Invasive species: impacts on forests and forestry
Prevention and early detection
Prevention is the first line of defence against biological invasions and is also the most cost effective since once an invasive species becomes established, it is extremely difficult and hence costly to eradicate it. An important first step in prevention is the identification of species capable of becoming invasive, possible susceptible sites and more importantly, the pathways in which they can be introduced. The more comprehensive approach of identifying pathways rather than individual species results in a greater concentration of effort where pests are more likely to enter a country which not only avoids wasting resources elsewhere but also helps in the identification of more species, vectors, and pathways. Once pathways are identified then potential prevention tools and methods can be more specifically developed.
Some of the important tools used to prevent the entry and establishment of invasive species include:
- public information and education;
- risk assessments and environmental impact assessments for intentional introductions;
- national and international regulations on prevention and quarantine measures and their enforcement with inspections and fees;
- treatment of imported commodities, including through fumigation, immersion, spraying, temperature treatment, ultraviolet sterilization, and pressure;
- trade restrictions.
Early detection of alien species should be based on a system of regular surveys - general, site-specific or species-specific, to identify newly established species. Although not all alien species become invasive, the costs of those that do become invasive suggest that a precautionary approach to the issue is best. If alien species are identified early, the chances for eradication will be high in particular because for some invasive species there can be a long lag period between initial introduction and subsequent population explosion. The longer species go undetected the fewer the options for its control or eradication and the more expensive any intervention will become.
Early detection is highly dependent on the capacity of individuals to recognize both native and alien species. As a result, a large component of this step is training, not only of national professionals responsible for surveying but also for any persons that spends time in the natural environment such as farmers, gardeners, forest workers, ecologists, tourism workers, photographers, hikers, etc. Trained professional national workers should be able to not only recognize native and alien species and the ecological effects of alien species but also they should be able to use databases, keys, manuals and other identification sources. Early warning systems which include lists and datasets of recorded or potentially invasives, in given countries, time sets and conditions are important tools in this regard.
Finally a contingency plan outlining the actions that should be taken once an alien species has been identified or an invasion is suspected, should be developed.