Invasive plants are exotic or non-native species that have displaced native plants in their own ecosystems and consequently damaged (simplified and/or depauperated) those natural habitats. An invasive plant can take over a new area because the insects, diseases, and foraging animals with which it coevolved, and which kept its growth in check in its native range, are missing from its new habitat. This gives the invasive species an ecological advantage over native species.
Before labeling a plant invasive, regional nonprofit organizations study natural habitats to determine the extent of harm done by that species. The term invasive is not assigned lightly.
Many native plants can be aggressive in urban/suburban landscapes, usually because of disturbed soils, but by definition native species are not invasive (although they might be labeled noxious). While most exotic plants are not invasive, any aggressive exotic could become so, given enough time.
Invasive species are problematic because they:
- Outcompete, weaken, or kill native plants that are needed to support local wildlife.
- Often do not supply the kinds of habitat services – food, cover, nesting sites – that native plants provide.
- Disrupt both natural and urban ecosystems
- Divert millions of public and private dollars for their control.
In addition, large-scale invasive plant removal efforts may include the use of power tools and large machinery, which have their own climate footprint. Disruption of the soil during these efforts releases sequestered carbon as co2 into the atmosphere. And the use of herbicides may damage remaining plants and animals as well as complicating the needed ecosystem restoration after the removal is completed.
Learn to identify local invasive plants (and animals). Each region has its own set of invasive species. What’s invasive in Florida will not be the same as in Massachusetts or British Columbia. There are many resources for plant identification including books, extension agents with their Master Gardeners, social media, and native land societies or invasive plant councils.
It is also helpful to know what plants are growing on your property or on community lands so that plans can be made to remove invasive species as soon as possible and to encourage the native plants, which will help make that property an important part of the effort to protect wildlife and pollinators.
Work to eliminate invasive plants from your landscape. Remove the plant sin question by using the most sustainable methods. If it’s a tree, girdling the trunk (removing a three-inch strip of bark around the total circumference near the bottom of the trunk) can be a good option, because this requires no fossil fuels or toxic chemicals, and the remaining snag will become habitat for birds and more. (Be careful about doing this with trees growing near a building.) For shrubs and herbaceous plants, the solution is likely to be more complex. We recommend consulting with a local invasive plant council or natural resources department to get specific instructions and guidance.
Any plant material that is removed from a property should be properly disposed of, which usually means either burning or bagging it for the landfill.
Plant material from weedy herbaceous invasives may harbor huge numbers of seeds or viable runners that could start whole new populations if they just go to a municipal yard waste facility or are added to backyard compost piles or bins, which do not generate enough sustained heat to destroy seeds.
Some people bring in goats, which can be hired for a time period, to get rid of invasive plants, but goats will eat anything and everything, so some controls are necessary. Goats do solve the problem of disposing of the plant materials, though.
Participate in workdays to help remove invasive plants from parks and other public wildlands. Volunteering for invasives workdays offers great opportunities to make a real difference in the local ecosystem; volunteering also provides good learning-by-doing education on the local flora and fauna. In addition, fellow participants may open doors to new educational opportunities or to new sources of locally produced native plants.
When you see invasive plants for sale, say something. Despite their damage to local ecosystems and the multi-millions of dollars spent on their eradication, many known invasive plants can still be found for sale in garden centers and big box stores. For the most part, it is legal to sell them. However, unsuspecting homeowners and commercial contractors may not have any idea of the potential for harm, especially because these plants have been so widely accepted and used as landscape plants for many decades. When informed of invasive plants’ capacity to displace valued native species, most people choose to avoid buying or using them.
Important caveat: There are claims that some cultivars of invasive plants are sterile and therefore harmless. This has been proven to be mostly false, as these cultivars eventually change into fertile forms that can interbreed with the native population. We need to completely abandon using any plants that have proved to be invasive. In addition, we should be looking into ways to identify and discontinue using any new plants that show likely potential for invading our natural areas.
It is commonly understood that invasive species cause problems for the environment by out-competing less aggressive species and thereby disrupting the working balance of relationships within established ecosystems. From the standpoint of climate change, invasive plants matter in several other ways too. First, every region needs stable, resilient ecosystems to keep ecosystem services working smoothly, and this is especially important as climate change stresses all ecosystems. And second, the cost of controlling and removing invasive species can be huge. This is true not only in terms of money spent, but also in the consumption of fossil fuels (getting crews to and from job sites, running equipment and tools), the application of herbicides (with their likely toxic effects) and, an often overlooked consequence, the emission of co2 in all of these activities.
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Excerpted from Climate-Wise Landscaping by Sue Reed and Ginny Stibolt, copyright © Sue Reed and Ginny Stibolt, 2018. Used with permission from New Society Publishers.