Seeds of Destruction
By Brad Fitzpatrick
Invasive species are the farthest things from most hunters’ minds when preparing to head afield. We prefer to focus instead on the brighter aspects of our sport: Sunrise views from a tree stand, mist rising over a freshly laid spread of decoys, or the picturesque point of a setter that has found birds. The fact is, though, that invasive plant species threaten wildlife by seriously altering the ecology of our favorite hunting areas — and hunters can inadvertently aid in the spread of these plants.
Decades ago, well-meaning government agencies encouraged sportsmen to cultivate exotic plants as food sources for faltering wildlife populations. Many of these plants were aggressive in nature and soon competed with native tree seedlings, fruit- and nut-bearing shrubs, and herbaceous plants and flowers for habitat. Other aggressive invaders were brought to this country to beautify landscapes or stabilize stream banks — with similar results. Multiflora rose (called “nature’s living fence”), certain varieties of imported barberry, and autumn olive are a just a few of the non-natives that have proliferated since they were introduced into the United States.
Invasive plants can completely change the ecology of an area. Without natural predators to keep them in check, they often crowd out native species — eliminating natural forage for wildlife, overrunning wildlife habitat, and altering soil composition. For example, common buckthorn can grow to be 25 feet tall and block sunlight needed by native plants; once established, it displaces native shrubs and mid-level trees needed for bird habitat. Fast-growing Japanese honeysuckle forms thick mats that prevent animal movement. Garlic mustard grows in almost any amount of sun and produces a chemical that inhibits the growth of plants around it, making it easier to crowd out native plants on which wildlife forage. Purple loosestrife, which grows in wet areas, is so aggressive that it can destroy marshes and make waterways impassible. Invasive plants often grow well in disturbed soil, which makes them some of the first plants to germinate after an area is developed.
“Invasive species harm the economy, the environment, and human health”, says Katherine M. Howe, coordinator of the Midwest Invasive Plant Network. “They reduce biodiversity and can even alter the ways the ecosystems function by increasing fire frequency, altering nutrient cycling, or altering hydrology. These ecological changes impact forestry, hunting, fishing, and outdoor recreation.”
Most hunters are familiar with the threats to wildlife posed by pollution, disease, habitat loss, and poaching. However, invasive plant species present a far more insidious threat to America’s wildlife because these plants eliminate food and habitat native birds and wildlife need to survive. In addition, invasive plants are often difficult (if not impossible) to contain and eradicate. To prevent damage to wildlife populations numbers due to the spread of invasive plants, it is essential that hunters and other outdoor enthusiasts educate themselves and take steps to reduce the risk of spreading invasives.
Stop the Spread
Part of the reason invasive plants are so difficult to contain is that they reproduce so well. It is entirely possible to spread invasive plants from one area to another by simply wearing the same boots and hunting clothes as we travel between hunting spots. So it is important that hunters have the knowledge required to prevent the spread of invasive plants. By following a few basic steps, you can greatly reduce the odds of infesting your favorite hunting spot with unwanted invaders.
Recognize Invasives: Every hunter should be able to identify local invasive plant species. Few people know what is happening on a certain parcel of land better than the hunters who spend time scouting and pursuing game in that area. Wild game numbers may suffer if invasives are not controlled, so early detection is key. “Learn to identify the invasive plants in your area and report any new sightings to local land managers,” says Howe.
Invasives vary from one area to the next, so learning about the plants in your area may require some research. Most states have an agency that deals with the spread of invasive plants, so start your research there and report sightings of invasive plants to that agency.
Don’t Spread Seeds: The best way to avoid transplanting invasive plants is to be sure that you do not move any seeds, fruit, or plant parts. This includes cleaning all equipment and gear — small seeds will stick to clothing, boots, backpacks, and even the oil coating on the surface of a freshly cleaned gun. Waterfowlers must take extreme care to clean off boots and waders that have been in water, because it is very easy for seeds floating on the surface of the water to adhere to waders and boots.
Don’t forget your “best friend.” Hunters and dogs that travel to multiple areas in a single day run the risk of spreading invasive plants to different hunting areas. Many invasive plants are referred to as zoochoric, which means their seeds are spread by animals. The fur of hunting dogs is a perfect way for invasive plants to hitch a ride to a new location. A thorough brushing before switching areas is often enough to get rid of any seeds on your dog’s coat. Be sure to check around the buckles on collars, too.
Using livestock such as horses or mules oftentimes requires packing hay into hunting areas. Many states require all feed going into wilderness areas to be certified “weed free,” which means the feed does not contain invasive plants that could damage the ecology of wilderness areas. (Feed grain and hay are tested by the state’s agriculture agency and tagged accordingly for purchase.) The best feed may be what is naturally growing in the hunting area — provided the forage is not an invasive plant. You may need to do some pre-season scouting to determine what feed is available in a particular area.
Avoid Food Plot Problems: Planting food plots for wildlife is not a new concept, but in recent years the popularity of food plots has grown tremendously. When properly managed, food plots can improve wildlife habitat and increase wildlife diversity and populations. Planting invasives in food plots may have a negative impact on the long-term ecology of your hunting area — but that’s exactly what some wildlife managers are recommending. According to Dr. Chris Moorman of North Carolina State University, this can be a very bad idea.
“Hunters should avoid planting species on invasive plant lists,” Moorman says. “In the Southeast, Japanese honeysuckle often is suggested for planting because deer are known to eat it. Yet Japanese honeysuckle is a terribly invasive plant [and is] on just about any invasive plant list; plus, its true value as a deer forage plant likely is exaggerated because of its overabundance.”
