Impacts of Climate Change on Global Fisheries
By IEF Member Elizabeth L Mclean, Ph.D.
Around the world, resources from aquaculture and fisheries make a significant contribution to food security and the livelihood of many people. Today, as climate change causes an increase in water temperature and sea-level rise, numerous ecosystems are rapidly changing [1, 2]. In marine ecosystems, both increase in ocean temperatures and ocean acidification are already affecting the distribution of fish, their migration patterns, as well as their productivity. Although declines have long been attributed to overfishing [3, 4], the added stress of climate change will challenge our ability to protect and sustain global fisheries.
The different habitats that lend themselves to fisheries and aquaculture along the coasts as well as in rivers and oceans support a wide range of fishing activities from small-scale subsistence practices to large-scale commercial practices. Presently, there is a worldwide concern that the open-access nature of many fisheries has caused numerous fish populations to plummet. This is referred to in the literature as the tragedy of the commons . To solve the overfishing dilemma, governments in several countries have established limit systems, such as the Individual fishing quota (see the United States, Canada, New Zealand, and Norway for some examples) to sustain fisheries and assist their industries .
As an industry, fishing is categorized as one of the fastest-growing food production systems . Over three billion people rely (directly or indirectly) on fisheries and aquaculture; for millions of people in poor countries this represents up to 50% of the animal protein that they rely on . Nevertheless, fisheries are a limited resource, which may be problematic as the world population continues to grow.
The wellbeing of humanity, its food security, and its ability to plan from season to season will be profoundly challenged by climate change. To better understand how climate change will impact global fisheries, livelihoods, and the stability of millions of people, it is important to recognize the interconnectedness of people, their environment, and their capacities. It is fair to say that different locations will respond differently to climate change; it is possible that some areas may respond favorably depending on the sensitivity, exposure, and stability of their environment. Without doubt, though, areas with scarcity of resources will be disproportionately more affected than others.
We know that coastal fishing communities are vulnerable to sea-level rise, changing storm patterns, and unpredictable weather events; and that fish habitats, such as coral reefs, mangroves, and estuaries, are crucial for sustainable livelihoods in these communities. However, the full measure of how global fisheries will be impacted is difficult to assess because of the complexity of the systems and the multiplicity of pathways that climate change affects . Oceans and coastal ecosystems play an important part in the global carbon cycle with some reports indicating that oceans absorbed and thereby removed from the atmosphere up to 25% of the anthropogenic carbon dioxide emitted from 2000-2007 . But this can all change. Already, changes in rainfall patterns due to drought and water availability affect freshwater fisheries and aquaculture; additionally, changes in ocean acidification processes will influence numerous biological and ecological processes.
As global temperature rises, fish productivity may be compromised with the ability of oceans to serve as a buffer likely to decrease . Another factor in fish productivity is ocean acidification which is driven by an increase in greenhouse gases released into the atmosphere. Since many organisms undergo a process of calcification to form their skeletons, entire marine food chains could be compromised because of these organisms’ inability to produce their calcium shells. As an example, a decrease in the commercially valuable fisheries of the Atlantic Cod in the Baltic seas can be linked to a decrease in the copepods (calcifying organisms) they rely on; cod fisheries are seeing a smaller population size and growth as well as a northward movement in distribution due to climate change stressors . Already research models predict an 11% decline in fish catch for tropical areas (by 2050) influenced by greenhouse gas emissions and warmer temperatures .
Effects of climate change on ocean temperatures and currents can cause entire fish populations to shift; as an example, a shift in the tuna species of the Pacific can bring uncertainty to food security . A comprehensive analysis of the global productivity of marine fisheries shows a 4.1% decline between 1930 and 2010 with some high-production areas experiencing losses of up to 35% . Similarly, during the last decade the North Atlantic lobster populations have been moving northward and into deeper waters as ocean temperatures have increased.
An overfished population is also more susceptible to other environmental stressors such as fish becoming smaller, having a lower genetic diversity, and having a lower age distribution. Coastal areas with high concentrations of human populations can also release nutrients into coastal habitats. Areas with high nutrient content, eutrophication, and increased temperatures present unfavorable scenarios for fisheries because of the depletion of oxygen in certain areas and because of the ability of the oceans to capture and store carbon (biological pump) . Hence, both production and distribution of fish globally, including species composition, are going to shift.
Countries with low-lying areas in the Pacific that are dependent on fisheries, like the Maldives and Tuvalu, are particularly vulnerable, not only to sea-level rise but also to flooding and typhoons. Livelihoods and fish production in some areas of the Mekong River in Laos, where over a million tons of catfish are produced annually, will suffer because of salt intrusion and sea-level rise .
To reduce the impacts of climate change, mitigation and adaptation actions are needed. Such undertakings include the reduction of greenhouse gas emissions, the adoption of sustainable practices that reduce and economize water use, and the diversification of livelihood activities. To build resilience in coastal communities, protection and conservation of coral reef systems, restoration and protection of mangrove forests, and the development of aquaculture systems are required. Addressing policies and governance needed to reduce the excess catch of fishing fleets in order to allow for rebuilding of the fish stocks is also important. A number of international organizations (such as the Food and Agriculture Organization and the World Bank) are helping communities around the world build their resilience by assessing risk and vulnerability, increasing awareness (through weather broadcasting), and assisting with adaptation plans (FAO) . In more developed countries, efforts include supporting newer trends, developing renewable energy, and accessing and utilizing biofuels.
Finally, it is crucial that attention be given to the most vulnerable people so that they can continue to adapt to climate change, reduce their risk, and increase their resilience. Effective adaptations that strengthen and sustain the productivity of fisheries and aquaculture will, in the long run, benefit food security for millions of people by meeting their day-to-day needs when droughts, floods, and storms affect crops and other alternative livelihoods disrupted by climate change.
Questions to consider
- What regulations in my country promote adaptation and mitigation of sustainable fisheries?
- What are direct, and indirect, ways in which communities can participate in climate change resilience?
- How do we set boundaries to open access fisheries while still safeguarding traditional practices?
- How can we meet the demands of sea food production as human populations increase?
- What are some of the social and spiritual implications of climate change justice?
- Blue Carbon and Carbon Sequestration
- Coastal Upwelling
- Individual fishing quota
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Last updated 16 September 2019