Seventh planetary boundary crossed officially

  Another crucial planetary boundary of oceans have been crossed officially     

The latest EU Copernicus Ocean State Report highlights mounting threats to Europe’s seas from acidification, plastic pollution and climate change. A ground breaking global scientific report has revealed a stark truth that we have now crossed seven out of nine critical planetary boundaries which keep life on Earth stable and healthy. The newest boundary breached is ocean acidification, a dangerous shift caused mainly by rising CO2 emissions from burning fossil fuels. This change is altering the very chemistry of our ocean, putting all marine life at risk, but especially fragile coral reefs which are already struggling under the weight of warming temperatures and pollution. The world’s ocean has moved past a chemical safety line that researchers once hoped it would never reach. A key ocean acidification metrics had already pushed into the danger zone for marine life, with especially strong changes in the upper 650 feet of water. The line is part of what scientists call a safe operating space for the planet. Crossing it means a higher risk that ocean ecosystems, and the people who depend on them, will face damage which is hard to reverse.

The latest EU Copernicus Ocean State Report highlights mounting threats to Europe’s seas from acidification, plastic pollution and climate change, sounding a clear alarm for urgent and stronger protective actions, while the European Environment Agency (EEA) is warning of the ‘deadly trio’ of acidification, de-oxygenation and warming temperatures for our seas and ocean. Scientists warn that crossing planetary boundaries puts the Earth’s life-support systems at serious risk. Now, more than ever, coordinated efforts at global, regional and local levels are critical to protect our seas and ocean, the vital blue heart which sustains life on our planet. Scientists use the term ocean acidification, the long term decrease in seawater pH driven mainly by absorbed CO2, to describe this chemical trend. The ocean takes up a large share of human carbon emissions, and in doing so quietly changes its own chemistry. One core measure is aragonite saturation state, a number which shows how easy it is for calcium carbonate shells and skeletons to form and avoid dissolving. When the value falls, it becomes harder for corals, shellfish and some plankton to build and maintain their structures. The original acidification boundary was set at a 20% drop in this global saturation state compared with conditions before large scale fossil fuel use. The limit was supposed to keep polar surface waters from becoming corrosive and to preserve conditions that still support healthy tropical coral reefs.

In a historic step forward, the recent ratification of the Biodiversity Beyond National Jurisdiction (BBNJ) agreement creates a global framework to conserve and sustainably manage marine life in international waters. This milestone works hand in hand with the Global Biodiversity Framework (GBF), which sets bold targets to preserve ocean ecosystems and reduce pollution on a worldwide scale. The new study also highlights how the subsurface ocean, roughly the top 650 feet below the surface, is changing more strongly than the very top layer. Independent work shows that the analysis of long term data finds the depth where waters become corrosive to aragonite shells has risen by more than 650 feet in some regions since 1800. The chemical shifts matter most because of what they do to calcifying species, organisms which build hard parts from calcium carbonate and anchor many marine food webs. As the ocean grows more acidic, suitable habitat for these builders shrinks and fragments. For warm water coral reefs, the team finds that suitable chemical habitat has already fallen by about 43% in tropical and subtropical regions compared with before industrial times. This loss means less space for the millions of species which use reefs as home, nursery or hunting ground. In polar waters, tiny pteropods, small swimming snails which carry fragile aragonite shells, are especially exposed to corrosive conditions. The analysis suggests their suitable habitat has declined by up to 61%, raising concerns for polar food webs which rely on them as prey. Coastal bivalves such as oysters and mussels show a smaller but still troubling contraction, with about a 13% loss of suitable habitat in chemically stressed coastal zones. A broader review of ocean acidification impacts notes that shellfish fisheries and aquaculture are among the industries most at risk, with knock-on effects for coastal jobs and food security.

Closer to home, the Commission is taking action through its EU Water Resilience Strategy, which focuses on integrated water management to boost the resilience of our waters and ocean against acidification and other climate impacts. With its Ocean Pact, the Commission has committed to an integrated approach to the protection of marine ecosystems, including against the impacts of climate change, and the development of a sustainable, decarbonised and circular Blue Economy. The Commission is also revising the Marine Strategy Framework Directive, one of the most ambitious marine environmental protection laws worldwide. The review will seek to better address the impacts of climate change on marine ecosystems in EU law. In 2009, researchers proposed the idea of planetary boundaries, global limits which marks the safe operating space for humanity, in a framework that has become central to global sustainability science. These boundaries cover nine big Earth systems, including climate, biodiversity, fresh water and the chemistry of the ocean.

The new work was led by Professor Helen S. Findlay, a biological oceanographer at Plymouth Marine Laboratory in the UK. Her research focuses on how climate change and acidification reshape marine ecosystems, particularly in the rapidly warming Arctic. They found that by 2020, ocean chemistry had already crossed into the uncertainty range. Her team estimates that 40% of surface waters and 60% of water down to 650 feet already lie beyond that level. Earlier versions of the boundary treated the ocean as one smooth layer at the surface and used a single global benchmark with no uncertainty range. This updated analysis adds error bars, separates regions and extends into the subsurface, where most marine organisms actually live and feed. The planetary boundaries framework identifies nine essential Earth system processes which regulate the planet’s stability, resilience, and ability to support life. These boundaries define safe limits for human activities, beyond which we risk triggering catastrophic environmental changes. Since its introduction, the framework has helped spotlight critical areas like climate change, biodiversity loss, land-use change, freshwater use and chemical pollution, all vital to maintaining a balanced and healthy Earth. Looking ahead, the fate of this chemical boundary still depends mainly on how fast people cut CO2 emissions. 

An IPCC assessment concludes that continued high emissions will drive further acidification, while strong and rapid emission cuts would slow or eventually stabilize these changes. Acidification also piles on top of ocean warming and falling oxygen levels, creating compound stresses for marine life. In many regions, species are already dealing with higher temperatures, less oxygen and more acidic water at the same time, which can make survival limits much tighter than any single stress would suggest. For people, the message is that the ocean is quietly moving out of its comfort zone even where the surface still looks blue and calm. Keeping marine ecosystems functional, and keeping food and climate services they provide, will require treating this chemical line in the water as seriously as temperature targets in the air. The researchers argue that a boundary based only on a 20% global chemical drop is not strict enough to protect key ecosystems. The results point to a tighter limit, one based on only a 10% decline in average surface saturation state from preindustrial conditions, which would better protect corals, pteropods and bivalves. Under that more cautious line, the surface ocean effectively left the safe zone in the 1980s, and by around 2000 the entire surface layer had crossed it. With its Plastics Strategy, the EU also aims to dramatically reduce marine litter and will continue global efforts towards an international Plastics Treaty. Meanwhile, ambitious climate policies target cutting CO2 emissions, the root cause of ocean acidification around the world.