Fisheries, aquaculture and climate change
This module addresses the following questions: What are the implications of climate change and climate variability for the sector? How can resilience be built and vulnerability be reduced within the communities that depend on fisheries and aquaculture? What does the sector need to do to reduce its greenhouse gas emissions, provide alternative sources of energy and support natural greenhouse gas sequestration and carbon storage services?
B4 - 3.1 Climate change processes and impacts
The Fifth Assessment Report from the Intergovernmental Panel on Climate Change (IPPC) provides evidence of the certainty of global warming and its effects on oceans, coastal areas and inland waterbodies (FAO, 2016a). Climate change, along with other phenomena that affect climate variability, such as El Niño-Southern Oscillation, and extreme weather events, are affecting the abundance and distribution of fisheries resources and the suitability of some geographical locations for aquaculture systems. Climate-related physical and chemical changes are linked to increasing carbon dioxide emissions. These emissions are being absorbed in large part by aquatic systems, which is triggering substantial changes in aquatic ecosystems and affecting the important services they provide for maintaining food security and livelihoods (FAO, 2016b).
Climate-related changes that affect ecological functions and the frequency, intensity and location of extreme weather events include: changes in salinity and freshwater content; oxygen concentration; carbon uptake and acidification; temperature and thermal stratification; sea levels; ocean circulation; surface wind, storm systems and waves (Cochrane et al., 2009; FAO, 2016b). These changes can be expected to have a range of impacts, both direct and indirect, on fisheries and aquaculture. These impacts are outlined in Figure B4.1. Scientific knowledge on the impact of individual climatic drivers varies, and information on is limited the combined effects of these drivers is limited. This uncertainty complicates adaptation planning within the sector. Human drivers, such as pollution, dam construction and unsustainable fishing, are exacerbating the harmful impacts of climate change (FAO, 2016b).
Evidence exists that climate change is modifying the distribution of marine species. Many species are migrating towards the poles and deeper waters to follow their ideal habitat conditions (e.g. oxygen levels) (Figure B4.2). These migratory shifts cause changes in interaction dynamics among species, trophic linkages and food webs. Where migration is not possible, many aquatic species are likely to undergo changes in their size, reproductive cycles and survival rates. The impacts, both positive and negative, will depend on the region and latitude. Certain commercial species are likely to move offshore and away from traditional fishing grounds, with new invasive species likely moving in to fill the vacuum. If these new species are fit for human or animal consumption, new livelihood opportunities may arise in some communities.
Despite the encroachment of species that are tolerant of higher temperatures and changes in the chemical content of coastal waters, ecosystem productivity is likely to be reduced in most tropical and subtropical marine environments, seas and lakes. Projected scenarios indicate increased productivity of capture fisheries in high-latitude systems, but decreased productivity in low- and mid-latitude systems (Figure B4.2). Coastal systems are particularly vulnerable to temperature increases, hypoxic zones, acidification, and extreme weather events (FAO, 2016b).
Figure B4.1. Example potential climate change impact pathways for fisheries and aquaculture
- Source: developed from Badjeck et al., 2010.
Rising sea levels can displace brackishi and freshwaterii systems in delta zones and wipe out a range of agricultural practices. The destruction of coastal wetlands also has an impact on the productivity of freshwater fisheries and aquaculture. However, rising sea levels may also create new environments and new opportunities for the sector (e.g. through marine aquaculture and the expansion of mangrove forests). Increased frequency and intensity of storms, coastal flooding, coastal erosion and saltwater intrusion due to sea level rise could directly endanger fishers and fishing-dependent communities on coasts and at sea, and damage housing, community facilities and infrastructure used for fisheries and aquaculture. Marine shellfish aquaculture systems are especially vulnerable to changes in carbon chemistry, which can affect shell development in some species. For most species, the sensitivity to acidification and pathogens becomes greater when they are forced into habitats at the edges of their thermal ranges (FAO, 2016b).
