There is a more than 60% chance that a “super” El Niño will develop by the end of this year.
This is defined as the strongest El Niño event you can get, and happens when sea surface temperatures in the tropical Pacific Ocean rise by more than 2°C. During a super El Niño, the ocean gives off extra heat into the air, which helps raise global temperatures. Because climate change is already warming the planet, a super El Niño could push global temperatures to the highest levels ever recorded.
El Niño conditions have already begun this year, according to the US National Oceanic and Atmospheric Administration. While El Niño is a natural phenomenom, climate change means that El Niños are becoming stronger and more frequent.
Hotter sea surface temperatures could spell big problems for marine wildlife and fisheries alike. As the oceans warm, they become more layered, leading to warm, nutrient-poor water sitting on the surface, and cooler, nutrient-rich water trapped below. This layering makes it harder for nutrients to rise to the surface. As a result, there are fewer nutrients available for phytoplankton, the tiny plants that form the base of the marine food chain.
With less phytoplankton in the oceans, there is less food for zooplankton (microscopic animals that eat phytoplankton), fish and larger animals including seabirds and marine mammals. This is even more pronounced for the tropical eastern Pacific. The Humboldt current usually brings cold, nutrient-rich water up to the surface, creating one of the most productive marine regions on Earth. But this current is disrupted and overwhelmed during an El Niño. This rich ecosystem supports both wildlife and important fisheries, making it one of the most biologically and economically important ocean regions in the world.
Met Office, CC BY
Dramatic effects on fisheries
Strong El Niño events are known to seriously affect Peruvian anchoveta stocks (Engraulis ringens). The super El Niño led a 55% decline in catch in 1972 and 51% on 1973, leading to severe economic hardship. The collapse was driven by El Niño combined with high fishing pressure, as fleets continued trying to maintain catch rates despite rapidly declining stocks. This forced government intervention in the fishery.
The Peruvian anchoveta (Engraulis ringens) is the basis of the world’s largest single-species fishing area, worth an estimated US$1-3 billion (£74.5 million-£2 billion) each year. Globally, this fishery accounts for about 20% of all fishmeal production, which in turn provides roughly half of the feed used in global aquaculture. This makes the species not only vital for Peru’s economy, but also essential for supporting fish farming and food production worldwide.
Reduced fishing quotas
These days El Niño conditions lead to reduced quotas and fishery closures. The anchovy fishery is currently closed due to El Niño. This has led to record-high fishmeal prices (US$2,500 per tonne) which will make aquaculture food more expensive and lead to higher fish farming costs globally.
While the Peruvian anchoveta fishery is perhaps one of the most severely effected and well-documented fisheries in response to El Niño, other fisheries across the globe are also affected by these changing ocean conditions. Along the Californian coast, squid landings plummet during El Niño years. Similarly, in the Indian Ocean, tuna catches appear to be at their lowest after a strong El Niño. Not all fish stocks decline, and some have been shown to increase in response to warmer temperatures. Declining and altered fish stocks during El Niño have been shown to lead to increased fish “wars” between countries in the South China Sea, as fishermen follow migrating fish stocks into other countries economic zones.
Corrado Baratta/Shutterstock
Dying coral reefs
El Niño can also have a major impact on marine habitats. One of the most widely recognised effects is on coral reefs, with warmer marine temperatures triggering bleaching, causing corals to expel the microscopic algae they rely on for energy, and in some cases die. During El Niño years, widespread bleaching becomes common across the tropical Pacific, Indian Ocean, south-east Asia and north-east Australia, highlighting the ripple effect of El Niño.
The recent 2023-24 El Niño triggered unprecedented heat stress across the globe, with extensive mortality documented in many countries (for instance Mexico, Australia and Costa Rica).
But it is not just coral reefs that are at risk. In the Galapagos Islands, seaweed and coral habitats have disappeared, or are extremely degraded, due to sensitivity to El Niño. Similarly, mangroves have suffered mortality in Australia, while in California, kelp populations have decreased by 50-70% during El Niño.
Starvation of seals and sea lions
Large marine animals have suffered during strong El Niño. Most notable has been the starvation of a large proportion of fur seals (Arctocephalus galapagoensis) and sea lions (Zalophus californianus wollebaeki) in the Galapagos, and the dramatic reduction in seabird populations in Peru. Many South American fur seals (Arctocephalus australis) and South American sea lions (Otaria byronia) along the southern coast of Peru died. The mother seals remained at sea for longer than ever recorded before, and this is likely to be because they were looking for food.
El Niño can trigger harmful algal blooms, which occur when tiny algae in the water grow really fast and produce toxins that can harm animals and people. These blooms have led widespread deaths of whales when they feed in affected areas near the coast.
It’s hard to determine what the extent of a super El Niño will be on marine life. But with our oceans already struggling under climate change, and little time for marine populations to recover from the last El Niño of 2023-24, it could be the most devastating one yet.
