Humanity has devastated the Earth's oceans by burning fuels that heat the planet, dumping plastics that persist for centuries and fishing species to the brink of extinction.
But actions today could keep most problems from getting worse.
Policymakers are meeting in Portugal this week to push solutions to protect the oceans. They are the main source of protein for billions of people and a foundation for tourism and fishing industries on which millions depend. They are also a vital line of defense in the fight against climate change.
"While time is running out, we do have enough to turn the tide and invest in a healthy ocean," said Kristian Teleki, an oceans expert at the environmental nonprofit World Resources Institute.
Stopping climate change
One of the most powerful solutions to protect oceans is to stop the planet heating.
Oceans absorb 25% of all carbon dioxide emissions and capture 90% of the heat generated from that pollution. By burning fossil fuels, humans have made oceans hotter, more acidic and less hospitable for fish and plants.
Coral reefs, for instance, will decline 70-90% if global warming reaches 1.5 Celsius (2.7 Fahrenheit) above pre-industrial levels — the target world leaders agreed to aim for in 2015 — and virtually all reefs will die if the world heats 2 C.
But despite a flurry of pledges to cut emissions since the Paris Agreement, current policies are set to heat the planet enough to blow past both of those temperature thresholds.
To honor their promises, policymakers would need to rapidly build sources of clean energy like solar panels and wind turbines, find ways to reduce excessive energy consumption and preserve natural ecosystems like rainforests. They would also need to urgently shut coal plants and stop exploring new oil or gas fields.
Still, oceans will continue to heat up even if all carbon pollution were to stop today. It takes such a long time to reverse trends in the oceans that most animals and ecosystems will continue to see conditions worsen, said Toste Tanhua, a chemical oceanographer at GEOMAR Helmholtz Center for Ocean Research Kiel, a scientific institute pushing for better ocean monitoring systems. "We can hope that young baby whales will see a better ocean when they get old. But that is just hope."
Protecting oceans from humans
In the short-term, policies to protect oceans from human interference will help marine life and the climate recover.
Marine ecosystems are threatened by unsustainable levels of fishing and dangerous practices like bottom-trawling, a way of scraping the seabed with huge metal-plated nets that devastate wildlife and release more carbon dioxide than the aviation industry.
"Fish stocks are depleted, coral reefs are dying and large iconic species such as whales have been pushed to the brink — the damage is extensive," said Minna Epps, head of oceans at the International Union for Conservation of Nature.
The UN and conservation groups are pushing for world leaders to protect 30% of the ocean by 2030. Today, marine-protected zones make up about 7% of the oceans but only 2% are fully or highly protected. A study published in the journal Nature last year found strategically protecting large parts of the oceans would help wildlife, store carbon and provide food.
But the policy also faces opposition from some of the people most vulnerable to ecological destruction.
Indigenous groups say they have been neglected in policy proposals to protect biodiversity despite recognition from scientists that they are effective stewards of nature. A study published in the journal Environmental Science and Policy in 2019 found land managed by Indigenous people in Australia, Brazil and Canada had more biodiversity than government-protected conservation areas.
If marine protections stop them fishing, coastal Indigenous communities could lose food and livelihoods. In other areas, though, they may benefit from healthier waters and fish populations safe from industrial fishing.
"I don't think we should say that every marine-protected area has to be fully protected," said Tanhua, comparing them to national parks in countries that still allow some level of interaction with humans. "We can look at the ocean in the same way — different levels of protection for different areas for different purposes."
Stopping pollution at the source
A third solution is to stop pollution before it enters the oceans.
When durable plastics are littered on the ground or dumped into rivers, they are often transported to seas. Once in the oceans, they are almost impossible to get out.
What's more, plastic continues to damage ecosystems as it breaks down. A study published in February by the World Wide Fund for Nature, a conservation group, found that the amount of microplastic in the ocean would double even if all plastic pollution were to stop today.
If countries were to sort and store their waste better, they could prevent plastic from leaking into the oceans. That would mean sending waste to secure landfills or incinerators, though burning plastic also releases planet-heating gases.
Environmental groups have instead called on policymakers to build better recycling facilities and pass laws to force companies and consumers to use less of the material.
Many countries have banned or taxed single-use plastic bags in supermarkets, as a wave of consumer awareness around plastic pollution pushed them to take threats to marine life more seriously. Last year, the EU banned 10 single-use plastic items including straws and cutlery. Still, plastic pollution in oceans is set to double by 2030.
There has also been little public support for action to protect oceans from other threats like climate change and overfishing.
People don't realize how much it means for their lives, said Judith Hauck, deputy head of the marine biogeosciences division at the Alfred Wegener Institute in Germany. "It's hard to relate to it. Even if we are at the beach we're just at the border with the ocean."
