REMOVING INVASIVE SPECIES

Humans have always had the ability to take plants and animals from their native habitats and introduce them to new lands. That is true today more than ever before, with our ability to rapidly move people and things all around the world. Increasingly it is recognized that some of these “foreign” species, both plant and animal, can have devastating effects on native ecosystems.

To be sure, many introduced species pose no problem. Dandelions, the bane of many homeowners, are weaklings when it comes to competing in healthy native communities. Of the 900 or so introduced plant species in our area, only a fraction are capable of invading our natural areas and replacing native species. That fraction, however, can severely damage the integrity of the system.

Buckthorn is an example of just how this can occur. Originally introduced as a hedge, this native of Europe produces large quantities of juicy black seed-bearing berries. Birds eat the berries, then fly into nearby forest preserves where their droppings “plant” the seeds. In time, the buckthorn grows into dense shade-producing thickets, killing off the sun-loving native grasses and wildflowers.

Using handsaws, volunteers cut and remove the buckthorn, letting the sunlight reach the woodland floor once again. To prevent resprouting, the cut stumps are carefully dabbed with Garlon, a low-toxicity herbicide that travels into the buckthorn roots, killing the plant.

The cut buckthorn is piled onto a brushpile and burned to get rid of it.

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EXAMPLES

Purple Loosestrife is beautiful but deadly to our native wetlands. Each plant produces thousands of seeds, which are carried downstream to produce new populations. Eventually, the native plants are choked out and what remains is a monoculture that supports far fewer insects and other animals.

Garlic Mustard is said to have come to our continent with the European settlers, who used it as a potherb in their cooking. It’s a biennial, growing as a first-year rosette that over-winters and then sends up a flowering stalk the second year. After producing many seeds, the parent plant dies. Its offspring begin the cycle again, and the colony rapidly expands, pushing out the native herbs.