Vulnerabilities - Global observations

The IPCC concluded that ocean warming in the 20th century and beyond has contributed to an overall decrease in maximum catch potential. In many regions, declines in the abundance of fish and shellfish stocks due to direct and indirect effects of global warming and biogeochemical changes have already contributed to reduced fisheries catches (46). Under a high-end scenario of climate change (RCP8.5), the maximum catch potential of fisheries is projected to decrease by 20.5 - 24.1% by the end of the 21st century relative to 1986 - 2005. This is three to four times larger than under the low-end scenario of climate change (RCP2.6) (46).

Higher ocean temperatures drive a number of changes: changes in ocean circulation and stratification, decrease of oxygen concentrations, and shifts of primary productivity following shifts in temperature. As a result, marine fish populations are experiencing large-scale redistributions (37), increased physiological stress (38), and altered food availability (39). Changes in fish biomass may impact long-term food provisioning. In addition to ocean warming, other factors can change fish productivity, such as changing primary production, dissolved oxygen, pH, and habitat availability (36).

Fish productivity can be expressed in a quantity termed the ‘maximum sustainable yield’: the maximum catch that can be repeatedly (sustainably) harvested from the ocean’s fish biomass. The effects of ocean temperature changes from 1930 to 2010 on the productivity of 235 global fish and invertebrate populations, covering 33% of reported global catch, have been modelled (36).

The results show that ‘maximum sustainable yield’ decreased by 4.1% in this period. The 95% confidence interval for this trend ranged from a 9.0% decline to a 0.3% increase. The greatest losses in productivity occurred in marine regions of East Asia and Europe (North Sea, French and Iberian coastal zones). The greatest gains occurred in marine regions near the east coast of Canada and the United States, and in Europe in the Baltic Sea. The great losses in East Asia are particularly worrying, since this region has some of the largest and fastest-growing human populations in the world. The gain for the Baltic Sea is due to the fact that currently cooler water temperatures delay and reduce spring zooplankton production and result in reduced survival of larval fish (40).

Studies that project fisheries productivity under future emissions scenarios often predict increases in productivity at the poles and decreases at the equator (41). These “winning” and “losing” ecosystems under ocean warming are not reflected yet in the changes from 1930 to 2010. Possibly this is just a matter of time.

Overfishing seems to strengthen the impact of ocean warming on fish productivity. Fish populations that had experienced intense and prolonged overfishing were more likely to be negatively influenced by warming. This interaction likely arises through several mechanisms. For instance, fishing can truncate age distributions and thus decrease reproductive output (42). Also, fishing can reduce intraspecific diversity, alter species interactions, and damage habitat (43). Overfishing has reduced the resilience of populations to climate change, and climate change will likely hinder efforts to rebuild overfished populations (44).

Vulnerabilities - Observations in Europe

In European seas, warming causes a displacement to the north and/or in depth of fish populations which has a direct impact on fisheries (4). In response to climate change and intensive fishing, widespread reductions in fish body size (5) and in the mean size of zooplankton (6) have been observed over time and these trends further affect the sustainability of fisheries (7).

North Sea and Northeast Atlantic

In the North-east Atlantic Ocean, 72 % of commonly observed fish species have responded to warming waters by changing their abundance and/or distribution. Traditionally exploited fish species have moved further northwards in the region, while new species have moved in, most likely as a result of a shift in the thermal regime (26). While warming can lead to an increase in fish biodiversity 
in a region, there is often a concurrent decrease in the size structure of the fish population. For example, in the Greater North Sea, the relatively small species sprat, anchovy and horse mackerel have increased in recent decades, whereas the larger species cod and plaice have decreased at their southern distribution limit (27). This change may have important socio-economic consequences, as the stocks moving out tend to have a higher value than the stocks moving in. Pronounced changes in community structures and species interactions of demersal fish are projected over the next 50 years, as fish will experience constraints in the availability of suitable habitat (28). 

The North Sea has witnessed significant warming over the past century at a rate of around 0.3 °C per decade (8). Projections suggest that the region will continue to experience warming, by around 2 - 3 °C over the next 100 years (9). Long-term changes in seawater temperature and/or other ocean variables often coincide with observed changes in fish distribution. In an analysis of 50 fish species common in waters of the Northeast Atlantic, 70 % had responded to warming by changing distribution and abundance (10). Specifically, warm-water species with smaller maximum body size had increased in abundance throughout northwest Europe while cold-water, large-bodied species had decreased in abundance.

