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Climate Change Forcing Insect Species Northward

The biggest harbingers of climate change may be some of nature’s smallest creatures: insects. A massive northward migration of insects is currently underway, signalling a rise in global temperatures, a scientific conference in Winnipeg heard. Over the past 25 years, 52 per cent of insects species have moved their natural habitats to the north by anywhere from 50 to 1,600 kilometres. The movement is widespread and affects every major insect group in the Northern Hemisphere.

The fact that so many insects are seeking cooler climes is strong evidence of global warming, said Camille Parmesan, an American conservation biologist specializing in insects and climate change.

She spoke at a recent joint meeting of the Canadian and Manitoba entomological societies.

ON THE MOVE

Species movement is not a new phenomenon for insects. But previous shifts occurred within the past several hundred thousand years when the climate was either similar to today’s or cooler, said Parmesan.

“Where we’re going to is a climate warmer than we’ve had in two or three million years. So we are losing whole climate spaces for a lot of our species that are basically cold adapted. Those cannot just move around because their entire climate space is disappearing,” she said in an interview.

What’s making it even harder for insects to move is that humans now dominate the landscape, Parmesan said.

“It’s very difficult for most species to cross, say, the L. A. (Los Angeles)-San Diego corridor or the Illinois-Midwestern crop fields. The species that can do that are the ones that are already urban or pest species, which are not necessarily the ones we care about.”

Climate change is already laying waste to some species, with more expected, Parmesan noted.

Scientists last year announced the likely extinction of the white lemuroid possum of Queensland, Australia, which lived only above 1,000 metres in altitude. It is the first mammal believed to go extinct because of rising temperatures resulting from climate change.

CAN’T TAKE THE HEAT

Parmesan’s own groundbreaking 1996 study of the Edith’s checkerspot butterfly, located along the Pacific coast of North America, found three-fourths of the insect’s populations had disappeared at lower latitudes, as compared to only a 20 per cent loss in Canada.

The checkerspot butterfly is sensitive to warmer temperatures because its host plant dries out and eliminates the insect’s food source while it is still in the caterpillar stage. Its decline is one indicator of a changing climate, Parmesan concluded.

Her study drew scorn from some pundits, including the acerbic U. S. radio talk-show host Rush Limbaugh, who derided Parmesan and her study.

But Parmesan believes recent developments support her conclusion that insects can signal alterations in climate.

“The individual butterfly may not make any difference. But a lot of these species are indicators of whole ecosystem changes.”

EXPLODING POPULATIONS

One example, according to another conference presenter, is the pine beetle currently ravaging forests in British Columbia. Cold winter weather used to keep the insect in check. But recent warm summers and mild winters have caused populations to explode, turning vast expanses of green forest into dead brown trees. An estimated 25 per cent of B. C. pine forest is affected.

But while the pine beetle is an invasive species requiring control, many insect species are non-invasive and need protecting, Parmesan feels.

Parmesan proposes a controversial approach to saving threatened insect species: transplanting them from habitats under pressure to friendlier ones.

The idea of assisted migration appalls some biologists, who say transplantation actually causes species endangerment: an exotic species comes in, takes over and pushes other species out.

But Parmesan said fewer than 20 per cent of exotic species are invasive and most settle into their new homes with no disruption to the ecosystem. [email protected]

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