The impacts of climate change on freshwater fisheries and aquaculture are expected to be significant. The increased variability in levels of precipitation and changes in air and water temperatures will affect the productivity of rivers, lakes and floodplains. Climatic drivers (e.g. higher temperatures) affecting inland ecosystems and species distribution are often intensified by non-climatic drivers, such as invasive species, pollution and habitat modification, and the fragmentation of rivers by dams. At the regional level, freshwater reservoirs will also be increasingly under pressure to meet the growing demand for irrigation. In general, inland fisheries will be at risk in areas where water stress is acute and the competition for water resources is high (FAO, 2016b). Case study B.4 provides an overview on how climatic and non-climatic drivers can contribute to changing the production potential of capture fisheries in aquatic inland systems.
Aquaculture systems will be affected by climate change through “gradual warming, ocean acidification, and changes in the frequency, intensity and location of extreme events” (IPPC, 2014a). Some production systems will need to be relocated (IPPC, 2014a).
For the fisheries and aquaculture sector, climate change may have significant impacts on post-harvest activities, the processes that add value to production and the distribution of fish to local and national markets. There may be potential changes in the location and variability of supplies, and changes in access to other key inputs, such as energy and water for processing. All these climate-induced changes will occur at the same time as other global, regional and national socio-economic pressures are being brought to bear on natural resources. This will expand the impacts on food security and nutrition, habitation and social stability.
Figure B4.2. Climate change effects on the distribution, body size and catch potential of marine fish and invertebrates
Figure B4.2 – Source: IPCC_AR5_WGII (A), chapter 6, p. 458. This graphic illustrates (a) Shifts in distribution range and reduction in body size of exploited fish driven by projected warming, oxygen depletion, and sea ice retreat. Whenever the shift in distribution does not fully compensate for warming and hypoxia, the result will be a decrease in body size. Shifts in (b) latitudinal and (c) depth distribution of 610 exploited demersal fishes are projected to have a median (central line of the box) of 31 km per decade and 3.3 m per decade, respectively, with variation between species (box boundary: 25th and 75th percentiles) from 1991–2010 to 2041–2060 under the SRES A2 (between RCP6.0 and 8.5) scenario (Cheung et al., 2011, 2013b). (d) Combining species’ range shifts with projected changes in net primary production leads to a projected global redistribution of maximum catch potential. (Analysis includes approximately 1000 species of exploited fishes and invertebrates, under warming by 2°C according to SRES A1B (≈RCP6.0), comparing the 10-year averages 2001–2010 and 2051–2060; redrawn from Cheung et al., 2010). (e) Changes in species distribution and individual growth are projected to lead to reduced maximum body size of fish communities at a certain site. The analysis includes 610 species of marine fishes, from 1991–2010 to 2041–2060 under SRES A2 (approximately RCP6.0 to 8.5; Cheung et al., 2013b), without analysis of potential impacts of overfishing or ocean acidification. Key assumptions of the projections are that current distribution ranges reflect the preferences and tolerances of species for temperature and other environmental conditions and that these preferences and tolerances do not change over time. Catch potential is determined by species range and net primary production. Growth and maximum body size of fishes are a function of temperature and ambient oxygen level.
B4 - 3.2 The growing demand for fish and other aquatic products
Oceans and inland waters can provide significant benefits to the world’s population, especially in the world’s poorest communities (The fisheries and aquaculture sector provides millions of people with food, income and livelihoods. According to recent estimates, 56.6 million people work in the primary sectors of capture fisheries and aquaculture (FAO, 2016b). If those who work in post-harvest activities of both subsectors are included in the figures, an estimated 660 to 820 million people, about 10 - 12 percent of the world’s population, derive their income and livelihoods from the sector (FAO, 2012). Ninety percent of those working in capture fisheries are engaged in small-scale operations.