Records from 57,870 fisheries-independent survey trawls from across the European continental shelf between 1965 and 2012 showed a strong ‘subtropicalisation’ of the North Sea as well as the Baltic Sea. In both areas, there has been a shift from cold-water assemblages typically characterised by Atlantic herring and sprat from the 1960s to 1980s, to warmer-water assemblages typified by mackerel, horse mackerel, sardine and anchovy from the 1990s onwards. The primary measure correlated to changes in all species was sea surface temperature (11). Haddock catches have moved very little in terms of their centre of distribution, but their southern boundary has shifted northwards by approximately 130 km over the past 80–90 years (12).

Global projections of changes in total catch of marine fish and invertebrates in response to ocean warming suggest a large-scale redistribution of global catch potential, with an increase in high-latitude regions and a decline in the tropics. In Europe, a considerable increase in catch potential is expected in the Arctic (29).

Mediterranean Sea

Fisheries landings have shifted significantly for nearly 60% of the 59 most abundant commercial fish. Most (~70%) declined (on average by 44%), but increases were also found — mostly for species with short lifespans, which seem to have benefited from increased temperature (30). Both climate change and overfishing undermine the future of Mediterranean fisheries (31).  

Vulnerabilities - Migrating fish and political conflict 

The impacts of climate change can lead to conflict, but conflict not necessarily leads to violence. This is exemplified with the so-called ‘’mackerel case’’. Like many fish species mackerel is migrating into northern Atlantic waters, possibly as a response to ocean warming. This led to a rapid change in the distribution of the northeast Atlantic mackerel stock after 2007. This mackerel became more abundant in northern Atlantic waters, which in turn triggered an interstate conflict over the size and allocation of fishing quotas between the European Union (EU), Norway, Iceland, and the Faroe Islands (20).

Situation before the mackerel shift

When mackerel stocks frequent the national waters of a nation, defined as a 200-mile exclusive economic zone (EEZ), that nation is considered a “Coastal State” for that stock and has the right to harvest it in their EEZ. As so-called Coastal States, these countries are responsible for management of the stock. They negotiate the division of fishing resources (20).

Before the mackerel shift in 2007 the “main players” in the Coastal State meetings were the EU and Norway. These countries had been dealing with the sharing of the stock since 1999, had the biggest mackerel fishing fleet, and worked together on the scientific surveys that are used to advise the States on quota allocations. The Faroe Islands only played a minor role in the quota negotiations, and Iceland was not considered as a Coastal State (20).

The start of the conflict

The interstate conflict started after the mackerel moved northwards. The area of migration has progressively expanded as far as Icelandic and south Greenlandic waters in the west, and as far north as Spitzbergen (21), may be due to changes in food availability, increased water temperature, and/or increased stock size. Due to this change in distribution, Icelandic and Faroe fishers got better access to the stock and therefore wanted to secure their fishing rights. The Faroe Islands wanted to enlarge their mackerel quota, while Iceland wanted to become an accepted Coastal State member to secure their quota share (20).

The conflict between the EU/Norway and the Faroe Island dissolved in 2014 with a new management agreement, which allocated a substantially larger mackerel quota to the Faroe Islands (22). The conflict with Iceland still persisted in 2017.

So far, even though Iceland has become a Coastal State, it has not been involved in the Coastal States’ agreements on the total allowable catch (TAC) and quota allocations per country. The main reason for this failure is that a social and political dispute between the Coastal States developed which persists to this day. The conflict prevents collaboration with Iceland in a joint management plan and subsequently sustainable management of the stock. As a result, the Coastal States overfished the mackerel stock increasingly from 2007 onwards (20).

A permanent shift, or not?

The reasons behind the mackerel shift are not quite clear. It has been argued that this allows countries to select the scientific explanation that best serves their interests (23). Accepting that the shift is caused by climate change would confirm the permanence of the shift. This explanation is advantageous for Iceland and the Faroe Islands, but not for the EU and Norway because they would have to accept a (semi)permanent decline in their share of the TAC. Consequently, the latter countries prefer to consider the shift as temporary and the result of ‘normal’ environmental fluctuations.

