20-year study: Scientists connected fragments of pine savanna and new species keep showing up
Before Europeans arrived in America, longleaf pine savannas sprawled across 90 million acres from present-day Florida to Texas and Virginia. Today, thanks to humans, less than 3% of that acreage remains and what’s left exists in fragmented patches largely isolated from one another.
Yet, hundreds of plant and animal species rely on these savannas, from understory grasses and the gopher tortoise, to the endangered red-cockaded woodpecker.
Habitat fragmentation is a major threat to biodiversity — not just in longleaf pine savannas, but in habitats across the planet. A new study published in Science demonstrates a hopeful new strategy in efforts to conserve plant and animal species confronting fragmented and shrinking habitats globally.
By connecting small, restored patches of savanna to one another via habitat corridors at an experimental landscape within the Savannah River Site in South Carolina, the nearly 20-year- long study has shown an annual increase in the number of plant species within fragments over time, and a drop in the number of species disappearing from them entirely.
“We need conservation solutions that can protect existing species and restore lost habitat,” said Nick Haddad, MSU integrative biologist. “When I created these experimental corridors as a graduate student 25 years ago, I never imagined that the effects of corridors on biodiversity would be so strong. It was inconceivable that the full effects would take two decades or more to be fully realized. I was and am astonished."
Over the 18-year study period, that equated to an average of 24 additional species in each connected fragment relative to the study’s control fragments, which were not connected by corridors. Each fragment is about the size of two football fields, and the corridors that connect them span roughly 500-by-80 feet each.
The long-term conservation and restoration study, which is still ongoing, is rare in the ecological world, in part because the study controls for the area and the connectedness of fragmented habitats. Most studies have examined habitat size alone.
The study is also unique in its longevity, which has been possible thanks to funding from the National Science Foundation, or NSF, Long Term Research in Environmental Biology program. Most ecological studies span just one-to-five years, or the lifecycle of a typical research grant, but the findings show that meaningful results take time to accumulate.
"The power of this long-term study is that small differences in species accumulation rates have a big impact over the long term", said Betsy von Holle, NSF program director. “This has major implications for restoration and conservation science."
The study has also relied on collaboration with the U.S. Forest Service–Savannah River, under the authority of the Department of Energy–Savannah River Operations Office, where fragments and corridors are being restored to longleaf pine savanna. Longleaf pine habitat has contracted since colonial times, as trees were exploited for timber, tar and turpentine, and lost to urbanization.
There are now also efforts underway in Virginia, the northern edge of the species’ historic range, to restore longleaf pine savannas, led by The Nature Conservancy, and the Virginia Department of Conservation and Recreation Division of Natural Heritage. The UW–Madison-led study provides results that come at a key moment for conservation decisions.
Habitat restoration is now a key priority across the globe. Earlier this year, the United Nations declared 2021 through 2030 the UN Decade of Ecosystem Restoration, with the hope of eliminating excess, heat-trapping greenhouse gases; improving food security and freshwater supplies; and protecting critical human and animal habitats.
Study coauthors include researchers from the University of Wisconsin, the University of Florida, the University of Colorado Boulder, the National Science Foundation, Future Earth and George Mason University.