Life on the Edge

Many species, such as vine snakes in the Amazon, favour the darker and more humid forest interiors. Photo: Professor Jos Barlow

Breaking up the rainforest into small, isolated patches is forcing more species to live at the forest edge and putting those that are dependent on the forest core at risk.

Research published today in the academic journal Nature highlights how biodiversity is changing as a result of deforestation - forcing some species to the brink of extinction while others flourish in the changing environment.

Collecting data for over 1,500 forest vertebrates, the research team led by Newcastle University, UK, and Imperial College London, and involving a Lancaster University conservation scientist, found that 85 per cent of species are now being affected by forest fragmentation.

The winners are those that seek out the forest edge while the losers are those that rely on the forest core and whose habitat is being constantly squeezed.

Developing a system to predict which species are likely to disappear first from our changing forest habitats, the team is now hoping to use this information to inform forest conservation and restoration efforts.

Professor Jos Barlow , a co-author of the paper and conservation scientist at Lancaster Environment Centre , said: “Although many previous studies have identified edge effects, this study demonstrates that almost all vertebrate species are affected in some way. In doing so, it provides clear evidence that we need to avoid large-scale development projects in the world’s most important ecosystems.”

Dr Marion Pfeifer, lead author now based at Newcastle University, said: “Tropical forests and the animals they harbour are being lost at alarming rates but in order to protect them we need to know exactly how fragmentation of the land is impacting on the animals that live there.

“This is critical for the hundreds of species that we identified as being clearly dependent on intact forest core areas - that is forest which is at least 200-400m from the edge. These include species such as the Sunda pangolin (Manis javanica), the Bahia Tapaculo (Eleoscytalopus psychopompus), the Long-billed Black Cockatoo (Zanda baudinii) and Baird’s tapir (Tapirus bairdii).

“These species were highly sensitive to the changing habitat and therefore more likely to disappear in landscapes that encompass only a small proportion of intact forest.”

Half the world’s forest habitat is now within 500m of a ‘forest edge’ due to the expansion of road networks, logging, agriculture and other human activity. These edges look different to the rest of the forest: with more light, less moisture and generally higher temperatures.

Using species’ abundance data collected from fragmented landscapes worldwide, the team analysed 1,673 species of mammals, birds, reptiles and amphibians to see how they respond to edges.

Using new spatial and statistical analyses developed at Imperial College London, they were able to show that 85 per cent of species’ abundances are affected, either positively or negatively, by forest edges.

More importantly, edge effects create species communities near edges that bear little resemblance to the communities of forest interiors, and this species turnover likely reflects dramatic changes to the ecological functioning of modified forest habitats.

Robert Ewers, Professor of Ecology at Imperial College London, said: “About half of species win from the forest change; they like the edges and so avoid the deep forest, preferring instead to live near forest edges.

“The other half lose; they don’t like the edges and instead hide away in the deep forest. The winners and losers aren’t equal though. Some of the species that like edges are invasive like the boa constrictor, while the ones huddled into the deep forest are more likely to be threatened with extinction - like the Sunda pangolin.”

The research has been published in the paper “Creation of forest edges has a global impact on forest vertebrates” by Nature.

Although many previous studies have identified edge effects, this study demonstrates that almost all vertebrate species are affected in some way.

Professor Jos Barlow


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