According to the authors of this study the mackerel dispute is currently experiencing a (re)balancing of power between the various Coastal States due to their growing interdependence. Iceland and the Faroe Islands probably will claim larger shares as the mackerel shift continues, and new countries (like Greenland) may also demand access (20).

An example of future conflicts

The mackerel case is an empirical example of a process of global environmental change that will manifest itself more pronounced and widely in the decades to come. Marine scientists anticipate large-scale changes in distribution and productivity of marine organisms under the influence of ocean warming (24), which are expected to increase the potential for international conflict over marine resources, impeding effective and sustainable marine governance (25). 

Vulnerabilities - Future projections

Global changes in vulnerability marine fisheries

It is highly likely that marine fisheries around the world are vulnerable to the various impacts of climate change. A country’s vulnerability to climate change depends on three variables: (1) its exposure to climate change impacts, (2) its sensitivity to changes in productive capacity associated with these climate change impacts, and (3) its adaptive capacity, or the ability to modify or adjust fisheries and livelihoods in order to cope with the negative impacts of climate change and pursue any emerging opportunities. The vulnerability of 147 countries’ marine fisheries was calculated; landlocked countries were not considered. This was done for the near future (2016-2050) and a distant-future projection (2066-2100), compared with 1900-1950 as a reference. Climate change projections were based on a large number of climate models and a low-end (RCP 2.6), intermediate (RCP 4.5) and high-end (RCP 8.5) scenario of climate change (19).

For the exposure, change in average sea surface temperature was computed. The sensitivity or dependence of countries with regard to marine capture fisheries was calculated as an index of five variables: number of fishers, share of marine fisheries exports in total exports, percentage of fishers in the economically active population, weight of total fisheries landings, and share of marine fish protein in total protein consumption. Adaptive capacity was calculated from fisheries subsidies, the ratio of industrial to small-scale fisheries, healthy life expectancy, governance capacity, education levels, and per capita gross domestic product (19).

The study shows that the countries most vulnerable to the effects of climate change on fisheries are primarily small island states in the Pacific Ocean and Caribbean, and countries along the Western and Eastern coasts of Africa. All 29 countries in Europe, on the other hand, appeared to be among the countries having the lowest vulnerability scores. The low vulnerability scores for Europe are due to Europe’s high adaptive capacity, a continuous drop in employment in the fisheries sector over the past decades, and relatively low economic importance of the fisheries sector (19).

Global changes in fish catch potential

Climate change yield impacts were projected for countries with different dependencies on marine fisheries, based on linked models of physical, biological and human responses to climate change (and the A1B SRES emissions scenario). The analyses were carried out for a large number of countries that in total yield approximately 60% of global fish catches. Projected impacts indicate increased fish productivity at high latitudes and decreased productivity at low/mid latitudes, with considerable regional variations. Increases and decreases in fish production potential by 2050 are estimated to be <10% from present yields (1).

The results are consistent with previous studies that predicted a 30-70% increase in fish catch potential in high latitudes and a 40% drop in the tropics, with a global 1% overall increase by 2050 (2,3). However, others projected global decreases of marine fisheries maximum revenue potential by 2050 relative to 2000 of 7.1% ± 3.5% and 10.4% ± 4.2% under a low-end (RCP2.6) and high-end scenario of climate change (RCP8.5), respectively (47). Marine fisheries maximum revenue potential may be negatively impacted in 89% of the world’s fishing countries under the high-end scenario of climate change by the 2050s relative to the current status (47). Overall, climate change impacts on the abundance, distribution and potential catches of fish stocks are expected to reduce the maximum potential revenues of global fisheries (48).

For Europe, there will be an increase in Iceland and Norway. Climate change and exploitation impacts are likely to be of greatest concern in the maritime countries of South and Southeast Asia, where fishing pressure is already very high and poorly regulated (1).

Potential increase sustainable sea food production

Food from the sea is produced from wild fisheries and species farmed in the ocean (mariculture), and currently accounts for 17% of the global production of edible meat (54). The sea can be a much larger contributor to sustainable food production than is currently the case, scientists recently reported in the journal Nature. They examined the main food-producing sectors in the ocean: wild fisheries, finfish mariculture and bivalve mariculture (53).

