Timing and magnitude of climate-driven range shifts in transboundary fish stocks challenge their management

Study key findings & significance

• Nearly half of the Earth's shared fish stocks are on the move due to climate change.
• By 2030, 23 percent of these 'transboundary' fish stocks will have changed their historical habitat range due to climate change.
• The study tracked the shifting ranges of 9,132 transboundary fish stocks, which account for 80 percent of catch taken from the world's exclusive economic zones (EEZs), starting in 2006 and projecting to the year 2100.
• Climate change will force 45 percent of the fish stocks that cross through two or more exclusive economic zones to shift significantly from their historical habitats and migration paths by 2100, a challenge that may lead to international conflict.
• Countries in tropical locations such as the Caribbean and South Asia will be hit first as water temperatures increase, but northern countries will also be affected. Overall, 10 shared stocks in Canada and the U.S. Pacific are projected to shift by 2033.

Author quotes

"By providing estimates of the size and timing of projected shifts, our study offers tangible reference points around which to consider climate change impacts and negotiate fair policies for sustainable management" said co-author .

Dr. Colette Wabnitz, co-author and lead scientist at Stanford's Center for Ocean Solutions and research associate at UBC's Institute for the Oceans and Fisheries (IOF)

"We must accept that climate change is happening, and then move fast enough to adapt fisheries management regulations to account for it," said co-author

Dr. Gabriel Reygondeau, co-author and research associate at IOF

Abstract

Climate change is shifting the distribution of shared fish stocks between neighboring countries’ Exclusive Economic Zones (EEZs) and the high seas. The timescale of these transboundary shifts determines how climate change will affect international fisheries governance. Here, we explore this timescale by coupling a large ensemble simulation of an Earth system model under a high emission climate change scenario to a dynamic population model. We show that by 2030, 23% of transboundary stocks will have shifted and 78% of the world's EEZs will have experienced at least one shifting stock. By the end of this century, projections show a total of 45% of stocks shifting globally and 81% of EEZs waters with at least one shifting stock. The magnitude of such shifts is reflected in changes in catch proportion between EEZs sharing a transboundary stock. By 2030, global EEZs are projected to experience an average change of 59% in catch proportion of transboundary stocks. Many countries that are highly dependent on fisheries for livelihood and food security emerge as hotspots for transboundary shifts. These hotspots are characterized by early shifts in the distribution of an important number of transboundary stocks. Existing international fisheries agreements need to be assessed for their capacity to address the social–ecological implications of climate-change-driven transboundary shifts. Some of these agreements will need to be adjusted to limit potential conflict between the parties of interest. Meanwhile, new agreements will need to be anticipatory and consider these concerns and their associated uncertainties to be resilient to global change.