Capturing Carbon: Beyond Woodland

From peat bogs to seagrasses, how can nature help us reach net zero carbon?
31 August 2021
Presented by Sally Le Page
Production by Sally Le Page.


Kelp underwater


This week we’re taking a deep dive into the world of carbon sequestration and how we can use nature to help us solve climate change. We'll be wading through peat bogs, getting serious about seaweed, and digging into the details of dirt...

In this episode

photograph of a forest

01:18 - Capturing carbon: why is it important?

And can we sequester carbon using nature-based solutions?

Capturing carbon: why is it important?
Ruth Gregg, Natural England

Climate change has been top of the agenda recently, as the latest IPCC report came out earlier this month. The Intergovernmental Panel on Climate Change produces one of these reports every 6 to 7 years to summarise the 14,000 scientific papers that have been published on historic climate models, global warming and its implications on the planet. And the findings of this report are clear: humans are responsible for the planet warming at a rate that is unprecedented in at least the last 2000 years. This warming is driven by increased greenhouse gas emissions, of which CO2 and methane are the major contributors. This is already leading to hotter heatwaves, wetter monsoons, more frequent droughts, and the oceans warming at their fastest rate since the end of the last full Ice Age. Some of the impacts us humans have had on the planet are now irreversible. We are going to warm the planet by 1.5ºC more than pre-industrial levels. No matter what we do, sea levels are going to rise by several metres over the next 2000 years, the ice sheets will continue to melt and the oceans will become more and more acidic.

But, the science is also clear: there is hope. If we can reduce our global carbon emissions to net zero by 2050, the planet will quickly stop warming. And if we start absorbing more carbon than we produce it’ll even start cooling down again and those extreme weather events will become less extreme again. Sally Le Page spoke with Ruth Gregg from Natural England about the role carbon sequesteration could play...

Ruth - The absolute priority that we need to tackle is decarbonising the sectors that contribute to climate change, but also actively taking carbon dioxide out of the atmosphere.

Sally - That's Ruth Gregg, a climate change specialist who earlier this year produced a 240 page report for Natural England looking into climate change and carbon storage.

Ruth - What our report aims to do is that we look at all the habitats that you'll find in England, and we try and capture how important they are for carbon storage and sequestration. So what we cover is everything from peatlands that you find on our mountains and the hills, everything down to our coastal and marine sites and everything in between.

Sally - And this is what we hear referred to as carbon sequestration, right? To sequester carbon, to draw down carbon.

Ruth - It certainly is. So what carbon sequestration is; it's the process of capturing and storing atmospheric carbon dioxide. So habitats can do this as I've just described, but they can also do it in other ways as well, in that they can trap carbon. So when we're dealing with habitats such as reed beds or salt marshes or sea grass, they actually capture carbon that's been released from elsewhere and store it in their sediments.

Sally - And when we think about carbon capture, a lot of people will automatically think about carbon capture technologies and Elon Musk put forward a big prize to try and develop some tech that will draw down carbon from the atmosphere. Do you think that we can reach net zero using these technologies alone?

Ruth - So all the pathways that we have to get to net zero do take into account some of these technological developments that haven't actually happened yet. At the moment, the main carbon capture and storage that we have is our natural environment.

We'll be coming back to Ruth and nature-based solutions very soon. But first is it true that carbon capture technologies don't really exist yet? Naked Scientist, Harry Lewis, has been looking into how far we've come and how far we've yet to go with removing CO2 directly from the air.

Harry - I'm stood on the intersection of the South Circular that cuts across Putney High Street. Now, as you might be able to guess, this is one of the most polluted streets in London - the second, actually, according to a report released earlier this year. If our technology is responsible for pumping out pollution, then surely tech can be responsible for sucking it back up.

Harry - Carbon dioxide capture and storage, or CCS, is supposedly the answer. It's a label given to any technique with the potential to remove CO2 from the atmosphere and durably store in reservoirs. So CCS is often used to refer to the stripping of CO2 from waste streams, and it's already commonly used in the oil industry. Earlier in August, however, a research team pointed out that these techniques are less efficient than we previously thought. They require a lot of energy to make any tangible difference. Now, ironically, in this instance, the stored gas tends to be used for enhanced oil recovery, so it's injected into the ground in an attempt to force out any remaining oil deposits. Ultimately that then slowly leaks out of the wells and settles back in the atmosphere. Of the 21 large-scale plants across the globe, all but five sell their stores to facilities involved in this enhanced oil recovery.

Harry - So looking for alternatives, the other man-made carbon sequestration technique is direct carbon capture and storage - DCCS - technologies that suck the carbon straight from the air around us. There are currently three industrial-scale storage projects, and the biggest by far is the Canadian Weyburn carbon dioxide project in Canada. After starting back in 2000, the phase one trial found that the thick cap rock required for geological storage of the CO2 wasn't an impermeable barrier to the upward movement of the gas as is still commonly assumed. In order to capture the carbon dioxide in the first place, the Weyburn project filters air directly through a potassium hydroxide drenched filter. These plants are really energy hungry. A 2019 report from Imperial College London found that 30,000 large scale DCCS plants would be required to negate global emissions. Every year it would require the entire global supply of this chemical six times over. And even then it would still take up to a sixth of the world's energy expenditure to power them. The other issue is finding somewhere to store this gas. So as we've discussed, our understanding of geological foundations and their ability to hold onto carbon dioxide is fine in theory, but not so efficient in practice. Perhaps we could store the gas deep in the ocean as is done in Norway or by creating mineral carbonates. Maybe even utilise it in a different form of industry. That's like a company just outside Zurich who sell their CO2 to Coca-Cola.

