Ecology and Management of Invasive Alien Species: Management

There are a large number of specific methods to control invasive species. Recognizing the highly complex nature of invasives ecology and the importance of local conditions, general statements about suitable control methods for groups of alien species, in specific habitats or world regions should be approached with great caution. Precise predictions of the behaviour, spread, and impacts of non-indigenous species introduced into new environments are not available, because too many of the parameters used to describe the situation are no more than informed guesses. In many cases even the taxonomic status of the invasive species is uncertain. However, descriptions are available of methods used to control certain species and their effectiveness under specific environmental factors. These experience-based reports are essential for invasives management and need to be made increasingly available, for example in databases accessible through the Internet. The goal of anyone involved in invasives management should be to use the best practices available and to disseminate information to serve the higher goal of preserving the earth's biodiversity and mitigating problems caused by invasive organisms on a worldwide scale.

In most cases the best practice to manage an invasive species may involve a system of integrated management tailored for the species and the location. Thus, it is important to accumulate the available information, assess all potential methods, and use the best method or combination of methods to achieve the target level of control. Always bear in mind that managing an invasive species is not the management goal, but only one tool in the process to achieve a higher goal, such as habitat restoration, preservation of an undisturbed ecosystem, re-installation of the natural succession rate and time, etc. These intact areas can provide sustainable use of ecosystem services to humans. As previously indicated these higher goals need to be clearly defined and quantified, and when planning a control programme it is worth setting a time scale for achieving these goals, with benchmarks and perhaps indicators if possible.

The successful control of the population of an invasive species itself can have indirect effects on native species, the ecosystem, and the entire local biodiversity. The potential effects of reducing or eradicating the invasive species in a habitat should be evaluated beforehand and measures taken to ensure that these effects are solely positive. For example, removal of an aggressive invasive plant from a site might need to be accompanied by planting of indigenous species to fill the gaps, to prevent these gaps being filled by other unwanted plants (cf. Case Study 5.31 "What Can Happen When an Invasive Alien Species is Controlled").

Below are briefly listed the control methods for dealing with biological invasions.

• Mechanical control

• Chemical control

• Biological control

  1. Biopesticides

  2. Pathogens for control of vertebrates

  3. Biological control of freshwater and marine targets

  4. Biological control of plant diseases

• Habitat management

  1. Prescribed burning

  2. Grazing

  3. Changing abiotic factors

  4. Hunting and other use of non-indigenous species

• Integrated Pest Management (IPM)