News: kelp! Save our hid­den forests

Kelp stores car­bon, en­hances bio­di­ver­sity, ben­e­fits com­mer­cial fish­ing and shields our coast­lines from storms. Surely it makes sense to save this won­der sea­weed?

BBC Wildlife Magazine - - CONTENTS - Re­port by Olive Heffernan

The won­der sea­weed that needs our help and pro­tec­tion

Con­sider, for a mo­ment, the great forests of Bri­tain. What springs to mind? The oaks and sil­ver birches, the holly and rowan trees of our royal forests? It might come as a sur­prise to you, then, that Bri­tain has twice as much for­est un­der­wa­ter – in the form of vast kelp beds – as na­tive wood­land.

Cov­er­ing an area the size of Wales, these lus­cious sub­merged seascapes are to the ocean what wood­lands are to life on land: a home to hun­dreds of di­verse crea­tures, from sea­horses to sharks. “Kelp is a crit­i­cal habitat in the amount of wildlife it sup­ports,” says Daniel Smale, a marine bi­ol­o­gist at the Univer­sity of Ply­mouth.

Yet this habitat is al­ter­ing with cli­mate change. We’re al­ready see­ing this in the south, where some kelp species have been de­clin­ing since the 1970s. As wa­ters warm and storms be­come more ex­treme, the con­cern is that this vi­tal ecosys­tem will de­grade fur­ther in the com­ing years.

The wa­ters off Sus­sex – from Brighton to Selsey – have ex­pe­ri­enced the worst losses. In the past few decades, the kelp habitat here has di­min­ished by an ex­cru­ci­at­ing 97 per cent, as com­mer­cial trawl­ing, sed­i­ment dredg­ing and storm dam­age have taken their toll. The vi­brant un­der­sea for­est that once dom­i­nated 40km of shore­line, and stretched 4km sea­ward, has now been re­duced to just a few scrappy patches of sea­weed.

Sea­weed SOS

In re­sponse, con­ser­va­tion­ists have launched an am­bi­tious project – backed by David At­ten­bor­ough – to re­store Sus­sex kelp. The hope is that by ex­clud­ing trawlers up to 4km from the shore, the area will see a re­turn of its once re­splen­dent marine wildlife, in­clud­ing the sea­horses, cut­tle­fish, lob­ster and sea bream that fre­quented these wa­ters just decades ago. Restor­ing kelp will also bring ben­e­fits for the cli­mate and for local fish­eries. “We want this to be a blueprint for other rewil­d­ing projects,” says Sarah Ward, Liv­ing Seas Of­fi­cer at the Sus­sex Wildlife Trust, which is lead­ing the project with the Blue Marine Foun­da­tion and the Marine Con­ser­va­tion So­ci­ety.

“Bri­tain is a Goldilocks zone for kelp – it’s just right.”

Kelp are large brown sea­weeds that thrive in cold, clear wa­ters. Un­like sea­grasses or man­groves, kelp have no roots and need a solid base, such as a rock or boul­der, to at­tach to. They form dense forests along the world’s tem­per­ate and po­lar shore­lines, but Bri­tain is a par­tic­u­lar sweet spot, boast­ing the rich­est kelp com­mu­ni­ties in Europe. Of the 14 species of kelp in Europe, seven are found in our wa­ters. “Bri­tain is a Goldilocks zone for kelp – it’s just right,” says Juliet Brodie, a sea­weed spe­cial­ist at Lon­don’s Nat­u­ral His­tory Museum. “We have beau­ti­ful kelp forests all around our coast.”

Within these dense watery jun­gles, each plant can sup­port up to 80,000 other crea­tures, in­clud­ing worms that bur­row into the kelp where it at­taches to a rock, sponges that set­tle on the stalk or ‘stipe’ of the kelp and fish that nib­ble on its large float­ing leaves. Bri­tain’s kelp forests can reach depths of 45m and, in spring, when there’s enough sun­light, each in­di­vid­ual blade can grow by as much as a 1cm a day, reach­ing lengths of 2m.

Wa­ter war­riors

These over­sized sea­weeds also hap­pen to be one of our best de­fences against cli­mate change. Cud­dling our coast­lines, they quell the de­struc­tive en­ergy of waves and storms. What’s more, as one of the ocean’s most ef­fi­cient forms of ‘blue car­bon’ (the car­bon stored in coastal ecosys­tems), they suck vast quan­ti­ties of CO2 from the air. “In Europe, the flow of car­bon into kelp forests is higher than for sea­grass mead­ows and it’s also higher than oak and pine forests,” says Smale. Glob­ally, al­gal forests can cap­ture around 1.5–2gt of car­bon per year. That’s an enor­mous amount – equiv­a­lent to around

20 per cent of hu­man-pro­duced CO2 emis­sions.

Around 15 per cent of the car­bon cap­tured by kelp makes its way to the deep sea via nat­u­ral leaf-fall, where it is locked out of the at­mos­phere al­most in­def­i­nitely. When kelp is dam­aged dur­ing a storm, it breaks up and trav­els, as de­tri­tus, on cur­rents to the open ocean. Even­tu­ally, the kelp – and its car­bon – sinks, and about two-thirds of it ends up be­low 1,000m, where it re­mains for cen­turies.

So, our kelp forests are well worth safe­guard­ing. “The bio­di­ver­sity is the one thing that we re­ally want to pro­tect,” says Ward, “but, of course, this has other po­ten­tial ben­e­fits for car­bon stor­age and for the fish­ing in­dus­try, be­cause some of the species – the crabs and lob­sters, for ex­am­ple – are com­mer­cially im­por­tant.”

It’s not all bad news for kelp, though. As wa­ters warm with cli­mate change, kelp forests have be­gun to flour­ish in the north, es­pe­cially around Scot­land and North­ern

Boosts local bio­di­ver­sity, such as worms and crus­taceans.

Re­duces local ocean acid­i­fi­ca­tion and de-oxy­gena­tion.

Cuts down local eu­troph­i­ca­tion (pol­lu­tion caused by an ex­cess of phos­pho­rus and ni­tro­gen).

Pro­vides coastal pro­tec­tion, by blunt­ing the en­ergy of waves and storms.

Off­sets cli­mate change – cul­ti­vat­ing just 0.001 per cent of wa­ters suit­able for kelp farm­ing could off­set the en­tire emis­sions of the global aqua­cul­ture in­dus­try.

Pro­duces cli­mate-friendly an­i­mal feed: feed­ing cows 1 per cent sea­weed in their di­ets can re­duce their meth­ane pro­duc­tion by up to 60 per cent, slow­ing emis­sions from agri­cul­ture and im­prov­ing an­i­mal health (find out more on p54).

Pro­vides a healthy food source – rich in min­er­als, vi­ta­mins and protein. It’s also a source of al­gi­nates that are used to make cos­met­ics and food thicker.

Found around the UK coast, kelp cre­ates an un­der­wa­ter for­est en­vi­ron­ment that’s teem­ing with marine life.

Top left: along with kelp, sea­grass of­fers pro­tec­tion for species such as the spiny sea­horse. Right: trawler ex­clu­sion zones could ben­e­fit myr­iad marine life around our coast.

Orkney has a long his­tory of har­vest­ing kelp. Above: sugar kelp is com­mon in Bri­tish wa­ters.

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