Environmental Factor, December 2008, National Institute of Environmental Health Sciences
Global Warming and Insect Populations
By Eddy Ball
The Scientific Research Society, Sigma Xi, headquartered in Research Triangle Park, N.C., hosted a presentation on November 17 by North Carolina State University (NCSU) ecologist Rob Dunn, Ph.D., as part of a monthly lunchtime lecture series. The talk, titled "Global Warming and the Neglected Majority," explored the impact of climate change on invertebrates - and ultimately humans - by focusing on ants, one of the best studied insect species
Dunn (http://www4.ncsu.edu/~rrdunn/) is part of the NCSU Conservation Ecology Research Group, which uses integrated approaches to study diversity, rarity, extinction and conservation. Within the group, research interests include microcosms, large-scale experiments on corridors, studies of rarity and diversity at continental scales, and diverse modeling approaches. Dunn is the author of a new book, Every Living Thing: Man's Obsessive Quest to Catalog Life, from Nanobacteria to New Monkeys.
"What I want to talk about today," Dunn began, "is what we can project about the ecological aspects of the future." What he also did was to turn the attention of his audience away from global warming icons, such as the polar bear and its Arctic habitat, to the temperate areas of the world where humans and their often unseen invertebrate neighbors coexist.
According to Dunn, these areas include the back yards of residents of central North Carolina where an average of 30 species of ants can be found. The back yard is also where people may encounter the three major invasive species of ants that "are doing better and better each year" in North Carolina, he added - the fire ant, the Argentine ant and the aggressive Asian needle ant (Pachycondyla chinensis), whose painful sting can trigger anaphylactic reactions in as many as one out of every 100 people it stings.
Dunn described the contributions of insects, some of them members of endangered species that could be threatened by global warming, as sources of pharmaceuticals, dispersers of seeds and pollen, and mediators of many, if not most, ecological processes. He added, however, that insects also make up the majority of pests, are capable of destroying crops and buildings, and can serve as disease vectors.
From what Dunn and other investigators have learned about the central importance of temperature to insect populations, global warming is likely to help at least some species of ants and other insects invade parts of the world where they are now less prevalent, such as higher elevations and, for fire ants, the interior of forests. Climate change is also likely to accelerate the dominance of invasive species - many of which, like the Asian needle ant, perform fewer ecologically beneficial activities and can pose a threat to human health and quality of life.
"It doesn't take much," Dunn asserted, "to go from a community [of insects] dominated by the processes we [humans] like to a community with a whole bunch of invasive species doing some pretty nasty things."
Dunn concluded his talk by re-emphasizing how little scientists understand about the world of insects and the specifics of what a warmer world will be like for humans and the "neglected [insect] majority." He noted that many of the tens of millions of insect species estimated to exist are still undiscovered. Even today, he observed, "You could still go out in Central Park and find a new species."
Because so much remains to be discovered about insects, human attempts to control them can easily backfire - just the way that the use of DDT ironically ended up accelerating the northwards spread of fire ants by ten or twenty years.
(Individuals interested in attending the Sigma Xi lunchtime lecture series should contact series organizer Catherine Clabby, associate editor of American Scientist.)