Over 35% of the world’s seagrass beds have been lost since 1980 and they are disappearing at a rate of one hectare per hour. Seagrass occupies around 0.1% of the seafloor but is home to thousands of species of animals who rely on it for food and shelter. It forms the basis of the world’s primary fishing grounds and is responsible for 11% of the organic carbon buried in the ocean.
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There are many reasons why restoring seagrass beds is important, but essentially, saving seagrass means saving the seas. Seagrasses are valuable habitats and an important climate buffer that could help mitigate some of the effects of climate change.
How can seagrass bed restoration be achieved; what projects are already underway, and what more can be done?
What is Seagrass?
Seagrass is a flowering plant that lives in shallow and sheltered areas along the coast. Their large, bright green leaves form meadows under the sea, and this underwater haven is full of life. It is home to thousands of marine species – including shellfish, seahorses, manatees and sea turtles – who rely on the seagrass not only for food and shelter, but as a reproductive habitat.
Seagrass meadows act as an indicator species for environmental issues; as it rapidly responds to changes in its environment it can be used to provide insight into the overall health of the area. It can indicate if there is pollution or poor water quality, for example, or if the area has been overfished.
Seagrass is quite sensitive and can be affected by several factors, including destructive fishing that disturbs the meadow, storms and hurricanes caused by climate change, and human-induced threats such as pollution and runoff reducing water clarity. This all contributes to the destruction of seagrass beds, which is happening on a large scale.
Seagrass and Climate Change
Seagrass bed importance cannot be underestimated: it stabilizes the seafloor and helps maintain good water quality. Seagrass ecosystems are highly resilient and very good at trapping carbon and nitrogen. It is responsible for sequestering 11% of organic carbon buried in the ocean and large quantities of nitrogen. Further seagrass bed restoration could have an important role in mitigating climate change, as well as improving biodiversity and enhancing food security.
Seagrass and Corals
Studies show that seagrass proximity to coral reefs can reduce coral bleaching. Ocean acidification is increasing because of anthropogenic activities, but it is shifting the equilibrium of dissolved inorganic carbon in the water. This additional carbon is reducing the calcification and growth rate of coral, which will have significant long-term consequences for species dependent on these colorful entities.
Tropical seagrasses among or adjacent to coral reefs take up this dissolved inorganic carbon, displacing the carbonate equilibrium. This benefits the reef and could enhance its resilience to future ocean acidification; this could be a useful tactic in managing marine parks.
Seagrass Bed Restoration: Virginia
There are many projects underway aimed at restoring seagrass beds and conserving seagrass ecosystems across the globe, but the world’s largest has been ongoing for the last 20 years and created 3,612 hectares of new seagrass beds.
The seagrass bed restoration project, between Virginia Institute of Marine Science and the Nature Conservancy, focused on an area along the coast of Virginia where a previous seagrass meadow was wiped out by a pandemic slime mold disease in 1933 and further devastated by a hurricane.
The area never really recovered, but it was not until the 1990s that scientists realized it was because of a lack of seagrass seeds, not because of the degraded environment. So, over the course of 20 years, they actively planted 74.5 million seeds – initially collected from established beds and then established restored beds – in over 500 individual restoration plots.
The area saw a rapid recovery, resulting in more than 3,500 hectares of well-developed meadows, with a diverse and productive animal community. The project serves as a blueprint on how to restore and maintain a healthy marine ecosystem, and a similar project is underway in Australia.
The area also sequesters substantial amounts of carbon and nitrogen; it is estimated that 3,000 metric tons of carbon and 600 metric tons of nitrogen are fixed each year. As the seagrass beds mature, they will be able to hold even more.
Seagrass Bed Restoration: Wales
As part of the UN Decade on Ecosystem Restoration 2021-2030, Project Seagrass aims to restore 10 hectares of seagrass along Europe’s coastline and in its oceans using harvested wild seagrass seeds to ensure maximum ecological benefits.
The marine conservation charity has already restored two hectares of seagrass beds, proving that restoration is possible in the area – namely North Wales. Utilizing a mix of cutting-edge technology, the area will be assessed, and field trials will be undertaken to ensure that seagrass bed restoration takes place where it is most needed, thus widening the project a further 10 hectares.
The Future of Seagrass
Seagrass importance should not be underestimated and restoring seagrass beds should be high on the environmental agenda. Not only are they valuable habitats for numerous species, some of which we rely on for food and fishing, but they also represent a climate buffer and play an important part in mitigating the effects of climate change.
References and Further Reading
United Nations (2021) PROJECT SEAGRASS: MAKING WAVES TO SAVE OUR SEAS United Nations Decade on Ecosystem Restoration 2021-2030 [online] https://implementers.decadeonrestoration.org/implementers/17/project-seagrass-making-waves-to-save-our-seas-wales-uk
Project Seagrass https://www.projectseagrass.org/
Samurović, K. (2020) The World’s Biggest Seagrass Restoration Project Is Good News for Marine Life and Climate, Geography Realm [online] https://www.geographyrealm.com/the-worlds-biggest-seagrass-restoration-project-is-good-news-for-marine-life-and-climate/
Orth, RJ. et al (2020) Restoration of seagrass habitat leads to rapid recovery of coastal ecosystem services, Science Advances [online] https://www.science.org/doi/10.1126/sciadv.abc6434
Unsworth, RFK. et al (2012) Tropical seagrass meadows modify seawater carbon chemistry: implications for coral reefs impacted by ocean acidification, Environmental Research Letters [online] https://iopscience.iop.org/article/10.1088/1748-9326/7/2/024026