Widely publicized reports about climate change, overfishing, pollution and unsustainable mariculture give the impression that sustainably increasing the supply of food from the sea is impossible. Indeed, the production of wild fisheries is approaching its ecological limits. The vast majority (over 80%) of edible meat from the sea comes from wild fisheries (55). Over the past 30 years, supply from this wild food source has stabilized globally despite growing demand worldwide, which has raised concerns about our ability to sustainably increase production. Of nearly 400 fish stocks around the world that have been monitored since the 1970s by the UN Food and Agriculture Organization (FAO), approximately one third are currently not fished within sustainable limits (56).

Current mariculture production, however, is far below its ecological limits and could be increased. This can be done by replacing environmentally damaging mariculture practices with environmentally sustainable expansion, and by using alternative feed ingredients instead of fishmeal and fish oil that is largely derived from wild forage fisheries. Mariculture production has grown steadily over the past 60 years and already provides an important contribution to food security (57).

Especially thanks to an increase of mariculture production, edible food from the sea could increase by 36-74% compared to current yields. This represents 12-25% of the estimated increase in all meat needed to feed 9.8 billion people by 2050. Increases in all three sectors are likely, but are most pronounced for mariculture (53).

North Sea and Northeast Atlantic

Model simulations suggest that distributions of exploited species will continue to shift in the next five decades both globally and in the Northeast Atlantic specifically (13). The current rate is around 20 km per decade for common fish in the North Sea (14).

Assessing economic implications: a number of studies have set out to investigate the vulnerability and adaptive capacity of the fisheries sector at a global scale (15,16). Vulnerability to climate change depends upon three key elements: exposure to physical effects of climate change, sensitivity of the natural resource system or dependence of the national economy upon economic returns from the fishing sector, and the extent to which adaptive capacity enables these potential impacts to be offset. North Sea countries were ranked very low in terms of overall vulnerability, largely due to low rates of fish consumption in the surrounding countries, highly diversified economies and only moderate exposure to future climate change (16,17).

Mediterranean Sea

Fisheries and aquaculture, crucial for food security and the economy of the Mediterranean (32), are currently impacted most by overfishing and coastal development. Ocean warming and acidification are very likely to impact fisheries more significantly during the coming decades, with more than 20% of exploited fish and marine invertebrates expected to become locally extinct around 2050. Mediterranean countries import more fish products than they export, as a result of the increasing demand for seafood. Despite being major exporters, France, Spain and Italy are the countries with the highest trade deficits for seafood. Global models project that by 2040 - 2059 more than 20% of exploited fishes and invertebrates currently found in the eastern Mediterranean could become locally extinct due to climate change (33). By 2070 - 2099, 45 of the 75 endemic Mediterranean species are expected to qualify for the IUCN Red List of Threatened Species, and 14 more could have become extinct (34). The expected migration of species to cooler areas as the ocean warmsis limited in enclosed seas. For this reason, the Mediterranean Sea has been described as a ‘cul-de-sac’ for endemic fishes, including commercial species, facing climate change (34).

Collaborative management of fisheries and oceanic food resources and sustainable management of the Mediterranean Sea will be increasingly more necessary as unsustainable practices in one country, enhanced by the effects of climate change and land-based pollution, will affect catches in all other countries (35).

Vulnerabilities - Simultaneous future impacts on agriculture and marine fisheries 

Climate change affects both agriculture and marine fisheries. Food security of a large part of the world population depends on both food sectors. What if climate change negatively affects both sectors at the same time?

The vulnerability of societies to the simultaneous impacts of climate change on agriculture and marine fisheries was analysed at a global scale. Changes in productivity of these food sectors were projected to the end of the century relative to the current situation. Two scenarios of climate change were used for this: a high-end (RCP8.5)] and a low-end (RCP2.6) scenario. For agriculture, changes of crop yields of maize, rice, soy, and wheat were evaluated. These projected impacts of climate change were combined with data on countries’ dependency on each of these sectors for food, economy, and employment. Also the capacity of countries to respond (adapt) to climate impacts was evaluated (49).

