Enlarge By Brian Snyder, Reuters A swimmer stands in Walden Pond in Concord, Mass., Oct. 12. Buttercups, dogwoods, lilies, orchids, roses and violets around the pond are at risk because of global warming, a study shows. QUICK QUESTION QUICK QUESTION From Walden Pond in Massachusetts to Yellowstone National Park in Wyoming, climate change has begun to dramatically affect the flora and fauna of these American treasures, according to two studies in Monday's Proceedings of the National Academy of Sciences. The studies show that the warming of the Earth's atmosphere over the past few decades has caused a loss of many of the flowers that Henry David Thoreau recorded in his book Walden and also has contributed to a decline in several species of native animals once common in Yellowstone. WEATHER GUYS: Global warming still a hot topic for voters Thoreau first recorded the plants and flowers of the Concord, Mass., area in 1854. Since then, Concord's average annual temperature has risen by 4.3 degrees, the studies show, and botanists have kept a record of the region's flora. ECO-SCORE:See where you can save energy, plus more environmental news Hardest hit are species that don't respond well to temperature increases, including buttercups, dogwoods, lilies, orchids, roses and violets, says Harvard University biologist Charles Davis, lead author of the article. Davis says that even though about 55% of all natural areas in Concord are undeveloped or remain well-protected, 27% of the species documented by Thoreau have been lost, and 36% exist in such low numbers that their local extinction may be imminent. The research points to climate change as the sole culprit and says the loss of species won't be random. "Certain lineages … are far more susceptible to decline under rapid climate change than others," Davis notes. In Yellowstone, researchers report that climate change and the resulting droughts and lack of snowpack have caused four species of amphibians — including three species of frogs and one of salamander — to go into severe decline. "Amphibians are a bellwether for environmental degradation, even in natural ecosystems such as Yellowstone … where species have been actively protected longer than anywhere else on Earth," writes lead author Sarah McMenamin of Stanford University. The findings are based on climate data going back 60 years and remote-sensing data from the past 20 years, she reports. Climate change is again fingered as the sole cause. "There is no other reason for the regional aquifer to be drying up, at exactly the same time we're seeing this change in climate," she says. McMenamin adds that "amphibian declines, population crashes and extinctions of entire amphibian species are becoming increasingly common." Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more