Invasive plants can disrupt ecosystems


November brings Thanksgiving and the start of the winter holidays. The thought of winter conjures up snow, cold, and icy conditions. Wildlife either hibernate or hunker down during windy, cold, and major snow events. Regardless of these winter conditions, our Ohio State bird the Northern Cardinal does not migrate and is a consistent year-round companion.

The Northern Cardinal (Cardinalis cardinalis) often can be heard singing and often can be seen near the top of the tallest tree in the area. The male cardinal has unmistakable brilliant red feathers with black facial markings and a crested head. Females also have a head crest, but overall are duller in coloration. Our state bird prefers woodlands, brush, and forest edges; however, they have also adapted to urban areas eating a variety of seeds, insects, and fruits.

The National Invasive Species Council describes an ‘invasive’ as a non-native that includes plants, animals, and other organisms such as microbes to be alien to the native ecosystem under certain conditions. These introductions cause or are likely to cause economic or environmental harm to human health.

A good example of an invasive species is the Emerald Ash Borer (Agrilus planipennis) a destructive wood-boring pest of ash trees (Fraxinus spp.). Native to China, Mongolia, North Korea, South Korea, Japan, Taiwan, and the Russian Far East. The Emerald Ash Borer beetle was unknown in North America until its discovery in southeastern Michigan in 2002.This insect is thought to have entered the United States of America on infected pallet wood. The Emerald Ash Borer, found in woodlands, brush, and forest edges, has significantly killed Ash trees in Ohio.

Native Ash trees created a canopy of shade in our woodland areas allowing native fauna to thrive. The decline of the Ash trees allowed sunlight to invade the understory. As the understory changed invasive plant species replaced the native fauna. The main invasive plant species include Garlic Mustard (Alliaria petiolate), European and common Buckthorn (Rhamnus spp.), and Amur, Morrow’s & Tatarian Honeysuckle (Lonicera spp.)

Amur, Morrow’s, and Tatarian bush honeysuckles are upright, deciduous shrubs that range from 6 to 15 feet in height. Often our native bush honeysuckle (Diervilla lonicera) and Canada fly honeysuckle (Lonicera canadensis) are confused with these invasives. Branches of the native species have solid stems; on the other hand, the invasives have hollow centers or piths. The invasive honeysuckles are highly attractive to birds including the Northern Cardinal because the fruit is brighter and sweeter with a higher sugar content. The other issue with these invasive honeysuckles is that they leaf out earlier in the spring and drop their leaves later in the fall. It’s been documented birds, including Cardinals which nest in these honeysuckles, suffer greater nest predation than those nesting in native shrubs.

Northern Cardinals begin nest building in April. Females construct the nest, usually in a dense bush or thick brush pile. The female chooses the male based off the red color of his feathers. The redder the male cardinal is the better condition it is in making it appear more ideal to the female. Unfortunately, the invasive honeysuckle’s high sugar content creates brighter red feathers on the males. Females mate with these males that may not have a strong natural genetic gene pool. Over time this may weaken the genetics of our beloved state bird leading to unknown genetics.

Besides the invasive honeysuckles, invasives that thrive in areas left by native Ash woodland areas are European and common buckthorns, and Garlic Mustard. Buckthorns tend to form dense, thickets crowding and shading out native shrubs and fauna, often completely displacing them. Garlic Mustard reduces growth of wildflowers in the early spring and suppresses soil mycorrhizae that are beneficial to trees. Garlic Mustard also has the capacity to produce massive quantities of seed that may remain viable in the soil for up to ten years.

Our native ecosystem is a tightly wined system of plants, insects, animals, and other wildlife including fish and amphibians not to mention soil dwelling insects and microbes. I find it amazing if not disturbing how one invasive insect the Emerald Ash Borer has disrupted woodland ecosystems for the immediate future and beyond.

Ohio citizens need to be diligent in protecting our natural resources from any nonnatives that may disrupt our environment. Healthy ecosystems are important for not only clean air and water, soil stability, but also food and shelter for wildlife and all of humanity!

The Author acknowledges the Ohio Invasive Plants Council, University of Cincinnati, Department of Biological Science for contributing information for this article.

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