Climate Change Study Offers “Realistic”, Win-win Fisheries Management Reforms

By Kam Kompani,

A new study of marine fisheries has found that climate-adaptive management reforms could lead to higher catches and profits than business-as-usual for most countries.

Marine fisheries are a vital source of food for more than half of the world’s population and support the livelihoods of over 56 million people globally.

But increasing ocean temperatures have started to affect the productivity of fisheries around the globe. Some regions have already experienced a decline of 35% in maximum sustainable yield (the largest annual catch that can be captured from a fish stock without damaging its reproductive process). Depending on which emission scenario unfolds, marine animal biomass is forecasted to decrease between 5% and 17% by 2100.

Additionally, warming oceans are expected to impact different marine fisheries differently.

The productivity of fisheries in tropical and temperate regions are forecasted to fall, while they are predicted to increase towards the poles. “These regional shifts in productivity, range, and fishing opportunity will result in regional discrepancies in food and profits from fisheries,” the authors highlighted.

“Even under the least severe emission scenario, 19 countries, 15 of which are in West Africa, are projected to experience reductions in maximum sustainable yield of 50–100%”, the authors found. “In the most severe scenario, 51 countries are expected to experience reductions in maximum sustainable yield of 50–100%.”

In contrast, maximum sustainable yields under both low- and high-emission scenarios are projected to increase for 22 countries. “The five most consistent and pronounced climate change “winners” are: Finland, Antarctica, Norway, Portugal, and Fiji.”

In response to the anticipated changes in the productivity and distribution of marine fisheries, the authors evaluated the potential benefits of two climate-adaptive measures — “full adaptation” and “realistic adaptation” — compared to business-as-usual.

The authors found that business-as-usual management will lead to lower catches and profits in the future compared to today — under both low- and high-emission scenarios — for the majority of countries (82-85% of countries).

Whereas full adaptation — whereby officials react annually to shifts in productivity and range to ensure that fisheries y management is fixed at sub-optimal harvest rates — would yield higher catches and profits in the future for most nations, except under the most severe emission scenarios.

Similarly, realistic adaptations — whereby officials recalibrate the optimal harvest rates at a predetermined interval (e.g., every five, ten or twenty years), rather than controlling fisheries management annually, which the authors believe is unrealistic — at five-year intervals would also generate both higher catches and profits for the majority (56–63%) of countries under less severe emission scenarios.

“The ability for management reforms to offset losses due to climate change is largely due to the global legacy of sub-optimal management: only 11.5% of the evaluated stocks were fished near optimal levels; thus, reforms that end overfishing and sustainably exploit new resources jointly improve long-term yields,” the authors explained.

The researchers, however, warned against the limitations of both full and realistic adaption measures: “Neither realistic (5-yr) nor full adaptation are sufficient to maintain fisheries outcomes into the future for all countries, but they are nearly always preferable to business-as-usual management.”

“Even perfect climate-adaptive management (“full adaptation”) is unable to maintain current catch and profits under high-end greenhouse gas emissions. Furthermore, although perfect adaptation could maintain global catch and profits under partial emission reductions, tropical and temperate regions would still incur dramatic losses in fisheries benefits. This underscores the fact that emission reductions consistent with the Paris Agreement could have significant impacts on the ability for fisheries to feed and employ people into the future.”

“In all but the most severe emissions scenario, both full adaptation and realistic adaptation yield both higher cumulative catches and profits than business-as-usual management for nearly all countries.”

“Overall, our results indicate that climate change will dramatically alter the distribution and productivity of marine fisheries, but plausible climate-adaptive management reforms could minimise or eliminate negative impacts in most countries,” the authors concluded.

Complementary Solution: Marine Aquaculture

Given the limitations of climate-adaptive reforms, the authors suggest marine aquaculture (the cultivation of marine animals and plants) as a way to compensate for losses in the productivity of fisheries.

“The biological potential for marine aquaculture is enormous and exceeds both current production and projected demand,” the authors stated.

They cautioned, however, that: “Although mariculture has the potential to feed millions of people, it also poses a number of environmental problems including pollution, habitat conversion, disease and parasite transmission, and escapement and hybridisation.”

“The expansion of large-scale mariculture for increased food and employment opportunities will thus require a better understanding of these environmental tradeoffs and the best practices for managing them.”

Study: Free CM, Mangin T, Molinos JG, Ojea E, Burden M, Costello C, et al. (2020). “Realistic fisheries management reforms could mitigate the impacts of climate change in most countries“. PLoS ONE 15(3): e0224347.