If you’re interested in invasive species, you’re likely familiar with their ubiquitous effects, impacting our lives from the economy to human health, and our specialty – the environment. Taking on invasive species can at times seem an impossible task, but LIISMA is up to the challenge. With specific strategies, we carefully prioritize our work to achieve the greatest impact, and you can too. By learning these tools, you can tackle invasives like a pro.
The Tier System
Starting in 2017, invasive species in New York State have been classified into tiers to reflect abundance, impact, and priority. This system was formalized by the PRISM network, state agencies, and New York Natural Heritage Program. Lower tiers reflect lower abundance from Tier 1: those not yet present, Tier 2: invasives that have just arrived, Tier 3: those in widespread abundance, Tier 4: well established species you’re likely to have seen, and Tier 5: species we need to learn more about. Let’s dive into the details of each tier and their significance.
Species with high, very high, or potentially high impacts:
Tier 1:
- Distribution: not present
- Goal: prevention and early detection
High impact species that are not yet in LIISMA are Tier 1. This is the highest level priority for invasive species management. Any potential occurrences regardless of location should be managed. Pathways should be investigated and managed to resist and prevent potential invasion. Our Early Detection and Rapid Response (EDRR) Manager at LIISMA practices “horizon scanning” to look out for species that may be on their way to our region, so we are prepared to respond if they do. We aim to prevent the introduction of Tier 1 species since prevention is the best and most cost effective way to minimize the impact of invasive species.
Tier 2:
- Distribution: low
- Goal: Regional eradication
High impact species with low enough distribution to make eradication possible are Tier 2. Surveys and community science reports through iNaturalist or iMapInvasives are necessary to understand their distribution. All occurrences regardless of location should be managed, though invasives present on private property at this level pose a challenge for eradication. Our EDRR Manager works to analyze reports of species we consider to be Tier 2’s and get our boots on the ground in the field to investigate, remove, or collaborate on removal of these species. Our Education and Outreach Manager promotes awareness of these species through presentations and fact sheets soon after their introduction with the goal of preventing their introduction and spread. iNaturalist and iMapInvasives reports for species in this tier are highly valuable in informing regional management!
Example: LIISMA collaborates with local agencies to control two populations of small carpetgrass (Arthraxon hispidus) across Long Island. With only two known populations, we have the power to fully eradicate it and prevent this moisture-loving grass from becoming the next stiltgrass (Microstegium vimineum, Tier 4)!
Tier 3:
- Distribution: widespread
- Goal: containment
High-impact species that are too widespread in LIISMA to fully eradicate, but low enough in abundance to consider local or regional containment are Tier 3. Targeting strategic management will slow the spread around the region. We may also consider efforts to exclude Tier 3 species from high quality natural areas. Our team collaborates with local partners to contain these widespread species. Our Conservation Area Manager works to suppress these species in highly biodiverse areas and prevent introduction where they are not yet present. Public awareness of any given invasive species typically begins around this stage.
Example: Our work managing floating water primrose at Artist Lake reduces the likelihood of its spread to the nearby Carmans River, thereby preserving recreational access and native biodiversity. In a few short years of management, we have begun to observe the native water primrose (Ludwigia palustrus) returning to Artist Lake!
Tier 4:
- Distribution: well established
- Goal: local control
High impact species that are well established are Tier 4. Unfortunately, eradication at the regional level is not feasible. Land managers may consider localized management to contain, exclude, or suppress these at a local level, especially when distribution is limited on a particular site despite high regional abundance. The LIISMA team provides guidance and training to local land managers to equip them with tools and recommendations for managing these species at their respective sites. Our Conservation Area Manager also works to suppress small populations of Tier 4 species in highly biodiverse areas and prevent introduction where they are not yet present. Our Education and Outreach Manager often fields questions about well known Tier 4 species when educating the public.
Example: Though phragmites (Phragmites austrailis) is widespread in Long Island’s wetlands, it poses a particularly strong threat to our coastal plain ponds. These rare, threatened ecosystems are home to several rare and endemic species, like the banded sunfish and tiger salamander (NYNHP). Managing small stands of phragmites suppresses populations to a reasonable level while still maintaining ecosystem structure and function as well as the high levels of biodiversity. After one or two seasons of spading or underwater cutting small populations of phragmites at coastal plain ponds, most stands show signs of stress and reduced density. LIISMA also monitors the native plant communities at these sites to determine impact of management efforts and notes that the native plants seem to thrive there!
Species with medium, low, or unknown impact:
Tier 5:
- Distribution: may vary
- Goal: research
Species of unknown impact and/or distribution that need more research, mapping, or monitoring to understand invasiveness are Tier 5. This includes naturalized species and species only present in cultivation that are predicted or known to be invasive in other regions. LIISMA investigates species with unknown impacts and distribution and relies on research by experts in the field to inform us about these species. This tier may also include what are called “sleeper species” – non-native species that are already present in an ecosystem but not currently causing significant ecological disruption, yet have the potential to become invasive if environmental conditions change, allowing them to rapidly increase in population and negatively impact the ecosystem (Invasive Species Center).
Taking Action
By getting familiar with these tiers and what they mean, you can gain insight into how LIISMA prioritizes protecting the whole region from the impact of new invasive species. It can help inform your work too. So how should concerned volunteers and land managers use the Tier System to maximize the impacts of their efforts?
Now that you’re an expert on the Tier System, you can keep your eyes out for our priority species wherever you go. Check out our LIISMA Emerging Invasives Fact Sheets and be sure to report any you find on iNaturalist or iMapInvasives. These actions will help protect Long Island as a whole, from Staten Island to Montauk!
Generally, following the regional invasive species tiers will point you in the right direction on how to prioritize your own invasive species management. Land managers and volunteers can use this system on a smaller scale to protect ecosystems, too. Regardless of its regional distribution, if a new invasive species arrives at your site, you can address it similarly to how LIISMA would treat a Tier 2 – by prioritizing its removal and eradication before it has a chance to establish and spread. If there’s a species that is only present in a few small populations at your park or preserve, working on suppressing it as we would a Tier 3 species will prevent its spread and protect high quality areas. Lastly, if there’s a species that’s everywhere on your site, there’s a good chance it’s both regionally and locally considered a Tier 4 species. Manage this one where it threatens conservation targets, and other locations when you have assistance or extra time on your hands.
Who knew the most powerful tool to address the threat of invasive species wouldn’t be a chainsaw, root-popper or machete – but a strategy to prioritize! Let us know if you found this helpful or want to know more about a particular invasive species topic.
Are you looking to get involved and make a difference through invasive species work? Join us at the kickoff webinar for our Invasive Species Spotters volunteer training program. As an Invasive Species Spotter, you can protect biodiversity by helping LIISMA priority invasive species quickly – learn more and register here!
