A new study, published by the journal PLOS ONE found 82 species of marine fish and invertebrates in the northwest Atlantic (or the northeast US) to be vulnerable to climate change (A write up of the study by the New York Times can be found here). These 82 species encompass every commercially managed fishery in the region as well as a few popular recreational species and endangered species.
Not all species were predicted to experience negative effects from climate change – only about half were likely to be negatively affected. 20 percent will be positively affected by climate change and the rest will be neutral, said Jon Hare, NOAA oceanographer and lead author of the paper. However a majority of the species studied did show a high potential for a change in habitat distribution, which could create significant management challenges
“Peter Baker, director of Northeast U.S. oceans for the Pew Charitable Trusts, said the report should be a motivator for fishing managers to protect more ocean habitat and preserve marine species.”
Comment by Doug S. Butterworth, Marine Resource Assessment and Management Group, University of Cape Town
In this paper, Hare et al. report the results of the application of Vulnerability Assessment methodology to assess the extent to which abundance or productivity of species on the Northeast US Continental Shelf may alter in response to climate change. More particularly, they consider, inter alia, directional effects (whether negative, neutral or positive) and potential for changes in distribution. The determinations are based on expert opinions which lead the authors to draw firm conclusions, e.g. that climate change is expected to negatively affect about half the species they consider.
The environmental conditions associated with the habitat preferences of different species may be determined from empirical studies for which considerable data are available. Hence there is a clear basis in data and analyses to formulate the opinions that have been consolidated in this report.
What is much less clear, however, is what bases could defensibly have been used by experts to comment on directional effects for abundance and particularly productivity under projected changes in environmental variables under climate change. The productivity, and consequently to a large extent, the abundance, of a population of a fish or invertebrate species is driven by the (typically) annual recruitments to that population. The inferences drawn by these experts must consequently have been based on knowledge of how environmental variables affect such recruitment.
Yet the difficulties of reliably establishing such relationships are well known in fisheries assessment science. The classic article on this topic by Ram Myers (When do environment-recruitment correlations work?) pointed to the failure of almost all such relationships that had been proposed when tested with new data.
This then begs the questions of what bases the experts contributing inferences concerning directional effects to the Hare et al. study used for their determinations and how reliable those inferences might be. If they are reliable, why are they generally not being used in the fisheries assessments from which advice on catch limits is formulated?
I agree with Hare et al. when they argue that the expert opinions they collated “can guide future monitoring, research, and monitoring studies.” However, they go further to state that their results can be used by managers to “guide management actions” (they provide examples of species for which they suggest decreasing fishing mortality). Should they not first meet the burden of justifying the bases on which the experts who contributed to their study drew their inferences about directional effects, and also explain the associated implications for the reliability of knowledge about fishery recruitment-environmental variable relationships?