For most, forests are something to be driven by or hiked through briefly. A new study shows just how much humankind has tailored these landscapes to our own devices at the expense of the rest of the natural world.
The findings, published this week in the journal Science Advances, offer some of the longest-term evidence available on how ecosystems and species react to habitat loss and fragmentation over time. The trend is distinctively negative.
“There is a consistent loss of species — birds, butterflies, plants — across every experiment, and these experiments varied widely,” Nick M. Haddad, North Carolina State University biologist and lead author of the study on habitat fragmentation, told ThinkProgress. “But they were all going downward.”
Hadded said he was “shocked” at the study’s findings on how much we’ve “sliced and diced” forest ecosystems through human development, which includes everything from building railroads to cutting down trees for cropland.
“I expected to see more forest that was more remote, and more wilderness,” he said.
Bringing together numerous studies chronicling global habitat divisions over the last 35 years, Haddad and his co-authors found that only two “big blobs” of forest remain on Earth — in the Brazilian Amazon and the Congo Basin. They also found that some 70 percent of all remaining global forest cover is within one kilometer, or 0.6 miles, of human development.
“When we summed it all up, if you stand in any forest in any part of the world, there’s a one in five chance that you are within 100 meters — the length of a football field — of the end of the forest,” said Haddad. “And there’s a three-quarters chance that you are within a kilometer away. That’s just a few city blocks; I can see farther than that from my office.”
The study also found that habitat fragmentation reduces biodiversity by 13 to 75 percent and impairs ecosystem functioning by messing up nutrient cycles, with effects being the most severe in the smallest and most isolated fragments.
Hadded said that even several decades after the fragmentation takes place, the impacts at an ecological level are still playing out, and we “don’t know ultimately know what the effects of habitat loss and fragmentation will be.”
In some ways, the study was conservative in its gauge of the impact of development. By focusing only on habitat fragmentation by roads, agriculture, and other infrastructure the authors ignored further negative changes taking place in forests, including climate change, nutrient deposition, and invasive species.
“In real landscapes, other changes are happening too,” said Haddad. “Climate change will definitely exacerbate the situation.”
For instance, in the northern Hemisphere warming temperatures are causing many species’ habitats to shift slowly northward. Haddad said that the “slicing and dicing” of ecosystems acts to pen these plants and animals in when they need to move in order to stay in their desired range of habitat.
Resource extraction through mining and fossil fuel development fragments some of the more remote regions, such as Canada’s Boreal forest. Hadded was surprised by the degree that Boreal forest in Canada and Siberia has already been sliced up. Once a forest is segmented, it loses something greater than just the missing square footage.
“All forest is not created equal,” said Haddad. “It matters how close you are to the edge of the forest — this effects the rest of the ecosystem.”
Haddad and the other 25 or so authors agree that something should be done about this situation, especially in light of the findings.
“These findings indicate an urgent need for conservation and restoration measures to improve landscape connectivity, which will reduce extinction rates and help maintain ecosystem services,” states the study.
Even as the global population grows, demanding more living space, agricultural yield, and resource extraction, the researchers warn the the long-term negative impacts of habitat fragmentation on biodiversity and ecosystem health have been “not fully appreciated.”
Dr. Lars Brudvig, an assistant professor of plant biology at Michigan State University and co-author on the study, told ThinkProgress that the biggest threat is to natural ecosystems is the conversion of the land for agriculture.
“Conversion of lands for agriculture can not only destroy parcels of natural ecosystems, but it fragments remaining natural areas, exposing them to the degrading influences of edges,” he said. “Clearly this is a complicated issue, since we need to feed humanity; however, it does suggest strong needs for careful planning of new agricultural and other development, as well as approaches to agriculture that might best balance food production with biological diversity conservation.”