Harry - Now, after walking around Putney, I stumbled across a sort of rudimentary direct carbon capture feature, a city tree, which might not be quite what you expect. It's an interesting little feature, really. It's roughly two metres high and around it is constructed this wooden lattice and trellis. And if you get really close, sprouting out the darkness between the shelves are dark and light shades of green. It's more like a small art installation, really. It's pretty out of place. It transpires that inside the cuboid are a large variety of different types of moss species, all of which are capable of drawing pollutants out of the air and supposedly making the air noticeably cleaner in a two to three metre radius.

It's obvious that direct carbon capture technologies are in desperate need of research and development. They're in need of incentivisation before they can make any real global difference. And stood here, I can't help but feel that in the next 20 years, it's preservation that's going to be essential. Something we still haven't entirely grasped. You know, the ecology and habitats that naturally suck up carbon. They're of paramount importance. Even if it is just to buy us some more time to learn from nature, like this little city tree, to help us further our technological efforts.

We don't have time to wait for carbon capture technologies to be developed if we want to reach net zero by 2050. So what's the alternative? Well Ruth Gregg reckons it's nature-based solutions.

Ruth - So what nature-based solutions are: they're about how protecting, restoring and managing natural systems can help societal problems. So it's looking at nature to provide us solutions and not just trying to use technology to help us out of these issues.

Sally - And what kind of problems can nature solve?

Ruth - We've already talked about mitigation and how habitats capture carbon in their vegetation, in their soils, but it can also help us with climate change adaptation, water regulation, water filtration. So we know that sensitive planting of woodlands on slopes, for example, can help us manage flood risk. Saltmarsh can help prevent or protect us from storm surges and sea level rise. So there's a whole host of benefits that they can give.

Sally - If we want to capture carbon with a nature-based solution, all of these buzz words, do we just plant trees? Is that it? Is the solution to climate change just trees?

Ruth - It's one of them. And it's a really important one. They offer us some of the most consistency sequestration rates and high sequestration rates. So they are a very vital piece of the puzzle, but you can only plant trees in so many places. We also need to consider what the marine and the coastal environments can offer us as well. So things like saltmarsh have been shown to store and sequester carbon at quite high rates. One of the things that we shouldn't be overlooking is protection of habitats, as habitats such as grasslands, our heathlands, have the potential to store huge amounts of carbon. And we want that carbon to stay where it is. We don't want that to be released. So no, not just trees, but trees are also very important.

Peat water works

12:25 - Protecting peat to protect the planet

What is peat, and how can we optimise land use to protect it?

Protecting peat to protect the planet
Lorna Parker, Water Works

Sally Le Page took a walk through this endangered habitat to find out more about the history and science of peat bogs and what is being done to save them...

Sally - I’ve managed to escape the home office to go on a little walk through one of the key ecosystems when thinking about climate change - peat bogs. Here in Cambridgeshire we have a vast expanse of lowland peat called the Great Fen, where I am now, part of the Fens that represents 27% of England’s peatlands. Peat is a remarkable substance, and we're not just talking about anyone called Peter! Peat is a type of soil that forms over thousands of years in wet, boggy conditions. Moss plants like sphagnum moss photosynthesise and absorb carbon dioxide in the air, using that carbon to grow. In normal soils, when plants die, microbes use oxygen to break down the dead plant material releasing some of that carbon dioxide back into the atmosphere. But because peatbogs are so waterlogged, there isn’t enough oxygen for the moss to break down and so as long as the peat stays wet, the carbon is trapped.

Sally - This makes our peatlands incredibly important stores of carbon. Peatlands cover only 3% of the world’s land surface, but hold 25% of the global soil carbon. And the UK has more peatland than vast majority of countries around the world - 10% of our land area is covered in peatland habitats. It’s estimated that there is over 3 billion tonnes of carbon stores in the UK’s peatlands, which is equivalent to all the carbon stored in the forests of the UK, Germany and France combined.

Sally - There we go. Over this little wooden bridge.

Sally - Now, not only is the peat disappearing into the atmosphere through oxidation, the dry peat can be literally blown away in the wind. As a result of all of this the land is sinking.

