Oceans are turning into deserts! How can we avoid the destruction of fisheries under climate change?

In recent years, climate change has led to the frequent occurrence of various abnormal events, such as the El Niño phenomenon and extreme weather events, which have had a significant impact on the abundance and distribution of fishery resources, and in turn had an impact on the development of the fishing industry.

Among them, the most notable conflict is the "Mackerel War" in the Northeast Atlantic. As global warming has caused changes in the distribution of mackerel resources in the North Atlantic, Iceland and the Faroe Islands have demanded an increase in fishing quotas, but Norway and some EU member states have opposed it. As a result, they have increased their own fishing output, leading to intensified conflicts between the parties, which is what Europeans call the "Mackerel War."

1. How important is the fishing industry?

The fishing industry and its related industries sustain the livelihoods of millions of people worldwide and make significant contributions to the food security and economic well-being of residents in coastal areas and freshwater basins. Specifically, 850 million people live within 100 kilometers of tropical coastal ecosystems and earn income from industries such as fishing, aquaculture and tourism. In addition, nearly 20% of the per capita animal protein intake of 3 billion people comes from fisheries, and the food security of 400 million people is heavily dependent on fish production.

2. How powerful is the impact of climate change on the global fishing industry?

1. Impact on the distribution of marine fishery resources

Climate change has led to changes in the distribution of fishery resources. Scientists' research on the distribution of fish resources in the coastal waters of the eastern United States shows that since 1962, the water temperature on the bottom of the North Sea has risen by about 1 degree, causing 15 species of fish to migrate northward, with the maximum migration distance reaching 400 kilometers. Climate change has caused marine fish and invertebrates to migrate to higher latitudes and deeper waters. More and more studies have shown that changes in ocean temperature caused by climate change are prompting most temperate fisheries to shift geographically. Fish populations may cross the borders of one or more countries, which may lead to more and more disputes over fishery resources and battles for fishery resources.

2. Impact on the global ocean system

The world's oceans (including coastal areas) and freshwater systems are influenced by both chemical factors, such as salinity, oxygen concentration, carbon uptake and acidification, and physical factors, such as changes in temperature, sea level, ocean circulation, and storm systems.

Expected response of the marine food chain to climate change Image from FAO

Studies have shown that the temperature of the upper ocean has increased globally over the past 30 years, but there are large regional differences. The sea level has risen by an average of 1.7 mm per year, with a faster rate in the western Pacific. In addition, regional changes have also occurred in long-term ocean circulation trends, surface winds, storm systems, and wave patterns. Salinity has decreased in high and mid-latitude regions, while it has increased in low latitudes. Rising surface temperatures have led to a decrease in oxygen in warm waters, and there has been a long-term trend of ocean deoxygenation. The ocean stores more than 50 times more carbon dioxide than the atmosphere, and global ocean carbon dioxide storage increased between 1994 and 2010, which has led to an increasingly acidic marine environment and may accelerate the rate of sea level rise.

3. Impacts on coastal systems and low-lying areas

Research shows that all kinds of extreme weather events are expected to occur more frequently around the world in the future. The number of abnormally hot days each year is likely to increase, and heavy precipitation will become increasingly frequent in many areas. Coastal and low-lying areas will be increasingly affected by threats such as flooding, coastal erosion, and saltwater intrusion caused by sea level rise. The sea surface temperature in coastal areas rises faster than in the high seas, and the pH value is lower, so the trend of higher acidification than in the high seas is likely to continue.

4. Impact on marine biological systems

Marine systems are likely to experience biological, geographic, and physical changes due to factors such as warming of the ocean surface, expansion of the anoxic zone, and decreases in pH.

First, the total global marine catch is facing a downward trend year by year. According to relevant statistics, the total global marine catch in 2020 is about 90 million tons, while the total marine catch has decreased by nearly 10% between 1980 and 2010. Experts predict that in the next 30 to 50 years, the output of marine capture fisheries in high-latitude areas will increase by 30% to 70%, while in mid-latitude and low-latitude areas, the overall catch potential may decrease. At the same time, long-term monitoring of the structure of coral communities in the Red Sea shows that corals are being affected by thermal stress and acidification, and the size of the group is decreasing. Although some coral communities in the northern Red Sea seem to benefit from warming, overall, the stability of coral reef ecosystems is declining.

Coral bleaching on Australia's Great Barrier Reef

Coral-dominated ecosystems are disappearing. Image courtesy of the author

Secondly, the size of the "subtropical gyre" in low- and mid-latitude waters has increased since 1993. This change is composed of two major gyres, the clockwise gyre in the North Pacific and the counterclockwise gyre in the South Pacific. Changes in sea temperature have led to changes in the populations of tunas such as skipjack tuna, yellowfin tuna, bigeye tuna and South Pacific albacore tuna, which are the main targets of distant-water fisheries. The catch of yellowfin tuna and albacore tuna is expected to increase, but the coral-dominated ecosystem may disappear by the middle of the 21st century, which is undoubtedly a worrying scenario.

