Jo Staley, Lisa Norton (UK Centre for Ecology & Hydrology) and Rob Wolton (Devon Hedge Group and Hedgelink) present their latest Perspective article calling for and providing recommendations for improving and expanding hedgerows as a valuable habitat and carbon store.
Hedgerows, and having more of them, are high on the policy agenda with a target for a 10% national increase by 2050 in the recent government Environment Improvement Plan, and a 40% hedgerow expansion in Net Zero scenarios by the Climate Change Committee. Hedges have substantial potential to help deliver UK targets for both biodiversity and capture carbon.
In our Perspective article, we explain how recent work suggests that the hedgerow network needs to be substantially increased for nature to recover across farmland.
Why hedgerows?
Hedgerows are lines of shrubs and/or trees, usually planted along field boundaries, and are a key wildlife habitat in agricultural landscapes. They provide shelter and resources for plants, birds, mammals and insects including beneficial species, such as pollinating insects and natural enemies of pests. As well as supporting wildlife, hedges can capture and store carbon, improve water quality, reduce flood risk, conserve soil, provide wood-fuel and give shelter and shade for livestock.
How many hedges do we need?
To get the most out of our hedgerows, we must assess how much hedgerow is needed across the country, and how hedges should be managed. Our Perspective article considered recent evidence to tackle these questions in relation to biodiversity.
While many studies show the value of hedgerows habitats for wildlife, only a handful have asked how much hedgerow is needed for a particular species or group of species. These few studies broadly agree that substantially increasing hedgerows would benefit biodiversity, for hedgehogs, pollinating insects and many birds.
The most recent estimate of hedgerow lengths, in landscapes where hedges are present, indicated that on average there were 4.2 km of hedges per 1km2 in Great Britain. The studies reviewed suggest that many wildlife species would benefit from a large increase to an average of 10km, although there will always be some species that require more open habitats.
Are UK hedgerow currently of good enough quality for wildlife?
Individual hedges vary in how well they support wildlife – short, gappy hedges with few plants at the base support less wildlife, while large, dense hedges made up of different plant species provide better habitat for most wildlife.
The quality of most of our hedges needs to improve – a national Countryside Survey in 2007 showed fewer than half of the hedges in England were in good condition for wildlife. Hedgerow quality can be improved with sympathetic management – restoring short, gappy hedges by planting in the gaps, hedge-laying, conservation hedging and coppicing. If hedges need to be cut with a mechanised flail, this should either not be done every year, or should allow some recent woody growth to be left to form blossom and berries for wildlife, or preferably both.
Are we likely to get more hedges in the UK with current targets?
As the benefits of hedges are more widely understood, enthusiasm for hedgerow planting has increased among farmers and conservation organisations. A recent survey by CPRE The Countryside Charity found over half of the farmers who responded had planted hedges in the last 10 years and had plans to plant more.
Whilst any planting is to be welcomed, our work suggests that hedgerows need to be increased by far more than the current 10% government target.
What do we still need to know?
We found some key gaps in the evidence on hedgerows. We lack information on the current state of hedges, as our last comprehensive survey was 16 years ago. We don’t yet know which landscapes would be the best ones in which to plant hedges to support a range of biodiversity.
For example, should new planting be concentrated in areas of intensive arable or livestock farming where hedges may provide the only resources for wildlife, or should more hedges be planted in areas which retain a good amount of semi-natural habitat, to make them even better and more connected?
Will the same types of hedgerows and woody species be best to both support wildlife and sequester carbon, or might we need different types of hedges for these two key goals?
Read the full Perspective: “Improving and expanding hedgerows – Recommendations for a semi-natural habitat in agricultural landscapes” in Issue 4:1 of Ecological Solutions and Evidence.