Sally - Here we are, this is where I was walking to. I am stood in front of two, what look like Victorian lamp posts on the edge of a wood in the middle of nowhere. Very bizarre. They are about three of me tall; what's that, four metres tall? And they're called the Holme Posts. As I get closer I can see these black labels with years on them, a bit like when you mark off your kids' height on a door frame to measure how much they're growing, but unfortunately these markers are not measuring growth. Quite the opposite. The first one at the very top I can just about make out says 1848. That is just the year before they drained the mere and with an awful lot of foresight they pushed these posts down as far into the ground as they could go until they reached the solid clay layer below. Back in 1848 the top of this incredibly tall post was level with the ground. Then as they drained the mere, I can see the next marker down is 1860, that's already a good one and a half, two metres down. That drop in the level of the land is mostly from all of the water being removed. Then we go down further 1870, 1875 we're now at my eye level, 1892 we're at my belly button. Then of course my feet are currently at ground level in 2021. That is four metres worth of carbon stored in that peat that is now released into our atmosphere.

The Wildlife Trust are behind restoring this Great Fen for biodiversity, but they're also researching ways in which we can use the land productively to grow food and building materials without draining and degrading the peat soil underneath. A few days earlier, Sally travelled down the road to an experimental farming site on the Great Fen called Water Works to find out more from restoration manager, Lorna Parker.

Lorna - The project is called the Water Works project, and it's an exciting opportunity to showcase a new form of farming. Up to two centimetres of soil lost in terms of land height every year. In places that soil is already very shallow, but even in the deeper areas, you might be looking at another 80 years of farming and then no more peat soil left anyway, and we need to find another choice.

Sally - What would the farmers do when the peat runs out?

Lorna - Underneath the peat is a layer of really heavy clay. So it's much harder to farm. And before you get there, a lot of this peatland is actually quite acidic as well because we were at the seaside about 5,000 years ago. There's all sorts of geology under our feet that make it very complicated to farm.

Sally - Either it's 80 years of farming vegetables, business as normal, and then kind of farming crisis for this area. What's the alternative?

Lorna - That's what we're hoping to show. We're kind of trying to demonstrate a new form of farming, which will look at crops that you can grow in wet soil. We can trap that carbon, lock that carbon back in, but also hopefully produce food, fuel, fibre and medicines.

Sally - This is the fab word 'paludiculture'.

Lorna - It's a good one isn't it? It will be a word that most people won't have come across before. 'Paludi' is 'swamp', so it's swamp agriculture. What we're going to do is go for a walk on our wet farming pilot project, the Water Works project, and have a look at some of the new crops that we're going to grow and hopefully excite you about the possibility of the things we can do with those crops in the future.

Sally - I'm already very excited. The cows are already very excited. Let's go. We've walked over some little raised strips. We walked over some ditches, where are we now?

Lorna - Okay, so we're in the corner of one of our new wet farming beds. This one we're sat in at the moment is what we're hoping will be a future food crop for the fens, and which is manna grass. It's a cereal crop, which would need some crop development, but could be a porridge or a sort of flour.

Sally - I'm looking at one of these seed heads now. I mean, it's not much to look at compared to an ear of wheat for example. You can barely see the seeds. What will the seeds look like?

Lorna - They'll be small, like a kind of millet-type grain, that you could have in your posh ancient grain porridge for example, or you could mill it into possibly low gluten flour.

Sally - You've got to ask, what does it taste like?

Lorna - I don't know yet, because this is our first year. So we haven't harvested any. I think the seed is so precious at the moment, we'll probably grow more plants with it rather than eat it.

Sally - You're going to spend years of work creating this food that you don't even know tastes any good?

Lorna - I hope so. We can add a jam to our porridge. I'm sure it'll be fine.

Sally - When you're thinking of plants that can feed lots of people in wet soil, the automatic choice would be rice. So why aren't you growing rice here?

Lorna - We're looking at rice. The climate in the UK is not ideal for rice at the moment, but you know, with global warming it's going in the right direction. Our plant nursery is actually looking at different strains of rice to find ones which grow in the most similar climate to what we have here.

Sally - As you can probably hear, this field is a lot wetter than the other one.

Lorna - Yeah. We've come to have a look at our bullrush field.

Sally - And what can we use bullrushes for?

Lorna - Bullrush is pretty epic as well actually. It's got a structure when it grows, where it traps lots of air inside its stem. It can be absolutely fantastic for fibreboard, so for construction materials that insulate at the same time. For cavity wall filling, you can shred it and blow it in, in place of artificial products. It would be really exciting, I think, to grow products and then build local houses from something that's sourced only a few miles away.

Sally - Yeah, totally.

Sally - We are next to probably one of the biggest plots, I would say, of the ones we've been to and it's covered in - very familiar to any allotment grower - a weed membrane. What is going to be here?

Lorna - Okay. So we've got about 150,000 plugs of this tiny bog moss that we're going to plant of several species underneath the mesh, and it will grow into a sort of carpet of green under there which will be a really good crop for us to harvest and lock that carbon in the soil.

Sally - Growing moss as a crop. How is that going to be useful?

Lorna - There's lots of ways. I could talk for hours just about the moss. Moss is really exciting. One of the most exciting things that we're hoping to do with the moss here is grow it and harvest it as a substitute for compost, for growing vegetables.

Sally - Right now there's been this big move of not buying compost that's got peat in it, right? Is this what's going to be in the bags of compost instead?

Lorna - We're hoping to go bigger than that. We're hoping this will be what growers of vegetables that you eat in the supermarket are going to use to grow their small lettuce plants, for example, rather than buying in peat from peat that's been harvested from peat bogs in the wild.

