Though pesticides are getting all of the attention from environmental groups when it comes to concern about bees, the science community instead knows it is mites and climate - were it as simple as pesticides, places like Australia and the United States, where the neonicotinoids often blamed by activists are common, would show losses, but instead they were limited to one section of Europe.

Instead, the most comprehensive study ever conducted of the impacts of climate change on critical pollinators finds that it's changing habitat and climate likely to blame. Of course, there is no way to know what is happening in the wild, bees may be fine there. Only a handful of the tens of thousands of bee species in existence even build hives, so there is no way to know if their hives "collapsed" at any point.

Since wild bees are a mystery, the researchers examined more than 420,000 historical and current records of many species of bumblebees and declare the problem is environmental rather than chemical.

Though anti-science groups like Natural Resources Defense Council will take out full-page advertisements in the New York Times blaming Dow for butterfly losses, those claims are specious, says the new study. Instead, butterflies are simple expanding their range. The northern edge of their range marches toward the North Pole while the southern edge remains in place. Northern populations of many bumblebee species are staying put while the southern range edge is retreating away from the equator. Their range is shrinking.

CLEARLY, IT'S CLIMATE

The new study shows that the culprit is not pesticides and it's not simply land use changes--two other major threats to bumblebee populations and health. Instead, the research shows clearly that this "range compression," as the scientists call it, tracks with warming temperatures.

The team also found that bumblebees are shifting to areas of habitat at higher elevation in response to climate change. The determination was made with geo-referenced databases from museum collections on both continents. Over the 110 years of records that the team examined, bumblebees have lost about 185 miles (300 km) from the southern edge of their range in Europe and North America, the scientists estimate.

There may be an evolutionary explanation for the problems bumblebees now face. Many other species of insects originated and diversified in tropical climates; as temperatures warm, their evolutionary history may allow them to better adapt. Bumblebees, however have "unusual evolutionary origins in the cool Palearctic," the scientists write, which may help explain their rapid losses of terrain from the south and lagging expansion in the warming north.

ASSISTED MIGRATION?

To respond to this problem, the research team suggests that a dramatic solution be considered: moving bee populations into new areas where they might persist. This "assisted migration" idea has been considered--and controversial--in conservation biology circles for more than a decade, but is gaining support as warming continues.

Published in Science.