Animals that evolved in environments subject to large-scale habitat-altering events like fires and storms are better equipped to handle forest fragmentation caused by human development than species in low-disturbance environments, new research shows.

Lancaster University scientists are among an international team, led by Oregon State University, whose work provides an important road map as conservation managers consider the effects of forest edges on wildlife.

Findings of the study are published in Science.

“Everyone knows habitat loss is bad for animals, but there’s been a longstanding debate about fragmentation – the arrangement of remaining habitat,” said co-corresponding author Matt Betts, a professor at Oregon State University. “How do we design wildlife reserves? Do we make many small ones, or fewer big ones, or do we make corridors?”

The study led by Professor Betts and Dr Christopher Wolf, also of Oregon State University, suggests the closer a forest is to the equator, the more sensitive on average its wildlife species are to fragmentation. Tropical species have historically encountered much less disturbance than those in the temperate zones.

“Biodiversity of vertebrates increases massively toward the equator, but even accounting for that, a greater proportion of species are more sensitive to fragmentation,” Professor Betts said. “Sensitivity increases six-fold at low versus high latitudes. That means that not only should we care about the tropics because so many species are found there that are found nowhere else on Earth, but those species are also more sensitive to how we treat the forests.”

Professor Jos Barlow of Lancaster Environment Centre and co-author on the paper said: “These results demonstrate the importance of avoiding further deforestation and degradation in tropical biomes, such as the Amazon.”

The researchers caution that the greater forest edge sensitivity at the lower latitudes, which are closer to the equator, does not mean there isn’t also edge sensitivity in temperate zones.

Researchers still found that almost one-fifth of species in temperate zones are edge avoiders. In comparison to the tropics. They add that in the temperate zones, the focus should be on conserving habitat itself “perhaps with less regard” for the configuration patterns.

To test the “extinction filter hypothesis” – which predicts that forest species that have evolved in high-disturbance environments should be more likely to persist in the face of new disturbances –researchers used 73 datasets of species abundances from around the globe. These datasets were collected by hundreds of field biologists over roughly the past decade.

The datasets contained 4,489 species from four major taxa – arthropods (2,682); birds (1,260); reptiles and amphibians (282); and mammals (265) – and the researchers used modeling software to separate the effects of fragmentation from other factors.

Researchers found that in low-disturbance regions, 51.3% of forest species tend to avoid forest edges compared to 18.1% in high-disturbance zones.

“Our work addresses why other fragmentation studies worldwide can yield different results from one another,” Dr Wolf said.

Professor Betts added that fragmentation will likely matter more in temperate zones in the years to come as species gradually move toward the poles in response to climate change.

"The novelty of this research is quantifying the degree to which geographic patterns in species sensitivity are predictable at the global scale", said Betsy von Holle, program director at the NSF, which funded the research. "Elucidating the ecological underpinnings of these patterns have major implications for conservation."

Already, 70% of the Earth’s remaining forest is within one kilometer of a forest edge, and fragmentation of the world’s most intact forest landscapes – the ones in the tropics – is predicted to accelerate over the next 50 years, the researchers said.

“It’s one thing to blow a whistle and another to figure out a way to deal with a problem,” Professor Betts said. “If we want to conserve the biodiversity needed for ecosystem services, and for its own sake, we must be particularly careful to minimize the creation of edges in the tropics, since fragmentation has a greater negative impact there.”