Researchers have long debated the consequences of introducing non-native species into ecosystems. Recently, these debates have centered upon the effects of invasive exotics, and dramatic pictures of grasslands filled with leafy spurge, water pipes clogged by zebra mussels, and forest trees killed by kudzu vines have fostered the publics understanding of the issue. But now, two Canadian scientists are suggesting that even the introduction of some less aggressive species may have far-reaching negative repercussions.
Janice Christian and Scott Wilson studied crested wheatgrass (Agropyron cristatum) to test a controversial hypothesis: that the consequences of introducing exotic species can extend far beyond the simple displacement of native plants and animals. Their work, published in the October issue of the journal Ecology, suggests that crested wheatgrass has precipitated a decline in soil quality and may have increased the amount of carbon dioxide in the atmosphere.
Crested wheatgrass (sometimes called fairway wheatgrass) has wrested the soil from native grasses on much of the northern Great Plains, but its conquest has seemed relatively harmless to the larger environment. The grass was originally brought to the Americas from Siberia during the drought-filled years of the Dust Bowl, when farms were failing and the local prairie grass was producing scant fodder for cattle. Farmers discovered that the wheatgrass was hardy, produced good hay, resisted drought and overgrazing, and had a long growing season. It was so successful that ranchers and government agencies still continue to spread it (and several close relatives) enthusiastically from the Great Basin to the Northern Plains. It currently blankets 25 million acres of prairie in North America.
To determine how crested wheatgrass affects the prairie ecosystem, Christian and Wilson compared hundreds of samples of grass and soil from Canada's Grasslands National Park in southwestern Saskatchewa
Contact: Alison Gillespie
Ecological Society of America