It seemed like a good idea. Let’s start a silk industry in the United States. Silk is a valuable cloth in demand all over the world. And insects do the work. All we need to do is import some gypsy moths from France; then just sit back and wait for the money to roll in.
So, the moths were imported. They escaped. And today, gypsy moths are a major threat to U.S. forests. Gypsy moths are just one example of an invasive species.
There are many more. Asian multicolored lady beetles, for example. You know, the invading swarms of yellow-orange ladybugs crawling and flying around in your home; congregating on windows, walls, and light fixtures and landing in your breakfast cereal. Because of their insatiable appetite for aphids, scale insects, and other soft-bodied agricultural, landscape, and garden pests, multicolored Asian lady beetles, commonly found in Japan, Korea, Russia, and China, were introduced as biological control agents on several occasions and in several North American locations throughout the 20th century.
These beetles were probably introduced accidentally as well, brought here as stowaways on board ships and in cargo transported from Asia. With few native natural enemies, they’ve flourished and dispersed across the continent. And they’ve proven themselves to be very aggressive, competing with our native ladybugs for food and habitat. Several native ladybug species that were once very common have become extremely rare. And it happened very quickly.
Giant hogweed was introduced as a perennial garden plant. It’s a native of Asia and a member of the parsley family. It reaches a height of 10 to 15 feet, with massive white umbels up to 2.5 feet in diameter, when in flower. Gardeners were impressed. What they didn’t realize, however, was that contact with the sap followed by exposure to sunlight could cause huge, painful, burning water blisters to form and leave purplish or blackened, light sensitive scars that can remain for years.
Wild (or poison) parsnip is native to Europe and Asia. It has an edible root, like the garden parsnip cultivars derived from it, and was likely brought to North America by European settlers who grew it for food. Since its introduction, wild parsnip has become established in abandoned fields and pastures, disturbed open areas, and along roadsides across the continent. Like giant hogweed, it too produces sap that soaks into your skin and reacts to sunlight, resulting in intense burns, rashes, blisters, severe scarring, and even blindness if rubbed onto the eyes.
Purple loosestrife is native to much of Europe and Asia. It was first introduced to the northeast in the 1800s and is now found across much of North America. It’s a very hardy perennial, which can rapidly reduce the value of wetlands for waterfowl and other wildlife by competing with and displacing native wetland food and habitat plants. Wetlands are the most biologically diverse and productive component of our whole-earth ecosystem.
The most widely used definitions of invasive species apply to non-indigenous flora or fauna whose introduction into an ecosystem cause, or are likely to cause, harm to the environment, the economy or to human health. Note that this references environmental boundaries, not political ones.
There are many native species (species that occur within a region or habitat naturally; without human intervention) within the U.S. that are invasive elsewhere in the country. Lake trout, for example, are native to the Great Lakes and much of the northeast, but are considered invasive in Yellowstone Lake in Wyoming, where they compete with native cutthroat trout for habitat.
Thousands of introduced species now prey upon or out-compete native species within the U.S.. The costs of this ecological upheaval, just in economic terms, is staggering. A 2014 report titled ‘The Actual and Potential Economic Impact of Invasive Species on the Adirondack Park: A Preliminary Assessment’; estimated the potential direct economic impact from the eight species evaluated in the study to be $468 to $893 million, with the greatest projected impacts on property value, recreation, and tourism.
Invasive species are among the top causes of biodiversity loss around the world. Gardeners can be part of the solution by:
– Checking to see if a plant is invasive and not planting, if it is;
– Learning to recognize signs and symptoms of invasive species;
– Keeping up to date on the status of invasive (and other) pests;
– Reporting any occurrence of invasive species.
You can make reports of invasive species to the DEC, Cornell Cooperative Extension, the Natural Resources Conservation Service, your county Soil and Water Conservation District, Adirondack Park Invasive Plant Program, or the Nature Conservancy.
Eradicate or control populations of invasive species on your land. Yank them out of the ground. Remove them from the water. And tell your neighbors if you see invasive species on their land.
Photo of rash from contact with the sap of giant hogweed (or poison parsnip), courtesy USDA Animal and Plant Health Inspection Service; Plant Protection and Quarantine Program (APHIS PPQ) – Oxford, North Carolina, Bugwood.org.