Saving our seagrass forests

What if a habitat could capture carbon faster than a rainforest? Neutralise an acidifying ocean? Stop plastic in its tracks? Provide homes for thousands of species? As Countryfile's Plant Britain campaign focuses on conservation on our coasts this year, Sophie Pavelle explores the wonders and opportunities that our dwindling seagrass forests can offer us

- Sophie Pavelle

Despite it being July, a steely Irish Sea grips me as I take a breath before a second dive. Here in Porthdinllaen, both sea and sky are anthracite. Moody, like the slate inland away from this bay on Wales's spectacular Llŷn Peninsula - 'Snowdon's arm', as it's known locally. But as I submerge, greys flush into yellows, greens and teals. Light persists in ways I haven't noticed before. A flick of my fins propels me onwards over a meadow of grass that sways below, like a field of wheat.

Buoyant in both wetsuit and mood, I am seeing a habitat that is new for me, but a precious antique of our planet. A habitat hailed as both conservation's 'wonder plant' and its 'ugly duckling' in the same breath. It's a habitat that lingers on the edge of survival in the UK, and the world.

Superficially, everything about seagrass suggests a habitat that thrives on simplicity. Vaguely resembling an abandoned underwater cricket ground, this complex and misunderstood environment can appear unremarkable. Upon first glance, you sense you have seen it before.

Seagrass varies in both morphology and ecosystem services. Some meadows are small garden-size, others vast enough to span 400,000 rugby pitches. Although seagrass covers just 0.1% of the ocean floor, the passage of climate and time has motivated the plant to diverge into 72 species worldwide, flanking bays on every continent except Antarctica.