That's disturbing news, because many plants and animals are already declining in eastern Massachusetts for other reasons. Though Concord has more parkland and natural spaces than many communities, thanks to strong local support for land conservation, human habits have changed over the past century and a half, and habitats have changed with them. River meadows, once mown for hay, have declined, along with local agriculture, and many have gradually turned to swamp forest. As hunting dwindled, white-tailed deer began devouring woodland plants. Invasive plants such as Oriental bittersweet and black swallowwort have infiltrated Concord, even covering the banks of Walden Pond. "The woods are being repopulated by things Thoreau never even knew about," says Peter Alden, a Concord native and veteran naturalist.
Of the nearly 600 plant species for which Thoreau recorded flowering times during the 1850s, Primack and Miller-Rushing found only about 400, even with the help of expert local botanists. Among the missing is the arethusa orchid, which Thoreau described with admiration in 1854: "It is all color, a little hook of purple flame projecting from the meadow into the air....A superb flower."
Walking the well-traveled path that circles Walden Pond, searching for the earliest flowers of the highbush blueberry, Primack says his results make him uneasy. "I don't think scientists should just be studying things until they go extinct," he says. "I think they should be doing something to make sure they don't go extinct." He supports "assisted migration," deliberately moving rare plants and animals to new, more promising habitats. The idea is controversial among biologists, many of whom fear that the transplants could interfere with native inhabitants. But Primack argues that the risks are low and the need is pressing. "In the past, some of these species might have been able to move on their own, but now there are barriers—highways, cities, fences," he says. "We have an obligation to move them."
Primack and Miller-Rushing argue good-naturedly about whether certain plants and animals can adapt to climate change, but they, and other ecologists, know such issues are far from resolved. "Now that we know what's changing, what are we going to do about it, and what are species going to do on their own about it?" asks Miller-Rushing. "Those are unanswered questions."
For now, Primack and Miller-Rushing are helping other scientists build a national network of observers—ranging from schoolchildren to amateur naturalists to professional ecologists—to collect data on flowering times, bird migrations and other signs of the seasons. The goals are not only to understand how plants and animals are responding to climate change but also to fine-tune future environmental restoration efforts and even allergy forecasts. It's a project that will require Thoreauvian stubbornness.
"These things are almost always heroic efforts by individuals," says Julio Betancourt, a hydrologist with the U.S. Geological Survey and a co-founder of the national observation network. "Thoreau, and those that came after him, made a decision to make these observations, and to make them routine. To continue that for decades takes a lot of commitment and stick-to-itiveness and vision."
Michelle Nijhuis lives off the electrical grid in Paonia, Colorado. She wrote about Winchester, Massachusetts.