Moorman suggests that hunters learn ways to use native plants (or non-native species that are not described as invasive, meaning they do not outcompete and overtake areas). Avoid species such as Japanese honeysuckle, which is listed as an invasive, and non-native plants that have the characteristics of invasive plants (e.g., rapid reproductive rate, spread easily by birds).
There are hundreds of species of invasive plants that pose risks to humans and wildlife. Here is a list of some of the worst non-native plants from across the country that you may encounter while hunting.
Common Buckthorn: This native of Asia and Europe was originally brought to the United States as an ornamental plant. Common buckthorn bushes can grow as tall as 25 feet with small, round leaves and produce black berries that are quickly spread by birds. When buckthorn is established, it quickly grows into dense thickets that crowd out native plants used for cover and food by wildlife. Buckthorn can grow in a variety of soils and thrives in both sun and moderate shade. Since buckthorn was introduced in New England, it has spread as far south as the Carolinas and west to the Rocky Mountains and is common in a variety of habitats.
Small buckthorn plants can be pulled out of the ground by hand, but larger plants generally require cutting and herbicide treatment. When hunting in areas where buckthorn is present, remove buckthorn seeds from clothes and gear to avoid inadvertently transporting seeds out of the area. Because buckthorn is commonly spread by birds, it is best to remove the crop (or craw) and stomach contents of dead game birds like grouse and doves in the field.
Common Reed: Reeds are found around the world, but the European common reed is the most destructive of them all, choking out ponds and lakes, reducing wildlife habitat, and growing to heights of over 12 feet. Abundant reed growth can alter the flow of water in and out of lakes and rivers, and eradication costs are very high. The best way to stop reeds is to not spread them in the first place.
Waterfowl hunters are most likely to come into contact with common reeds. When hunting in lakes and marshes where common reeds can be present, it is important to learn to identify the plants (which is usually easy, considering the height of mature reeds) and avoid transporting their seeds or any part of the living plant. Prevention methods involve washing off waders and cleaning live plant materials off all hunting gear. Also, be sure to give your retriever a thorough washing at the site of contamination — cleaning off reed seeds at your house may result in spreading this obnoxious invasive into nearby waters. Reeds are found across the lower 48 states and thrive in areas with sufficient year round surface water.
Garlic Mustard: This European native ranks among the worst invasive plants for several reasons. First, garlic mustard is very easily spread. Hunters can carry the small black seeds on clothing and gear, and the seeds also stick to the fur of harvested animals and hunting dogs. In addition, garlic mustard grows quickly in disturbed soil. Garlic mustard grows in dense clusters that choke out all but the hardiest native plants. Even worse, garlic mustard seeds can remain viable for up to five years and are highly adaptable, surviving in disturbed and undisturbed soils from Quebec to Georgia and across the Great Plains. Garlic mustard populations are also established in the Pacific Northwest, western Canada, and Alaska.
Garlic mustard, when ground between the fingers, produces a very distinct garlicky aroma. The plant typically grows to a mature height of around three feet and has small, white flowers with four petals. The leaves are kidney shaped. Garlic mustard is very hearty, and pulling plants rarely does anything to slow their spread. Herbicide treatments are the best option to remove established plants. Better yet, avoid spreading garlic mustard to unaffected areas by ensuring that you do not transfer the small, oblong, black seeds.
Purple Loosestrife: The bane of habitat managers across the country, purple loosestrife grows in wetland habitats and quickly overtakes native species. Purple loosestrife was originally brought to the United States from Europe in the 1830s. Dense stands of purple loosestrife alter the flow of water and quickly suppress native species, sometimes irreparably damaging habitat. Loosestrife is exceedingly hard to control, although one solution may be to bring in weevils and beetles that feed on the plant in its native habitat (as the League’s Dwight Lydell Chapter in Michigan is doing).
Waterfowlers must take special precautions not to spread this damaging invasive. Loosestrife grows in stalks with purple flowers that, when fertilized, can produce up to two million seeds per plant. These seeds spread in a variety of ways, including contact with waders and in mud on hunting boots. Be sure to thoroughly clean all of your gear before exiting an area that is infected with purple loosestrife to prevent spreading the small, oval, khaki-colored seeds. Loosestrife can be found across the United States except for the extreme southeast and Arizona.
Honeysuckle: European and Asian honeysuckles are among the most destructive of all invasive plants. Growing either in bush form or as vines, honeysuckle quickly and thoroughly overtakes an area and overwhelms native species. The woody stems of bush honeysuckles make them of little use as forage for wildlife, and the understory of many eastern forests is now overrun with bush honeysuckles. Herbicide treatments are one of the few methods that slow the spread of honeysuckle.
One of the main ways honeysuckle spreads is by birds that carry undigested seeds in their digestive tracts. These seeds are spread into new environments through bird waste. Honeysuckles come in a variety of shapes. The most common are the vine honeysuckles, which form a thick carpet of interwoven vines on or near the ground, and bush honeysuckles, which are woody shrubs. Bush honeysuckles are often easiest to locate in the winter months because they retain their green, elliptical leaves throughout the fall and winter. Honeysuckles can be found across the lower 48, with the exception of the upper Great Plains states.
Learn to recognize the berries (which contain the seeds) of the various honeysuckles and be sure to avoid unintentionally carrying them from one destination to the next. Shrub honeysuckles produce pea-sized, round berries that are red to orange. Vine honeysuckle berries are similar in size and shape but are black. Again, the digestive tract of game birds should be left where the bird was killed.
You can find photos of all of these plants, plus an “Invasive Plant Atlas,” on the Center for Invasive Species and Ecosystem Health Web site.
More articles from the Fall 2011 edition of Outdoor America....