Impact assessment of coastal marine range shifts to support proactive management

Amy K. Henry, Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA and Cascade J. B. Sorte, Ecology & Evolutionary Biology, University of California, Irvine, CA

Background/Question/Methods
Climate change is reshuffling Earth’s biota as species ranges shift to track increasing habitat temperatures. While redistribution may be necessary for species persistence, it can also result in significant impacts to existing communities due to the arrival of novel, range-shifting species. Anticipating the beneficial versus deleterious impacts of range-shifting species is essential for evaluating management options spanning facilitation (via managed relocation) to suppression (via prevention and control). We employ an impact assessment protocol developed for invasive species (Environmental Impact Classification for Alien Taxa, or EICAT and the Socio-Economic Impact Classification of Alien Taxa, or SEICAT) which assesses existing literature to evaluate the potential consequences of native species range shifts of coastal marine species in North America. We used EICAT and SEICAT to evaluate both detrimental and beneficial impacts of range shifts. We collated impacts data from 188 papers on both the expanded and native ranges of 40 shifting coastal marine species of North America. In addition to quantifying maximum impacts, we tested the hypothesis that species’ community impacts increase as they move outside of their native ranges.
Results/Conclusions
Our study highlights the ways that invasion impact assessment combined with species vulnerability assessment could support decisions about management of range shifts. Sufficient data was available to evaluate 33 (83%) species for environmental impacts, but only 11 (28%) had documented socio-economic impacts. Our results suggest that ~50% of shifting marine species have negative impacts in their expanded range. The greatest impacts documented resulted in the loss (by consumptive effects, two species) or gain (by habitat provisioning, four species) of a native species in the expanded range. In species assessed in both ranges, effects in the expanded range were more often negative than positive, and negative impacts (those resulting in a decrease in fitness or population size of a native species) in the native range predicted much stronger negative impacts in the expanded range. We conclude that interactions in the native range can inform impacts in the expanded range. The diversity of positive and negative impacts highlights that there is no “one size fits all” approach to managing range shifts. The importance of proactive assessment of range shifts will increase as the number and extent of range shifts accelerates.