Nov 1, 2017

Smaller forests are hurting some species and helping others

A forest fragment. Photo: Carlos Peres

Human encroachment into forests that is parceling dense forestry into smaller and smaller areas called forest edges, is affecting 85% of forest vertebrates — sometimes positively (46%) and sometimes negatively (39%), an international team of researchers said in a study published in Nature Wednesday.

Why it matters: Study author Marion Pfeifer tells Axios it's "fair to say that we did not expect to find a relatively high proportion of species actually 'winning' when forest fragmentation occurs. However, we do emphasize that the species that lose out under forest fragmentation, i.e. the species we call forest core species...are more likely to be species that are already of conservation concern."

Study details: Funded by the EU's European Research Council, the team examined 1,673 species of arboreal vertebrates on five continents over a five-year period. They created and used two new measurements to quantify the abundance of each of the 1,673 species around the world and any chances determined by how close they were to the edge of forests.

The findings:

  • 85% of the species analyzed were impacted by forest fragmentation and in particular edge effects.
  • 39% of those need the dense forest core to survive and are being squeezed into smaller areas. "This leads to some of them becoming endangered, such as the Sunda pangolin," Pfeifer said.
  • 46% of those like conditions at the edges and are thriving, she said, while adding "these species are not necessarily ones that benefit the local ecosystem." Predators sometimes thrive on the edge since the conditions makes it easier to locate their prey.

Powerful approach: Deanna Olson, research ecologist for the U.S. Forest Service who was not part of this study, tells Axios: "The importance of this lens on habitat degradation cannot be overemphasized."

"[This] is a powerful approach to examine patterns of biodiversity responses to forest edge effects. This mirrors approaches being used for examining effects of climate change projections or disease on species, but is novel for application to habitat fragmentation," Olson said.

Limitations and applications: However, Olson pointed out not all forests are simply an edge and a core. For example, she said in the Pacific Northwest forests of North America, changes in topography plus natural disturbances like landslides or fires make the forests more complex and potentially more sensitive to human-derived fragmentation. She says these areas should be studied further.

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