|Bee on flower. Credit: USFWS.|
Bees do it. Flies do it. Pollinate, that is.
But what happens when the piñon and Ponderosa pines and aspens of northern Arizona -- vegetation pollinators call home -- move up the mountain as precipitation patterns change due to climate change?
Some pollinators rely on specific plants. But can they use a broader spectrum of plants? Can they live at higher elevations to get to the plants they need? And what if they can’t?
The U.S. Fish and Wildlife Service’s Arizona Ecological Services Field Office is addressing those research questions as it works at five sites with the Merriam-Powell Center for Environmental Research Center at Northern Arizona University to compile the first-ever baseline about the diversity and behavior of pollinating insects at varied elevations in northern Arizona.
Changes in the precipitation patterns in northern Arizona are affecting Ponderosa pine in the highest elevations of the San Francisco Peaks. Photo by Ron Hemberger/USFWS
Pollinators are critical to maintaining diverse, healthy ecosystems. The Service is entrusted to protect at-risk pollinators, such as hummingbirds and pollinators on national wildlife refuges – and threatened or endangered species that rely on animal pollination. More than 75 percent of flowering plants, which provide fruits, seeds nuts, and nectar for wildlife, depend on pollinators. Recent studies indicate some pollinators are already being impacted by climate change.
Launched in summer 2009, the northern Arizona study is looking at bees and other pollinating insects across elevations, from 5,000 feet in the desert grasslands to almost 9,000 feet in the mixed conifer and aspen forests of the San Francisco Peaks. Piñon pines have already experienced die-offs after being weakened by drought and therefore becoming susceptible to insect pests.
The Research Center has a fully computerized weather station at each study plot, collecting such data as precipitation, temperature and wind speed. The Service has set up native pollinator survey transects on each study plot, using 12-ounce plastic cups, painted vibrant blue or yellow or left white to mimic flower colors.
The cups are filled with a 50-50 water and propylene glycol mixture. Insects, attracted to the cups, land on the water, sink and drown. The propylene glycol preserves the sample. Traps are set from April through October.
“We anticipate that we will see changes in the vegetation community as the climate dries out,” says Service Field Office wildlife biologist Dave Smith, who is leading the study. “If the vegetation moves upslope, will the pollinating insects follow? Are they more adaptable then we thought? To date, no one has looked at what pollinators who move up to higher elevations are pollinating.”
Smith notes that while researchers in Arizona have looked at deserts, which have the highest bee diversity, less research has been conducted at higher elevation, where flies are more adapted and more prevalent among the mixed conifer aspens. Flies pollinate nearly all flowering plants at high elevations: lupines, yarrow, larkspur, Indian paintbrush, sunflowers and willows, to name a few. They may also be important for the endangered San Francisco Peak groundsel, found only in that particular habitat.
The study has already yielded some results from data collected from August-October 2010. Smith and Northern Arizona University undergraduate Jacob Burton found at least 85 different species of bees at the five plots, including five species found at all elevations. “The diversity in vegetation from the desert site to the mixed conifer and aspen site is so great that we were surprised to see the same species of bees at all sites,” says Smith.
They also found bees that normally pollinate prickly pear cactus in the foothills of the San Francisco Peaks at the 9,000-foot elevation, where no prickly pear cactus grows. So, are the bees more adaptable than once thought, Smith asks. Are they pollinating the same plant species as the flies pollinate, although to a lesser degree?
Those are questions yet to be answered; the study is expected to go on for some years. “I have a freezer full of baggies with bees,” says Smith.