Managing Hedgerows - Planet Earth Online
Chris - In England there are 450,000 kilometres of managed hedgerows, often containing hawthorn and often dubbed "corridors for wildlife" - be it beetles, bird, butterflies or even dormice.
Most farmers trim their hedges every year. But now new research by DEFRA and Natural England involving Dr Jo Staley, from the Centre for Ecology and Hydrology together with independent hedgerow consultant Nigel Adams has shown that less frequent trimming is best for wildlife.
Planet Earth podcast presenter Sue Nelson met up with both of them at one of the sites on the Waddesdon estate in Buckinghamshire.
Jo - The research that's just been published shows that if farmers cut their hedgerows every three years, that can have a substantial benefit for wildlife. It results in more berries being produced for over-wintering birds and small mammals to feed on and also in more flowers being produced in the spring for pollinating insects.
Sue - How significant an increase in provision for the wildlife was there?
Jo - We were comparing cutting every two years or every three years with cutting every year, and we found that particularly the cutting every three years has a huge benefit. We're finding three and a half times as many berries as on the plots that were cut every year and we're finding twice as many flowers as on the hedges that were cut every year. The plots that were cut every two years had a sort of intermediate benefit, but there we were finding that the timing of cutting was absolutely critical. So in order for there to be an advantage to cutting every two years in terms of increasing berry abundance, these hedges really have to be cut in late winter rather than in the autumn. So the hedges are there during the winter at the critical time when the wild life needs them.
Sue - And what sort of knock on effect then would this have on wildlife that use hawthorn hedges?
Jo - We know that with a lot of our farmland bird species, the thing that defines their population sizes is actually over-winter survival rather than breeding success. So, having these resources in the winter are really absolutely key...
...I've just stopped a couple of over-wintering ladybirds here that are hiding in a crevice in the hedge, so that shows how even some of the more common species do rely on the shelter of the hedgerow during winter.
Sue - Let's go through to the unmanaged bit - oh yes, are these sloe berries?
Jo - That's right. So these are blackthorn berries. We're standing next to a bit of a hedge here that hasn't been trimmed, so this is the bit that will be cut next year as part of our 3-year rotation and there's a nice patch of sloes here which are still providing food for birds and for small mammals that want to come along. Especially on a really frosty day like today, they may not be able to get into the ground to search for worms and things so that's when these berries become really important.
Sue - Nigel Adams, you're a hedgerow consultant, you were involved in selecting some of the sites that are being used to extend the project. For you, is this a sort of vindication of the benefits that a hedgerow can bring, but through better management can actually improve it?
Nigel - Most certainly. If we start with the point that hedgerows are one of the most important and understated habitats in the whole of the country, and yet if we cut them every single year at the same height, we are liable to destroy the potential that they have. So this research, as Jo has said, is looking at two-year and three-year cutting - not only for the over wintering fruit and berries but even the blossom in the spring is very important for invertebrate populations as well, so it's crucial. We only have to have a look at hedges that haven't been trimmed for years and the vast amount of berries that are on them and the flocks of redwings and fieldfares that come down on them in the winter to see that something is going on. So we're just trying to encourage farmers not to trim every year.
But so much money is being spent on this policy of giving farmers help towards that, that we need to get that right and we need to look at whether perhaps if we're trimming every two years, but we trim in September immediately after the harvest of that second year when the ground's dry and the farmers want to get in, they've got an opportunity to get on the field, get it trimmed and that's it. But is that money well spent because of course they're taking off that fruit potential for the over wintering birds right there. So we've got to know whether that is working or do we need to go into the three-year trimming.
Sue - Nigel, when an organisation like Hedge Link receives backing through scientific research, that a certain way of management is beneficial for wildlife, does this make it easier for you to advise people in terms of how to manage their hedgerows or do you find that people don't want to know? It's their hedge; they trim it, job done.
Nigel - I think it's a delicate balance. You certainly do need the scientific backing and the facts about what you're doing, you just say well this works and this doesn't work. But also pure science can sometimes turn landowners off, dare I say, in the sense that they want a practical way of doing things and practical outcomes. So you have to tie the two things together; very practical advice but backed by good science.
Chris - Sue Nelson on the Waddesddon Estate in Buckinghamshire speaking with Dr. Jo Staley from the Centre for Ecology and Hydrology, and Independent Hedgerow Consultant, Nigel Adams.