May 4, 2010
by Dennis T. Avery
Biologists are again predicting massive species losses as the world warms. But where are the corpses? There have been few findings of extinctions among continental bird and mammal species over the past 500 years. The species extinctions have been virtually all on islands, as humans have brought such alien predators as rats, cats, and Canadian thistles to places where they had no natural enemies.
A new study shows that flying squirrels have been adapting to recent warming since the 1990s by both moving and hybridizing. C.J. Garroway and his research team trapped more than 1600 of the flying squirrels in Ontario and Pennsylvania between 2002 and 2004. The flying squirrels' DNA shows the southern G. volans flying squirrels are increasingly mating with the northern G. sabrinus flying squirrels. The researchers say this is the “first report of hybrid zone formation following a range expansion induced by contemporary climate change.”
That's certainly interesting, but hardly earth-shaking. Ice cores and fossil pollen show the earth has had six major global warmings since the last Ice Age, interspersed with centuries-long cold periods. The earth's temperatures are always cycling up and down.
We have even more dramatic evidence of creatures moving to stay at the right temperatures from the city of York, England. Excavations under the city find that the nettle ground bug was common in York during the Roman occupation in the first century, and during the Medieval Warming. In between those warm times, it has typically been found in the much-warmer south of England.
On the other hand, Italian researchers have just finished surveying bird species in a high Piedmont valley where the temperature since the early 1990s has increased about 1 degree C. How did the birds adapt? They did nothing. Sixty-eight bird species were detected in both the 1992-94 survey and the 2003-05 survey. The researchers report “the number of species whose mean elevation increased (42) was higher than the number whose mean elevation decreased (19).” But the birds move up and average of just 29 meters—not statistically different from zero.
Why didn't the birds move? We'd advise asking whether the birds' food sources moved. Higher levels of CO2 allow vegetation to adapt to higher temperatures—without moving. Perhaps the foliage, fruits and insects on which the birds depend didn't change much either.
We might even think about humans adapting to a one-degree change in global average temperatures, rather than destroying our only available energy sources. The net warming since 1850 has been something less than 0.7 degree C when we allow for the increasing impact of urban heat islands on our thermometer 1–3 degree total warming in the early decades. Then the warming rocks along in 30-year up-and-and-down spurts, as we've seen in the earth's 1915–1940 warming, its 1940–1975 cooling, and its 1976-1998 warming. For centuries at a time. Until the sun brings the next global cooling.
We need to get rid of the biologists' “climate envelope” theory that predicts species extinctions will occur unless their climate environment remains absolutely stable (never has been, never will be). Looking at real global history, specie extinctions are more likely to happen when the next asteroid collides with earth. Those are the times the earth has lost the vast majority of its species.
Dennis T. Avery is based in Churchville, VA, and is director of the Hudson Institute's Center for Global Food Issues.
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