Climate change is a central concern for fisheries and aquatic conservation research. Will commercial and threatened species shift their ranges and jurisdictions in the coming decades? Will coral reefs survive the century? How will ocean warming and acidification affect aquatic food webs? How will climate pressures on oceans and coastal communities interact to produce challenges as well as solutions and resilience? To answer these questions, we need to know how much warming and acidification to expect. To know how much warming and acidification to expect, we need to predict future greenhouse gas emissions and their effects.
Researchers assessing climate impacts typically use climate change scenarios to explore different possible emissions and climate futures. Representative Concentration Pathways (RCPs) and Shared Socioeconomic Pathways (SSPs) are the main scenarios used by the Intergovernmental Panel on Climate Change (IPCC) and the scientific community, including fisheries and aquatic conservation.
Recently, there has been a major debate in climate and energy science surrounding high-emission scenarios—RCP8.5 and SSP5-8.5—especially their use as "business-as-usual" (BAU) scenarios. While these are the most commonly cited scenarios by the IPCC's Assessment Reports and other major syntheses of climate impact research, recent studies suggest that these scenarios' emissions pathways and underlying assumptions are now implausible, and scenarios such as RCP4.5 and SSP2-4.5 may be more plausible BAU scenarios.
The authors of the latest Editor's Choice article in ICES Journal of Marine Science reviewed this debate. They assessed scenario use in fisheries and aquatic conservation papers focused on climate change published in nine major journals from 2015 to 2022, and recommend best practices for scenario use in future fisheries and aquatic conservation research.
The authors found that over 90% of fisheries and aquatic conservation papers use climate change scenarios RCP8.5 or SSP5-8.5, though most do not treat them explicitly as BAU scenarios. The use of RCP4.5 and SSP2-4.5 has increased since 2020 when the debate about scenarios became prominent in climate and energy science. In studies using multiple scenarios, the projected climate change impacts were sometimes substantially different between lower- and higher-emissions futures.
The authors recommend that researchers in fisheries and aquatic conservation using climate change scenarios should: (i) be transparent about the purpose and intended plausibility of scenarios chosen; (ii) qualify results in light of rationales used for scenario choices; (iii) be aware of the media's tendency to sensationalize; and (iv) try to avoid internal contradictions in scenario use (e.g. combining scenarios whose assumptions contradict each other), and acknowledge these contradictions when they arise. Following these recommendations will make scenario use in fisheries and aquatic conservation research more precise and transparent which will help to align conservation priorities with management challenges.
Read the full paper, Climate change scenarios in fisheries and aquatic conservation research, in ICES Journal of Marine Science.
Fossil-fuel and industry (FFI) CO2
emissions projected by Intergovernmental Panel on Climate Change (IPCC) marker
scenarios from the Sixth Assessment Report, compared to historical observations and the International Energy Agency’s Stated Policies and Announced Pledges scenarios. The amount of global
warming the IPCC scenarios are
expected to produce by 2100, relative to 1850-1900 temperatures
(5%-95% range indicated in brackets), is indicated at right. Click to enlarge. Adapted from
Figure 2a in Burgess et al., 2023.