Sally - Wow. Not only will this moss stop people digging up the peat for the sake of the peat. It will also stop the peat here from drying out and we still get vegetables.

Lorna - Absolutely. The moss is amazing because it can control its own environment. It can control its own water. It can control weeds. It's antibiotic. It's super absorbent. It's like a hero plant.

Sally - You really are in love with this moss aren't you.

Lorna - It's a bit of a worry, isn't it?

Sally - If you had a magic wand, what would you do with all of the peat bogs and former peat bogs in the East of England?

Lorna - Most of the peat here is farmed. I would like to see ways that we can use it productively because that's a really important part of the local economy and the local culture, but in a way that can protect it forever. If we don't do something now it will be gone for future generations. If we can do that in a sustainable way, which has all these other benefits and build our houses from it, then what's not to like about that.

A red barn in a farmer's field

25:28 - Carbon-friendly farming techniques

How can farms be optimised to sequester carbon, without sacrificing productivity?

Carbon-friendly farming techniques
Becky Wilson, Farm Carbon Toolkit & Sophie Alexander, Hemsworth Farm

The Cambridgeshire Fens pose some unique challenges for farming in a carbon friendly way. But across the country, farmers are going to be vital as we push to make the UK net carbon zero by 2050. Agricultural land makes up about 70% of the land area in the UK; that’s a massive potential area for storing carbon. Becky Willson is the technical director for the Farm Carbon Toolkit, a farmer led organisation that’s translating all the carbon sequestration research into simple, practical management techniques that farmers can implement. She spoke with Sally Le Page who wanted to know, right now, do farms tend to be net emitters or net sequesters of carbon?

Becky - There are a complete mix of activities that happen on a farm. Some of those will be emitting greenhouse gas emissions, and then depending on how we manage our landscapes in terms of what we're doing with cropping and cultivation and grass, all that sort of thing, that will be pulling carbon in, out of the atmosphere in terms of being held in our soil. For the vast majority of our farms, a lot of those processes that are taking place on farms in terms of how we apply our fertiliser, what we're doing in terms of livestock management and other bits and pieces, are generating those greenhouse gas emissions. Those emissions that are going back up into the atmosphere that are causing climate change. But farming is unique in its opportunity to actually provide one of those climate solutions, depending on how we manage our land.

Sally - Can you tell me how can a farm draw down and store carbon from the atmosphere?

Becky - There's two key areas that farmers need to really focus on. Firstly, it's protecting their asset that they've currently got in terms of the carbon that's already in the soil. Soil is an incredibly large carbon store and we need to make sure that we protect that existing carbon and don't release it back up into the atmosphere through our management practices. That's area number one. Area number two is then looking at understanding how much carbon we've already got and then looking at the potential that we have to improve that. That improvement comes very much down to how we're managing that land. If we're talking about a cropping based system, it's very much focusing on what we're growing in terms of the length of time that the crop's in the ground, how diverse that rotation is. Are we growing the same crops over and over again, or are we making sure that those times that we're not growing those annual crops we're protecting that soil and we're covering it through the use of cover crops? How often we're disturbing that soil.

Sally - Why does ploughing make a difference?

Becky - Ploughing makes a difference because when we turn that soil over, which is the action that we have through plowing, that sudden flush of oxygen that goes into the soil that has been nicely asleep underneath, suddenly stimulates the soil bugs that live within the soil to respire madly. Obviously a byproduct of respiration is carbon dioxide, which goes back up into the atmosphere. If we move over to our livestock systems, which predominantly are focused on grass, quite often the question and the discussion there is because we've got crops that aren't cultivated every year, because grass tends to be down for many seasons, is there potential for those areas to be able to sequester more carbon? Then it very much comes down to how is that grass now being managed? How are you grazing it? Are you continually stocking? So, you're putting the same number of animals on that grassland and leaving them there throughout the whole grazing season or are we actually starting to move those animals around? What species are in that grassland? There are lots and lots of opportunities, but it very much comes down to management. The really exciting thing for farmers is actually there is really good correlation with improved soil carbon and improved soil function. Actually, if we can pull more carbon into our soils, we're actually going to get a much more healthier functioning soil, which is going to be able to hold more water when we're in these periods of drought. To be able to do all the things that actually allow us to have this really healthy functioning soil ecosystem that not just provides brilliant food quality for us as consumers, but also allows those farmers to have a real resilient business that can deal with these different climatic conditions that are coming.

Sally - Farmers aren't helping us save the climate at the expense of their farm business? It can actually help their farm business too?

Becky - Definitely. That's what's been really exciting over the last few years with the farmers that are starting to really get on board with these sort of practices. They're seeing that they may not be achieving record-breaking yields, but actually the inputs and their costs that need to go into generating those yields are much lower. There are significant economic benefits that can be had, and also as I say, we are generating those benefits in terms of soil health and resilient ecosystems for the future.

Sally - Do you have any figures or numbers after farms have implemented some of the suggestions from the Farm Carbon Toolkit? How they've reduced their carbon emissions or even gone carbon negative?

