This summer we’ve experienced some extremely hot and dry conditions, with the UK seeing its highest ever recorded temperature in July. Along with prolonged dry conditions through the year this has led to severe impacts on natural habitats and agricultural land, including wildfires. Over the last year we have been working at our Blean Woods reserve in North Kent to counter the effects of dry conditions by making some areas of the woodland wetter. By re-wetting some of the woodland, we're aiming to benefit wildlife and improve the resilience of the woods to climate change. Ecologist Gareth Fisher explains more about this exciting and timely work.
Straw-like grass and wilting plants have become the norm for many this summer. Climate change predictions for the UK indicate that parts of the country will become drier, and that generally we will see wetter winters and drier summers in the future. We are concerned about how these drier conditions will affect wildlife and the habitats they use, including woodlands.
Man-made changes exacerbate the problemIn woodlands, just as in other habitats, human activities can exacerbate the problem. Drainage ditches have often been dug into woodlands to improve conditions for management operations and timber extraction. These ditches reduce the amount of time that a site retains water, making the site drier. Whilst this can assist woodland management, we are concerned that it could be adversely affecting the woodland habitats and the species that use them.
Why are we concerned about drier woodlands?Drier woodlands are unlikely to be the main cause of woodland biodiversity declines in the UK and so far evidence of woodlands becoming drier and the impact on species is limited. However, some of our rapidly declining bird species, including lesser spotted woodpecker and willow tit like wet conditions, as do some insects. Molluscs and earthworms are more active when it’s damp, and can be found more easily by things that will eat them.
Lesser spotted woodpecker Dendrocopos minor is one of the species that likes wet woodland conditions. © Ben Andrew (rspb-images.com).
Slowing the flowThe RSPB’s Blean Woods reserve in north Kent is a mixture of mature woodland with tall oaks and other species, areas of scrubby coppice, and patches of heathland. In the spring you can hear lesser spotted woodpeckers drumming and nightingales singing. Heath fritillary butterflies can be seen fluttering through the woods in the summer, the area being a stronghold for them. It's here that we recently completed a year-long project to benefit the wildlife and habitats on the reserve by slowing the flow of water out of the wood, with the aim of retaining as much water as possible through the year.
RSPB Blean Woods is an important site for heath fritillary butterflies, lesser spotted woodpeckers and nightingales © Gareth Fisher.
Parts of the reserve contain drainage ditches and the main small river running through the middle of the wood has historically been straightened along part of its course. Building on re-wetting work we have previously carried out at our Highnam Woods and Wolves Wood reserves, we started thinking about the situation at Blean in early 2020.
Whilst the Covid pandemic delayed the project for a year it also provided an opportunity, in the form of the UK government’s Green Recovery Challenge Fund. A joint bid with Kent Wildlife Trust (KWT) meant that we were able to work not only on the RSPB reserve, but also on their landholdings within the wider Blean complex, expanding the scale and scope of the work.
Ditches were blocked up using earth dams, or leaky dams (which are made of either large timber, smaller branches and brash, or a combination of both). Some of the meanders to the river channel were restored and we also installed some leaky dams, and carried out habitat restoration on an area of bog owned by Kent Wildlife Trust. Some of this involved machinery, but hard-working volunteers helped to create lots of brash leaky dams on some of the smaller ditches.
A large timber leaky dam on the river channel with a smaller brash dam behind. Coarse woody debris in rivers can be important for insects like craneflies © Gareth Fisher.
Watching to see the benefitsIt’s early days, but we are seeing some encouraging signs from the work we have carried out.
In February we saw that pools had formed behind the dams, and the restored river meanders were flowing again. More impressively in mid-June there was still water in the river channel despite months of little rainfall. The river is often dry through the summer but this year we saw pools with fish, amphibians, and insects in them, and dragonflies zipping around above.
A brash leaky dam, encouragingly holding water in June © Gareth Fisher.
We will continue to collect information to understand the effects that re-wetting has on the woodland. In time we hope to see benefits for biodiversity such as lesser spotted woodpeckers and nightingales which are some of our key species at Blean Woods, as well as for the long-term health of the habitats.
In the future we’re planning to examine the information we already have from our woodland re-wetting work, and to carry out similar restoration on other suitable sites. You can read more about the re-wetting already carried out in the February 2018 edition of British Wildlife.
Working together
The project was made possible through funding from the UK governments Green Recovery Challenge Fund. The RSPB worked in partnership with Kent Wildlife Trust to deliver the project, along with the help of over 150 volunteers.
Blean Woods is owned by six separate landowners who are RSPB, Woodland Trust, Natural England, Kent County Council, Canterbury City Council and Swale Borough Council. These organisations have come together to form a partnership to ensure that management of the whole National Nature Reserve (NNR) is holistically delivered to the highest environmentally-sound standards. The RSPB undertakes the management on behalf of the partnership. We are also working with the Woodland Trust and Kent Wildlife Trust to develop a Wilder Blean partnership, with a dedicated development officer to push this forward.
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Great work!