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Fragmentation from agriculture and sprawl is ‘dooming species to extinction’
Laura Ingalls Wilder’s beloved series of novels about life in the American frontier begins in Wisconsin with the novel Little House in the Big Woods. Less than a hundred years since its publication, a study in Conservation Biology finds that these Midwestern ‘big woods’ are experiencing a worse-than-expected decline and would likely be unrecognizable to Wilder herself.
The new study of forest patches in Wisconsin finds that the temperate forests are losing abundance and diversity of native species due to increasing land-use changes and fragmentation. Bordering Canada, Wisconsin is apart of the Midwest region of the United States where temperate forests were first felled for agriculture beginning in the 1800s. Since then remaining forests have been lost due to housing developments, sprawling suburbs, roads, and strip malls.
Researchers from the University of Wisconsin, Madison looked to the forest floor—surveying shrubs, grasses, and herbs—to determine the impact of humans on the ecosystem. Checking their findings against detailed records made by ecologist John Curtis in the 1940s and 1950s, what the researchers discovered was worse than they expected: even when the patches of forests appeared healthy, they were no longer capable of preserving the region’s biodiversity. They found a widespread decline in abundance and diversity of native plants, especially in southern Wisconsin where forests have been increasingly lost due to land-use changes.
“Things may look healthy, but over time we see an erosion of biodiversity,” co-author Don Waller says, a professor of botany
Furthermore, the researchers found that biodiversity was even in decline in state parks and other protected areas.
“These forest patches are not just losing species — their whole biological nature is changing,” says David Rogers, an assistant professor of biological sciences who led the study. “Surrounding landscape factors, like urbanization and agricultural dominance, are now determining which species can survive in these little patches.”
Waller explains that the forests still appear healthy because there has been a time-lapse between the loss of forests and the visible affect on the ecosystem. “When we isolated these forest patches 50 or 100 years ago, we were dooming species to extinction,” he explains. “It may not happen right away — and in that sense it’s an ‘extinction debt’ — but it will accumulate over time.”
The isolation of these forest patches into small islands has made it difficult, if not impossible, for native plants to re-colonize areas where their populations have been lost, according to the researchers. With increasing distance between local plant communities, one community is no longer able to mix with another.
“Plant species might go locally extinct for lots of different reasons,” Waller explains. “But typically the area will be re-colonized very soon by nearby populations of the same species. That’s what does not happen once a habitat becomes isolated or that patch becomes smaller.”
While the researchers have a general idea as to why the forests are hemorrhaging native diversity and abundance, they are working next to determine the specific factors behind the decline.
“People are a really important part of the system,” Rogers says. “We are having a greater influence over our local ecology, whether we want to or not. That puts the responsibility on people to take care of it, protect it and maintain it.”
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