In 2014, the global population was 7.3 billion and it is expected to reach 9-10 billion by 2050. Population growth, but “more importantly the combination of urbanization, increased levels of development, living standards and income are key drivers of increased demand for fish and of fisheries development” (HLPE, 2014). With increased demand for fish and seafood, fisheries resources and production systems will grow in importance. Along with population growth, rising incomes, especially in developing countries, will create higher household demand for fish and seafood, as consumption of these foods tends to rise as the spending power of middle income consumers increases. This situation does not apply to the poorest of the poor, who fish at a subsistence level.
Population growth is increasing the demand for food, but unsustainable fishing practices have caused production from marine fisheries to level off. Aquaculture will have to satisfy the gap between capture fisheries, which produces approximately 93 million tonnes of food per year, and the projected growth in utilization, which is estimated to reach 261 million tonnes by 2030 (FAO and World Bank, 2015). To meet this demand, the aquaculture sector needs to increase production by 70-100 percent above current levels over the next two decades. There are several ways this could be done, for example, through innovations in feed conversion ratios, improved disease control, the intensification of production at existing sites and the development of new sites in underutilized areas. However, aquaculture development also faces growing constraints as competition for land, water, energy and feed resources intensifies. These constraints, combined with potential impacts of ocean acidification and climate change on ecosystems and dependent communities, present significant challenges to the entire sector (Brander, 2007; Béné et al., 2016; Little et al., 2016). Reducing waste and discards, strengthening the management of capture fisheries, increasing access to harvest and improving the distribution of fish and seafood products are also crucial for meeting the growing demand for fisheries and aquaculture products.
The successful and continued delivery of benefits from fisheries and aquaculture will require the development of clearly targeted policies, sound management, technical changes and investments.
B4 - 3.3 People, communities and vulnerability
When is climate change a risk?
To improve the understanding of how to support the adaptation process of natural and human systems to climate-related changes, the IPCC has modified its theoretical risk framework in its Fifth Assessment Report by recognizing that “climate change is not a risk per se” (IPPC, 2014a, p. 1050). Climate change only becomes a risk in systems that are unable to cope with it. Risk is explicitly linked to 1) the likelihood of climate-related events or change (e.g. sea level rise, acidification, increased water temperatures); 2) the degree to which the system is exposed to the hazard (e.g. the number of coastal communities in a region where the climate event occurs, the number of commercially important fish species in a lake, the existence of coral reefs); and 3) the vulnerabilities within the system (e.g. the lack of an early warning system, overfished resources, undiversified practices and livelihood strategies).
Who is at risk and where?
Hundreds of millions of people who depend on fisheries, aquaculture and fish processing for their livelihoods, food security and nutrition are at risk from the impacts of climate change (FAO, 2016a). Fishers, coastal communities and sector-related infrastructure are particularly threatened by extreme events (e.g. storms and cyclones) and sea level rise.
The IPPC's Fifth Assessment Report noted that one model projects that the annual landed value of marine fish in West Africa is estimated to decline by 21 percent, resulting in a nearly 50 percent decline in fisheries-related employment, and a total annual loss of US$ 311 million to the region’s economy relative to 2012 (IPCC, 2014b, p. 1221). A number of other studies have examined the potential impacts of climate change on fisheries and aquaculture. Allison et al. (2009) looked at the vulnerability of national economies by examining the impacts of climate change on their fisheries (see Box B4.1). Bell et al. (2011) considered the vulnerability of species, food webs and ecosystems, and explored issues related to tunas, feeding patterns, coral reefs, mangroves, freshwater habitats and fisheries activities in the tropical Pacific islands. Cinner et al. (2012) built upon the IPCC model by imbedding the vulnerability of coral reef systems to climate change into measurements relating to the vulnerability of the fishing communities that depend on the coral reefs as a way of capturing the links between the human activities and aquatic systems. Barange et al. (2014), by combining dependence of economies and food systems on fisheries with projected impacts of climate change, suggest that these impacts will be of greatest concern in South and Southeast Asia, South West Africa, Peru and some SIDS in the tropics. A good overview on the vulnerability of national economies to the impacts of climate change through fisheries is provided in Box B4.1.
