Invasive plants are non-native species that reduce native biodiversity, alter habitats, impact the economy, and pose significant threats to ecosystems.
The task of managing invasive plants can quickly become overwhelming due to their aggressive establishment and the time, money, and persistence required to achieve positive outcomes. One practical approach is to use triage, an assessment practice that prioritizes invasive species management strategies by the degree of ecological damage to the site and the economic resources required for management.
This paper explores the fundamentals of a triage approach to invasive plant management, including its components, challenges, and implementation strategies for effective invasive species management. This approach can be applied to both terrestrial and aquatic habitats.
Widely used in medical contexts to prioritize patient treatment based on severity, triage can be adapted to habitat management and restoration. Triage consists of systematic assessment, prioritization, and strategic treatment of affected areas, with the goal of increasing native plant and animal biodiversity. Two main actions inform a triage approach to invasive plant management.
-First, identify the habitats at risk from invasive plant populations.
-Second, select areas for intervention where the greatest biodiversity outcomes can be achieved with the fewest resources.
Steps of a triage approach
Prevention, early detection, and rapid response
Preventing invasive species from entering and establishing in new areas is critical. Identifying and controlling small infestations before they can establish
and expand is more effective than managing existing, large infestations.
Prevent the introduction of new invasives by:
- Educating the public and employees about how invasive plants spread;
- Educating boaters to prevent the spread of aquatic invasive plants by using the Clean, Drain, Dry method (Figure 1);
- Ensuring equipment does not contain fragments or seeds of invasive species before transporting to a new location;
- Obtaining mulch or fill from reputable sources that are not infested with invasive species;
- Preventing current infestations from going to seed.
Assess the populations of native and invasive species
Before initiating a management program, assess the plant populations at each site. What are the current and desired conditions and expectations for each site? Be as thorough as resources allow.
- Assess and understand the site conditions (e.g. soil characteristics, water quality, light and moisture conditions, disturbance);
- Properly identify both the native and invasive plant populations; assess the abundance of each at the site to help prioritize management;
- Understand vectors for seed or propagule spread of both native and invasive species;
- Keep detailed records of plant populations at each site and document changes in species and abundance over time;
- Use the resources listed in Table 1 to assist with identifying site conditions, critical habitats, and information about specific species.
| National Diversity Database Map: | Connecticut Department of Energy and Environment (DEEP) Protection offers maps of every town in Connecticut, showing locations of critical habitats and where state or federally listed species are present. |
| Connecticut Environmental Conditions Online | This map database provides maps by town, including soil types, drainage, topography, and water quality classifications, among others to inform management decisions. |
| US EPA Ecoregions Maps | The ecoregions maps categorize the United States into regions based on ecosystem characteristics to assist with restoration strategy. |
| Connecticut Agricultural Experiment Station Office of Aquatic Invasive Species Web app | This tool provides up-to-date information on aquatic invasive species throughout the state. |
| Connecticut Invasive Plant Working Group and UConn IPM | These websites contain resources for invasive plant identification and management. |
Table 1: Additional resources to assist with site assessment, identification of invasive species, and habits at risk.
Set management goals
Identify what you want to achieve:
-Slow the spread, reduce the abundance, or eradicate invasive plants at a given site?
-Increase native species biodiversity, expand access for recreation, improve visibility on roadsides?
Set realistic goals based on economic circumstances and access to available resources (time, labor, equipment). Management goals can be specific to a site or more broad for multiple sites.
Prioritize sites
Use the worksheet in Table 2 to determine your priority sites and/or priority species at each site.
| Species: | |
| Area: | |
| 1. How large/size of the undesired invasive plant population? | |
| 1 | None, but there is a substantial population is nearby |
| 2 | Covering ≤ 25% of the area and spreading |
| 3 | Covering ≤ 50% of the area and spreading |
| 4 | Covering ≥50% of the area and spreading |
| 5 | Covering the whole area completely |
| Q1 Score: | |
| 2. Value of the habitat being invaded? | |
| 1 | An important habitat with high biological diversity |
| 2 | A habitat with some dominant native species |
| 3 | A degraded habitat or area of low diversity |
| Q2 Score: | |
| 3. Impacts of invasive plant presence? | |
| 1 | Altering the biodiversity of an area so much that few native species are present |
| 2 | Invading undisturbed areas and outcompeting native species |
| 3 | Not outcompeting native species, but natives don’t regenerate |
| 4 | Invading disturbed areas like edges |
| Q3 Score: | |
| 4. How hard is it to control? | |
| 1 | One targeted and appropriate treatment to reduce population |
| 2 | Requires multiple treatments in-season to manage, but population can be reduced to allow for continued growth of desired native plants |
| 3 | Requires multiple treatments and native plants don’t re-establish or come back readily |
| 4 | No effective treatment has been identified |
| Q4 Score: | |
| Total: |
Table 2. Criteria and factors for prioritizing invasive species management (adapted from Jacquart 2009). At each site, complete this worksheet for each identified invasive species to determine the priority sites and/or priority species at each site. Add the total points for each species. The lower the score, the higher the priority of action required.
