Climate Crisis

Oceans are dying, and we remain fundamentally dependent on them for food, energy, and even oxygen

Combined pressures of over-exploitation and climate changes are not without consequences for human development

The world is now facing its fourth mass coral bleaching event. Photograph: Anddrey Pol/iStock

Sadhbh O'Neill
Thu Apr 25 2024 - 06:00

The sheer vastness of the world’s oceans makes it hard to imagine the combined and overlapping threats posed by global heating, acidification, biodiversity loss, sea level rise, plastic pollution, oil and gas exploration and over-fishing.

If that list doesn’t move you, perhaps the news that the world is facing its fourth mass coral bleaching event might. The sad, lonely sight of dead and decaying coral reefs, with the attendant loss of incredible beauty and species diversity, will become more frequent as the ocean keeps heating up past the point at which coral can adapt.

We are fundamentally dependent on healthy oceans. We depend on the oceans for food, energy, our temperate climate, and even oxygen. The ocean is the planet’s primary heat reservoir, oxygen supplier and carbon sink.

Ocean biodiversity is central to maintaining these critical services, but is becoming endangered or vulnerable as a result of climate change. Sixty-six per cent of the ocean is facing human pressures and the diversity and abundance of ocean ecosystems is weakening steadily. On top of this, industrial fishing fleets, and bottom trawling in particular, are driving declines in wild fish populations in every region of the world.

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The combined pressures of over-exploitation and climate changes are not without consequences for human development. Sea level rise is a major threat to coastal cities, driven by the combined effects of melting glaciers and ice sheets, and the thermal expansion of water. At present, about 40 per cent of the global population lives within 100km of coastal areas. No wonder that UN secretary general, António Guterres, warned last year that the increase in the pace of sea level rise threatens “a mass exodus on a biblical scale”.

While the immediate threat from severe storms and flooding is to human life, the impact of storms, tidal surges and sea level rise on property assets, infrastructure and coastal biodiversity is often underestimated as policymakers continue to believe (wrongly) that the impacts of sea level rise will not materialise for decades or centuries. In fact, many parts of Ireland’s coastline are already being impacted, and coastal erosion and sea level rise could lead to a 50-65 per cent loss in permanent beach areas globally, with profound consequences for the Irish tourism model (and Donald Trump’s Doonbeg golf resort in Co Clare too).

Scientists have warned that Sustainable Development Goal 14: Life below Water is dangerously off track with most targets unlikely to be met by 2030. These include agreed measures to sustainably manage and protect marine and coastal ecosystems, and to regulate harvesting and end overfishing.

Perhaps the gravest threat posed by climate change to Ireland’s climate is the weakening of Atlantic Ocean currents, notably the Atlantic Meridional Overturning Circulation (Amoc) as a result of arctic ice melt. It is a three-dimensional ocean current – a sort of “conveyor belt” connecting water on the surface of the ocean to deep water below, moving warmer water (and air) from the tropics up towards northwestern Europe.

While scientists agree the Amoc is in decline, there is far less agreement on whether (and when) it might shut down altogether. The trouble is that while measurements will signal whether in fact it is shutting down, by that stage it will be too late to do anything to stop the cascading feedbacks that would result.

[ Ireland’s ability to meet climate targets being undermined by ‘inexcusable delays’ to marine legislation ]

The impacts of a complete Amoc shutdown would be catastrophic. Not only would temperatures in Europe plummet, wildlife would suffer too, as essential nutrients for marine life would not as readily reach the Northern Atlantic. And all of this would happen on top of the sea level rise that is already expected to disrupt so much of our world.

A recent climate change assessment report produced by experts warned that for Ireland, the Amoc is the most immediately important potential tipping point for the Irish climate, given the importance of the North Atlantic in determining our climate and agricultural productivity. It noted that it will almost certainly weaken over the 21st century, and a full collapse cannot be ruled out, leading to considerably colder winters and “very profound implications” for the Irish climate and society.

To the degree that there are solutions for these crises, they lie in the willingness of governments to prioritise ocean health by slashing fossil fuel emissions and co-operating on the designation of at least 30 per cent of marine areas for protection by 2030.

Research shows that strategically placed marine protected areas that outlaw bottom trawling can support sustainable fisheries and food security. Yet Ireland still has not imposed a ban on bottom trawling in marine management plans, and recent decisions by the European Parliament will reverse progress in tackling destructive fishing practices.

If there is anything to be learned from recent climate policy initiatives it is that our oceans will not recover with weak legislative proposals that take too long to implement and that are heavily influenced by sectoral lobbies.

Sadhbh O’Neill is the senior climate adviser to Friends of the Earth Ireland

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