Ecology and Management of Invasive Alien Species: Management

The first step of a management programme is to assess the current situation by determining the management goal, the extent and quality of the area being managed, the invasive target species affecting the area, and the native species threatened. The management goal should be the conservation or restoration of intact ecosystems that support the delivery of ecosystem services. Eradication and control options need to be evaluated on the basis of the likelihood of success, cost effectiveness and any potential detrimental impacts.

Invasive species need to be arranged in a priority list that takes into consideration the extent of the area infested by the species, its impact, the ecological value of habitats invaded, and the difficulty of control. Species with the highest priority would be those known or suspected to be invasive but still in small numbers, species which can alter ecosystem processes, species that occur in areas of high conservation value, and those that are likely to be controlled successfully.

1.  Initial Assessment

The first step is to determine the management goal for any invasives management project. Second, the target area needs to be defined. It may be an entire country, all or part of an island, or all or part of a reserve or conservation area. In some instances regional projects will include more than one country and need good co-ordination between countries. Thus, it is often advisable to base an eradication or control programme of alien species on an ecosystem, which may cross-political boundaries. However, sometimes the political situation might prohibit this approach.

2.  Priorities for Management

Priority setting is considered principally from the viewpoint of ecosystem and species values. However, managers should recognize that political and public support and the availability of external support may drive a pest specific project that might not be a priority from this more rigorous viewpoint. Priorities are set in the hope of minimizing the total, long-term workload, and hence cost of an operation, in terms of money, resources and opportunities. Therefore, we should act to prevent new infestations and assign highest priority to existing infestations that are the fastest growing, most disruptive, and affect the most highly valued area(s) of the site. We also consider the difficulty of achieving satisfactory control, giving higher priority to infestations we think we are most likely to control with available technology and resources.

The priority-setting process can be difficult, partly because you need to consider so many factors. It has been found that it helps to group these factors into four categories, which you can think of as filters designed to screen out the worst pests:

• current and potential extent of the species on or near the site;

• current and potential impacts of the species;

• value of the habitats/areas that the species infests or may infest; and

• difficulty of control.