Two different studies separated by more than 1,700 miles hammer home the same point: evidence of global warming is everywhere. In Yellowstone National Park, researchers found that amphibian populations have declined dramatically over the past 15 years as some of their pond habitats have dried up and disappeared. Meanwhile, in Massachusetts' Walden Pond, botanists discovered that more than a quarter of the plant species observed by Henry David Thoreau have disappeared since the author went to the woods to "live deliberately" in the 1850s. The twostudies, which both appear in the Proceedings of the National Academy of Sciences [subscription required], show that changes to the planet's flora and fauna are already well underway. The Yellowstone study compared data from an amphibian survey done in 1992 and 1993 to data from a new survey conducted over the last three summers; researchers looked at the park's
"kettle" ponds, which are re-filled in spring by groundwater and snow melt running down from the hills [BBC News].
The researchers found that the number of permanently dry ponds had quadrupled, and even in the ponds that remained, amphibian populations had plummeted. Because the study was conducted in Yellowstone, which has been protected as a national park since 1872, researchers say they can clearly pin the blame for the amphibians' decline on global warming.
"It's not that there's an exotic species invasion. It's not that there are human impacts like plowing or irrigation. It's not like direct habitat degradation due to humans has any role to play here," [study coauthor Elizabeth] Hadley said. "There's nothing upstream in this place except mountains and water" [Discovery News].
Across the country in the protected woods around Walden Pond, researchers compared Thoreau's careful field notes about the area's trees and wildflowers with present-day observations of the ecosystem, with troubling results.
They determined that 27 percent of the species documented by Thoreau have vanished from Concord and 36 percent are present in such small numbers that they probably will not survive for long.... “It’s targeting certain branches in the tree of life,” [lead researcher Charles] Davis said. “They happen to be our most charismatic species — orchids, mints, gentians, lilies, iris” [The New York Times].
Since Thoreau's Walden days the average temperature in Concord has risen by four degrees Fahrenheit, and researchers say some flowering plants that thrive only in narrow ecological niches can't adapt to the rapid changes.
According to Davis, one explanation for why the plants ... have been in decline is that their pollinators - insects and birds - have adapted to arrive earlier in the season. The birds and insects arrive when some of the plants have not yet flowered, so the pollinators can't spread their seeds. "Climate change is throwing off the synchronicity of nature," he said [Boston Globe].