The natives are restless, but not often and mostly when disturbed

Simberloff, D., Souza, L., Nunez, M. A., Barrios-Garcia, M. N., & Bunn, W. (2012). The natives are restless, but not often and mostly when disturbed. Ecology, 93(3), 598-607.  PDF.

Summary

With climate change, both non-native and native species are likely to shift their ranges.  In order to enable native species and communities to adapt to climate change, we will need to facilitate their movement poleward and upward in elevation into more suitable climate conditions.  But, what is the likelihood that these native species could begin to exhibit 'weedy' tendencies when introduced into a new range?  Simberloff et al. (2012) set out to answer this question by comparing the proportions of non-native and invasive plants vs. native and invasive plants within the U.S. They conducted a literature survey to identify all species characterized as invasive and found 350 non-native invaders and 53 native invaders.  But, there were only 3000 total non-native plants introduced and over 18,000 native plants.  Therefore, proportionally, we can expect about 12% of non-native plants to become invasive, but only 0.3% of native plants to become invasive.  Moreover, native invasions characterized in the literature tended to be localized and associated with disturbance.  In the context of climate change, native plants that shift their ranges (either assisted or unassisted)  are much less likely to become invasive than non-native plants.

Take home points

  • Non-native plants are 40 times more likely to become invasive than native plants.

  • About 12% of non-native plants introduced to the U.S. have become invasive.

Management implications

Native species that shift their ranges under climate change are unlikely to become invasive, particularly when introduced into broadly similar ecoregions (e.g., within Northern Temperate Forest).  Therefore, assisted migration (the movement of species to help them 'keep up' with warming temperatures) is much less likely to cause novel invasions than the continued and widespread introduction of non-native species as ornamentals.  Shifting native species is not risk free, but assisted migration of natives poses a much lower risk than the non-native pool that we are currently facilitating.

Keywords

Range Expansion; Review; Invasive Plant; Risk Assessment; Assisted Migration