Prioritize management areas by considering where the most significant biodiversity outcomes can be achieved, with the fewest available resources.
Evaluate each site to determine:
- the ability to achieve effective control of an invasive plant population (Figure 2);
- the impact invasive plants have already had on the site; and
- the health of native species/communities at the site.
A low priority site might be one that is difficult to access, where the invasive population will not be easily managed, the native habitat is already degraded, and/or management may negatively impact existing native species.
The existing native seed bank is an important consideration. How long the invasive species have inhabited the area may affect the viability of the native seed bank. Once the invasive species are removed, what species are likely to reestablish the area? If the answer is more invasive species, the site will require more active monitoring and maintenance.
A high priority site may be one that is easily accessed, where the invasive population can be effectively managed, the native habitat is not completely degraded, and control measures will not harm the existing native species.
Considering where the greatest biodiversity outcomes will be achieved is not always straightforward at the beginning of the triage process. However, identifying possible outcomes before management begins can help to prioritize resources.
Determine specific management strategies
Once priority areas are established, management strategies should be tailored accordingly. The appropriate management strategy will vary by species, location, time of year, and potential negative impacts on native species. It is critical to properly identify the best management strategy for the site and for the species you are targeting. Follow an Integrated Pest Management (IPM) approach - consider all management options, including mechanical, chemical, cultural, and biological. Research strategies or speak to other land managers to determine best practices that are sustainable and make economic sense for each location or circumstance.
Implement management practices at high priority sites first
After evaluating the ecological and economic impacts and developing a targeted management strategy, begin work on the identified high priority locations. This process might require two to three years of repeated active maintenance to achieve desired results. Ongoing monitoring of the site is crucial, allowing adjustment of management strategies based on real-time outcomes or changing environmental conditions.
Restore ecosystem services
Monitor for the return of native species. If necessary, facilitate habitat restoration by planting native and ecologically important species. Native plants can be established by seed, plugs, container, or bare root plants. Revegetation method will depend on the site conditions, resources, species, and goals. Consider implementing competitive exclusion or the planting of aggressive native species to outcompete the return of invasive plant populations.
Target low priority sites as resources allow
Sites identified to be of reduced priority might be maintained through less intensive methods (such as preventing invasives from setting seed by repeated mowing or cutting vines that are strangling mature trees). These efforts may be all that can be accomplished at low priority sites. Organizing and scheduling groups of volunteers for mechanical pruning or removal methods should be completed on an annual basis, at a time of year when these strategies are effective. If resources don’t allow for maintenance at low priority sites, continue to monitor invasive populations for change overtime.
Challenges to Consider
As with any habitat management strategy, challenges will emerge. A triage approach may require more initial time and effort to plan systematically and allow for staff training as they adjust their approach. Identifying and assessing plant species before and after treatment can be arduous, but it is a critical component of the triage method. Consider hiring professional surveyors.
Deer and other herbivores also present a challenge to habitat restoration; they browse on native species more frequently than invasive species, and can contribute to the decline of native plant populations. When attempting to maintain or reestablish native habitats, a critical component is to identify ways to reduce herbivore browsing. Examples include caging to protect new plants, adding exclusion fencing, or using slash walls.
Implementing effective management activities can be overwhelming and difficult to employ when multiple invasive species are identified, or labor and financial resources are limited.
The triage method maximizes resource efficiency and effectiveness by focusing efforts where they have the most significant impact. Approaching invasive plant management systematically and incorporating triage as part of the overall strategy will produce more attainable outcomes.
Action will always be better than inaction when it comes to reducing invasive plant populations. Using the triage method to assess and develop an action plant will guide efforts to successful invasive plant management.