Becky - Absolutely. On all farms that we work with it's fairly simple to reduce their carbon footprint by about 10%, all those things, which actually are just efficiency measures. I challenge every farm. Every farm can reduce their carbon footprint by 10 to 15% without having to make any significant changes. We've got farms that we've also been working with over the last few years, which we have transitioned from being a net emitter to a net sequesterer. Taking a hundred cow dairy unit, taking it from contributing about 815 tons that's then sequestering about a hundred tons, so removing about 900 tons out the atmosphere. Also within the arable sector; those farms which have been emitting anything between about five and 600 tons, taking those to sequestering 200-300 tons. It is possible.

Sally - That's an incredible difference.

Becky - It is, and that's about taking account of what's going on within our soils, because what's important to remember is that you don't have to be doing a huge amount of building organic matter to actually be sequestering a lot of carbon, the numbers can be quite staggering. If you can build your soil organic matter within your soil 0.1%, that sequesters an additional nine tons of carbon per hectare

Sally - At the moment the farming sector as a whole and the food production sector does contribute a large amount of the UK's greenhouse gas emissions. With changes in land management do you think that overall it will be able to actually remove carbon from the atmosphere? Be a net carbon negative for the UK?

Becky - I think it's a challenge. We've always got this issue in terms of the fact that we're not just producing these emissions for the sake of producing these emissions. We're producing these emissions because we're producing food. Agriculture is responsible for about 9% of total emissions from the UK. Yes, we are a significant sector, but we do have some of these solutions. To offset all of our emissions with the current technologies that we have out there, it's going to be a real challenge, but just because it's going to be a challenge doesn't mean that we don't need to have a go. I think that's really trying to highlight the benefit that actually improved soil health will not just improve carbon sequestration, but it will also help the resilience of our landscapes and our ecosystems, and allow our farmers to continue to do what they need to do in terms of producing food but doing that in a way which is environmentally restorative.

Sally wanted to hear from a farmer who has been putting some of these carbon management techniques into practice in a financially viable way. Sophie Alexander manages a 400 hectare organic farm in Dorset with a mix of arable crops and livestock. Does someone with a large farm to run and a bottom line to meet still think about carbon when farming?

Sophie - I've always thought about the soil health. Particularly because it's an organic system. It begins and ends with the soil and there are no other get-out avenues of applying something short term. Actually calling it carbon sequestration, carbon farming, is a more recent terminology but storing carbon and looking after the soil are really synonymous.

Sally - How do you as a farmer who has to make a livelihood off a large farm - we're not talking about some smallholding where you can do everything by hand - how do you go about adding carbon to your soil in a financially stable way?

Sophie - The single most important aspect of boosting the carbon content of my soil is probably my livestock enterprise. The cows are outside 24/7. They're grazing the grass and then also fertilising the ground with their dung. Then when we're growing crops, which is the other half of our rotation, I chop straw nearly always, I hardly ever bale it. That's adding soil organic matter and nutrients.

Sally - We were hearing earlier in the show about the effects that ploughing can have on the soil and its ability to store carbon. Have you been looking at your ploughing regimes to see if that can improve your soil health?

Sophie - Yes, definitely. It's a very hot topic, obviously. For instance, in my system we plough maybe three times out of six or seven years. There's time for the organic matter to build up, the carbon in the soil to build up, and then we are reducing it when we start cultivating to establish grain crops but then we build it up again. It's not a direct line of improvement. It's a gradual improvement.

Sally - Two steps forward, one step back, but overall you make progress.

Sophie - Something like that.

Sally - Do you think that farmers all around the UK should be prioritising climate change mitigation?

Sophie - Yeah, I think everyone should. I don't think just farmers. It applies to all of us: day-to-day in your garden, the chemicals you're using, what you're flushing down your drains. But yes, farmers are absolutely on board to play their part.

Sally - You think that the farming community is willing to prioritise...

Sophie - I can't speak for the whole farming community, of course I can't! But the people I meet and talk to, yes. Most farmers really take it as a responsibility and a huge privilege to be looking after a large part of the natural world.


36:10 - Blue carbon: using our oceans to remove CO2

From kelp forests to seaweed-based 'plastic' packaging

Blue carbon: using our oceans to remove CO2
Sally Ashby, Sussex Kelp Project & Ayca Dundar, SoluBlue

The hot new topic in the world of carbon sequestration is blue carbon, that is using our seas and oceans to remove CO2 rather than our terrestrial ecosystems. The biggest benefit of blue carbon is that it doesn’t compete with land that could be used for farming or for building homes.

In the UK, salt marshes, kelp forests and seagrass meadows all have the potential to either rapidly draw down carbon dioxide from the atmosphere or trap carbon in muddy sediments or both. We’ve only recently begun to appreciate just how good these ecosystems can be in reducing climate change, and as a result, we’re still missing a lot of the key research to quantify blue carbon. But some estimates suggest that saltmarshes, for example, might draw down carbon as quickly as an established woodland.

