Diana Wall: What Can Soil Creatures Say About Climate Change?
Diana Wall and colleagues sample soils for nematode worms in the Taylor Valley, Antarctica | Wall Lab
CHICAGO -- In a valley of dry Antarctic dirt wedged between a mountain range and a glacier, a worm half the length of an eyelash was causing Diana Wall some concern.
The Scottnema lindsayae nematode curls up into an inactive state when temperatures become too cool or too warm for it in Antarctic soils. Wall and colleagues' models of this phenomenon suggest that a 65 percent decline in the activity of these worms over 12 years could lead to a 30 percent reduction in soil carbon cycling.
It's just one way that "a single species can have a magnified effect on an ecosystem," the Colorado State biologist said in a 16 February topical lecture at the AAAS Annual Meeting.
The Antarctic nematode, Scottnema lindsayae | Wall Lab/NSF LTER
The trials of this nematode may hold a lesson for the health of the world's soils as they are altered by climate change. Scientists and policymakers alike are worried that degraded soils are having a significant impact on food supply, clean water, human health and carbon storage, Wall said. "The investors for food, cities, paving -- they realize that the soils have the nutrients, and it's the soil fertility that the wealth of our nation depends on."
But soil is just more than dirt, and "it's only been recently that we've begun thinking about soil biodiversity as a resource we need to know something about," said Wall, who serves as the director of the School of Global Environmental Sustainability at Colorado State.
A tablespoon of soil is packed with 10 million bacteria and hundreds of other animals that form a complex food web rivaling anything above ground. Any time natural soils are torn up, compacted or paved over, these intricate webs are disrupted.
But what are the species that live underground, and what roles do they play within global ecosystems? "We know that they rip, tear, chew, shred, dissolve, transform and store and release water, carbon and nutrients," Wall said. But with such a hubbub of activity in most soils, she wanted to find a place where she could look at just a few species at a time to see how they respond to changes in climate.
That place turned out to be a cold desert in Antarctica's McMurdo Dry Valleys, where "there wasn't a sound anywhere after the helicopter left us," Wall recalled. Earlier explorers of the landscape have called the soils sterile and Mars-like, but Wall and her colleagues found that animals like nematodes, microscopic waterbears and rotifer zooplankton are abundant in the ground there.
After 25 years of research, the scientists have discovered that there are patterns in how features like moisture and salinity can affect the distribution of the animals. They have traced the fortunes of Scottnema lindsayae and other species during shifts in temperatures, but they are still uncertain how resilient these populations will be in the face of these changes.
Researchers are also beginning to examine the soil in other regions throughout the world to discover more about the species diversity these soils contain, and how these animals might respond to drought and other aspects of climate change, Wall said.