The effects of climate change on the ecological role of bees
The timing has been beautifully choreographed by nature. Rising spring temperatures prompt many bee species to begin their search for the flowering plants they depend on for food—and which they propagate through pollination. But what would happen if this vital, mutually beneficial relationship goes out of synch due to climate change? That's what Assistant Professor of Biology Daniel Bunker and PhD candidate Caroline DeVan intend to determine with the help of a $150,000 grant from the National Science Foundation.
According to Bunker and DeVan, the consequences could be dire if this relationship unravels as a result of global climate change, consequences that include poor crop pollination and lower yields. In one troubling scenario, the pollinating bees may respond strongly to climate warming and emerge earlier in the growing season, while their preferred flowers respond less strongly and emerge later. Such a mismatch in timing could severely impact both bees and plants, and the productivity of many agricultural crops.
A local outdoor laboratory
DeVan became interested in climate change and the ecological role of bees after majoring in environmental studies and ecology at the University of Tennessee. "I find bees really interesting, and there are a lot of good questions that haven't been asked," she says. Pursuing her PhD in biology at NJIT has given her the opportunity to ask some critical questions and to work with Bunker, who is also very much interested in researching the ecological interdependence between plants and other organisms.
Looking at areas relatively close to NJIT that might be suitable as research sites, DeVan found that Morristown National Historical Park at Jockey Hollow has a substantial bee community—including cavity-nesting bees that forage among various flowering trees as well the "understory" plants beneath the trees. Unlike social bee species, such as honey bees, cavity-nesting bees lead solitary lives in the wild, pollinating many types of flowering trees as they search for food. In some parts of the country, orchard owners provide a hospitable nesting environment to encourage pollinating visits to almond, apple, cherry and other types of fruit trees.
The Morristown site also is appealing because it is a temperate forest, with a comparatively narrow window of time when the bees emerge in the spring and the trees leaf out. In addition, Morristown is part of the Northeast Temperate Network (NETN) established by the U.S. National Park Service to monitor ecological conditions in 12 parks located in seven northeastern states as well as six more states traversed by the Appalachian National Scenic Trail. Working at a NETN site enables DeVan and Bunker to integrate their data into the network's larger ecological picture.
"We realized that Morristown could give us a really nice model system for looking at how bees and plants might respond differently to the effects of climate change," Bunker says. He explains that the primary experimental focus is on the bees since their activity is influenced mainly by temperature, whereas plants respond to changes in the length of the day, the photoperiod, along with temperature. And the cavity-nesting bees at Morristown are especially sensitive to spring temperature changes.
Out and about early
To enlist the Morristown bees in their work, the researchers place nesting boxes they have built near 28 NETN forest-monitoring plots in the park. Adult bees create the nests. The nests have several cells with an egg in each one that metamorphosizes—like butterflies do—through the summer. By fall they are adults in their cocoons, where they overwinter. The initial phase of the program that Bunker and DeVan have initiated with the help of other NJIT colleagues and students involves waking the bees from winter dormancy earlier than usual during the spring by gently warming the boxes.
At this point, the researchers are still fine-tuning their experimental techniques, which include affixing micro-tags to the backs of the bees while they are still dormant in their cocoons. A video camera placed at each nest will allow building a database of the bees' response to manipulated changes in their natural schedule, and how their well-being might be affected by corresponding disruptions caused by climate change.
The tags on the bees, a special variant of the widely used Quick Response "QR" code, will make it possible to monitor individual bees using computer-assisted image recognition, which is being developed under the lead of Associate Professor of Biology Gareth Russell. Physical examination of pollen in the nests also is expected to yield information about the food sources the bees visit, and analysis of the ratio of females to males to provide indications about how temperature variation may affect reproduction.
This effort could help to answer key questions about the possible impact of climate change on agriculture. At large and foraging for food before their normal sources are available, bees may not be able to adapt. DeVan emphasizes that this could devastate the cycle of plant pollination and reproduction. Or bees may adapt by feeding on different plants that flower earlier. While this could be a positive sign that bees are adaptable, it also may mean they are feeding on less nutritious plants, which could have a deleterious impact on bee populations.
For the solitary cavity-nesting bees, starting to forage earlier because they are out of synch with the flowering of their food sources could keep them away from their nests for longer periods. This, too, presents a potential threat. It may give flies, wasps and other predators greater opportunities to attack undefended eggs and larvae. As a result, it may be necessary to devise new strategies for protecting and managing these vital pollinators.
The data that Bunker and DeVan anticipate collecting over the next few years could confirm a disturbing possibility—that the critical relationship between temperature-sensitive bees and the plants they pollinate is in danger. Yet they may find that pollinators such as the bees at Morristown can adapt in ways that do not seriously undermine their role in pollination, and by implication in agricultural production. Whatever the research reveals, it will shed additional light on the relationship between bees and plants—and on one of the most important connections that humans have with nature.