We’re first going to dive into the world of seaweed and in particular, kelp. This giant seaweed forms underwater forests that have, rather like their terrestrial counterparts, been suffering from habitat destruction and now only small patches remain. But restoration teams like the Sussex Kelp project are hoping to change that, as Sally Le Page heard from project leader Sally Ashby. But what exactly is kelp?

Sally Ashby - Kelp is a term given to the large brown seaweeds or macro algae. They have a holdfast where they attach onto rocks or hard substrate, which are almost like roots, but exposed, clinging to a rock. Then they have a stem that's called a stipe, which extends up, and then they have these fronds, like leaves, that are long and can be up three metres long. So they're large seaweeds.

Sally Ashby - Kelp specifically forms habitats or aggregations like a forest, so highly dense areas. And because they're like trees in their structural form, it has this feeling of a forest. Not only is it a nursery for fisheries, it's also providing shelter and habitats for a whole raft of species that then sustain a healthy functioning ecosystem and food web.

Sally Le Page - So that's like how in a traditional forest you'll have spaces for nesting birds and small mammals. It's the same underwater?

Sally Ashby - Yeah, exactly, it's the same underwater. Ultimately we are aiming to restore a crucial marine ecosystem that supports huge amounts of biodiversity, boosts our fisheries and also protects and maintains those marine carbon stocks that are really important for climate change.

Sally Le Page - How does kelp help us with climate change in terms of carbon?

Sally Ashby - Kelp is highly productive, which means it draws down huge amounts of carbon dioxide from the atmosphere, much like trees and plants do. The difference with kelp is that it doesn't then sequester that carbon into the soil or sediment directly. It takes that carbon and then feeds the secondary production, so the fish that we eat and all the other animals. We think that approximately only 10% of kelp carbon would be permanently sequestered and almost 90% then goes into feeding coastal ecosystems.

Sally Le Page - And what is the state of kelp forests in the UK?

Sally Ashby - The kelp in the south of the UK has experienced serious decline. In Sussex, historically, there were these vast kelp forests in the eighties, but we've lost almost 96% of those kelp forests.

Sally Le Page - And what is that in terms of absolute area? If we've lost 96% and we're down to 4%? What is that in terms of square kilometres?

Sally Ashby - It used to be that the historic kelp bed was about 170 square kilometres. So it's a huge area.

Sally Le Page - And that's just Sussex.

Sally Ashby - And that's just Sussex, but ultimately, globally, kelp is an ecosystem that is in decline and highly threatened by a variety of anthropogenic factors.

Sally Le Page - What is causing the decline in kelp?

Sally Ashby - The impacts on kelp are complex and varied, but pollution, eutrophication, impacts of fishing - there's a whole variety of factors.

Sally Le Page - As part of the Sussex Kelp Project, you are in charge of the restoration. So how do you restore a kelp forest?

Sally Ashby - Specifically in Sussex, what we would hope for is that the kelp is naturally restored. There's 300 square kilometres where bottom towed trawling has been banned, which means the seabed has a chance to recover.

Sally Le Page - What is this kind of trawling? What is it used for?

Sally Ashby - Bottom towed trawling is used to fish for sole and plaice that inhabit the seabed. So it is a very destructive practice for the seabed because ultimately you're towing very heavy gear and picking up everything and anything in its path.

Sally Le Page - And obviously people aren't trawling for the sake of trawling, they're trawling because fishing is their livelihood and it's what allows them to make a living. So will this project just stop the local fishing industry from surviving?

Sally Ashby - No, not at all. We're working closely in this project with the local fishing community. The Nearshore Trawling Byelaw was brought in specifically by the Sussex Inshore Fisheries and Conservation Authority who managed the fisheries. The point of the byelaw is to restore the kelp, to restore the ecology and the ecosystem, so that it supports a really booming fishing industry.

Although this particular project is aiming to restore a natural ecosystem with all of its biodiversity benefits, material scientists have also been looking at seaweed's remarkable ability to photosynthesise and trap carbon. And they're trying to put it to use, to solve some of our other global crises. One such entrepreneur is Ayça Dündar, who was frustrated by the climate crisis and also our plastic waste problem. Her solution was to invent a fully compostable alternative to plastic film made instead from sustainably farmed seaweed. Along with her husband Francis Field, they cofounded the startup company, Solublue. Sally Le Page went to visit them both in Cambridge to find out more about this material that they claim can help trap carbon from the atmosphere, prevent food waste and reduce plastic pollution - all from seaweed.

Ayça - Seaweed is a great material that doesn't need land use. It doesn't need fresh water to grow, unlike trees. It captures a lot of carbon - more than trees - and grows really fast. So it's a great material and resource.

Sally - How do you go about turning seaweed into packaging?

Ayça - The main process is seaweed is harvested and, most of the time, it is dried and it goes through a cleaning process. You blend the seaweed with water if it is dry, so you hydrate it and then you cook it. That's the bit that we engineered.

Sally - And in front of us, we have a whole table of goodies here. Can you talk me through what we're looking at?

Ayça - We have samples of some of the structural containers we made as well as film samples. And what we did was several tests of putting fresh food in our packaging. As you can see with this cheese sample, the one that we packed in our packaging is still preserved after two years in unrefrigerated conditions, whereas the same cheese sample packed in plastic got mouldy after three weeks' time in unrefrigerated conditions.