Win or lose

In countries that depend on both food sectors, four situations may unfold: both sectors are favoured by climate change, both sectors are negatively affected, losses occur in one sector and gains in the other, and there are no impacts at all.

Under a high-end scenario of climate change, almost the entire world population (97%) is projected to be directly exposed to high levels of change in at least one of these food sectors by 2100. Under this scenario, 90% of the projected world population in 2100 would live in countries with productivity losses in both sectors. Only up to 3% of the world population would live in regions projected to experience productivity gains in both sectors by 2100 (49).

Under a low-end scenario of climate change, still about 60% of the world’s population will be directly exposed to productivity losses in both sectors by 2100, according to these future projections. The world’s population living in regions projected to experience productivity gains in both sectors by 2100 will be about 5% (49).

A “perfect storm” in the tropics


For tropical areas, particularly in Latin America, Central and Southern Africa, and Southeast Asia, a “perfect storm” is projected. These areas are generally highly dependent on agriculture and fisheries for employment, food security, or revenue, and for these areas exposure to lower agriculture productivity and lower maximum fisheries catch potential is projected by 2100. Besides, most developing countries in these areas lack the capacity to respond to and recover from climate change impacts (49).

In Europe and North America, the situation is completely different. At these higher latitudes, food, jobs, and revenue depend less on agriculture and seafood production, while the losses these regions will experience are much less than those in the tropics. In fact, food security will even improve in some cases, such as Canada and Russia (49).

Losses are inevitable

According to these results, losses in productivity potential are inevitable in many cases. The fact that a large part of the world’s population will be negatively affected even under a low-end scenario of climate change is not hopeful. However, the magnitude of the losses would be considerably lower under this low-end scenario compared with the high-end scenario. For countries facing lose-lose conditions, moving from the high-end to the low-end scenario of climate change results in a shift of productivity losses from −25 to −5% for agriculture and from −60 to −15% for fisheries. Main improvements would occur in Africa (all crops and marine fisheries), Asia (mostly marine fisheries and wheat), and South America (mostly wheat and soy), but also in Europe (mostly marine fisheries) and North America (mostly wheat and marine fisheries). Hence, although negative consequences of climate change cannot be fully avoided in some regions of the world such as Africa, Asia, and Oceania, they have the potential to be drastically lowered if mitigation actions are taken rapidly (49).

Other food sectors

In this analysis, other food sectors were disregarded, including aquaculture, freshwater fisheries, and livestock production. In the scientific literature, also for these food sectors negative impacts of climate change are projected. Some vulnerable countries have a notable freshwater fishery sector. There seems to be little potential to increase inland fisheries productivity because of increased competition for waters and the current high proportion (90%) of inland catch coming from already stressed systems (50). The global potential of marine aquaculture production that does not rely on inputs from wild-capture feeds (i.e., shellfish) is expected to decline under climate change, although regions such as Southeast Asia may become more suitable in the future (51). For the livestock sector, decline in pasture productivity in many regions with notable broad-care grazing industry, such as Australia and South America, combined with additional stresses (stock heat and water stress, pests, rainfall events) is likely to outweigh potential benefits. Besides, the intensive livestock industries may be affected by disruption of major feed crops and marine fish stocks used for fishmeal (52).

Adaptation strategies

Prompt improvements in fisheries management could maintain global wild-capture fisheries yields and profits into the future (45). It is essential to prevent overfishing and develop management strategies that are robust to temperature-driven changes in productivity (36). 

Adaptive responses to climate change in fisheries could include: management approaches and policies that maximize resilience of the exploited ecosystems, ensuring fishing and aquaculture communities have the opportunity and capacity to respond to new opportunities brought about by climate change, and the use of multi-sector adaptive strategies to reduce the consequence of negative impacts in any particular sector (3).

Despite projected human population increases and assuming that per capita fish consumption rates will be maintained, ongoing technological development in the aquaculture industry suggests that projected global fish demands in 2050 could be met. This conclusion, however, is contingent on successful implementation of strategies for sustainable harvesting and effective distribution of wild fish products from nations and regions with a surplus to those with a deficit (1).

