and if the variations within a species also decrease, many characteristics are lost, says Eric Capo at the Department of Ecology, Environment and Earth Sciences at Umeå University, who is one of the researchers behind the study.

Swedish environments

Together, the researchers compiled data from over 2 000 studies comparing biodiversity at nearly 50 000 sites affected by humans in different ways. These have been compared to almost 50 000 reference sites that have not been affected by humans, including in Sweden.

The studies cover terrestrial, freshwater and marine habitats around the world and involve all groups of organisms, from microbes and fungi to plants and invertebrates, fish, birds and mammals. The researchers analysed the impact of the main areas where humans have affected biodiversity, such as hunting and fishing, pollution, climate change and invasive species.

On average, the number of species at human-impacted sites was almost 20% lower than at similar unaffected sites.

– We saw a particularly large decrease in the number of species among vertebrates such as reptiles and amphibians, but also among mammals, says Eric Capo.

Becoming more fragile

The study, published in the scientific journal Nature, shows that it is not only the number of species that is decreasing, but also the variation within species and groups of plants and animals. In the long term, this means that there will be a homogenisation of all living things, making us more vulnerable to various stresses. If we only have one species growing in a field and it is wiped out by a pest, for example, it is devastating. Variation is needed to increase resilience,’ says Eric Capo.