Sally - You say cheese - what I'm looking at is a black and white splurgy, mouldy mess. I'm going to have to take your word that this is cheese, or was cheese, because it's certainly not cheese now. So this is the standard clear plastic film that cheese normally gets wrapped in. Now I've picked up the Solublue sample - your seaweed alternative sample. In terms of the plastic film, it feels the same. I would never have guessed that it's made of seaweed. It's completely transparent, it's very thin, it's very flexible. But it looks like cheese. I mean, it looks like hard cheese.

Ayça - We have tried it and it tastes a little bit like mature cheddar.

Sally - Do you agree with that?

Francis - Yes. I thought it was closer to Parmesan, but it was edible. The discovery that we could actually extend shelf life and reduce food waste was a real breakthrough for us, because today 40% of food produced is never even eaten. We need to tackle that urgently and one way to do that is with our packaging. The seaweed that the farmers are growing is capturing a lot of carbon and it's doing that more effectively and faster than trees are doing it. When we take that seaweed and we make it into our packaging, that carbon remains captured. And as part of the way our product works in use, we're capturing food waste as well. All of that can be placed in the same composting bin - we're simplifying waste streams - and that carbon is captured, retained. And when composted, biomass is getting locked back into the soil.

Sally Le Page - Talk me through it as an example, because right now at the bottom of my fridge I have got a cucumber half wrapped in plastic and it's gone really soggy and mushy and kind of disgusting. What is the alternative if we were to make that packaging out of seaweed, instead of out of plastic?

Ayça - What we have observed is that after three weeks there was no sogginess. There is no mould forming because the seaweed material that we have developed is hydrophilic - it absorbs excess moisture from food. It is not a good environment for bacteria to grow.

Francis - So your cucumber doesn't go to waste and you don't need to cut the packet off it. You don't need to feel guilty about throwing it in the bin because you're putting it to compost.

Ayça - It will be very good for big retailers that right now had to throw away tons of spoiled cucumber to landfill. It can be used as an animal feed or can be composted.

Sally - You said your packaging is edible - edible by humans?

Ayça - Yes, it is edible by humans. And also animals.

Sally - Can I try some?

Ayça - Of course, you can try it.

Sally - Do you have scissors so I can snip off a little quarter?

Sally - Okay, this feels really weird. It's literally just looks like plastic. This is definitely the seaweed one and not the non-seaweed one I'm putting in my mouth, right? Wow, it really absorbs the moisture. It's stuck to the roof of my mouth. It's like eating rice paper. I mean, I've never really eaten plastic so I can't really tell you how it differs from eating plastic.

Sally - I can tell that I can bite through it. It's not just a solid sheet. It's now slightly turning into like a dried out fruit leather almost. It doesn't taste of anything at all, but there we go. And if I haven't died by the time the show is broadcast, we can say that it is edible by humans.

Francis - We don't encourage people to eat it, but you can if you want. And it means that if an animal eats it, it's not going to clog their digestive system or something like that.

The surface of the ocean.

47:44 - Seagrass meadows: creating underwater soil

Trapping tiny particles of organic matter to prevent greenhouse gas release

Seagrass meadows: creating underwater soil
Leanne Cullen-Unsworth, Project Seagrass & Loveday Trinick, Ocean Conservation Trust

Kelp forests and seaweed farms aren’t the only way our oceans can trap carbon. Seagrasses are remarkable plants that form underwater grassy meadows, and are able to trap tiny particles of organic matter and form a stable, carbon-rich sediment that prevents greenhouse gases from being released into the atmosphere. Sally Le Page chatted with Leanne Cullen-Unsworth, the director of research at Project Seagrass to find out more about this unassuming ecosystem...

Leanne - They're a plant that lives in the sea and they are a plant that creates this incredible habitat that supports very high biodiversity. So it supports lots of animals.

Sally - What does it look like?

Leanne - It just looks like a terrestrial grass, really, so a grass that you find on land. They flower and they produce seeds in the same way that land grasses do.

Sally - And why are seagrasses so important?

Leanne - They're a really important habitat for marine animals and birds as well use seagrass to forage in. They're also super important for things like carbon sequestration. And at the moment, there's a lot of interest in seagrass meadows to help mitigate the climate issue.

Sally - How do seagrasses store carbon? Because we've just been hearing about kelp, which draws down carbon, but then they can't hold onto it as much. Is it the same with seagrasses?

Leanne - It's not the same with seagrasses. Seagrasses have got the capacity to store large amounts of carbon. They store it within their own leaves, their roots and their rhizomes under the sediment, but they also then pack it down and store it underneath the sediment. So their capacity for storage is really huge - they can keep storing the carbon underground. As long as those habitats are maintained, then that carbon is locked in under the sediment. They're also really important in the nitrogen cycle, so they cycle other nutrients as well. They're very important for coastal protection - they hold the sediment together and stabilise coastlines and help protect our coasts from the coastal erosion. But they are important as well for commercial fisheries - they provide nursery grounds for a lot of the big offshore commercial fish species, cod for example. They're important for so many reasons.

