Centuries-long analysis suggests biodiversity is differentiating and homogenizing to a comparable extent

According to a new study, the trends in communities and the species within them are roughly balanced published I Advances in science.

Led by researchers from the German Center for Integrative Biodiversity Research (iDiv) and Martin Luther University Halle Wittenberg (MLU), the researchers collected 527 datasets from ecosystems such as grasslands, scrublands and coral reefs dating back 500 years. Analyzed.

This analysis provides a first-of-its-kind comprehensive assessment of how local and regional biodiversity changes are integrated across landscapes over centuries.

“We wanted to test the idea that the biotic harmony is a clear feature of the biodiversity crisis,” says first author Dr. Shane Bellows of iDiv and MLU.

“By combining a classic measure of scale-dependent biodiversity change with an unprecedented collection of data, we found that communities are likely to become more diverse over time in response to ongoing human impacts on the environment. likely.”

A change doesn’t mean more than you think.

The analysis included integrated measures of change in the number of different species (Species richnessWithin a landscape or geographic region, changes occur at multiple sites within a single site. This allowed researchers to determine whether species composition was becoming more similar or different across sites.

They found no change in spatial variation of species composition, which was the most common result. This was despite many instances of convergence and divergence between communities over time. Indeed, net trends in biodiversity change across scales were so weak that they were often indistinguishable from zero.

The data also showed a trend of weak convergence across large regions over many hundreds of years due to the increasing number of species in communities. However, this trend was balanced by differences in small-scale communities. These findings were consistent across many forms of life, from fish to birds to plants and mammals.

Studies on biodiversity changes present a complex picture, and researchers are often of two minds about how species’ responses to human-driven changes should be characterized. However, the concept of convergence is a widespread expectation in the scientific community and the wider public.

“Our analysis exposes the complexity of this issue,” explains Professor Jonathan Chase, senior author of the study and professor at iDiv and MLU. “This doesn’t mean that the world isn’t changing drastically, it just means that we need to move beyond the belief that the primary way to change biodiversity is through coordination.”

Patterns for multi-scale conservation.

The researchers also presented scenarios in their study that characterized changes in species occupancy: convergence was mostly driven by an increase in average occupancy, while divergence was driven by a decrease in average occupancy.

The scenarios illustrate that even small changes in occupation—the fragmentation of the landscape by man-made roads or fences, the introduction of plants and animals into areas outside their historic ranges, and Climate changeThat can drive species to change their range—pointing a community toward convergence or divergence.

The bright red Louisiana crawfish (Procambarus clarkii), native to northern Mexico and the southeastern United States, is an example of an introduced species that is thriving in Germany’s freshwaters, creating a symbiosis.

“We’re seeing more and more that many threatened species require protection at multiple sites or landscape scales to be effective,” adds Blues.

“A simple framework can help move towards the multi-scale approach needed to understand biodiversity management and conservation. Biodiversity Change completely.”