Ecological-economic sustainability of the Baltic cod fisheries under ocean warming and acidification

Rudi Voss,Martin F Quaas,Martina H Stiasny,Martin Hänsel,Guilherme A Stecher Justiniano Pinto,Andreas Lehmann,Thorsten B.H Reusch,Jörn O Schmidt

doi:10.1016/j.jenvman.2019.02.105

Abstract

Human-induced climate change such as ocean warming and acidification, threatens marine ecosystems and associated fisheries. In the Western Baltic cod stock socio-ecological links are particularly important, with many relying on cod for their livelihoods. A series of recent experiments revealed that cod populations are negatively affected by climate change, but an ecological-economic assessment of the combined effects, and advice on optimal adaptive management are still missing. For Western Baltic cod, the increase in larval mortality due to ocean acidification has experimentally been quantified. Time-series analysis allows calculating the temperature effect on recruitment. Here, we include both processes in a stock-recruitment relationship, which is part of an ecological-economic optimization model. The goal was to quantify the effects of climate change on the triple bottom line (ecological, economic, social) of the Western Baltic cod fishery. Ocean warming has an overall negative effect on cod recruitment in the Baltic. Optimal management would react by lowering fishing mortality with increasing temperature, to create a buffer against climate change impacts. The negative effects cannot be fully compensated, but even at 3 °C warming above the 2014 level, a reduced but viable fishery would be possible. However, when accounting for combined effects of ocean warming and acidification, even optimal fisheries management cannot adapt to changes beyond a warming of +1.5° above the current level. Our results highlight the need for multi-factorial climate change research, in order to provide the best available, most realistic, and precautionary advice for conservation of exploited species as well as their connected socio-economic systems.

Highlights

Marine fisheries play a central role for world food supply
Using the example of a well-studied fish stock, the western Baltic cod stock, we considered the combined effect of two stressors
While improved management might be able to successfully cope with either ocean warming or ocean acidification as single stressors, the combined effect of OAW renders the ecological-economic future of western Baltic cod very uncertain

Summary

Introduction

Marine fisheries play a central role for world food supply. Fish provides at least 15% of per capita animal protein intake for 4.5 billion people (Béné et al, 2015). Worldwide approximately 500 million people are directly dependent on fisheries for their livelihoods (FAO, 2014). Ocean warming (OW) has been identified as a potential major stressor to marine fisheries, threatening the sustainable use of these renewable resources and their associated socio-economic systems. A global temperature rise this century well below 2 degrees Celsius above pre-industrial levels ... For the recent 3 decades, Baltic Sea surface temperature warming trends have been determined between 0.4 and 0.7 °C per decade (Lehmann et al, 2011, BACC II, 2015). The 2 °C threshold will already be crossed in the mid of this century

Methods

Results

Discussion

Conclusion