Kelp Forests of Devon: England's Rugged Southwest Reefs

Devon is the only county in England with two separate coastlines, and both of them grow kelp. The south-facing shore — Plymouth Sound, the drowned estuaries of the Dart and the Salcombe, the hard promontory of Start Point — catches the soft light and the mild Atlantic drift; the north coast stares across the Bristol Channel at Wales and takes the swell on its basalt and sandstone. Between them lies the birthplace of British marine biology. If you want to understand English kelp — what it is, what lives in it and how it is changing as the seas warm — this is the atlas entry to start with.

Two coasts, one kelp province

Devon sits in the sweet spot where the English Channel's waters mix with Atlantic swell rolling in around Cornwall's shoulder. The result is a warm-temperate kelp province: cooler and more oceanic than the eastern Channel, milder than Scotland, and positioned exactly at the thermal meeting point where several kelp species reach the edges of their ranges. That position has made Devon's reefs a living laboratory for more than a century.

The south coast's defining feature is its drowned landscape. The ria estuaries — Dartmouth's Dart, Salcombe's Kingsbridge estuary — are valleys flooded by post-glacial sea level rise, and they carry kelp-like seaweeds, seagrass and rich sheltered communities far inland on the tide. Outside them, the open coast is bedrock: Devonian slate and sandstone reefs off Wembury and the Mewstone, the long limestone-ish reefs of Tor Bay, the tidal races off Start Point and Prawle Point, where the current rips and the kelp stands in clear, fast-moving water.

The north coast is rawer: Exmoor's cliffs run to the sea at places like Valley of Rocks, reefs fringe Croyde and Morte Point, and the Bristol Channel's enormous tidal range — among the largest in the world — shapes everything. Out in the channel's mouth, eleven miles off Hartland Point, sits Lundy, the granite island whose reserve we cover separately and whose kelp beds are Devon's most famous underwater landscape.

The kelps themselves

Devon's forests are classic northeast Atlantic Laminaria country, but with a twist that makes them nationally important: this is where the warmth-loving species have their strongholds.

• Oarweed (Laminaria digitata) dominates the low shore and shallow subtidal — the familiar frilled, fingered kelp of British rocky shores, flourishing in the surge channels of headlands.
• Tangle kelp (Laminaria hyperborea) — cuvie to harvesters — builds the true subtidal forest, its stiff stipes holding fronds above a shaded understorey of red algae. Off Start Point and around the offshore reefs it forms proper multi-metre forests.
• Golden kelp (Laminaria ochroleuca) is the southwestern signature: a warm-affinity kelp at its northeast Atlantic stronghold in Devon and Cornwall, recognisable by its smooth, glossy, gold-toned blade. Its local expansion over recent decades is one of the clearest climate signals in British marine life.
• Sugar kelp (Saccharina latissima) fills the sheltered spots and the estuary mouths.
• Furbelows (Saccorhiza polyschides), the big annual with the warty holdfast, storms up each summer to several metres on open-coast ledges — the fastest-growing thing in British seas.

Together these species structure a reef that British divers call, without irony, England's best kelp diving: clear green water, kelp to the surface, and reef life stacked into every shaded overhang.

What lives in Devon's kelp

The forest's cast is the full southwest repertoire. Ballan wrasse — big, territorial, brick-red or mottled green — are the forest's foremen, and their role as cleaners means you can watch smaller fish queue at wrasse stations. Pollock hunt in loose packs above the canopy. Cuttlefish arrive in spring to lay black grape-bunch eggs on the kelp stipes and wrecks; Tor Bay's eelgrass beds support breeding populations of both of Britain's seahorse species. On rockier reefs, conger eels, tompot blennies, crawling armies of spiny spider crabs in their summer aggregations, and jewel anemones in pink and orange carpeting the shaded walls. Grey seals haul out on the south coast's outer ledges and all around Lundy; basking sharks pass westward in early summer; and the Eddystone reef, miles offshore, gathers dolphins and seasonal bluefin tuna over its pinnacles.

One oddity to name: the pink sea-fan gardens and ross coral on deeper exposed reefs mark how Atlantic this county is — Devon's deep ledges carry species most of England has lost or never had.

The science capital

Devon is where British marine science grew up. The Marine Biological Association, founded in the 1880s, still runs its citadel laboratory above Plymouth Hoe; Plymouth Marine Laboratory and the university have made the city a genuine European hub of ocean research. The continuous plankton recorder and long-term benthic time series off Plymouth — including the century-spanning Eddystone and L4/L5 station records — are among the longest-running marine datasets on Earth. For kelp, they have proved priceless: researchers here documented the classic climate pattern of our time on these very reefs — cold-loving oarweed pulling back as golden kelp expands — and Plymouth Sound's designation as the UK's first National Marine Park formalised the city's identity as a place where people and the sea are managed together.

