Tim has worked closely with FFI since 1999. He has edited &FFI (formerly Fauna & Flora magazine) since its inception in 2001 and is lead author of With Honourable Intent - A Natural History of Fauna & Flora International, published in 2017.
What is the only flowering plant that lives in the sea? Clue: it has something in common with the largest animal that has ever lived. Like the ancient forebears of the mighty, record-breaking blue whale, the ancestors of the plants collectively known as seagrass were originally terrestrial species – land-dwellers, in other words – that have since made their home in the ocean.
The expression ‘out of sight, out of mind’ perfectly encapsulates the lot of seagrass. Superficially, it’s the submarine equivalent of a suburban lawn, which goes some way to explaining why this unassuming underdog of the undersea world has been largely unheralded. By showcasing seagrass, The Green Planet has helped spread the message that, far from being merely part of the scenery, this plant does, in fact, play several pivotal roles on our planet.
Seagrasses are marine plants that evolved from a variety of land-based species and recolonised the ocean many millions of years ago. Not to be confused with seaweed, which are algae with no real roots, stems or leaves, seagrasses are flowering plants that produce fruit and seeds. Despite their name, they are more closely related to lilies, palms and gingers than to true grasses.
Anchored to the seabed by their roots, seagrasses spread in a similar way to nettles in a garden, sending out horizontal stems called rhizomes that knit together and produce new growth. Over time, they form extensive carpets known as seagrass meadows.
Seagrass meadow bathed in sunlight. Credit: Matt Curnock/Ocean Image Library
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Seagrass occurs in shallow coastal waters throughout much of the world, with the exception of Antarctica. Some of the 70-plus species of seagrass are adapted to life in cold climates, while others thrive in warmer waters. Access to sunlight – which the plant needs in order to photosynthesise – is the limiting factor; provided that the water is clear enough, it can grow at depths exceeding 50 metres. Many types of seagrass can survive exposure at low tide.
By pulling carbon out of the atmosphere and storing it in their leaves, stems and roots, plants play an important role in slowing the rate of climate change. Seagrass is no exception. One of the unsung blue carbon heroes, it’s a key ally in our fight against global heating, capable of sequestering and storing carbon in much greater volumes and at much faster rates than, for example, tropical forests – up to 35 times faster, according to the latest research.
The carbon in seagrass meadows is stored mainly in sediments that are held in place by the plants’ root system and, if undisturbed, can remain intact for millennia. One particular seagrass meadow in Spain’s Portlligat Bay has accumulated carbon-rich deposits that are up to 10 metres deep and more than 6,000 years old.
The enormous carbon sink capacity of healthy seagrass meadows is just one of the many economic and ecological benefits they provide. They also protect against storm surges, prevent coastal erosion, regulate water quality, provide habitat for commercially important marine species, and improve food security for coastal communities.
Seagrass forms the botanical bedrock of one of the world’s most productive ecosystems. It provides an important haven for myriad marine species from shrimps to seahorses and represents a vital food source for the endangered green turtle and the dugong, whose colloquial name ‘sea cow’ sums up its dependence on these marine pastures. A seagrass meadow supports around 40 times more animals than a sandy seabed.
Dugong grazing on seagrass. Credit: Anett Szaszi/ Ocean Image Library
Arguably the greatest threat to seagrass is our apparent indifference to its fate.
Despite their global importance, seagrass meadows have been neglected, mistreated and inexorably degraded by human activities. As a result, they are dwindling – and, in many areas, disappearing completely – at an alarming rate.
An estimated 90% of the seagrass around the UK has been lost, a figure that has been described as catastrophic. Elsewhere, a paucity of data means that the true extent of seagrass depletion across the globe is sometimes harder to quantify, but it is thought that we have lost a third of the world’s seagrass within the last century, and there are numerous instances of entire pastures being wiped from the map.
Coastal development and pollution have taken a particularly heavy toll. Sediments, chemicals and agricultural waste washed into the ocean diminish water quality to the point where seagrass cannot survive.
Coastal development is contributing to the dramatic decline in seagrass meadows. Credit: Ben Jones/Ocean Image Library
Unsustainable levels of fishing also have a knock-on effect on these delicately balanced ecosystems. Removal of apex predators such as sharks, for example, leads to an increase in numbers of herbivorous fish. Conversely, a reduction in the fish population may result in a population explosion among sea urchins, which then overgraze their meadow home.
Other activities such as bottom-trawling and dredging serve to compound the damage. A habitat that has taken many millennia to establish itself can be destroyed virtually overnight.
These plants may be allies in the fight against climate change, but they are also among its many casualties; seagrass density has been shown to reduce as a result of sudden and repeated spikes in ocean temperature. Literally rooted to the spot, a seagrass meadow cannot migrate to cooler climes.
When degraded or destroyed, seagrass meadows will release carbon back to the atmosphere and ocean. We urgently need to ensure that the world’s remaining seagrass habitat is protected from further disturbance. Without appropriate safeguards to conserve these habitats, it is estimated that a further 30-40% of remaining seagrass cover could disappear by the end of the century.
FFI is working with our in-country partners to safeguard seagrass meadows and the rich biodiversity and carbon stocks they support at many of our project sites across the globe, from the UK to far-flung corners of Indonesia.
In the marine paradise of Raja Ampat at the epicentre of the Coral Triangle, FFI has worked closely with Yayasan Nazaret Papua, an indigenous people’s NGO, to establish a customary protection zone for dugongs and their seagrass habitat. We aim to ensure that these seagrass meadows are incorporated into Indonesia’s official protected area network.
The slow-growing Neptune grass Posidonia oceanica is endemic to the Mediterranean. It is threatened by destructive fishing practices, as well as tourism, coastal development, aquaculture and sand extraction. In Turkey, FFI is working with Akdeniz Koruma Derneği, our in-country partner, to build the resilience of the marine ecosystem – including the remaining seagrass meadows – via a network of effectively managed marine protected areas.
Juvenile fish sheltering in a bed of Neptune grass, Turkey. Credit: Zafer Kizilkaya
As part of the national action plan for sea turtles that it helped draft, FFI’s Cambodia marine team is advocating greater protection for turtle foraging habitats, including the seagrass beds on which green turtles depend for food. It has also conducted seagrass surveys and produced a brace of short animated films highlighting their mutual dependence.
Scotland’s coastline and inshore waters support a wealth of marine species and ecosystems, much of it crucial to local livelihoods, but all too often its coastal communities have not been given a voice in how their seas are managed. FFI works closely with coastal communities and local NGOs to support their efforts to ensure a better future for Scotland’s inshore waters, including its globally important seagrass beds.
Plant blindness is one of the main threats to the world's plants.
They receive far less conservation attention than their animal counterparts,
and are disappearing unnoticed at an alarming rate. Help us safeguard
the species that are the lifeblood of our planet.
Credit: Matt Curnock