The benefits of the Paris Agreement to mitigate future changes of critical marine forests.

White paper

The present white paper summarizes the importance of the Paris Agreement for safeguarding global marine biodiversity. It outlines the scientific basis for major climate change threats to critical marine forest species of kelp and seagrasses and assesses the potential of the Paris Agreement to address these threats. The paper argues for a policy-driven approach that considers climate resilience strategies in national action plans submitted under the Paris Agreement.

Faro, 15 February, 2024
BiodiversityDataScience, Centre of Marine Sciences, University of Algarve

Marine forests, encompassing kelp forests and seagrass meadows, are underwater havens teeming with life. These underwater forests provide critical habitat and food for a vast array of marine creatures. They act as nurseries for young fish, feeding grounds for larger species, and even help stabilize the seabed, protecting our coastlines from erosion. Additionally, marine forests contribute to a clean and healthy ocean by filtering nutrients and capturing carbon dioxide from the atmosphere. Over recent decades rising sea temperatures among other drivers have led to regional losses of these vital ecosystems. Climate change projections suggest these threats will only intensify, potentially leading to further declines. As marine forests are among the most important components of marine communities, their loss can have magnified effects on the vast array of species they support, triggering cascading effects and potentially leading to the collapse of entire ecosystems.

The Paris Agreement, a landmark accord within the United Nations Framework Convention on Climate Change (UNFCCC), adopted by nearly 200 nations in 2015, has the central ambition of limiting global warming below 2°C and ideally 1.5°C. The Agreement obliges countries to substantially reduce their greenhouse gas emissions (i.e., the nationally determined contributions; NDCs), consequently mitigating the severity of expected environmental changes and, therefore, the threats to marine biodiversity. To project how future climate might unfold, researchers consider the Shared Socioeconomic Pathway (SSP) scenarios, which describe varying trajectories of global environmental changes and socioeconomic development, offering a range of plausible futures.

To demonstrate the span of environmental changes and their effects on marine biodiversity, high-performance machine-learning algorithms forecasted changes in marine forest species under two contrasting SSP scenarios:

SSP1-1.9: Sustainability, taking the Green Road
This pathway emphasizes sustainable development, inclusive growth, reduced inequality, and strong environmental policies. It represents a very optimistic future where rapid transitions to sustainable practices lead to the best-case scenario for mitigating climate change, closely aligning with Paris Agreement goals.

SSP3-7.0: Regional Rivalry, A Road Less Traveled
This pathway depicts a world of increasing regional competition and fragmented trade. A focus on national and regional security leads to less focus on global development or tackling environmental problems. There's a moderate increase in fossil fuel use as populations grow. Expect significant climate change impacts alongside challenges like food insecurity and decreased international cooperation.

kelp forest changes

kelp forest changes

Figure 1. (a) Present-­day species richness patterns of kelp forests predicted with Species Distribution Modelling (SDM). Future projected (b, c) losses of species richness under contrasting Shared Socioeconomic Pathway (SSP) scenarios of end-­of-­century climate change conditions.

Projections indicate an extensive redistribution of kelp forests toward higher latitudes and deeper waters, driving the reconfiguration of coastal communities. At the same time, projections suggest losses in lower latitude regions, due to changing local conditions making them unsuitable for the survival of kelp forests. Overall, kelp forest coverage is projected to reduce by 8.27% under SSP1-1.9 and by double under SSP3-7.0 scenario, resulting in a total loss of 15.69%. In addition to habitat loss, a decrease in species richness is anticipated, with regional losses totalling up to 24 species, such as along the North-eastern Pacific Coast. Regions most vulnerable to climate change were projected in Australia, Southern Africa and South America, where complete loss of kelp forests is anticipated.

Seagrass changes

seagrass changes

Figure 2. (a) Present-­day species richness patterns of seagrasses predicted with Species Distribution Modelling (SDM). Future projected (b, c) losses of species richness under contrasting Shared Socioeconomic Pathway (SSP) scenarios of end-­of-­century climate change conditions.

Much like the future trajectory of kelp forests, seagrass forests are anticipated to experience significant shifts in their geographical distribution. Projections indicate a reduction in seagrass coverage by 5% under SSP1-1.9 scenario, while doubling under SSP3-7.0, reaching a loss of 10.82%. These declines are anticipated to have profound effects on regional diversity, resulting in species richness losses of 12 species. Particularly vulnerable are regions of the Tropical Atlantic, the Indo-Pacific, Australia and the Tropical Eastern Pacific, which are forecasted to face the complete extinction of seagrass species.

The projected losses of these essential marine forest habitats can have profound impacts on the hundreds of organisms that depend on them, potentially cascading to the collapse of entire ecosystems. Projections clearly show that complying with the Paris Agreement and reducing greenhouse gas emissions can drastically reduce the negative effects on marine biodiversity, thereby offering our oceans a better chance of survival.

Conclusion remarks

Our oceans are rapidly changing under the pressure of climate change, threatening food security, coastal protection and global climate stability. Scientific evidence shows a clear trend of localized losses and changes in the distribution of marine forest species. The message is evident: higher greenhouse gas emissions will lead to broader negative impacts on marine biodiversity. Swift and comprehensive action is vital, and the Paris Agreement offers a critical step towards safeguarding the biodiversity of our oceans. Embracing the goals of the Paris Agreement with urgency and ambition offers a beacon of hope for a healthy future. The health of our oceans is intricately linked to the well-being of our planet. Strengthening the connection between climate action and ocean protection is not simply crucial, it is a necessity for a sustainable future.

  • Key references


Jorge Assis [PhD, Associate Researcher]
Centre of Marine Sciences, University of Algarve [Faro, Portugal]
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