An annual scientific check on the planet’s health shows that the Earth is moving closer to the danger zone, as warming climate and polluted ecosystems are weakening its natural resilience. One key indicator for ocean health has significantly worsened, the report warns.

The report from the Potsdam Institute for Climate Impact Research (PIK), released on Wednesday during Climate Week NYC, revealed that seven of nine safety limits, called “planetary boundaries” have now been breached, one more than last year.

The ocean acidification boundary has been crossed for the first time, driven mainly by fossil fuel burning and worsened by deforestation, the report said, meaning that the oceans’ ability to act as Earth’s stabiliser is weakening. Oceans turn more acidic by absorbing CO2 from the atmosphere, a process that can threaten marine life.

Levke Caesar, co-lead of the Planetary Boundaries Science Lab, and one of the report’s authors said the intensifying acidification of the seas, combined with warming and loss of oxygen, affects everything from coastal fisheries to the open ocean.

“The consequences ripple outward impacting food security, global climate stability, and human wellbeing,” she added, noting that the ocean’s ability to act as a sink for planet-warming carbon dioxide is declining.

Since the start of the industrial era, the ocean’s surface pH – which measures the level of acidity – has fallen by around 0.1 units, a 30-40% increase in acidity, pushing marine ecosystems beyond safe limits.

Tiny sea snails known as pteropods – which are an important part of the marine food chain – are already showing signs of shell damage, for example. Cold-water corals and tropical coral reefs are especially at risk from intensifying acidification, the report said.

Commenting on the findings, Chris Thorne, senior oceans campaigner at Greenpeace UK, called on states to urgently develop proposals for a network of ocean sanctuaries on the high seas, after a new pact to protect international waters last week gained enough ratifications to enter into force.

“We must give marine life space to build resilience to severe changes in the marine environment,” he added.

Improvements in ozone, aerosols offer hope

The other breached planetary boundaries include climate change, extinctions and natural productivity, forest loss and human impacts on freshwater systems, and pollution caused by overuse of fertilisers.

“More than three-quarters of the Earth’s support systems are not in the safe zone. Humanity is pushing beyond the limits of a safe operating space, increasing the risk of destabilising the planet”, said Johan Rockström, director of the Potsdam Institute for Climate Impact Research and a report co-author.

He added at a press conference in New York that the ocean is under multiple pressures from several boundaries, “and that makes us particularly nervous”.

Work is ongoing to understand when and how systems subject to a range of stresses – such as coral reefs, the Amazon rainforest and polar ice sheets – can tip into a state from which they cannot recover and maybe irreversibly lost or transformed, he added.

But he and other scientists behind the report stressed it is not too late to bring the planet back within safe environmental limits.

They pointed to the two areas where progress has been made: a drop in aerosol pollution and healing of the ozone layer, which has improved after governments got together to tackle the issue under the Montreal Protocol.

Chief planetary scientists for governments?

Speaking to journalists in New York, former Irish President Mary Robinson, who also belongs to a group of Planetary Guardians who support the annual scorecard, called on governments to appoint a “chief planetary scientist”.

“Just as chief economists safeguard financial policy, chief planetary scientists would ensure decisions from budgets to food systems to disaster planning keep us within Earth’s safe operating space,” she said.

Climate Home News understands that Indonesia and the UK are considering appointing such a scientist.

“Imagine if every national budget, every security plan, every trade deal, began with the question: does this keep us within planetary boundaries?” Robinson asked.

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Planet’s health in rising danger, as ocean acidification crosses safety limit