Launching the Help Our Kelp campaign today, Sir David said that the algae seaweed was “vital” for tackling climate change.
The campaign hopes to restore a vast underwater kelp forest off the Sussex coast in the first ever marine kelp rewilding initiative.
Kelp forests had previously stretched along 40 km of the West Sussex coastline, extending at least 4 km seaward. But storm damage, changing fishing practices and the dumping of sediment by dredging boats had diminished them to “almost nothing”.
Sir David said: “The loss of the Sussex kelp forests over the past 40 years is a tragedy.
“We've lost critical habitat that is key for nursery grounds, for water quality and for storing carbon.
“This marine rewilding project, if approved, will ensure the Sussex seas remain healthy for generations to come, and could have far-reaching impact for other parts of the UK coast.”
Sarah Ward, Living Seas Officer at Sussex Wildlife Trust said the pioneering rewilding project will help to “fight climate change”.
She said: “Kelp forests can absorb and lock up carbon just as effectively as woodland, if not more so, and we’re able to create this habitat on a scale that simply couldn’t be replicated on land.
“This will be a huge step forward in addressing the escalating climate crisis.”
Globally, kelp forests absorb 600 million tonnes of carbon which is roughly twice the amount of carbon that the UK emits per year, explained Dr Ian Hendy, Head of Science at Blue Marine Foundation, in a film made in conjunction with the campaign.
Kelp forests, which range along 25% of the world's coastlines, also provide habitat in the UK for seahorses, cuttlefish, lobster, sea bream and bass.
Narrating the film by Big Wave Productions, Sir David said the “magical” underwater forests are “one of the most biodiverse environments on the planet”.
He added: “The forests are vital nursery grounds, giving sanctuary to the young of many commercial fish, as they feed and hide among its fronds.
“We’re discovering these underwater forests are vital, not just for sea life, but in climate change.”
The Help Our Kelp campaign supports a new bylaw proposed by the Sussex Inshore Fisheries and Conservation Authority (IFCA) to stop trawling within 4 km of the coast.
It is led by Sussex Wildlife Trust, Blue Marine Foundation and the Marine Conservation Society, who are now urging the public to respond to the consultation, which closes on the 10th October.
Once the trawling management is in place, the partnership will be able to take forward plans to restore the forest.
Dr Sean Ashworth, Deputy Chief at Sussex IFCA said: “If we want healthy seas that are sustainable for wildlife and fishing for generations to come, we urgently need to give our kelp forests a chance to regenerate.
He added that the new bylaw was “critical” and that they needed “support from the local community to make sure this happens”.
Alice Tebb, Project Coordinator at the Marine Conservation Society said the restoration of the kelp forests would benefit the fishing industry.
She said: “Local fishermen used to row their boats off the beach before starting their engines to get clear of the kelp.
“Now, the kelp is gone and fishermen are reporting fewer fish.
“Restoring the local kelp forest would bring back this vital fish nursery and feeding ground, helping important commercial species to recover and thrive.”
The forest will also improve water quality and reduce coastal erosion by absorbing the power of ocean waves.
The new campaign comes following the announcement of the biggest seagrass restoration scheme in the UK last month, which will see one million seeds planted off of west Wales in a bid to help tackle climate change.
The project, launched by Sky Ocean Rescue, WWF and Swansea University aims to restore 20,000 m2 of the marine plant in Dale Bay, Pembrokeshire.