Friday, April 28, 2017

Half of All Species Are on the Move—And We're Feeling It


[National Geographic] The shrubs probably responded first. In the 19th century, alder and flowering willows in the Alaskan Arctic stood no taller than a small child—just a little over three feet. But as temperatures warmed with fossil fuel emissions, and growing seasons lengthened, the shrubs multiplied and prospered. Today many stand over six feet.
Bigger shrubs drew moose, which rarely crossed the Brooks Range before the 20th century. Now these spindly-legged beasts lumber along Arctic river corridors, wherever the vegetation is tall enough to poke through the deep snow. They were followed by snowshoe hares, which also browse on shrubs.
Today moose and hares have become part of the subsistence diet for indigenous hunters in northern Alaska, as melting sea ice makes traditional foods like seals harder to chase.
That's just one of thousands of ways in which human-caused climate change is altering life  for plants and animals, and in the process having direct and sometimes profound impacts on humans. As the planet warms, species are shifting where, when, and how they thrive. They are moving up slopes and toward the poles. That is already altering what people can eat; sparking new disease risks; upending key industries; and changing how entire cultures use the land and sea.
"We're talking about a redistribution of the entire planet's species," says Gretta Pecl, lead author of a new study in Science that examined the implications of wildlife on the move.

The changes already are quite dramatic. Malaria, for example, now appears higher up mountain slopes in Colombia and Ethiopia, as rising thermostats make way for mosquitoes at higher elevations. Leishmaniasis, a sometimes-fatal, once primarily tropical affliction, has moved into northern Texas as the sandflies that host the disease-causing parasite head north.
Agriculture is feeling the effects too, as crop pests expand their range. Diamondback moths, which ravage the cabbages, kale, and cauliflower grown by poor urban farmers, are spreading in South Africa. In Latin America, coffee plant funguses and pests are appearing in new areas, threatening a key industry. The same is happening to French olives, wine grapes, and lavender. And in the United States, scientists suspect climate change has promoted the increasingly rapid spread of Johnson grass, a highly invasive weed that reduces yields for legumes, corn, sorghum, and soybean. Read More