Wednesday, January 6, 2010

Forced Migrations

We’ve all read a description of the Smokies along these lines:

The wide range of elevations mimics the latitudinal changes found throughout the entire eastern United States. Indeed, ascending the mountains is comparable to a trip from Tennessee to Canada. Plants and animals common in the country's Northeast have found suitable ecological niches in the park's higher elevations, while southern species find homes in the balmier lower reaches.

I was thinking about that observation after encountering The Velocity of Climate Change, a recent article from Nature.

Discovery News summarized the research:

As climate changes, species will need to relocate to follow their ideal climate, generally by uphill or to higher latitudes. But how quickly will this change occur?

In a new study, researchers calculate that climates will shift about a third of a mile per year, on average, over the next century.

"When most people think about a rate of climate change, they're thinking about how much climate is changing in time," said study lead author Scott Loarie of the Carnegie Institution for Science at Stanford University.

"But there's also a spatial gradient," he said. "How far do you have to go from a given point to change your climate? On a mountain, it's not very far. But if you're in the middle of the Amazon basin, you have to go very far to change your climate."

The researchers combined these two aspects -- how fast climate is predicted to change over time with how temperatures vary by location -- to create a global map of how climate will move across the landscape over the next 100 years.

In mountainous areas, the velocity is slower, because temperatures change quickly up and down a slope. This means organisms won't need to move as far to track their climate. Mountains may offer refuges for some species by providing a range of climates in a small area, Loarie said.

One thing’s for sure - adaptation to climate change will be an interesting process in these mountains. We already live in a dynamic environment, with the forests changing before our eyes. Long ago, the spruce-fir forests covered ten times as much of the Southern Appalachians as they do now. Go back far enough and you might find saber-tooth cats and mastodons on the icy slopes. Whatever the forest was yesterday, it will be something different tomorrow.

A 2001 article discusses the mystery of megafauna extinction on this continent:

WASHINGTON — As recently as 20,000 years ago, North America had an array of large mammals to rival the spectacular wildlife of modern Africa. Mammoths bigger than African elephants, as well as smaller, pointy-toothed mastodons, ranged from Alaska to Central America.

Herds of horses and camels roamed the grasslands, while ground sloths the size of oxen lived in the forests and bear-size beavers built dams in streams.

By about 10,000 years ago, all these animals — and others, such as saber-toothed cats and giant bears — were gone. Some 70 North American species disappeared, three-quarters of them large mammals. Why?...


Anonymous said...

It is curious that no deer have returned to Jackson County. One would have thought they would have migrated here after local deer were killed by hunters from Buncombe and Haywood counties as most species do.

Betty Cloer Wallace said...

Anonymous, that is curious (no deer in Jackson County). Macon County is becoming overrun with deer, as well as raccoons, possums, and coyotes to the point of being a real nuisance (for gardens and cornfields) in some areas of the county.

GULAHIYI said...

I think they're scarce in most of Jackson County. One strolled by my house a couple of years ago, but it was the only I've seen here in 20+ years. There's a lot more open farmland in Macon County, and I'm guessing that's a big factor in the difference.