In the Lower Mekong Delta in Asia, Cambodia and Viet Nam are among the countries that are most vulnerable to the impacts of climate change on fisheries (IPCC, 2014b, p. 1355). The Fifth Assessment Report identified Colombia and Peru as the South American countries whose fisheries are the most vulnerable to the impacts of climate change impacts. Their vulnerability is due to the combined effects of observed and projected warming trends; shifts in species and productivity in oceanic upwelling systems; the relative importance of fisheries to national economies and diets; and the limited capacity to adapt to associated risks and opportunities (IPCC, 2014b, p, 1526). Countries that have borders on semi-enclosed seas and/or depend heavily on their inland fisheries are likely to experience adverse impacts of climate change.
Coastal countries and communities, and those with major rivers and lakes, are particularly vulnerable to extreme climate events. An assessment conducted by FAO between 2003 and 2013 concluded that, in developing countries, the agriculture sector, including fisheries and aquaculture, absorbs approximately 22 percent of the economic damage caused by medium- and large-scale natural disasters (FAO, 2015a). SIDS, whose economies are highly dependent on fisheries and where the sector plays an important role in food security and employment, tend to suffer more from the effects of climate change and climate variability (FAO, 2015a).
Supply and value chains are likely to be effected by changes in temperature and humidity. For example, traditional food processing in the Arctic (e.g. the drying of fish) is at risk due to increasingly wet conditions (IPCC, 2014b p. 1583). Evidence of rising rates of food-borne illnesses, such as ciguatera fish poisoning, are heightening concerns about the impact of climate change on food safety (IPCC, 2014b, p. 1624). Along with its impacts on food security and safety, climate change may also threaten human health by increasing the incidence of other types of diseases. The impacts are likely to affect infrastructure in all sectors, as well as social services, causing displacement of communities and subsequent migration and/or conflict.
Countries that rely the most on fishery resources tend to be most likely to suffer the consequences of climate change (Barange et al., 2014). Small-scale fishers, who are heavily dependent on coastal and inland fisheries, are particularly vulnerable to climate change. Small-scale fisheries provide jobs for approximately 47 million people, with about 12.5 million directly engaged in fishing and another 34.5 million engaged in post-harvest activities (IPCC, 2014b, p. 1701). These fisheries, especially in tropical countries, are often vulnerable due to an number of factors, including: the high exposure of low-latitude regions to the impacts of climate change; poor governance and management structures; and little or no data on fish stocks (IPPC, 2014a, p. 776). The bulk of the world’s aquaculture production is done in the tropics, where population densities are high, which also makes the sector especially vulnerable (De Silva and Soto, 2009).
Box B4.1 Global mapping of national economies' vulnerability to climate change impacts through fisheries
Following the IPCC definition of vulnerability, which integrates exposure, sensitivity and adaptive capacity, and using available data, the relative vulnerability of national economies to the impacts of climate change on fisheries has been calculated for 132 countries. The analysis indicated that, in Africa, there were 16 least developed countries, and in Asia, three least developed countries, that were listed among the most highly vulnerable countries. Unfortunately, limited data precluded many SIDS from being included in the analysis. However, given their high dependence on fisheries, low adaptive capacity and high exposure to extreme events, they are also likely to be among the more vulnerable countries.
While many African marine coastal fisheries are not likely to experience major physical impacts, the region’s adaptive capacity to respond to climate change is relatively low and fish consumption high. As a result, some economies are highly vulnerable to even minor changes in climate and temperature. In the northern hemisphere, the Russian and Ukrainian economies were ranked highly vulnerable due to the impact higher temperatures are expected to have on their fisheries and their low adaptive capacities.
- Sources: Allison et al., 2009 and Daw et al., 2009