Monday 18 March 2024 marks the start of The Word Forest Organisation’s ‘Trees are the Key’ awareness week 2024. Dartmoor Biodiversity Officer Morwenna explains some of the projects she’s working on with South West Water to improve biodiversity at our lakes and reservoirs with the help of trees:

Trees and Green Recovery

At present we have two locations with South West Water under the ‘Green Recovery’ scheme, as a branch of the Upstream Thinking project to improve biodiversity, water quality and water retention in two catchments. Burrator and Venford reservoirs are the locations for the current cycle, with works carrying on until 2025 to complete 925 hectares of improved biodiversity.

A hugely important part of this work is trees. Trees have endless benefits for biodiversity, water quality, river quality, livestock and more. We are aiming to capture as many of these benefits as possible through planting various types of woodland, and managing our current forests and trees. Working with our tenant farmer, and many other stakeholders we will plant new woodlands and improve the state of our current woodlands over the next year and into the future.

Mixed broadleaf

Our most common type of woodland at Burrator, and now Venford, is lowland mixed deciduous woodland. This is a priority habitat (according to the Natural Environment and Rural Communities Act 2006) and is made up of a mix of native broadleaf species, with an understorey of wildflowers and shrubs.

At Burrator, a lot of the work of our volunteers revolves around these woodlands, and keeping them in favourable condition. Removing invasive species, such as Rhododendron ponticum and hemlock and sitka spruce which seeded these areas when they were commercial conifer crops, is an ongoing and important job which prevents these plants from overcrowding the understorey and shading out native species. In time, without this management, some of our woodlands would revert to a conifer woodland with little diversity where native flowering species struggle to grow, leaving loose soils which runoff into water courses. 

Coppicing is another important job in these woodlands, especially where willows and hazel are prevalent. These are species which have evolved to survive large animals, such as the woolly rhinoceros, crashing through woodlands, leaving rides and glades. The species therefore thrive when they are regularly cut back to allow new growth, leaving open glades where wildflowers can thrive. In these open spaces, many invertebrate species such as butterflies, bees and dragonflies can enjoy nectar from the abundant wildflowers and bask in the increased woodland sunshine.

At Venford, we have recently planted new mixed deciduous woodland, where commercial conifer crops were removed at the end of 2023. Working with the lovely team at Moor Trees, with their volunteers and ours, we planted around 1,300 native trees. Almost half of these were hawthorns, which we have planted in clusters to dissuade predators from nibbling the less thorny species. These hawthorns will also be a great source of food for birds and the dormice we have recently found using the site.

Other trees planted include oak, rowan, birch, alder, alder buckthorn and blackthorn, which will grow into an open woodland with plenty of berries for wildlife, and will create a corridor between the wet woodland area to the south of the reservoir to the Dart Valley oak woods beyond the dam. Additionally, the trees will act as a transition habitat between the Dart woods and the moorland.

Wood pasture

One tree habitat we are aiming to create more of at Burrator is wood pasture. This is an open habitat with spaced out trees, clusters of trees and open, grassy spaces. The wood pasture habitat was studied extensively by Frans Vera, in his quest to create the Oostvaadersplassen, in the Netherlands, a huge project which aimed to create a landscape as it would have been after the last Ice Age, before human intervention. Whilst we are not aiming for the same ancient effect at Burrator, the wood pasture element of this work is a fantastic habitat which benefits biodiversity and livestock farming in equal measures.

By creating dense clusters of trees, with thorny and shrubby species on the outside and taller growing canopy species such as oak and birch on the inside, we create habitats and forage for wildlife and livestock. Another benefit is improved drainage capacity in the soil, allowing more water to sink into the ground, rather than running over the hill causing erosion, and adding unwanted organic materials to drinking water.

Additionally, the areas where we aim to plant are currently covered by dense bracken, allowing little else to grow in the later summer months. The bracken itself is probably a good sign that trees once grew in these areas and the soils will be ideal for trees to grow in once more. Once the trees have established, the dominance of bracken will be reduced by shading, allowing more grasses and wildflowers to grow, bringing benefits for pollinators, as well as grazing livestock. The livestock will also benefit from the extra shade gained from these trees, as we get hotter summers, this will be vital for these animals, which lose less water by shading from the sun.

Another feature of trees in grassy landscapes, is that the grass surrounding trees is far less susceptible to browning and scorching in droughts, due to the water storage capacity improved by root systems, as well as the shade provided by leaves.

Finally, livestock will have improved diversity in their diets, with tree forage abounding from clusters of trees which provide important minerals that they might not be getting from grass alone. Willow, for example, contains salicylic acid, similar to aspirin, and is a natural pain relief for injured animals.

Riparian woodland

Riparian woodland is a key habitat which consists of ‘wet-loving’ trees such as willow, alder, downy birch and black poplar, growing alongside rivers, and catching floodwaters in their root systems. These woodlands, are hugely important for rivers, and make fantastic corridors for wildlife, connecting woodlands through river valleys which span the whole country. It is not always appropriate to plant trees along a river’s banks, as habitats such as flood meadows and valley mires are equally important and home to a separate array of wildlife. However, varying densities of trees along a river's course can benefit the wildlife inside and outside the river in many ways. 

