Climate change

Experts focus on protecting carbon-eating seagrass before Marseille summit

With no help from humans, seagrass balls may collect nearly 900 million plastic items in the Mediterranean alone every year
With no help from humans, seagrass balls may collect nearly 900 million plastic items in the Mediterranean alone every year Jordi REGAS UNIVERSITY OF BARCELONA/AFP/File

With the world's biggest biodiversity summit set to kick off Friday in the Mediterranean city of Marseille, experts are sounding the alarm over a long-overlooked seagrass - nicknamed 'the lungs of the ocean' - increasingly threatened by human activity.


The meeting, organised by the International Union for the Conservation of Nature (IUCN,) will be held from September 3-11. The IUCN counts over 1,400 members in over 170 countries, and is ruled by a council headed by Zhang Xinsheng, a former Chinese vice-Minister of Education. 

The IUCN was founded on 5 October 1948, in Fontainebleau, France. The initiative came from UNESCO and its then Director General, the British biologist Julian Huxley.

Over the coming week, discussions will cover a wide range of topics - from "business and biodiversity" to environmental law and preservation of natural forests. 

One topic was highlighted even before the meeting began: the widely-underreported threat to seagrass, plants that cover wide stretches of the bottom of seas and oceans and that are crucial for feeding fish and absorbing carbon.

"Neptune grass"

Named posidonia oceanica -- or "Neptune grass" -- after the Greek god of the seas, the plant covers at least one million hectares of the Mediterranean seabed from Cyprus to Spain.

The Mediterranean Network for Posidonia says the real area is probably much larger than that, with data largely unavailable for countries on the sea's eastern and southern shores.

But neptune grass meadows have long fallen prey to boating activity, with official figures estimating some 7,500 hectares damaged along the French coastline alone.

"The biggest culprit is mooring," says Thibault Lavernhe, spokesman for the Maritime Prefecture of the Mediterranean.

"When a boat drops its anchor, it hits the ocean floor and has a devastating effect... that repeats when the anchor is pulled up."

Since seagrass grows just a few centimetres each year, the plant can take years to recover.

In an open letter published on 9 August in French daily Le Monde, 10 scientists from France, Italy and Spain emphasised the essential services the humble seagrass provides "to all of humanity".

Global warming

"Seagrass meadows serve as spawning beds and nurseries for species of fish living along our coasts from the most common to the rarest," they wrote.

A wide range of animals depend on them, including tiny invertebrates that are a food source to fish prized by small-scale, artisanal fishing operations.

Arnaud Gauffier, conservation director for the World Wide Fund for Nature's French branch (WWF), says the plant's ability to absorb carbon make it a crucial ally in the fight against global warming.

And he says the plants protect the coastline from erosion -- both when firmly rooted to the seabed and when they wash up on shore.

Dead blades of grass collect along beaches and mix with sand to form large banks that protect the coastline.

But for some, the phenomenon is just an unsightly inconvenience.

"Unfortunately the ecosystem is poorly understood," says Gauffier.

"Often people just think, 'Oh no, it's a dead thing on the beach that's keeping me from swimming'."

In an effort to fight damage to Mediterranean seagrass, France has made it illegal for boats measuring more than 24 metres to drop anchor in sensitive zones.

Spain's Balearic islands took similar measures in 2018 and enforces them with regular patrols.

Their conservation efforts, which include awareness campaigns in schools and a seagrass festival, have been highlighted as exemplary by the WWF.

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