Neighbouring Cornwall carries the story west; see our atlas guide to Cornwall's coast for the kelp, maerl and history just across the Tamar and around Land's End, and the Isles of Scilly for where this province tips into the open Atlantic.

Pressures and the protection picture

Devon's kelp faces the signature modern pressures, in local accent:

• Warming. Southwest England is the Atlantic's warm gateway into British seas; heatwave summers have grown common, and the species composition of forests is visibly shifting from cold toward warm affinity.
• Mobile fishing gear. Scallop dredging and trawling on reef margins damages the slow-growing invertebrate turf and maerl that forests depend on; the county's inshore pot-and-line fleet is comparatively low-impact, and debates over gear and seabed protection are live in Devon's coastal politics.
• Invasives. Wireweed — Japanese Sargassum muticum, naturalised since the 1970s — and the kelp wakame now share the shallow reef with natives, especially in marinas and estuaries.
• Water quality. Storm-sewage spills and agricultural runoff, infamous in the southwest in recent years, cloud the water and add nutrient stress to estuaries and sheltered bays.

Against that, protection has grown: Lundy carries a full stack of designations including England's original no-take zone, marine protected areas and highly protected marine areas now tile parts of the county's coast, and Devon's estuaries host pioneering seagrass restoration. The trend line is genuinely hopeful, if slower than the biology would like.

Getting in the water

Devon is England's most accessible kelp-diving county. Plymouth is the hub: charter boats work the Sound, the Mewstone, the Eddystone and a famous wreck fleet — including HMS Scylla, the ex-frigate sunk in Whitsand Bay in 2004 as an artificial reef, now a kelp-and-jewel-anemone garden and the most-dived wreck in the southwest. Shore divers head for Wembury, Fort Bovisand's beaches and the rock shelves around Start on slack tides. North Devon offers wilder, swell-dependent snorkelling on calm summer days; Lundy itself, reached by ferry or charter from Ilfracombe, is the jewel — clear channel water, seals, and kelp forest against granite slopes.

Water runs 9–10°C in winter to 17°C in a warm September. Visibility is 2–8 metres typically, better on the offshore reefs and after calm spells. A 7 mm wetsuit or drysuit is the realistic kit; the season for most people runs May to October.

Key takeaways

• Devon is England's only two-coast county, and both coasts grow forests: the mild ria-and-headland south and the slab-tide, swell-struck north.
• The kelp mix — oarweed, cuvie, warm-loving golden kelp and the annual furbelows — makes Devon a climate-change laboratory, with golden kelp's documented expansion as the headline shift.
• Plymouth has been a global centre of marine science since the 1880s; its long-term records made Devon's reef changes visible to the world, and Plymouth Sound is the UK's first National Marine Park.
• Lundy, eleven miles offshore, holds the county's diving crown and England's original no-take zone.
• For divers, Plymouth's boats and the Scylla artificial reef, Wembury's shore dives and Lundy's granite slopes are the circuit; May–October, in 7 mm or dry.

FAQ

Is Devon good for kelp diving?

It is England's best for it. The mix of accessible shore sites (Wembury, Bovisand, Start Point at slack), a large charter-boat fleet in Plymouth, the Scylla wreck and Lundy's clear-water granite slabs gives the county a spread matched nowhere else in England, all in real kelp forest.

What kelp species will I see in Devon?

Expect oarweed on the low shore, cuvie (tangle kelp) forming the deeper forest, golden kelp on the warmer open coast, sugar kelp in shelter, and the fast-growing annual furbelows on open ledges. Golden kelp's southwest stronghold is Devon's special signature.

When is the best season to dive or snorkel Devon?

May to October. September often combines the year's warmest water (around 17°C) with thinning crowds; spring brings cuttlefish laying on the kelp and wrecks. Offshore reefs like the Eddystone and Lundy offer the clearest visibility after calm spells.

How is climate change affecting Devon's kelp?

Devon sits at a thermal crossroads, so it shows the shift first: warm-affinity golden kelp has expanded locally over recent decades while cold-loving oarweed has pulled back — a documented, ongoing rearrangement rather than a collapse. Heatwave summers, invasive seaweeds, mobile fishing gear and runoff events complicate the picture, but Devon's forests remain among Europe's healthiest.