In Europe the estimated annual cost of adaptation to climate change in the fisheries sector is USD 0.03 - 0.15 billion, a small fraction of the costs (USD 1.05 - 1.70 billion) anticipated for East Asia and the Pacific (18). 

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Europe.

1. Barange et al. (2014)
2. Cheung et al. (2009, 2011), in: Barange et al. (2014)
3. IPCC (2014)
4. Daufresne et al. (2009); Cheung et al. (2010); Cheung et al. (2013); Tasker (2008), all in: IPCC (2014)
5. Daufresne et al. (2009), in: IPCC (2014)
6. Beaugrand and Reid (2012), in: IPCC (2014)
7. Pitois and Fox (2006); Beaugrand and Kirby (2010), both in: IPCC (2014)
8. Mackenzie and Schiedek (2007), in: Pinnegar et al. (2016)
9. Lowe et al. (2009), in: Pinnegar et al. (2016)
10. Simpson et al. (2011), in: Pinnegar et al. (2016)
11. Montero-Serra et al. (2015), in: Pinnegar et al. (2016)
12. Skinner (2009), in: Pinnegar et al. (2016)
13. Cheung et al. (2009), (2010), (2011); Lindegren et al. 2010, all in: Pinnegar et al. (2016)
14. Dulvy et al. (2008), in: Pinnegar et al. (2016)
15. McClanahan et al. (2008), in: Pinnegar et al. (2016)
16. Allison et al. (2009), in: Pinnegar et al. (2016)
17. Barange et al. (2014), in: Pinnegar et al. (2016)
18. Sumaila and Cheung (2009), in: Pinnegar et al. (2016)
19. Blasiak et al. (2017)
20. Spijkers and Boonstra (2017)
21. ICES Advisory Committee (2013); Nøttestad et al. (2014a), both in: Spijkers and Boonstra (2017)
22. Government of the Faroe Islands (2014); Droesbeke (2015), both in: Spijkers and Boonstra (2017)
23. Gänsbauer et al. (2016), in: Spijkers and Boonstra (2017)
24. Cheung et al. (2010); Gattuso et al. (2015), both in: Spijkers and Boonstra (2017)
25. Miller (2000), in: Spijkers and Boonstra (2017)
26. European Environment Agency (2017)
27. Perry (2005), in: European Environment Agency (2017)
28. Rutterford et al. (2015), in: European Environment Agency (2017)
29. Cheung et al. (2009); Gattuso et al. (2015), both in: European Environment Agency (2017)
30. Tzanatos 
et al. (2014), in: Cramer et al. (2018)
31. Coll et al. (2012), in: Cramer et al. (2018)
32. Piante and Ody (2015), in: Cramer et al. (2018)
33. Jones and Cheung (2015); Cheung (2015), both in: Cramer et al. (2018)
34. Ben Rais Lasram et al. (2010), in: Cramer et al. (2018)
35. Cramer et al. (2018)
36. Free et al. (2019)
37. Pinsky et al. (2013), in: Free et al. (2019)
38. Deutsch et al. (2015), in: Free et al. (2019)
39. Stock et al. (2017), in: Free et al. (2019)
40. MacKenzie and Köster (2004); Bartolino et al. (2014), both in: Free et al. (2019)
41. Blanchard et al. (2012); Barange et al. (2014); Moore et al. (2018), all in: Free et al. (2019)
42. Barneche et al. (2018), in: Free et al. (2019)
43. Planque et al. (2010), in: Free et al. (2019)
44. Britten et al. (2017), in: Free et al. (2019)
45. Gaines et al. (2018), in: Free et al. (2019)
46. IPCC (2019a)
47. Lam et al. (2016), in: IPCC (2019b)
48. IPCC (2019b)
49. Thiault et al. (2019)
50. McIntyre et al. (2016), in: Thiault et al. (2019)
51. Froehlich et al. (2018), in: Thiault et al. (2019)
52. Thornton et al. (2009), in: Thiault et al. (2019)
53. Costello et al. (2020)
54. Edwards (2019); FAO (2020), both in: Costello et al. (2020)
55. FAO (2019), in: Costello et al. (2020)
56. FAO (2018), in: Costello et al. (2020)
57. Belton et al. (2018), in: Costello et al. (2020)