SEAGRASS AND HOW WE CAN PROTECT IT
WHAT IS IT?
Seagrasses are the only flowering plants able to live in seawater and pollinate while submerged. They require a large amount of sunlight for photosynthesis to grow and therefore are only found in shallow waters, such as bays and lagoons around the world. Seagrass has been given its name because of its long, narrow leaves, which share a resemblance to some terrestrial grasses you might come across on your country walks
WHY IS IT IMPORTANT?
Seagrasses are a vital part of the marine ecosystem, as they:
- Provide food and habitat for other marine organisms
- Maintain water quality by helping trap fine sediments and particles that are suspended in the water column, which increases water clarity
- Support local economies
- Protect coastlines by helping slow down erosion as large meadows slow down ocean waves as well as the seagrass roots help to stabilise and strengthen sediment and so protect the coastline from erosion
BLUE CARBON
Much like rainforests, seagrass meadows absorb and store huge amounts of carbon dioxide. Seagrass are commonly known as the "lungs of the sea" because just 1 square meter of seagrass can generate up to 10 liters of oxygen every day through photosynthesis. It’s been calculated that seagrass is responsible for 15% of the ocean’s total carbon absorption.
HOW CAN WE PROTECT IT?
Unfortunately seagrass is one of the most rapidly declining ecosystems on Earth. A lack of awareness about the importance of seagrass has resulted in poor conservation and management. But not all is lost. Seagrass is also one of the most resilient plants on the planet and will be able to bounce back rapidly with enough support.
Some of the ways you can help:
- Visit Seagrass conservation websites, such as Sea Grass Watch, Dugong Conservation and Project Seagrass
- Volunteer and help support seagrass conservation efforts and the wildlife that lives there
- Go visit a seagrass meadow, grab a snorkel, go for a dive and see what you can find
The scale of the loss
Seagrass is one of the most rapidly declining habitats on Earth, and the losses are steepest in exactly the shallow, sheltered coastal water where people live and work. The United Kingdom is estimated to have lost a very large share of its seagrass meadows over the last century, driven by a combination of coastal development, dredging, anchor and mooring damage, and — most persistently — nutrient run-off from land, which fuels algal growth that shades the plants out. Wasting disease, a slime-mould infection that swept European and North American beds in the 1930s, removed much of what remained before any of that began.
The consequences run further than the plants themselves. A seagrass meadow is a nursery: juvenile fish that later support commercial fisheries shelter in it, and the invertebrates that feed wading birds live in its sediment. Losing a meadow does not simply remove a habitat, it removes a stage in the life cycle of species that spend most of their adult lives elsewhere, which is why the effects show up far from the site of the damage.
Restoration, and why it is hard
Seagrass restoration projects are now running in several places around the British coast, mostly by collecting seeds by hand from healthy donor meadows, storing them over winter and planting them out in hessian bags anchored to the seabed. The technique works, and survival rates are improving, but it is slow, labour-intensive and vulnerable at exactly the point where restoration is most needed — a site that lost its seagrass to poor water clarity will lose replanted seagrass to poor water clarity too.
That is the argument for protecting what still exists rather than relying on replacing it. An established meadow holds sediment, clarifies the water above it and reseeds itself; a newly planted one does none of those things reliably for years. The cheapest seagrass conservation available is a mooring that does not scour the seabed and a catchment that does not send nitrogen into the bay.
What actually helps
At an individual level the useful actions are unglamorous. If you boat, use an eco-mooring that lifts the chain clear of the bed rather than dragging it in a circle, and anchor over sand rather than grass. If you swim or snorkel over a meadow, do not stand on it. Support catchment-level work on nutrient run-off, which is where the largest single pressure originates. And treat seagrass surveys as worth contributing to — most of the mapping of British meadows has been done by volunteers, and knowing where the beds are is the precondition for protecting them.