Invasive species are one of the most significant environmental issues in many ecosystems. They can reduce biodiversity, degrade habitat, and transform ecosystems to less robust and less desirable states.
Most invasive species do not spread randomly and often move along corridors through suitable habitat. For example, roads and trails through forests can often allow new species to spread into the adjacent forest. Invasive species are much more common near these corridors than farther from them. Invasive species often also need some type of soil or canopy disturbance to increase light and open up empty sites in the soil.
Corridors Can Spread Invasive Species to New Areas
Forest roads are excellent corridors for seed spread by vehicles and wind.
Trails can disperse seeds on hikers' boots, animal feet, and by water runoff.
Creeks and other waterways can spread seeds long distances to other low-lying areas.
Disturbances tend to Encourage Invasive Species
Timber harvesting creates soil disturbance allowing new seeds to germinate and canopy openings that provide more light to the understory.
Treefalls due to storms or natural mortality create canopy gaps that increase light and can also cause soil disturbance from increased water runoff.
Flooding along creeks, lakes, and in low-lying areas allows many seeds to float on the water surface to new areas. When the water recedes the seeds are left behind in moist, high-nutrient soil where the previous vegetation has often been washed away.
Early Detection and Rapid Response (EDRR) management of invasive species is recommended by the USDA and other agencies. This involves preventing new invasions before they happen and eliminating new invasive species when they first arrive at a site. This is much more cost-effective than trying to eradicate large, well-established invasions.
To practice EDRR land managers need to locate new invasive species when they are still rare. This requires having some idea of where to search for new invasive species. Models that can predict what areas are most likely to be invaded can help land managers focus their search efforts.
We are developing a predictive model to predict what locations on a given property are most likely to be invaded by new species. We use a geographic information system (GIS), computer software that allows visualization and analysis of spatial patterns, and existing data on corridors and environmental conditions to predict the most likely areas for new invasions. We have used the invasive forest grass, Japanese stiltgrass, as an example invasive species to develop this model, but we hope to generalize it to invasive species in general.