Partner blog: This National Tree Week, don’t forget our rich hedgerow habitats
As public attention on trees and tree planting grows, Megan Gimber from the People’s Trust for Endangered Species makes the case for the UK’s iconic hedgerows
Right now tree planting is getting a lot of press, and quite rightly so! Increasing our tree cover is more important than ever, not only for carbon storage but to help give our wildlife the chances of survival they deserve.
Political parties are falling over themselves to show their commitment to tackling climate change, and so there are some huge tree planting targets being discussed. But where are they all going to go? Well, allow me to make the case for increasing the trees in our iconic British hedgerows.
As a habitat, hedges are incredible for wildlife, with one study counting over 2070 different species within an 85m stretch of hedge in Devon. And this is great news for our wildlife, as 70% of our country is agricultural land it’s great to have such a rich habitat connecting it all up in one big network.
One of the secrets of their success is that hedgerows mimic the rich habitat structure of a woodland edge. This is a place where two habitats overlap, where the wildlife of each can meet and interact. This means that to an extent hedges can accommodate woodland species, scrub species and even some that prefer more open areas. And trees are a vital component of this this vital hedgerow habitat.
But to maintain this ‘edge’ structure, a hedge needs management, and there’s a balance to be struck. Too much management and you end up with a strip of short, sad bushes with ever-increasing gaps between them; but too little ends up with a line of trees. Now this may not sound like a bad thing, but a hedgerow that has slowly turned into a line of trees will have lost that shrubby dense undergrowth so valuable to hedgehogs, other small mammals, and many nesting birds.
What have hedgerows ever done for us?
Even if we didn’t give two hoots about wildlife, the benefits of healthy hedgerows speak for themselves. For farmers they help protect soil from erosion, shelter animals in winter reducing deaths from exposure, provide shade for livestock helping maintain milk yields, fertility and condition. They sustain pollinator populations such as bees, as well populations of species that act as natural enemies to crop pests, reducing the amounts of pesticides we may need. They shelter our crops from the wind reducing crop lodging and physical damage that cold wind can cause such as fruit damage or chilling injuries. Trees in hedgerows can also be used as a cash crop, providing a sustainable source of wood fuel.
The potential of hedgerows for delivering environmental benefits is equally impressive. Hedgerows, especially those in good condition and with plentiful hedgerow trees, can help reduce pollution and store carbon both above and below ground. They can also reduce flooding by increasing the speed at which water is absorbed into the soil. By channelling water deeper into the soil profile with their deep roots, they increase the amount of water our soils can absorb. They slow flood waters, giving us more time to respond to flood warnings. And they can reduce the amount of silt in our waterways that can cause so many problems after heavy rainfall.
Do hedgerows need more trees?
Our hedgerow trees have had a hard time in recent decades. We have lost trees to diseases first to Dutch elm disease and now more recently to ash dieback, to hedge removal and to changes in management. Unfortunately replacement planting hasn’t been able to keep up.
And hedgerow trees are particularly valuable as they are what we call ‘open-grown’ trees. Growing up with space, and importantly light, on all sides enables a tree to grow into a full crowned tree. Open-grown trees live longer than their woodland grown counterparts giving more complex, rare and valuable habitats. Wherever you find open-grown trees in hedgerows, wood pasture and traditional orchards - you tend to find a rich habitat teeming with life.
Losing hedgerow trees faster than we are replacing them will only end one way unless we step in. As the old saying goes; the best time to plant a tree was ten years ago, the next best time is now.
Ok, how do we get more trees in our hedges?
There are a couple of ways of increasing the number of trees in our hedgerows. Firstly there is nature’s tried and tested method – natural regeneration. The shrubby structure of a hedge is actually made of tree species; these have just been trimmed to produce a thicket. This gives a hedge the remarkable capacity to generate its own full-size trees through natural regeneration. In some hedges, all that is needed is to pick a healthy-looking young stem and make sure this is spared when trimming the rest of the hedge. If you don’t see a healthy-looking stem where you want your tree, coppice a small patch and choose a nice one from the regrowth. These have the potential to grow into full hedgerow trees, and have a few advantages; they don’t cost anything, you don’t have have to plant them yourself and, best of all, you are helping retain the natural genetic diversity of your area alive for future generations.
However not all hedges are suitable for natural tree regeneration, or you may want to speed the process up a bit. In which case, planting is your other option.
Call me an optimist, but I see gaps in our hedgerows as an opportunity here. They are an opportunity to plant more hedgerow trees, and an opportunity to increase the diversity of plant species in your hedge. Planting a tree in a hedgerow gap is easy, but if you’re lucky enough to have a healthy robust hedge you may want to clear an area around your planting and keep that managed until your new tree is established.
As for what type of tree to plant, have a look at what is around you. Whilst I’d always advise planting to increase diversity in your hedge, it also makes sense to pick something that’s locally appropriate and that works for you. If you’re looking to get wood fuel, fruit or timber then this may affect your choice of tree, as well as your choice of tree management.
If you buy your trees as whips, it’s important to avoid imported trees which, while sometimes sold at cheaper prices, may carry or spread diseases. If you have the time and inclination I suggest you grow them from nuts and seeds gathered locally. This way you are representing the local genetic diversity in your new hedgerow trees and, although it takes a little longer to get them in your hedge, it doesn’t cost you anything financially. I love collecting acorns from my favourite oak in late summer - it has been in the corner of my village for over 400 years and I like to think that planting its acorns will keep its legacy alive for many more centuries to come.
Megan Gimber is Key Habitats Project Officer at the People’s Trust for Endangered Species, a conservation charity working to ensure a future for endangered & threatened species and habitats worldwide, and a member of Hedgelink, the UK steering group for hedgerows.