An invasive plant species is a non-native organism that takes root in a new ecosystem and starts causing trouble. Before they become invasive, the species of plant or animal may have been brought into the country intentionally, sometimes unwittingly, before eventually becoming invasive.
Bear in mind that many of our plant species were introduced into the country as crops, e.g., wheat, tomato, and rice. However, others were intentionally brought in as ornamental or landscaping plants or were unintentionally introduced with shipments of grain and other produce. For example:
Purple loosestrife (Lythrum salicaria)
- Native to Europe and Asia
- It was introduced to the United States during the 1800s as a medicinal herb and as a contaminant in shipments of ballast.
- For over a century it was a harmless species within habitats then it went rogue and became an invasive species.
Water hyacinth (Eichhornia crassipes)
- Native to South America, specifically the Amazon basin of Brazil, Venezuela, and Peru.
- Introduced to the United States in 1884 as an aquatic ornamental plant.
- For over a century, water hyacinth remained ‘under the radar’ and was eventually listed as an invasive species in the 1980s.
Kudzu (Pueraria montana)
- Native to Asia
- Brought to the United States in 1876 as an ornamental plant and was used from the 1930s to 1950s for soil erosion control.
- Kudzu was listed as an invasive species in the 1990s.
Whatever the route of their introduction, it is only when the introduced species damages the surrounding ecosystem by crowding out other organisms and altering the habitat that it becomes invasive.
How can you detect an invasive plant?
It is hard to predict if an introduced species will become invasive and a threat to the habitat or ecosystem. A reasonable, but not perfect, predictor of behavior in a new place is behavior in the place of origin (the home range).
- Bad behavior at the place of origin may indicate that the plant is likely to behave badly in its new habitat.
- Be mindful that not all non-native plants become invaders. In fact, most non-native invaders do not become problems. They become naturalized and fit into their new habitats as they did in their place of origin.
- In addition, not all invasive plants are non-natives. Some are natives that ‘go rogue’ and become invasive. For example:
- Common waterhemp is native to North America but has become an invasive weed of agricultural fields, stream banks, and flooded areas in many states.
- Many pigweed species are native to North America and have become invasive in agricultural habitats.
- To be successful, an invasive plant needs to produce several seeds, or propagules,that are deposited a distance away from their original location.
What does a successful plant invasion look like?
- First, a successful invasion is a rare event. How rare? It is estimated that 10% of species pass through each transition from being imported, to becoming introduced in the wild, to becoming established, and finally to becoming an invasive plant.
- Second, a successful invasion requires that a species arrives, establishes, reproduces, spreads, and integrates with other members of a plant community.
- Third, naturalized species are those that can persist solely through reproduction but are not necessarily increasing in distribution.
- Fourth, to become invasive, a naturalized plant must be able to disperse and withstand the environmental conditions of its new habitat.
- Fifth, there is usually a lag between the time when a species is introduced and when its population growth explodes. The time lag phase usually lasts from 20 to 100 years.
If left undetected, invasive plants can have devastating effects on the environment, our livelihoods, the economy, and more.
The impact of invasive plant species.
According to the USDA, invasive species have contributed to the decline of 42% of U.S. endangered and threatened species. In addition, invasive plants can:
- Compete directly with native species for moisture, sunlight, nutrients, and space.
- Cause a decrease in overall plant diversity within a habitat.
- Degrade wildlife habitat.
- Reduce the quality of agriculture lands.
- Degrade water quality.
- Increase soil erosion.
- Decrease recreation opportunities.
These impacts change nature’s balance on which all species depend.
This means that invasive plants is everyone’s problem and we must take on the responsibility for their mitigation.
Combating invasive species
In 2004, the U.S. Department of Agriculture Forest Service unveiled a national strategy to prevent and control the threat of invasive species and non-native plants in the United States.
In 2010, the USDA Forest Service developed a national strategic framework for invasive species management. The strategy includes programs which provide a consistent approach to the prevention, detection, and control or management of invasive species, and the restoration of affected habitats.
- Prevention: Identify, forecast, and prioritize invasive species threats and recommend and implement appropriate actions to prevent introductions and establishment.
- Detection: Survey aggressively to detect new invasive species and monitor priority species. Report invasive species detection findings in standardized databases. Develop tools and technologies to detect and monitor invasive species.
- Control or Management: Develop tools, technologies, and methods necessary to prioritize and implement effective invasive species management or eradication activities.
- Restoration and Rehabilitation: Develop, synthesize, and evaluate effective rehabilitation and restoration methods, tools, and technologies.
Other attempts at mitigating the impact of invasive species include raising awareness.
Invasive species awareness campaigns
Understanding how and when invasions occur is complicated by the fact that most invasions fail. Furthermore, it is difficult to identify successful invaders during the important early stages of an invasion.
Being aware of the issues regarding invasive species through organizations that host events like the National Invasive Species Awareness Week (NISAW) helps keep a spotlight on the importance of invasive species. NISAW is an international event to raise awareness about invasive species, the threat that they pose, and what can be done to prevent their spread.
NISAW is observed during the last week of February each year. The commemoration aims to shed light on the recognized impacts, prevention measures, and invasive species control. It also celebrates individuals and organizations creating a sustainable, biodiverse ecosystem.There are events held across the globe during this observance to create awareness of the dangers of invasive species.
INVASIVE PLANTS ARE EVERYONE’S PROBLEM.
SPREAD THE WORD, NOT THE INVASIVE PLANTS!
USDA Forest Service
- Benefits of the Fine Line: Aquatic Organism and Alien Plant Invaders
- Control Invasive Aquatic Plant Species
- The Importance of Forest Vegetation Management
- Staying a Step Ahead of Invasive Weeds in Pasture
- USDA Forest Service. Forest Service National Strategic Framework for Invasive Species Management.[Accessed, December 2, 2022].
- USDA Forest Service.Invasive Plants. [Accessed, December 2, 2022].
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