Culm Restoration


Background
An area of our land which is approximately 1.5 acres is designated as a site of wildlife interest Devon Biodiversity Records Office. It gained this designation as a patch of species rich (Culm) grassland which had survived the post-war period when 97% of species rich grassland was drained, or planted up as conifer plantation. This designation has no statutory protection and didn’t prevent the owner, at the time, from planting conifer on it, thereby shading out the grassland species or “improving” some of the grassland.

Soon after we bought the land, we started removing the conifer. We then managed the grass, by cutting it with a strimmer and removing the cuttings, to lower the nitrogen levels. This allows the wildflowers to compete with the grass. We tried planting it with yellow rattle in 2011, but this didn’t take well because the nitrogen levels were still too high and 2012 was exceptionally wet. However, the nitrogen levels on the ground have now been reduced considerably and wildflowers are increasing as a result as the grass has become weaker.

The Plan
Devon Wildlife Trust (DWT) have created a management plan for the area on our behalf. We have removed the remaining scrub from county wildlife site, leaving some trees, but opening the area up considerably. We have also cleared some other grazing on our land, which will be wood pasture. We’ve partially blocked some ditches to rewet the land. The county wildlife site will be fenced with help from DWT.

Ground that has been grazed and harrowed ready for seeding

Initially, we will graze it with Shetland sheep. They’re a hardy breed which will eat the regrowth on the scrub and brambles as well as grass. Sheep graze the grass right down to the ground, removing vegetation which could shade out seeds. Then we’ll scarify the ground to expose the soil and reseed with green hay and seed collected from local species rich grassland.  The sheep will then stay on the culm over winter, to keep the grass down.  This will ensure that the wildflower seedlings get adequate light.

The land will then be managed on an ongoing basis, by lightly grazing it with Dexter cattle. The right grazing regime is essential to manage the culm grassland. If you graze too low to the earth, you release carbon from the soil. For this reason, there will be some carbon loss during the reseeding process, but this is limited and enables greater environmental benefits, including carbon sequestration. If you don’t graze at all, the dead grass builds up and shades the lower wildflowers and other vegetative growth. Scrub will eventually take over. We intend to get a cow with a calf at foot, to start with and will probably never have more than 3 cows at any time, including calves. We will continue rewetting the land over time, by blocking more ditches. This will be done as and when we can afford to improve our tracks enough, so that we can get around in the boggy conditions that it will create.

The Benefits

Habitat
Our land was once part of a vast area of species-rich culm grassland. Very little now remains of this vital habitat. The patches that remain on our land, provide habitat for a rich diversity of wildlife including water voles and a number of red-list birds. These are specialists which require boggy ground. This boggy ground is undesirable to humans, which is why it has been drained almost everywhere that it used to exist. Wildflowers within the grassland are a great food-source for pollinators. By enhancing and expanding this habitat, we hope to mitigate some of the habitat loss that has occurred.

Flood Prevention
Our land lies right at the top of the catchment area for the River Taw. We have previously redirected and blocked ditches to give a less direct route for water to leave our land as part of an “upstream thinking” approach to flood prevention. This culm restoration project will make our land much more effective at preventing flooding downstream. Culm grassland, especially if it has a high sphagnum moss content, holds water like a sponge, then slowly releases it over time. This delay in releasing the water, prevents all of the rainwater from entering the river at once, which can cause flooding.

Carbon Sequestration

Sphagnum Moss

When managed correctly, wetlands have the potential to sequester large amounts of carbon. Peat is created when sphagnum moss and other plant matter is submerged in acidic water, effectively pickling the vegetation. This prevents it from releasing its carbon through decomposition. As cattle walk on the wet grassland they trample the vegetation down into into the acidic water. Then more vegetation grows on top, which in turn is trampled down on top, creating an ever deeper layer of pickled and compressed vegetation. For this to be successful, the land has to constantly remain wet. If it dries out, the carbon will be released. It is partly for this reason that we are blocking ditches to rewet the land. The peat bog will sequester more carbon than an equivalent area planted up as woodland.

Produce
We intend to milk our cow, using the “calf at foot” method. The cow will produce more milk than the calf requires. The idea of this method is to just take the excess milk. This should be more than ample for our milk requirements, when we’re milking. There will eventually be grass-fed beef when the calf reaches full size, unless we decide to keep it on, in which case this will be delayed further.

Cows and Climate Change
There are 3 main issues with cattle and climate change. They are:carbon loss through overgrazing, nitrous oxide from the manure and methane from cow burps and nitrates. We will address these issues as follows:

Carbon Loss
Through careful management of grazing and a low stocking density, we will sequester carbon in the soil, reversing this issue.

Emissions from Manure
The cattle will be housed overnight in a shed by our polytunnel. The majority of a cows manure is produced at night. The shed will be mucked out into a section of the shed designed to store manure. This will have a solid floor and drainage into a catchment which will allow us to retain the nitrogen for use in the polytunnel. When rotted, the manure will be used in the polytunnel. This minimises the nitrous oxide and nitrate loss.

Methane
Some of the carbon that is taken up from the grass that the cow consumes is released as methane.  We have investigated 2 methods of reducing methane in cow burps.

The first method has a level of serendipity, as we’re charcoal makers and it involves feeding the cattle ground up charcoal (referred to as biochar in many research papers). The research in this area is ongoing, but it has been shown to reduce the methane from goats by 25% when fed at 0.6% of total dry matter (DM). We can use charcoal fines, which are left when we grade our barbecue charcoal for this. The inclusion of charcoal in the diet of livestock also has health benefits, such as a reduction in parasitic worms.

The second method, involves feeding seaweed to cattle. The practice of feeding cattle seaweed has probably been going on as long as cattle have been kept and was certainly recorded during the Highland clearances in the 18th and 19th centuries. Research has shown for a while that feeding cattle seaweed as part of their diet, reduces their methane output. It has been found recently that 2 seaweeds (asparagopsis taxiformis and asparagopsis armata) reduce methane emissions to almost zero. The effect is so significant that at first, researchers thought that their instruments must be malfunctioning. Both of these seaweeds originate in Australasia, but asparagopsis armata grows in cold water and has established itself as an invasive species in British waters. Its establishment has been assisted greatly by it being farmed in the Irish Sea as an ingredient in anti-wrinkle cream. If fed at 0.6% of total DM, it reduces methane output by up to 80%. At 2% of DM it reduces methane by up to 99%.  We were experimenting with growing this, but movement restrictions have prevented us from collecting samples to grow on and the current situation has given us different priorities.

Obtaining The Seaweed
We have 2 potential plans for obtaining the asparagopsis armata. The straight forward method is to go to the beach and pick it from the rocks. The more interesting method is to grow it. Growing it is an experiment that may fail. If it succeeds, we can have a clean supply of asparagopsis which we don’t have to leave home for. It certainly seems like a game worth playing.