Citation: Sandvik, H., and B.-E. Sæther (2012) Kriterier og metoder for kartlegging og overvåkning av fremmede arter [Criteria and methods for monitoring and surveillance of alien species (in Norwegian with English abstract)]. Utredning for Direktoratet for naturforvaltning, 10(4), 1–25.

Key words: Alien species, invasion biology, monitoring, prioritisation, sampling design, surveillance.

Rosa rugosaAbstract: There is a great need for dedicated monitoring programs of alien species in Norway. The development of such programs hinges on criteria to identify and prioritise the species to be monitored, and on an appropriate and standardised method. This report summarises the state of knowledge in this area and derives a few recommendations.
    The state of knowledge in comparative invasion biology – both internationally and particularly in Norway – is still too poor to develop a well-founded set of morphological, physiological, ecological or demographic selection criteria for the monitoring of alien species. For the time being, prioritisation of monitoring efforts should thus be based on the experience with invasive species in other countries. This information should be combined with knowledge about the species’ spread potential in Norway and their ecological risk category according to the Norwegian classification system of alien species.
    In carrying out the monitoring programs, it is essential that detection rates are high, that monitoring effort is as constant as possible and that both positive and negative findings are reported. This entails that (1) a network of monitoring plots should be established along transects; (2) the monitoring plots are not switched or discontinued after establishment; (3) monitoring effort must vary as little as possible through space and time; (4) monitoring effort should be quantified. Monitoring plots for an early warning system should not be arranged along transects but as a fixed grid in prioritised areas. The data to be sampled are population counts (rather than mere presence/absence data) of both the alien and relevant native species as well as relevant abiotic environmental factors.

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