Seagrass: A vital ally in climate regulation and ecosystem conservation
Seagrasses are a nature superhero, playing a crucial role in both climate change mitigation and ecosystem conservation. Acting as carbon sponges, they trap and store carbon, while also providing crucial support to various marine life forms and sustaining ecosystem balance.
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The ocean's role in combating climate change
The world's vast oceans, divided into five essential basins (Arctic, Atlantic, Indian, Pacific, and Southern) collectively cover 71% of the Earth's surface.
These immense bodies of water play a crucial role in the processes that sustain life on our planet.
In addition, the ocean actively regulates earth's climate through a complex "conveyor belt" action that transports heat from the equator towards the poles, contributing to the cooling of our planet.
While rainforests are often hailed as "the lungs of the planet," many scientists argue that it's the ocean that deserves this title, providing 50-80% of the oxygen we breathe.
The ocean is an indispensable ally in combatting climate change, absorbing 50 times more carbon dioxide than our atmosphere does. However, it's not solely the ocean itself, but rather the life within it that contributes to this significant absorption.
Many forms of aquatic life naturally absorb and hold carbon, which is taken down to the seabed and kept there when they die. From microscopic phytoplankton to gigantic whales, life of all shapes and sizes plays a part in feeding these “carbon sinks” (areas that absorb more carbon dioxide than they release).
And perhaps one of the most incredible forms is the humble seagrass.
Seagrass against climate change
With over 70 species worldwide, seagrass forms vast underwater meadows across 159 countries.
INTERESTING RESOURCES ON SEAGRASS Our Ecosystems Monitoring Program (EHMP) monitors seagrass Depth range monitoring across the Bay - check this link Microsoft Power BI. Our Report Card Interactive map shows extent and species of seagrass in the Bay.
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Surprisingly, despite covering a mere 0.2% of the seafloor – an area equivalent to Italy – seagrass absorbs 10%-18 of the ocean's carbon annually. Even more impressively, it captures carbon up to 35 times faster than tropical rainforests, acting as a crucial player in mitigating climate change.
A hectare of seagrass can annually absorb 15 times more carbon dioxide than a similar-sized portion of the Amazon rainforest, underscoring its importance in global carbon mitigation efforts.
Seagrass can also help protect our coast from damaging storms and erosion through dampening the force of waves and is very effective at removing pollutants from our waters.
Seagrass ecological value
Thousands of species depend on seagrasses for food, nursery grounds, and shelter. Many others may use seagrass habitats as an important site for feeding along their migratory routes.
Migratory birds and waders prey on fish, crustaceans and many other invertebrates that use seagrass meadows as nursery grounds. Juvenile sharks as well find those habitats ideal for hunting. Endangered species such as Dugongs and marine turtles use seagrass meadows as foraging and breeding grounds.
Only a select few creatures, including dugongs, green turtles, sea urchins, and specific fish species, possess the ability to digest cellulose and directly consume the seagrass leaves. However, the significance of seagrasses extends far beyond these direct consumers. Their leaves serve as support for various attached seaweeds and minute filter-feeding organisms like bryozoans, sponges, hydroids, and the eggs of ascidians (sea squirts) and molluscs. These organisms constitute a crucial food source for smaller fish, consequently sustaining larger fish populations.
Seagrass meadows play a critical role by offering sheltered havens and feeding grounds for juvenile fish and prawns. These habitats are so crucial that in certain coastal regions, entire fisheries rely on the productivity of these seagrass beds.
The rhizomes and roots of seagrass plants serve to bind sediments at the seabed, fostering a cycle where nutrients are recycled by microorganisms, benefitting the marine ecosystem. Additionally, the leaves slow down water flow, aiding in the settling of suspended materials onto the seabed. This process enhances light penetration, benefiting the seagrass bed and fostering habitat for numerous species.
Threats to seagrass
Human-induced pollution stands as the primary contributor to seagrass decline worldwide. Among the most critical pollution threats are elevated levels of plant nutrients. Often stemming from runoff, these high nutrient levels trigger algae blooms that overshadow seagrass. Reduced light penetration hampers seagrass growth, potentially leading to the demise of entire populations. The presence of suspended sediments further exacerbates light reduction. These sediments, originating from land development runoff and drainage systems, limit light availability.
Additionally, seagrass faces threats from physical damage inflicted on their leaves, stems, and roots by boat propellers, rising temperatures and violent storms, coastline development, and unregulated fishing.
Seagrass’ remarkable longevity – some clones dating back 200,000 years - contrasts with slow growth rates, making it vulnerable to degradation. The pace of growth often fails to match the degradation caused by human activities, resulting in significant losses.
According to the UN Environment Programme, a football pitch-sized seagrass area is lost every 30 minutes worldwide, with a global decline of approximately 7% annually.
Gaps and opportunities
The World Resources Institute's publication, "The Ocean as a Solution to Climate Change: 5 Opportunities for Action”, highlights the significant potential of seagrass conservation in mitigating climate change. While the carbon sequestration potential per unit area is slightly lower than that of saltmarshes or mangroves, seagrass conservation boasts exceptionally high mitigation capabilities, surpassing those of saltmarshes and mangroves.
However, despite its potential, there remain critical uncertainties surrounding seagrass ecosystems. The availability of data on regional cover and carbon stocks in seagrass meadows is notably sparse, particularly in regions like the Indo-Pacific, Africa, and South America. This limited understanding extends to factors influencing the variability in carbon sink capacity among seagrass meadows, inhibiting the formulation of effective strategies for climate change mitigation based on these capacities.
Nonetheless, the global recognition of seagrasses ability to sequester carbon is gaining momentum, especially in the face of the escalating climate emergency. The recent Intergovernmental Panel on Climate Change (IPCC) report, focusing on oceans and the cryosphere, underlines the substantial carbon storage potential of mangroves, salt marshes, and seagrass meadows.
These ecosystems can collectively store up to 1,000 tonnes of carbon per hectare, surpassing the storage capacity of most terrestrial ecosystems. This acknowledgement highlights the importance of further research and concerted efforts to harness the potential of seagrasses in combating climate change.
Want to take a deep dive into seagrass?
You can learn more about seagrass on the Queensland Government’s website.
Resources:
https://www.qld.gov.au/environment/coasts-waterways/marine-habitats/seagrass
https://oceanpanel.org/publication/the-ocean-as-a-solution-to-climate-change-five-opportunities-for-action/
https://www.ipcc.ch/srocc/home/
https://environment.des.qld.gov.au/management/water/seagrass
https://www.qld.gov.au/environment/coasts-waterways/marine-habitats/seagrass