Cuvie Kelp Forest of the Sea

29 Jan 2020 16:11 | Rachel Lambert

by AoF member Susanne Masters 

Dive down past swirling green ribbons to rocks where kelp strikes its hold. Denizens of cooler seas, kelps are a group of seaweeds better appreciated by swimmers than rock poolers, as their beauty unfurls in deeper water. Cuvie (Laminaria hyperborea) is the kelp that skirts Britain and Ireland along their rocky shores. Growing in water from 1m to 47m deep, cuvie is only visible to land lubbers at low tides when its rigid stipes emerge upright from the water while its fronds are crumpled in the shallows.

Trees have roots, trunks and leaves; kelps have holdfasts, stipes and blades.  Holdfasts are tentacle like domes that grip on to rocks and resist being torn away by currents. Brittle stars and worms can be found living inside the shelter of holdfasts. Cuvie’s stipe has a rough surface that makes it easy for red seaweeds like dulse (Palmaria palmata) to attach and grow on it. Animals such as sea squirts, bryozoans, hydroids and sponges also settle on the stipes. While plant life slumbers on land, cuvie starts to grow new blades from its stipe in November. It sheds its old blades in early summer. Fish graze and hide amongst the underwater canopy of blades. Providing three tier accommodation in the holdfasts, on the stipes and amongst the blades, cuvie forests are packed with a range of wildlife making them the temperate equivalent of a tropical coral reef.

Cuvie forests lit by shafts of light shifting as water moves its blades are a living cathedral deserving of reverence. They shelter shores from rough weather by absorbing wave energy, and for hundreds of years the cast off blades that washed up on beaches were essential for farmers using them as fertiliser for their crops on land. Cuvie was burnt to produce an ash that was essential for glass and soap manufacture in the 18th and 19th centuries.  Cuvie and other kelps are now harvested for the extraction of alginates that are used in food, pharmaceutical, and other industries. Hand harvesting kelp allows the stipes to regenerate – individual cuvie can live for 15 years. Mechanical harvesting via dredging rips up the holdfast and stipe as well as the blades. It takes years for kelp forests to regrow after large-scale mechanical harvesting.  Even 4 years after mechanical harvesting the kelp is smaller and there are less animals and other seaweeds living amongst it than in a mature kelp forest.

I have objected to a few mechanical harvesting applications. Singular mechanical harvesting events that extract a resource and profit from it are not good sources of local employment and economic benefit for small communities: which is precisely why I recommended a local hand-harvester for supplying Harris Distillery for sugar kelp for the gin.

If more people walked amongst our underwater forests they would be better cherished. I am an ethnobotanist who is regularly immersed in seaweed and phycology - reading publications and reports at my desk, product sampling, and literally swimming through their fronds. I would not countenance clearcut felling a whole forest for a crop of timber, equally mechanical harvesting of seaweed is a destructive way to make use of our natural resources. In this I am not alone. Certainly on Scotland's land forests horselogging is regaining practice as its gentle harvest maintains intact ecosystems. Our cool waters are a source of wealth as industrial as well as food applications of seaweed increase. It is foolhardy to discard our underwater forests in a sole bounteous harvest of mechanical felling followed by slow and incomplete recovery. Individual cuvie kelp (Laminaria hyperborea) can live up to 15 years, this allows a host of other organisms - epiphytic seaweeds and sedentary animals - to grow on them. Hand harvesting has lower yields and the harvest is more diffuse, allowing kelp and species depending on it to remain as an intact ecological community. But hand harvesting's more sustainable approach leads to greater yields over time, whereas mechanical harvesting can only maintain yields by clearing increasing areas of the seabed.

When considering harvesting of wild ingredients it is imperative to scan the horizon and consider not only immediate conditions but what approaches. Already warming sea temperatures are exerting an influence on our cool water bounty of seaweeds. In the south of England warmer temperatures seem to be shifting kelp forests to Golden kelp (Laminaria ochroleuca) dominated communities - which support less biodiversity. Scotland is a stronghold for Sugar (Saccharina latissima) and Cuvie kelp forests. Mechanical harvesting is likely to speed up the shift in composition of kelp forests.

Hundreds and thousands of years ago the British Isles was denuded of its land forests as pastoral and agricultural practices yielded crops of our demands. Slowly and with much effort some progress is being made in restoring Caledonian forest. With the benefit of hindsight on what happened with our land forests why destroy the Caledonian underwater forests? Mechanical harvesting of seaweeds is a bitter harvest of fleeting profit followed by enduring loss not only of seaweed but the life that lives amongst it. It is also foolish to disregard the role that kelp forests have in absorbing wave energy and buffering our shorelines from storm damage. The annual natural discard of blades (seaweed equivalent of leaves) is a means by which nutrients are given to the land by the sea. As we have to consider our dependence on petrochemicals, seaweed fertiliser washing up as an annual bounty from kelp forests discarding their blades is another useful product. One of the world's rarest habitats - machair - was formed by the interaction between farming on land and nutrients returned from the sea as seaweed.

The richness of seaweed around Harris, biodiversity that dwells in it and the longstanding cultural importance of seaweed are why I selected a seaweed for Harris gin - so that people might connect with a part of the island that is less visible but particularly important to local culture. I specifically identified a local hand harvester as a means of reaching the sugar kelp that would furnish Harris gin with its flavour for as long as the stills are running. Hand harvesting offers a sustainable way of accessing seaweed for commercial ventures.

In many ways I encourage the harvesting of seaweed as a socioeconomic resource supporting sustainable income when the seaweed is either cultivated or hand harvested. Mechanical harvesting is catastrophic for seaweed and the marine life that depends on it. Mechanical harvesting removes seaweed beyond its seasonal renewal rate, and this can trigger ecological changes i.e. once harvested mechanically kelp forests may not grow back. Mechanical dredging of maerl beds has caused abundance of maerl to decline.

Perhaps because I am swimming outdoors all year round it is easier for me to appreciate the complexity and vibrancy of kelp forests. It is the kelp that provides a substrate for all kinds of life to inhabit, everything from 1mm long blue-rayed limpets that have an electric blue stripe of a hue rarely seen in nature, to otters- everyone's favourite water clown. Kelp forests offer an economically valuable resource, provide ecosystem services, and are a seat of biodiversity. Mechanical harvesting of kelp operates from a short-term perspective as it damages the resource it uses. Hand harvesting is the best way to utilise kelp as an economic resource while maintaining kelp forests for their biodiversity and ecosystem value, and to ensure that the economic harvest of kelp can continue indefinitely.

SWIM IN A FOREST OF CUVIE

Cuvie grows along rocky shores, where entry and exit points are often limited, so be sure to check tides and currents before swimming.

  • St Kilda, Atlantic Ocean – in the clear water surrounding the archipelago light penetrates deep into the sea allowing cuvie to grow up to 47m below the surface
  • St Abb’s, Berwickshire, Scottish borders
  • North west coast, Isle of Coll, Inner Hebrides
  • St Brides Haven, Pembrokeshire, Wales
  • Bantry Bay, Co. Cork, Ireland – a legendary area of kelp, potentially threatened by the issuance of the largest ever license for mechanical extraction of kelp in Britain and Ireland

-------------------------------------------------------

This is a combination of an article published in Outdoor Swimmer and my input requested on the Scottish Government's consultation on an application for mechanical seaweed harvesting license. 

© The Association Of Foragers 2019 | Follow our activities on social media via the hashtag #AOF