Abstract:
Biosecurity schemes aim to prevent the introduction of species with a high invasion
potential, without unduly restricting personal freedom and commercial activities. But
invasive species risk assessments are time consuming, data intensive and
expensive. Consequently, resource poor nations cannot implement these schemes.
Here we develop a method for creating watch lists using the consistent predictors of
invasion success—history of invasion, environmental suitability, and propagule
pressure (measured respectively using the Global Invasive Species Database 2
(GISD), environmental modelling, and tourism and trade data). We tested the
approach for South Africa, at a national level for various taxa and at a provincial level
for plants. Of 884 alien species listed in the GISD, 400 were potential invaders, with
most occurring in high risk regions. When alien species in South Africa were
evaluated there were many false-negatives (sensitivity of 32% for terrestrial and 40%
for marine species), because the GISD is not comprehensive, but few false positives
(specificity of 91% for terrestrial and 89% for marine species). The methodology was
easy to apply at different political levels, but we found substantial overlaps between
the national and provincial watch lists of plants. This simple technique is rapid, easily
repeatable, flexible, transparent, works across taxa, and does not require substantial
financial or scientific input. It can be used in any region of the world and at various
political levels as an initial assessment of key threats. As such it may be an
important step in developing biosecurity schemes for resource poor regions.
