Marine ecosystems in a changing climate – Insights from the IPCC’s Sixth Assessment Report

By Ocean & Climate Platform (OCP) | March 28, 2023

This month, the IPCC released the Sixth Assessment Report (AR6) Synthesis Report which sounds the alarm on the unprecedented acceleration of climate change, its impacts on land and sea, and the increasing exposure and vulnerability of ecosystems and human societies. As underscored by the IPCC, transformational changes must be carried out to jointly and effectively deploy adaptation and mitigation responses at a large scale. Given the multitude of benefits they provide to the living world, marine ecosystems are cornerstones of the transition to a more sustainable world.

Promoting a wide and better understanding of these phenomena, as well as the inclusion of marine ecosystems in all climate and environmental policies, the Ocean & Climate Platform (OCP) published “What ocean for tomorrow? Marine ecosystems in a changing climate: insights from the IPCC Sixth Assessment Report”, featuring a foreword from High-Level Champion of the UAE: Her Excellency Ms. Razan Al Mubarak. Below are the key takeaways.

Marine ecosystems play a critical role for the climate, biodiversity and human societies

From coastal areas to the depths of the ocean, the diversity of marine ecosystems is considerable. They are critical to climate change mitigation and adaptation. The ocean absorbs close to 30% of CO₂ emissions from human activities. The so-called “biological carbon pump”, partly relies on phytoplankton or blue carbon ecosystems (mangroves, seagrass meadows and salt marshes) which absorb CO₂ emissions through photosynthesis. Ecosystems and marine biodiversity are closely intertwined. Certain marine ecosystems, such as kelp forests, provide habitats and shelters for a multitude of species to feed, reproduce and grow. Besides, our societies, livelihoods and cultures highly depend on the ocean. From food provision, to the protection against extreme events, or even the supply of resources for medicines and materials for infrastructure, human well-being is closely linked to the health of marine ecosystems.

Towards a tipping point: marine ecosystems on the front line of climate change

Marine ecosystems are increasingly vulnerable to climatic and human stressors, so much that some are already reaching a tipping point. Their collapse is conducive to the extirpation and extinction of marine species, with significant consequences on life in the sea or on land. Over the last century, days of marine heatwaves have increased by 54% leading to mass mortality in many marine species. Without a drastic reduction of greenhouse gases emissions, the frequency of these phenomena is bound to increase.

The IPCC is unequivocal: in the scenario of a temperature rise beyond 2°C by 2100, the “risks of extirpation, extinction and ecosystem collapse escalate rapidly”, cascading over marine species, as well as the mental and physical health of human societies, their economies and food security. Some populations will be disproportionately vulnerable, depending on their geographical location, wealth, gender, age, type of employment or the political context in which they evolve.

Towards a sustainable world: adapting and mitigating the impacts of climate change thanks to marine ecosystems 

Protected and healthy ecosystems are more resilient and provide solutions to the challenges of climate change. In this respect, the IPCC highlights marine Nature-based Solutions, i.e. actions designed to protect, restore and sustainably manage marine ecosystems to better prepare nature and populations for the impacts of climate change. Marine Protected Areas, ecological restoration and protection as well as sustainable fisheries provide a multitude of co-benefits to all life on Earth, thereby contributing to the achievement of the Sustainable Development Goals. Nonetheless, their effectiveness relies on the rapid reduction of greenhouse gases emissions and the elimination of human-induced stressors on ecosystems.

To lead action and large-scale change, inclusive and fair governance, scaled-up financial efforts and strengthened international cooperation are indispensable levers. The increasing integration of marine ecosystems into international climate and biodiversity agreements reflects a growing awareness of both their vulnerability and their mitigation and adaptation potential. Notwithstanding, the final declaration of COP27 underscored for the first time the crucial role of marine ecosystems in achieving the objectives of the Paris Agreement. In light of the climate emergency the IPCC is reminding us it is essential to pursue international cooperation and translate commitments into informed action.

Click here to discover “What Ocean for Tomorrow? Marine Ecosystems in a Changing Climate: Insights from the IPCC’s Sixth Assessment Report