Galapagos Invasive Species:
Management basics
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With a list of introduced plant species at around 550 and growing (more than the total of native plant species), we face several, related,
prioritisation-evaluation problems:
- Evaluate proposed new introductions, to judge whether they are likely to become invasive in Galapagos. This is important for assessing proposals by local residents to introduce new crop species and
varieties;
- Assess the actual or potential invasiveness of plant species that have already been introduced to
Galapagos;
- Estimate the feasibility of their eradication. This is important to enable us to allocate scarce financial resources to the species that are, or are likely to become, serious problems but where we have a good chance of achieving successful eradication.
Staff from the Botany Department of the Charles Darwin Foundation are therefore developing a weed risk assessment (WRA) system and feasibility model to meet these requirements with the help of Paul Pheloung, who developed the WRA model used in Australia, and adapted for use in New Zealand and Hawaii. Paul also received the necessary inputs for incorporation into the system from the technical staff in the Galapagos National Park Service.
Prioritization: Weed Risk Assessment
On the basis of information on the biology of an introduced plant, its known behaviour in and outside of Galapagos, and its approximate distribution (collected through the inventories and other observations), we can evaluate the likelihood of a species becoming invasive and harmful (affecting native species or causing major alterations in community composition and structure). This is done through a weed risk assessment system which includes a series of questions about the plant’s history of invasiveness elsewhere and in Galapagos, its biology and ecological characteristics that contribute to its invasiveness, and its impacts. After answering these questions, the system assigns an invasiveness score to each species, and the information is stored in a database, shown as it appears on the computer screen.
Feasibility is a measure of our ability to successfully eradicate a species from an island. Important factors that influence feasibility include the persistence of the seed bank, dispersal distances and mechanisms, the size and number of infestations, our ability to find plants and reach all infestation sites, the availability of a control method, and the costs involved. We have developed a simple computer model that uses a few key input variables (characteristics of the plant and its distribution that influence eradication feasibility) as well as the effort put into control (search frequency,
etc.) to simulate changes in the density of a weed over time during an eradication attempt. This model allows us to predict the relative effort required to result in a high probability of successful eradication (without even initiating an eradication program). The model results are complemented and refined by experimental eradication field work.
Source: Charles Darwin Foundation.
The noxious weeds page gives more information on current work being carried out on introduced plant species.
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Questions/comments? Write: galapagos@hear.org
This website
was created on 25 October 2004 by PT and JK