Fragmented Forests Lead to Declining Biodiversity
The fragmentation of forests reduces biodiversity at multiple scales, according to new study from a global collaboration of ecologists and support from the University of Michigan.
First published on 25th February 2025, ‘LandFrag: A Dataset to Investigate the Effects of Forest Loss and Fragmentation on Biodiversity’, provides critical insights to the conservation debate over whether habitat fragmentation leads to biodiversity loss, through an analysis of more than 4,000 species at 37 sites across the world.
Habitat fragmentation is the process by which sections of an ecosystem become disconnected, leaving behind smaller, isolated areas. This can arise from natural causes, such as wildfires, but in recent centuries its incidence has increased through human activity and dramatic increases in deforestation.
For decades, ecologists have disagreed as to whether habitat fragmentation, beyond the initial loss of forest, benefits or harms biodiversity. Fragmentation accompanies and intertwines with habitat loss and changes to its structure, making it difficult to define, measure, and compare previous academic studies. Biodiversity can also be measured through a variety of ways and scales, adding to the complexity. This has led to mixed views among ecologists and conservationists as to whether to concentrate resources on preserving smaller isolated patches of forests, or larger continuous sections.
Robert J. Fletcher Jr, Miriam Rothchild Professor of Conservation Biology at University of Cambridge, writes that Gonçalves-Souza et al. have made “key progress in relation to these challenges”. These include utilising modern methods that enable standardised reporting of biodiversity and account for variations in sampling efforts. This has enabled them to deduce and quantify that fragmentation has negative effects on biodiversity at multiple scales.
Fletcher Jr comments that the implications of the study are clear: “Local biodiversity declines in remaining forest fragments and conservation and management strategies that focus on local scales need to invest in restoration strategies that can reduce species loss.”
“Fragmentation is bad,” said study author Nate Sanders, Chair and Professor of Ecology and Evolutionary Biology at University of Michigan: “This paper clearly shows that fragmentation has negative effects on biodiversity across scales. That doesn’t mean we shouldn’t try to conserve small fragments when we can with our limited conservation dollars, but we need to be wise about conservation decisions.” This is more important than ever, given recent cuts to development and aid budgets and their effects on conservation efforts.
Thiago Gonçalves-Souza, joint first author of the study and Assistant Research Scientist at the University of Michigan, hopes that the findings help move conservation on from the debate about continuous vs. fragmented landscapes. He commented, “Restoration is crucial for the future, more so than debating whether it’s better to have one large forest or many smaller fragments.”
The study is somewhat timely, given the urgent need to close the biodiversity finance gap and achieve the target of mobilising at least 200 million dollars a year by 2030, as agreed upon at the resumed CBD COP16 in Rome.
Read the full study here