Good Oak News

Tuesday, October 18, 2011

Honeysuckle: Really Quite Terrible for Wildlife

Clearing invasive brush is a big part of Good Oak's business. After all, most midwestern woodlands suffer from the negative effects of honeysuckle, buckthorn, multiflora rose, Japanese barberry... and others.

People always want to know why these plants are so bad for our local ecosystems. First and foremost they simply displace native plants. Either buckthorn or honeysuckle can effectively take up all of the growing space on the ground layer in a woodland, leaving nothing but bare dirt on the ground below them. They're also bad for our birds, especially migrating birds. I usually explain that both honeysuckle and buckthorn produced berries, but these berries are not nutritious for our birds and other wildlife. Honeysuckle berries for example are the nutritional equivalent of cola. Berries from native plants are more like a glass of milk or orange juice, with protein, fat, vitamins and minerals and more complex carbohydrates.

But some new studies have found that honeysuckle harms wildlife in ways I could never imagine. A study titled Invasive shrub alters native forest amphibian communities recently published in Biological Conservation found that honeysuckle can change the "forest understory microclimate", reducing the habitat quality for native frogs and salamanders. Essentially, I think what is happening is the honeysuckle kills off all the other plants so there are no ground layer plants, and very little leaf litter or duff layer either, meaning the soil and air near the ground dry out faster, which is not good for animals who need to stay a little moist all the time. The abstract of this article concludes "invasive [organisms] may affect native organisms with which it shares no trophic connection, and suggests that changes in microclimate may be one mechanism by which alien plants affect communities where they invade.

It has been known for a while that the red berries of honeysuckle (which, now that fall has come are quite visible on these shrubs in our region) can change the color of bird's plumage. Specifically a study has been done exploring the effects of eating honeysuckle berries on cedar waxwings, with an unknown effect on the mating success of the affected birds.

Now, an new study has found that honeysuckles have created an "evolutionary trap" for cardinals. In essence, consuming honeysuckle berries artificially enhances the plumage of a cardinal, making it look brighter. A bright red cardinal is more likely to attract a mate that a duller one, usually because a brighter bird is stronger and healthier. In this case however, the opposite may be true, since these birds eat more "junk food" honeysuckle berries and have territory in poor quality habitat (infested with honeysuckle)... thus tricking birds into choosing a poor quality mate!

Add to that the fact that not one but two recent studies have found that birds nesting in honeysuckle and buckthorn have less success rearing young than birds nesting in native trees. Suddenly you can what broad ranging effects just a couple species of invasive plants can have on ground layer plants, amphibians and locally nesting and migratory birds.... Basically these plants are causing damage on all levels of the ecosystem and altering natural communities in many profound ways that.

So that is why we work so hard clearing invasive brush from our midwestern woodland and grasslands. Honeysuckle flowers may be pretty in the spring, but we shouldn't trade this fleeting beauty for the long term stability of our ecosystem.