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Jul 11, 2019

Ocean predicted to lose 5% of life per degree of global warming

Climate change is harmful to the ocean and bad for fisheries. We have chronicled many studies linking climate change, fisheries, and conservation and have not shied away from overtly suggesting that climate change is the largest threat to fisheries and biodiversity in the ocean (as opposed to other popular and well-known ocean issues). A recent paper is the strongest evidence yet. Lotze et al. 2019, a groundbreaking study published open access in June 2019 predicts that life in the ocean will decrease by about 5% per degree of global warming.
Predicted changes in ocean biomass under different emissions scenarios and temperature changes. From Lotze et al. 2019.
Predicted changes in ocean biomass under different emissions scenarios and temperature changes. From Lotze et al. 2019.
This is a powerful figure that clearly shows a linear relationship between biomass and temperature change. Climate change studies and the gloomy figures they produce can be discouraging, but the figure here can be interpreted positively: Reducing warming by any amount will move up the scale and prevent the deaths of countless marine animals.

Explaining the science: an ensemble of models

Lotze and dozens of scientists from across the world incorporated climate models into ecosystem models to determine how rising global and ocean temperatures (and their associated impacts) will affect animal populations over time. Nearly every paper measuring something about climate change uses RCP scenarios* to set up a computer model to measure some kind of physical change. For example, a paper from last year used RCPs to measure physical changes inside and outside of marine protected areas (MPAs). What makes Lotze et al. 2019 groundbreaking is that researchers used RCP scenarios to inform a composite of ecosystem models that predict ecosystem changes, not just physical changes. Co-author Marta Coll of the Institute of Marine Science in Barcelona said, “Our study represents a major undertaking, where we used for the first time a comparative and standardized approach of 6 global marine ecosystem models forced with 2 Earth-system models and 4 emission scenarios with and without fishing. The process of incorporating RCP scenarios into an ensemble of various ecosystem models was 6 years in the making, according to another co-author, Tyler Eddy. There are two major takeaways concerning fisheries:
  1. The composition of fish in the ocean will change dramatically and
  2. Fishing has very little impact on what will happen.
Read the article. Editor's note:  AquaBounty is doing its part to reduce negative environmental impacts by reducing the carbon footprint of salmon production.

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