The Mother Lode
The tropics are renowned bastions of biodiversity. But scientists are finding that our own backyard rivals the rainforests as they uncover dozens of new species each year in Great Smoky Mountains National Park.
How the Smokies' rich assemblage of flora and fauna got there and why in many instances it's thriving involve ancient climate change and topography. Before the great melt of the last ice age began about 10,000 years ago, glaciers pushed far to the south across North America. While stopping just short of plunging the southern Appalachians into a deep freeze, they herded countless avian, mammalian, reptilian, amphibian, insect, and even plant species ahead of them toward warmer, more hospitable habitats. When the ice flows retreated, those species stayed behind, finding refuge in the Smokies. Some that now thrive in the cooler climate near the park's roof, such as velvet-leafed blueberry and the spruce-fir forest, are more typically found hundreds of miles north.
Setting out from the lush valley of Cades Cove, it's an arduous up-mountain, five-mile hike along a trail worn by generations of feet to Spence Field, a clearing atop the park's spine just below 5,441-foot-tall Rocky Top. From here my eyes sweep out across an undulating mountain range that trends northeast to southwest. This tilt allowed species to move south ahead of the glaciers and find new habitats that suited their needs. Had the mountains been stretched more fully east to west, they likely would have blocked this ecological escape and a lot of species might have been lost to the ice age. Instead, many of them are alive and well in the Smokies, particularly in the section protected within the national park's borders.
This bulldozing of life left the landscape with tree species in numbers equal to or exceeding all those of Europe, and nearly 1,600 flowering plant species. Even though scientists have been digging deeper and deeper into the park's aquatic and terrestrial landscapes, the overall richness and depth of biodiversity remains to be fully understood. The ATBI has so far identified about 9,000 species; scientists speculate the park could have as many as 100,000.
Trying to grasp all the measures of life--native and nonnative--within the park's borders has been intense. The inventory has revealed the obvious species: the black bears, white-tailed deer, and elk. It has also unearthed life-forms that, while out of sight, help keep the overall ecosystem in balance. Though bugs, bacteria, and fungi tend to be afterthoughts when you consider the elements of a healthy ecosystem, they are among the key drivers here. They pollinate plants; keep the organisms they parasitize in check; feed birds, reptiles, fish, and amphibians; and, in the case of worms and other soil dwellers, cultivate the park's loamy foundation.
They also can be pests, which makes it valuable from an economic perspective to understand them. That's what brought Gary Steck to the Smokies in 1999. A taxonomic entomologist for the Florida Department of Agriculture, Steck's interest lies in, among other things, fruit flies: apple maggot flies, cherry maggot flies, blueberry maggot flies, and hundreds of others.
In eight years Steck and his colleagues have expanded the roster of fruit flies in the Smokies from 10 species to more than 50. "Every time we go we come up with something astounding," says Steck, who recalls one trip that seemed to be a bust until a last-second stop yielded a fruit fly whose day-to-day existence was unknown. "A lot of these astounding finds we made were things that may have been known from as few as three or four specimens in museums. They had never been collected or described. And some of these, it turns out, are actually abundant in the park. So what you find is that while they were seemingly rare, once you know where to find them, they're not rare at all."
Better understanding the flies' ecology, such as the range of plants they thrive on, can help agriculturalists combat the insects. "It's a big problem we face in Florida," explains Steck. "A lot of these fruit flies have extremely broad host plant capabilities, so that they can attack not just citrus, for example, but maybe dozens or even hundreds of other fruits. So knowing about alternate host plants is really important."
Some species that have turned up in the park have been on earth for so long that it's surprising so little is known about them. Take, for example, water mites, which have been around for 250 million years. An aquatic relative to terrestrially rooted spiders, most of us have unknowingly encountered water mites as we've walked through ponds, lakes, and streams. "If you realized how much stuff was in [the water], you wouldn't step in again," jokes Andrea Radwell, whose forays into Great Smokies waters have led to dozens of discoveries. "But we're not prey. They don't bother us. They're microscopically small and they prey on insects--and thank goodness. You look at the number of insects that emerge from rivers, and it would just be an uninhabitable planet if they all hatched out. Mites are controlling their populations."
A rich aquatic stretch, when it comes to water mites, is Twin Creek, a gurgling, mossy, boulder-chocked, and densely shaded stream a short walk from the park's science center. With more than 2,100 miles of streams overall, Great Smoky is amply populated with water mites. Sixty genera have been documented so far, and almost every major genus that occurs worldwide has turned up here.