Remember the comedy routine, or maybe the children’s book by Margery Cuyler called That’s Good! That’s Bad!? This time of year, when it comes to invasive species, there is good (well, sort of), and there is bad (mostly).
For people intent on removing invasive species, this is the best time of year to do it. That’s good.
Almost all of the nonnative plants that degrade our parks, preserves and private lands start showing leaves in April, enabling early detection. Property owners and land managers should check their properties now, when the green of honeysuckle, buckthorn, barberry and garlic mustard stands out against the brown of last year’s growth. Knowing one has a problem is the first step toward addressing it. That’s good.
Most years, the ground is soft during the early spring, and small plants are easiest to pull when the ground is moist. That’s good. (If we would get significant rain, that would be very good.)
Any plants pulled in the spring obviously will not be around in the fall to produce seeds and berries. That’s good.
But by leafing out early and holding on to their leaves late into the fall, these invasive species have an extra-long growing season – an estimated 30 days longer than native plants – so they have more time to grow each year. That’s bad.
The plants with early leaves get most of the sunlight, shading out their neighbors. They take up more of the moisture and nutrients in the soil. A number of invasive plants (and, to be fair, some native plants) give off chemicals to weaken and even stop the growth of neighboring plants in order to further their own growth. Therefore, areas that were once rich in spring wildflowers can be degraded forever by an invasion of nonnative plants. That’s bad.
In the larger scheme of things, invasive plants quickly diminish the biodiversity of a forest. That’s even worse.
But what about the songbirds? When shrubs such as honeysuckle leaf out early, the dense foliage is extremely attractive to songbirds. They can build nests that can be completely hidden in the lush early leaves. That’s good.
Wait. That’s bad. Honeysuckle has multiple thick stems, so nest predators such as raccoons, snakes, squirrels and skunks can easily climb up to eat the eggs or nestlings.
Nest predation in honeysuckle is significant, at least in rural areas.
Some researchers point out that in urban settings, nest predation is not as serious, presumably because pet food, bird feeders and garbage provide an easier source of food for nest predators. That’s good, I guess.
Finally, if you look at the leaves of nonnative species, you rarely find little holes, chewed edges or other signs of insect damage. Often catalogs and nurseries tout nonnative plants and cultivars as being “insect resistant.” Presumably, marketers think that’s good.
But for people who love birds and butterflies – and also frogs, toads and fish – that’s bad.
Without native host plants, butterflies and moths would not be able to lay their eggs. Without eggs, there would be no caterpillars. And according to the Audubon Society, “These insects are a major source of food for birds and other wildlife. In fact, 96% of songbirds raise their young by stuffing them with high-protein insects. Most of our native insects need native plants to survive – they simply don’t recognize nonnatives as food.”
In the early spring, seeing green can seem hopeful, but it almost always indicates nonnative plants. If these plants invade and take over an area – and remember, they have a competitive advantage – the area loses its value as a bird and wildlife habitat and as a healthy, biodiverse ecosystem. That’s bad!
Coggin Heeringa is the president of Wild Ones of the Door Peninsula and the program director and naturalist at Crossroads at Big Creek in Sturgeon Bay.