Ann Arbor Times

Large, undisturbed forests are more effective at preserving biodiversity than fragmented landscapes, according to a study by the University of Michigan. The research addresses a long-standing debate among ecologists about whether it is better to conserve large continuous areas or many smaller fragmented ones.

The study, led by U-M ecologist Thiago Gonçalves-Souza and published in Nature, concludes that "fragmentation is bad," as stated by Nate Sanders, a U-M professor of ecology and evolutionary biology. He emphasized that while conserving small fragments is important, conservation decisions must be made wisely due to limited resources.

Researchers from the University of Michigan, Michigan State University, and the German Centre for Integrative Biodiversity Research analyzed 4,006 species across 37 global sites. They found that fragmented landscapes had an average of 13.6% fewer species at the patch scale and 12.1% fewer at the landscape scale compared to continuous landscapes.

The study also highlights that generalist species tend to inhabit fragmented areas. It investigated alpha diversity (species number in a patch), beta diversity (species composition differences between areas), and gamma diversity (biodiversity over a whole landscape).

Gonçalves-Souza explained that some argue fragmentation isn't detrimental because isolated habitats have different species compositions, potentially increasing gamma diversity on a larger scale. However, he noted previous research often lacked comprehensive comparisons between fragmented and continuous landscapes.

Co-author Jonathan Chase from the German Centre for Integrative Biodiversity Research pointed out that past debates were unresolved due to inadequate data and statistical tools for evaluating biodiversity at various scales.

Gonçalves-Souza's team corrected sampling differences across landscapes in their analysis. They discovered fragmentation decreased species numbers across all taxonomic groups without compensating through increased beta diversity.

Nick Haddad from Michigan State University noted this study resolves a half-century-old debate on conserving biodiversity in natural areas—a discussion initiated by scientists like E.O. Wilson and Jared Diamond.

Gonçalves-Souza added that fragmentation affects not only biodiversity but also carbon storage capacity in landscapes: "Fragmented landscapes are not only going to affect biodiversity by decreasing alpha and gamma diversity, but it also has implications for carbon stock as well."

He hopes the study will shift focus from debating landscape types towards forest restoration: "Restoration is crucial for the future," he said. Sanders highlighted this global collaboration was supported by the University of Michigan's Department of Ecology and Evolutionary Biology.