For Some Species, Die-Offs, Not Migration, Response To Warming Climate, Study Shows - Baltimore Sun

CAPE TOWN, South Africa - High in the Silvermine nature reserve, proteas here and there unfurl skyward like floral fireworks in soft pink and yellow. Guy Midgley's eye is drawn elsewhere, though, to ugly brown lesions on the otherwise green landscape - dead protea plants. "Nobody's quite sure what's going on," says Midgley, a plant scientist, scanning the bushy vegetation. But he suspects global warming is behind the recent protea "die-back," in which one-third of the plants have shriveled up in some parts of the Western Cape region.

Midgley bases his hunch partly on fresh evidence that rising temperatures threaten another species nearby: the quiver tree, so named because the semi-nomadic San, or "bushmen," carried arrows in its hollowed-out stems. Half the quiver tree's range is in danger as warming turns semi-arid areas of Namibia and northern South Africa less hospitable, he says. The trees, which can live up to 350 years, are dying in the northern half of their range, according to a study in the September issue of Diversity and Distributions. "It's the canary in the coal mine," said Midgley, a co-author of the study, calling it the first proof that a desert plant's whole range is shifting. "It's one species, but it's an index."

The research echoes findings on butterflies in Europe and frogs in Central America, bolstering the view that a hotter planet is affecting biodiversity far beyond the Arctic, said University of Texas biologist Camille Parmesan, who was not involved in the study. As study co-author Lee Hannah of Washington-based Conservation International noted, "It's not just about polar bears anymore. Here is evidence that species in many other parts of the world are at risk."

The quiver tree, a species of aloe distantly related to aloe vera, shows the potential for a gradual migration toward cooler and wetter conditions: trees at the southern range are doing well. The fear is that the species will be squeezed so fast from the north that it could face eventual extinction. Plants, dependent on seed dispersal, naturally shift at a glacial pace.


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