Finally, freshwater ecosystems are severely affected by both climatic and non-climatic factors, making them among the most threatened ecosystems on Earth. Rising water temperatures cause changes in the distribution ranges of river fish populations, while reducing recruitment and survival of fish stocks. For example, cold-water fish species such as rainbow trout have experienced a reduction in their range.

3. Why is Asia the first to be hit by dramatic changes in fisheries caused by climate change?

Asia dominates the global fisheries, accounting for more than half of the world's capture and aquaculture production. However, climate change is expected to have an adverse impact on Asia's food security by the mid-21st century, especially in South Asia. In addition, as early as 2010, some people predicted the redistribution of Asia's marine capture fishery resources, pointing out that fishery resources in high-latitude areas of Asia will increase significantly, while fisheries in tropical areas, such as Indonesia, Cambodia and Vietnam, may face a significant decline in resources due to the fragility of coral reefs in their waters and the serious impact of ocean acidification.

Climate warming will allow corals to expand their habitats northward, but acidification will limit their expansion. It is expected that by the middle of the 21st century, coral reefs dominated by corals will be greatly reduced, which will have a huge impact on the millions of people who depend on them for their livelihoods. In addition, acidification will also have a negative impact on calcifying algae, mollusks and echinodon larvae, but the specific impact on non-calcifying species is not yet clear.

Third, more than 90% of the world's population is exposed to extreme events, and Asia has the largest population and faces the most climate-related risk factors compared to other continents. The increased threat of tropical cyclones in Asia, combined with sea level rise, is likely to further increase the chances of flooding and exacerbate the loss of coral reefs and mangroves. In addition, much of Asia is likely to face higher sea level rise in the future than in recent decades.

Ocean Desertification

The "Dusuruis" have just wreaked havoc, and now the "Puppies" are coming again. Faced with this reality, we must seriously consider how the fishing industry should respond?

IV. Strategies and measures for the fishery sector to cope with climate change

In the face of climate change, we need to adopt an ecosystem approach to improve ecosystem resilience, adaptability and flexibility to quickly respond to climate change. War is not a solution. To this end, the international fisheries community has proposed adaptive selection strategies or resilient fisheries strategies, which aim to promote fisheries development models and practical measures that adapt to climate change and address social, economic and environmental challenges.

First, implement a scientific fishery management system and governance mechanism as soon as possible; second, predict future changes in ocean conditions and rationally plan the geographical distribution of fish populations; third, strengthen international cooperation and establish a shared international fishery management system; fourth, improve the state of the marine ecosystem and ensure that the marine ecosystem can help fisheries recover from the impact or interference caused by climate change; fifth, adhere to the principle of fair and just decision-making and reduce the aggravation of inequality among socioeconomic groups caused by climate change.

Climate-friendly fisheries Image from FAO

5. How to achieve the above goals?

1. Improving the ability to collect, analyze and apply information is the foundation

Strengthening information collection capabilities will help understand the socio-economic impacts and vulnerabilities of fishery and aquaculture systems, develop adaptation plans, improve collaborative mechanisms, study alternative livelihood strategies, increase the added value of aquatic products, and help improve livelihood capacity in fishery regions.

2. Promoting the construction of marine protected areas is fundamental

Marine protected areas have the potential to maintain resilience in aquatic systems, but more information is needed to design and implement them in response to environmental and biological changes. Marine protected area types should adapt to these changes, taking into account both direct and indirect community needs on aquatic resources.

3. Promoting a resilient fisheries development model is key

Timely adjustment of fishery development patterns in response to climate change is a key strategy to meet future demand for aquatic products. Through adaptive and forward-looking management, the ability of marine ecosystems to cope with climate change can be strengthened, and future changes in the marine environment, fishery productivity and fish distribution can be predicted to ensure that fish populations and fish-dependent areas are more resilient.

In recent years, my country's fishery administration has achieved real results in its "Sword-drawing" action. The supply of aquatic products is sufficient, prices are stable, and the industrial structure continues to optimize. At the same time, we have vigorously promoted the green development of aquaculture, implemented the total amount management system of marine fishery resources, strengthened the protection of aquatic biological resources, and implemented strict measures such as the Yangtze River fishing ban. In addition, the construction of marine ranches has been rapidly promoted, the offshore fishery has developed in a standardized manner, and the income of fishermen has steadily increased.

Fishing moratorium photos provided by the author

For the whole world, responding to the impact of climate change on fisheries is a very important and serious issue, which requires all parties in the industry to work together to formulate scientific response strategies and strictly implement various measures.

Author: Liu Yadan (Researcher, National Chief Science Communication Expert)

Scientific review: Wang Qingyin (Researcher, former director of the Yellow Sea Fisheries Research Institute of the Chinese Academy of Fishery Sciences, former chairman of the Chinese Society of Fisheries)

Planning: Wu Yuetong

Editor: Han Chengguo (intern)