Move over. Your farm is being invaded. You already know some of these costly interlopers, such as kudzu, emerald ash borer and the European Starling. Others, such as feral hogs, 20' tall giant reeds and deadly Africanized honeybees, read like aliens straight from science fiction.
Ranchers in the western U.S. battling leafy spurge know the threat is real. The weed causes $200 million in losses annually as it displaces vegetation and produces a milky-white sap that is toxic to cattle and horses.
It's estimated that more than 50,000 nonnative species of plants, animals and microbes have been introduced since the Pilgrims brought the first seeds from Europe. Some are benign, such as the crops that fill our agricultural breadbasket. Corn, wheat, barley, potatoes and soybeans are all nonnatives. So are cattle, hogs, sheep, chickens and the loyal farm dog. We use nonnative European honeybees to pollinate crops.
Still, other aliens, such as johnsongrass (introduced as a forage crop) and the gypsy moth (introduced for possible silk production), are now serious pests. A team of researchers from Cornell University, headed by ecologist David Pimentel, estimate invading nonindigenous species cause $120 billion in damages and control costs each year.
The definition of an invasive species is one that is non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.
The accompanying article on garlic mustard launches Farm Journal's series on the invasive species currently threatening our agricultural spaces.
It's important to remember that not all nonnative species are harmful or invasive. Organisms introduced for biological control of invasive species—such as parasitic wasps, fungi and even fish—can be good and useful. At the same time, indigenous species can spread to another part of the U.S. and become invasive.
During the next few months, our Space Invaders series will explain the struggle. We will introduce you to the scientists that are protecting our borders, and you will learn why some species go bad and others remain beneficial.
Expect some surprises along the way. Did you know some earthworms are nonnative and might be to blame for spreading weeds? Are you aware that some of our most promising biofuel crops hold the threat of becoming invasive? Some new studies show nitrogen levels in soil may be a key factor in determining whether exotic invasive plants flourish and consequently damage wildlife habitats, ecosystems and native species.
Managing invasive species is critical because not doing so negatively affects biodiversity and causes other consequences—environmental and monetary.
Have an invasive story? E-mail firstname.lastname@example.org to let us know how you're fighting back.
- Late Spring 2009