The forests of the southeastern United States are increasingly facing the impacts of non-native invasive species (plants, animals and pathogens). Many invasive plants affect forest health, productivity, access and use, and forest management costs, and limit species diversity on millions of acres of southeastern forests. These plants displace native plants and associated wildlife, and can alter natural processes such as fire regimes and hydrology. As foresters, landowners and land managers, we must be proactive and meet this issue head-on to maintain the health, function and long-term productivity of our forests.
Images of Forest Invasions
|PHOTO 1: Cogon grass (Imperata cylindrica) invasion in pine stand, Central Florida.|
|PHOTO 2 (right): Old World climbing fern (Lygodium microphyllum) invasion in Southeast Florida cypress stand. (Image courtesy of USDA ARS Photolab)|
|PHOTO 3 (left): Air potato (Dioscorea bulbifera) invasion in Central Florida mixed hardwood stand.|
|PHOTO 4 (right): Japanese climbing fern (Lygodium japonicum) invasion in northwest Florida pine plantation.|
|PHOTO 5 (left): Kudzu (Pueraria montana var. lobata) invasion in the Eastern United States. (Image courtesy of www.invasive.org)|
|PHOTO 6 (right): Melaleuca (Melaleuca quinquenervia) invasion in Southwest Florida pine flatwoods.|
Non-native invasive plants are essentially "weeds in the woods" (or in other natural areas). The two characteristics are:
Non-native: Plants which are not originally from Florida/United States, these plants are often introduced intentionally or accidentally by human activity. The most common sources of plant introduction in Florida are: import for ornamental/horticultural purposes, introduction for agricultural purposes (forage, erosion control, etc.), and accidental introduction. Approximately one-third of the plant species growing on their own without cultivation in Florida are non-native.
Invasive: Invasive plants are plants which escape cultivation, become established in a forest or natural area, and start expanding and reproducing on their own. Once established, these plants often alter native plant communities, out-compete and kill native species, or otherwise affect natural ecosystems.
Why Should I Care About These Plants?
There are many reasons to be concerned about the expanding problem of invasive species. Whether your primary interest in forestry is timber production, aesthetics, recreation, wildlife, or a combination of many benefits, all aspects of forest management can be affected by these plant invasions. For example, approximately 46 percent of the federally listed threatened and endangered species in the United States are considered to be imperiled in part due to impacts of invasive species. Economists have estimated that across the globe, $3-5 trillion may be lost annually to the impacts and management of invasive species (this figure includes impacts by introduced plants and animals, diseases, agricultural weeds and others).
Several of these species either possess the potential to, or have already begun impacting various forest product industries. An established example is that of Kudzu, which infests an estimated 7 million acres in the southeast, and costs approximately $500 million dollars in lost farm and timber production annually. The most recent example of this is the impact the Japanese climbing fern infestations have begun to have on the pine straw production industry in Florida. Pine straw producers have had to abandon leased pine stands in some cases where the Japanese climbing fern infestation made harvest of a clean and legally saleable product impossible.
As a state, Florida is at a high risk for invasion for many reasons. Our subtropical climate, the number and importance of our shipping ports, the extent and importance of the plant-based industries in the state, and the highly transitional population, couple with other factors to facilitate introduction, escape and spread of these problem plants. In Florida, approximately $30 million taxpayer dollars are spent annually on invasive plant management on natural areas and waterways.
How Do These Plants Get to My Forest?
Invasive plants are spread in many ways:
- Humans through movement of equipment, and/or soil contaminated with seeds or roots
- Wildlife (especially deer and birds)
- Water and wind
Forest managers need to be aware of how our actions can promote the spread of these plants. Many forestry techniques involve soil disturbance (e.g., harvesting, site prep, planting) and alteration of the canopy (e.g., harvesting) which affects sunlight and water penetration to the soil level. These activities may aid in the introduction or spread of these species on your property.
Where Might I Find These Plants on My Forest?
Generally the first place you find these plants is in areas of human activity, such as: forest boundaries, common dumping sites, old home sites, roadways and ditches, disturbance areas (timber sales, mining sites etc.), and firelines.
Managing Invasive Plants
There are many reasons to start controlling these plants on your property. There are both economic and environmental benefits, such as: reducing further spread on your property and expansion of your problem, maintaining the ability to produce forest products on your property into the future, restoring natural communities and/or forest health, and complying with state and federal laws.
Preventing Invasion on Your Property
Management of non-native invasive plants should use an integrated pest management approach, incorporating mechanical, chemical, cultural and biological techniques in combination. However, the first and best step to take, when possible, is to prevent the introduction or spread of these plants onto your property by making management decisions that consider the presence or movement of these plants.
Identification and Control Guides
Another important step is to learn the key problem plants for your area. There are different preventative action and treatment approaches for each invasive species. By knowing your "enemy" you can choose the most effective and efficient approach in managing these plants. Several books, websites, and other publications are available.
Invasive Plant Laws
Some of these plants are regulated by state, federal, or local government. respective invasive plant laws that pertain to Florida.
EDDMaPS Invasive Species Mapping System:
Report non-native invasive plants in Florida's Natural Areas: http://www.eddmaps.org/florida/
Prescribed fire, a critically important forest management tool, may contribute to the spread of some invasive species such as cogon grass, Japanese and Old World climbing ferns, and melaleuca, while negatively impacting others. However, the specifics of the relationship between fire and invasive plants in land management have not been adequately quantified. A commonly referenced species which can be readily transported or promoted through techniques such as: discing, skidding of timber, chopping, fireline establishment, prescribed burning, and road maintenance, is cogon grass, a highly problematic species in Florida and southern Alabama which is slowly expanding its range in the southeast (Shilling et al. 1998).
Florida Invasive Species Partnership website
FloridaInvasives.org is an online resource of management assistance programs to help in your fight against problematic plant species. The Florida Invasive Species Partnership has created the website to help connect Florida's land owners and land managers with the best invasive species management programs available. These programs have been collected, evaluated and categorized in a single resource to make it easier for you to find the financial and/or technical assistance that meets your personal needs.