Ecology and Management of Invasive Alien Species: Management

In order to evaluate the success or failure of the management efforts, it will be necessary to monitor aspects such as the population of the invasive species, the condition of the area under consideration, and changes in species composition and importance. A management programme is not complete unless it is based on thorough preparation, persistent efforts during the programme, and follow-up studies. Control activities, whether they involve eradication efforts, control actions taken, or taking no action at all, must be monitored over the period of the programme. The targets set at the beginning will help to evaluate the success or failure of the programme.

The overarching goal is preservation or restoration of natural habitats to a predetermined level. To evaluate progress, a subset of targets should be set up which are on the way to the final goal. These targets for success may be the removal of the invasive species if the option chosen was eradication, but if it was control then the criteria for success may be a measure of some other feature, such as the return of a plant or an increase in abundance of a bird. These criteria for success will help decide whether the programme is succeeding in controlling the pest and preserving or restoring the species and communities wanted.

It is worth pointing out that monitoring the numbers of a pest species killed or removed is a measure of the work being done but is not a measure of success of the project. Success of the project can only be measured by monitoring numbers of the pest species that remain, and ultimately the condition of the ecosystem they are in. It should not be assumed that removing an invasive alien species from an ecosystem will automatically lead to the return of the indigenous flora and fauna. Often this will happen (see for example, Case Study 5.17 "Reptile Recovery on Round Island"), but in other cases, removal of one alien species may simply open the way for colonization by another (Case Study 5.31 "What Can Happen When an Invasive Alien Species is Controlled"). Monitoring of the impact of control actions needs to be put in place, preferably starting with small-scale activities to verify the impact of control operations, and if the results are not as expected, the management plan may need to be reconsidered and adapted in light of this new knowledge.