Sally - How are seagrass meadows faring around the world?

Leanne - Seagrasses are struggling. Across their range they face threats from poor water quality, from physical damage, from inappropriate boating activity, anchor dragging, insensitive moorings, propeller damage, bait digging.

Sally - So things that are physically digging up the grass?

Leanne - Yeah. The UK has lost a lot of its seagrass. Over the past 40 years it's lost around 50% of its seagrass meadows. And we know that the figure could be up to around 92% loss over the last 100 years.

Sally - That's huge. Why have we lost so much?

Leanne - It's huge. It's huge. Across Europe in the 1930s, there was a widespread wasting disease that has been blamed basically for a huge wipeout of massive areas of seagrass, but that also coincided with industrialisation and the peak of the worst water quality that we've had. And so it's not totally clear. However, on a positive note, and particularly in the UK where we've lost huge amounts, there's been a lot of effort put into improving water quality around our coasts. And so we are in a position now where we can start to think about restoring large areas of seagrass.

Sspeaking of restoration, a new project called Reducing and Mitigating Erosion and Disturbance Impacts Affecting the Seabed, or ReMEDIES for short, has recently received £2.5 million of funding from the EU and Natural England, to both replant new seagrass meadows along the south coast of England and protect existing meadows by developing and promoting seagrass-friendly mooring systems for boats. But how exactly do you plant a meadow underwater? Sally Le Page spoke with Education Officer Loveday Trinick from one of the project's partners, The Ocean Conservation Trust, to find out just what it takes...

Loveday - It starts by collecting a lot of seeds. The seeds are not the primary way this plant reproduces, it reproduces mainly through its roots, so taking the seed doesn't impact the bed. So we go to these beds and we collect the seeds. This is done by scuba divers.

Sally - What do the seeds look like?

Loveday - They're tiny, they're weeny. They're like a grain of rice.

Sally - I suppose rice is also a species of grass, so that makes sense.

Loveday - Yeah, similar scenario. And then it's the process of bringing all of those seeds back to the National Marine Aquarium, which is where The Ocean Conservation Trust is based. We have a purpose-built lab that was funded through the project to look after those seeds, care for them, nurture them. And then some of those are planted straight into little seeding units, which are made of a hessian bag.

Sally - Why do you have to put the seeds in bags?

Loveday - That's really because they would get eaten.

Sally - So is it like a seed bomb? Those little parcels of clay that you chuck with wildflower seeds, but instead you're using seagrass seeds.

Loveday - It's exactly that. That's entirely what it is.

Sally - And then once you've put all of these seeds in the bags, how do you plant them?

Loveday - It's a really fun trip actually. We take the thousands of bags out on the barge and we've got two big pipes on the back of the boat and we go along very slowly. We just drop the bags down the pipes.

Sally - And how big a project is this?

Loveday - So the goal of the restoration part of ReMEDIES is to restore eight hectares of seagrass meadow.

Sally - How many seed bombs does it take to plant eight hectares of seagrass meadow?

Loveday - Lots. We're collecting 3.2 million seeds this season.

Sally - Wow. Who's counting?

Loveday - One at a time. 1, 2, 3..! And they are growing. We've had monitoring dives on that site and we've seen little plants growing in our seeding bags, which is very exciting. It's lovely to see.

A forest of tall, thin trees lit by sunlight

54:30 - Capturing carbon: will it be enough?

Can we sequester enough carbon to avoid cutting emissions?

Capturing carbon: will it be enough?
Ruth Gregg, Natural England

So many of the habitats in Cambridgeshire and the UK have the potential to help us fight the climate crisis. But will it be enough? Sally Le Page spoke with Natural England’s Ruth Gregg...

Ruth - So modelling has shown that we can look to sequester around 9 to 10% of our emissions by 2030. So it's a significant chunk, but it's not a silver bullet.

Sally - And how much of the land would we need to convert for that 10%?

Ruth - So what the climate change committee has put forward - that we're going to need to see around 20% of land that's currently in agricultural production set aside for climate change mitigation approaches. So that's a significant amount.

Sally - Do you think it's possible?

Ruth - I think it has to be possible! I think we have to be really ambitious and really positive and optimistic in how we look at how we change our land use for climate change. We don't have an alternative. So we have to be really optimistic in how we approach this. And when we say 20% set aside for agricultural production, that doesn't mean that we can't still use that land. We just have to be mindful that we're bringing in approaches to reduce greenhouse gas emissions and capture carbon.

Sally - Obviously this show has been thinking all about carbon. Is carbon the be-all and end-all?

Ruth - Carbon isn't the be-all and end-all! It's an incredibly important part of the issue. So nature-based solutions offer huge benefits in terms of carbon capture and can support climate change mitigation. But that's just a small part of the puzzle. The bigger picture is that it makes society a much nicer place to live in, a nicer environment to be in. It gives us water regulation in terms of flood risk management, water quality, air quality benefits. It's great in terms of recreation and cultural heritage. So yes, nature-based solutions offer such a huge amount of benefits that they very much should be on the table as we look to tackle climate change into the future.


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