First of all, dappled shade is an important feature in rivers where native fish breed. If the river is too open for much of its length, the water warms up, reducing its habitability for fish and invertebrates which breed in the rivers. However, if trees grow too densely surrounding a river, the shade can become too thick, and leafy debris from the trees can choke the river. Our volunteers at Burrator, do a brilliant job of this, by coppicing the willows that cast too much shade on rivers, but with the extensive wooded streams we have, the job is difficult to achieve at a regular interval. 

As well as the right level of shading, riparian woodland creates a network of roots which allow better connection of the river to the floodplain. At Burrator, many of the rivers are hugely modified by tin streaming over thousands of years, which has lowered the river valleys in to many steep V-shaped valleys, and caused disconnection of the river from the floodplain, drying out marginal habitats and reducing habitability for many species. By planting willow trees along the steep sided river banks, roots will stabilise these banks, reducing erosion and allowing the river bed to be raised by increasing sediment deposition and slowing the flow of water. This will eventually lead to more regularly flooded floodplains, and better habitats for wetland species. 


As highlighted in Guy Shrubsole’s recent book, ‘The Lost Rainforests of Britain’, Dartmoor is the perfect home for our most enchanting woodland habitat. The exact definition of a British Rainforest is still yet to be fully defined and understood with various names for the habitat changing and evolving over the last few years form ‘Celtic’ to ‘Atlantic’, and definitions focusing largely on the heavy abundance of mosses and lichens within these woodlands. The prevalence of sessile oak (Quercus petraea) is also a key factor.

We can be certain, however, that the warm and extremely wet climate along Britain’s west coast, especially in upland areas where rainfall is even higher, create unique conditions which allow these woodlands to hold huge pillows of moss in abundant variety, and trees covered with lichens with lovely names like 'old man’s beard' and 'strings of sausages'. These habitats would once have been much more prevalent across the west, and we can work to improve and expand the remnants and allow new growth. 

This habitat may be particularly important for water storage, as mosses and lichens have the ability to hold masses of water within woodlands, on the trees and rocks. The total effect of this is unknown, but for comparison, a single tree in a South American temperate rainforest can hold up to 669 litres of water. Though these trees are likely to be much larger than ours, the effect of this mossy landscape marks a huge potential for water storage, adding up to reduced flash flooding events and improved hydrology throughout the catchment.

At Burrator we currently have two areas of ‘upland oakwood’ (another priority habitat) which has potential to be rainforest. The climate is right, and lichens and mosses are prevalent, but historically,  overgrazing and trampling by animals has prevented natural regeneration by trees, leaving a woodland with many mature oaks but few to replace them. We have been working with our tenant farmers to enhance the shepherding in this area, and reduce the impact of grazing so that more oaks and other species can grow and hold mossy ecosystems with an enchanting appeal and brilliant water storage capacity!


We have recently planted two new orchards at Burrator, with the help of the children from Meavy Primary School. Each of the orchards has an array of local Devon apple varieties and are a mix of cider, cooking and eating apples. These will provide some great days for the local community in the future, apple picking, apple pressing, wassailing and pruning. We hope they will be of great benefit for visitors to Burrator, and wildlife alike.

Fruit trees are very important for biodiversity, providing a long season of flowers for pollinators as well as abundant fruit in the autumn which once we have had our pick, will provide high energy food for birds, insects and small mammals. To ensure the flowering and fruiting season lasts as long as possible, different pollinator groups of trees are chosen. For apples to be able to fruit they need to cross-pollinate with each other, so they are split in to four pollinator groups, A, B, C and D, each flowering later on in the year. This way we can make sure each tree has a match in its own pollinator group and the flowering occurs as long as possible throughout the season.


Though forestry often gets a poor reputation for biodiversity, it can be very important for some of our species and it is a great use of land for carbon storage. 

Whilst there are some downsides to commercial forestry, such as dark crowded woodland allowing little to grow on the forest floor, leading to looser soils and increased runoff into rivers and reservoirs, this can be carefully managed by improved forestry practices. For example some of our forestry will be planted with a mix of conifer species resulting in a more structured woodland with improved light penetration to the ground, allowing more vegetation to grow under the trees.

Additionally, we can replace some of our forestry compartments with riparian woodlands to create a buffer for rivers, reducing the soil runoff into the water system. 

These commercial plantations, are also an important harbour for species such as Goshawk, which nest in dense conifer blocks; nightjar, who forage among shrubby clearances brought about by recent clear-fells; and crossbills, which gain their energy from abundant pine cones. Without forestry, these species would struggle to find habitats, and we would miss their presence among us.

As well as the benefit to these rare species, the use of conifer plantations is an important carbon storage facility. Timber, in the UK, is the most sustainable building material, and when 40% of our energy use and 100 million tonnes of waste comes from the construction industry, it is important that we choose more sustainable and home-grown options. When timber is used in construction, the carbon stored in that tree is held within the building for its lifetime, which if constructed effectively can be for hundreds of years. 

This effect makes forestry up to 269% more effective at carbon sequestration over its lifetime than a slow growing but biodiverse broadleaf woodland. This doesn't mean that we should plant only conifer woodlands however, as broadleaf woodlands still have bountiful benefits.