August 19, 2012
Investigating Animal Movements In Response To Climate Change
redOrbit Staff & Wire Reports - Your Universe Online
As part of an effort to better understand and predict how animals will respond to changing environmental conditions associated with global warming, researchers at the University of California-Berkeley (UC Berkeley) have published a pair of studies investigating why some species move in response to climate change and where they go.
According to Sarah Yang of the school's media relations department, the first study, published August 6 in the Global Change Biology, addressed the role of fluctuations in precipitation in forcing various bird species to relocate. The other study, published August 15 the journal Proceedings of the Royal Society B, investigated the declining habitat range of one type of squirrel species.
As part of the bird study, researchers studied 99 species in 77 different survey locations, including several national parks and national forests. They discovered that over the past century, summer and winter temperatures increased by an average of one or two degrees Celsius in the Sierra Nevada, while Yosemite National Park experienced increased of 3 degrees Celsius over that time and other locations actually got colder. Meanwhile, as many as one-fourth of the bird species they studied shifted direction in response to the changing temperatures.
"Our results redefine the fundamental model of how species should respond to future climate change," lead author Morgan Tingley, who started the research while studying as a graduate student in UC Berkeley´s Department of Environmental Science, Policy and Management, told Yang on Wednesday. "We find that precipitation changes can have a major, opposing influence to temperature in a species´ range shift. Climate change may actually be tearing communities of organisms apart."
"Among the bird species that moved upslope are the Savannah Sparrow, which shifted upward by 2,503 meters, and other meadow species such as the Red-winged Blackbird and Western Meadowlark," Yang explained. "The ones that shifted their range downslope include both low-elevation species like the Ash-throated Flycatcher and Western Scrub-Jay, and high-elevation species like the Cassin´s Finch and Red-breasted Nuthatch."
The researchers say that temperature alone did not explain the shifts, and that while rising temperatures typically led birds to go upslope to cooler regions, increased precipitation had the opposite effect, coaxing them downslope to warmer regions. They also discovered that more than half of the species studied did not change their habitat range, in spite of climate change-related factors, leading Tingley and colleague to express concern about how -- or if -- the birds were adapting to the changes in temperature and precipitation.
The second study investigated similar issues, but instead of focusing on avian life, it studied the Belding´s ground squirrel, which is typically found in the mountainous regions of the western US.
"Through visual observations and trapping surveys conducted throughout the mountains of California, they discovered that the Belding´s ground squirrel had disappeared from 42 percent of the sites where they were recorded in the early 1900s," Yang said. "Extinctions were particularly common at sites with high average winter temperatures and large increases in precipitation over the last century."
“We were surprised to see such a dramatic decline in this species, which is well-known to Sierran hikers and was thought to be fairly common,” added Toni Lyn Morelli, lead author of the study and a former National Science Foundation postdoctoral researcher who worked out at UC Berkeley. “In fact, the rate of decline is much greater than that seen in the same region for the pika, a small mountain-dwelling cousin of the rabbit that has become the poster child for the effects of climate warming in the contiguous United States.”
She noted that the squirrels had managed to find a home in areas that had been modified by humans, and that given the dire predictions about the possible disappearance of the species from California by century's end, those types of living spaces could prove to be of utmost importance not just to them, but to all other species that have been affected by global warming, increased in greenhouse gases, and other, similar environmental factors.
"Taken together, these two studies indicate that many species have been responding to recent climate change, yet the complexities of a species´ ecological needs and their responses to habitat modification by humans can result in unanticipated responses," UC Berkeley Department of Environmental Science, Policy and Management professor Steven Beissinger, who served as senior author on both studies, told Yang. “This makes it very challenging for scientists to project how species will respond to future climate change.”