Editor’s note: Two weeks ago, Doug Butterworth posted on this website (here) commenting on a new paper discussing climate change effects on fisheries in the Northeast. The authors of that paper have responded below.
Comment by Jon Hare, Wendy Morrison, Mark Nelson and Roger Griffis
We appreciate Doug Butterworth’s comments on our paper and CFOOD for highlighting our work (Hare et al. 2016). Here we reply to two of Dr. Butterworths points: the seemingly opaque nature of our analyses and reference to prior work by Ransom Myers on “When do environment–recruitment correlations work”. But first, we clarify the objective of our study, which was to provide an evaluation of the future effect of climate change on a broad range of fish and invertebrates species in the Northeast U.S. Continental Shelf Large Marine Ecosystem.
Our analyses were based on expert elicitation, which is often used to evaluate a broader set of relevant factors than can be included in simulation models (for an excellent summary of expert elicitation see Morgan et al. 2014). We defined experts as scientists actively working with species included in the assessment. We also had climate scientists participate in the assessment, as well as advise on the inclusion of climate factors. All scientists formally involved in the assessment are co-authors on the paper. We evaluated 82 species from the Northeast U.S. Shelf – incorporating a broad set of commercial, recreational, protected, and ecologically important fish and invertebrate species. It is important to note that the scale of our assessment was species in the region, not specific stocks. While Dr. Butterworth is correct that there are considerable data available in the region, there are not detailed data available for all 82 species, and therefore we used an expert-elicitation approach. Our goal was not to conduct detailed analyses on a handful of managed species. These detailed analyses have been done and are ongoing (e.g., Fogarty et al. 2009, Hare et al. 2010, Bell et al. 2014). Thus, we view our vulnerability assessment as complementary to quantitative approaches, including stock assessment modeling, not as a replacement.
Dr. Butterworth questioned the bases by which we evaluated the overall impacts of climate change on species (positive, neutral, or negative). The methodology we used is fully described in Morrison et al. (2015), which was cited in our paper. The general idea is to use current life history characteristics to infer a species vulnerability to environmental change. For example, we considered a generalist to be less vulnerable to change and a specialist to be more vulnerable to change. These traits and the rationale for vulnerability are fully described in our paper (Sensitivity Attributes). Similar trait-based expert-elicitation assessments are used in a wide variety of disciplines including fisheries (Patrick et al 2014). Scientists participated in the entire assessment before estimating the impacts of climate change. Life history characteristics were evaluated by scientists individually and then discussed as a group during a workshop. Representative of regional fisheries management organizations were observers at the workshop. Scientists also contributed to Species Narratives, which provide species specific summaries of the results of the assessment, prior studies related to climate change, and of the life history. After participating in the assessment, reviewing the results, and reviewing the species narratives, scientists estimated whether a species would be positively or negatively affected by climate change in the region (a negative effect is a decrease in abundance or productivity or a shift out of the region). The metrics from the assessment also have uncertainty associated with them, which were estimated using a bootstrapping approach of the scientists’ scores. We feel comfortable that the effect of climate change on a species in the region was estimated using the best data available data across all 82 species and using a transparent methodology. In fact the, methodology is now being used in the Bering Sea and the California Current Large Marine Ecosystems and is specified in the NOAA Fisheries Climate Science Strategy (Link et al. 2015) for national implementation; again as a complementary method covering a broad range of species, not as a replacement, for more quantitative methods on individual species.
Dr. Butterworth points out that Myers (1998) found most environment-recruitment relationship break-down when re-evaluated, thus questioning our link between climate change and changes in productivity and abundance. First, our study does not attempt to identify the mechanistic relationships between recruitment and the environment. As mentioned above, our assessment was based on an evaluation of current life history characteristics. Second, there is an important caveat to the conclusion of Myers; “There is one generalization that stands out: correlations [between environment and recruitment] for populations at the limit of a species geographical range have often remained statistically significant when re-examined.” In our vulnerability assessment, a majority of species estimated to be negatively impacted by climate change are at the southern-extent of their range and a majority of species estimated to be positively impacted by climate change are at the northern-extent of their range. Thus, our results are not contradicted by the Myers study and largely follow his generalization. Further, progress is being made incorporating environmental terms into stock assessment models generally (Maunder & Watters 2003, Keyl and Wolff 2008) and in the Northeast U.S. Shelf specifically (Miller et al. 2016). Again, the vulnerability assessment is complementary to, not in place of more quantitative approaches.
We also feel it is important to point out that Dr. Butterworth’s critique was prompted by the statement provided by the CFOOD organizers, which ended with, “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.” We also disagree with this characterization of our study. We estimated that 17% of the species assessed would be positively impacted by climate change in the Northeast U.S. Shelf ecosystem and 51% would be negatively affected. In the region, there will be winners and losers; opportunities and challenges. Our results do not lead to the simple conclusion of more protection and more preservation. The results of our study suggest that addressing climate change impacts on living marine resources in this region will need coordinated action involving many stakeholders and considering science, management, regulation, and governance issues in combination
In summary, we feel that we have met the burden of explaining our methods and results. Further, we have provided these results to the Regional Fisheries Management Councils and the Atlantic States Marine Fisheries Commission and are discussing the implications for science and management in the region.
We thank Dr. Butterworth for his comments and we are happy that our work has prompted broader discussion and reflection.
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