In Hot Water
Challenges and solutions to ocean warming
From microorganisms to beluga whales, ocean warming is impacting many species and its effects are cascading through ecosystems, as outlined in a new IUCN report. Here, we look at the resulting challenges – and how the ongoing IUCN World Conservation Congress is addressing them.
Up to now, the oceans have shielded us from the worst impacts of climate change by absorbing most of the heat caused by rising greenhouse gas emissions, and capturing around a quarter of the carbon dioxide released. The resulting ocean warming and acidification have added to other pressures on marine life, such as pollution and over-fishing, and the populations of many species are shrinking or shifting in response.
From the poles to the tropics, plankton, jellyfish, turtle, fish and seabird species are on the move, shifting by up to 10 degrees of latitude to find cooler habitats, while some breeding grounds for turtles and seabirds disappear.
Species on the move
The distribution patterns of species like pelagic tuna, Atlantic herring and mackerel, and European sprats and anchovies are gradually shifting in response to changing ocean temperatures. Some fish are moving tens to hundreds of kilometres per decade.
But not all species are able to cope.
Over the last three decades, as the planet has warmed, the frequency of coral bleaching has increased three-fold. In Western Australia, extensive areas of kelp forest were wiped out during a marine heatwave. In the Southern Ocean, progressive warming has been associated with a decline in krill, with populations of many seabirds and seals also decreasing.
"Mangroves are invading marsh-dominated ecosystems around the world, representing one of the most dramatic plant range shifts occurring today" - IUCN report, Explaining Ocean Warming
Ocean warming drives a chain of impacts that link to human society. Communities that rely on the ocean for daily subsistence – typically the poorest coastal nations – are likely to suffer the greatest losses. Ocean-based fisheries, tourism, aquaculture, coastal risk management and food security are all threatened by ocean warming combined with over-fishing and population growth.
"The effects on food security are likely to be greatest in tropical and subtropical countries where the largest reductions in fisheries production are generally expected to occur. However, as profound as the effects of ocean warming on productivity of marine fisheries are likely to be in many of these countries, population growth and the quality of resource management will probably have a much greater influence on availability of fish per capital for the next few decades" - IUCN report, Explaining Ocean Warming
Oceans at the crossroads
The report recommends a series of actions to address these impacts, including mitigating CO2 emissions, enhancing marine protected areas, and protecting the high seas and ocean seabed under the Law of the Sea and by expanding the World Heritage Convention.
Participants at the ongoing IUCN World Conservation Congress in Honolulu, Hawai'i, are working to address some of these challenges.
This week, hundreds of delegates will vote on a motion to increase marine protected area coverage for effective marine biodiversity conservation. Not far from where they are meeting, the Papahānaumokuākea Marine National Monument off the coast of Hawai'i, a UNESCO World Heritage site, was expanded last week to create the world's biggest marine reserve.
"I profoundly hope Papahānaumokuākea Marine National Monument doesn't keep the designation for long, that someone else will step forward and protect even more" - US Secretary of Interior Sally Jewell, speaking at the IUCN Congress opening
Another motion to be voted on at IUCN Congress deals with advancing conservation and sustainable use of biological diversity in the high seas, which account for two-thirds of the world's oceans.
A motion to achieve representative systems of protected areas in Antarctica and the Southern Ocean will also be voted on.
The Congress is also expected to decide on motions dealing with regional approaches to tackling the global problem of marine litter, and on the protection of marine and coastal habitats from mining waste. In recognition of the important role that oceans play in climate change, another motion proposes to take greater account of the ocean in the climate regime.
Explore all the ocean-related events at IUCN Congress here.