In the last blog, I mentioned that Harry’s research on the conservation hedge laying (CHL) we do at Underhill Wood Nature Reserve (UWNR), was looking very promising. Recently I spent a day with Harry and the results are amazing – more than that, they are mind-blowing! More on the survey results in a moment…
What is CHL and why is it deployed at UWNR?
Back in the winter of 2015 / 16 it became clear that the hedges at UWNR needed to be managed - the hedgerows lacked density and individual plants had raced skyward leaving huge gaps at their base. The ecologist Gareth Harris, who over the years has given me so much valuable advice and guidance, talked me through CHL. I was up and running. (And CHL is now a key element of winter activity at the land).
CHL is a bit like conventional hedge laying with distinct differences. As individual hedgerow plants are being laid, lateral growth is retained and not pruned back, the base of the hedge is mostly left untouched and the retained plants are not pinned. It is the messy, unruly cousin of conventional hedge laying. (There is a description in the UWNR rewilding manual on pages 26 and 27).
A section of hedge which had not been laid for many years
The same section after conservation hedge laying. Immediately the profile of the hedge changes - greater density, more cover close to the ground and broader in profile.
What effect does this method have? Almost immediately the hedge is broad, dense and the gaps have closed. A few springs on and this is what you have….a massive species rich, natural structure!
This was conservation laid 4 years ago. Imagine this in say 8 - 10 years…..
The results from Harry’s research at UWNR are amazing…I think this could be a complete gamechanger, in terms of how hedges are managed. (Let’s hope one day soon, those who make decisions in this field get to see these data…).
Firstly, looking at average species counts, for each class of hedge within the area of study:
1. Control hedges, which have not been conservation hedge laid (CHL), have an average of 27 species.
2. Hedges which have been CHL in the past 1 / 2 years have an average of 31 species.
3. Hedges which have been CHL in the past 3 / 4 years have an average of 40 species. The highest number of species in hedges which have been CHL in the past 3 / 4 years is 43.
The rate of increase over a short period of time is way ahead of the expectations of Harry and his Professors.
Next and strikingly the Individual numbers of invertebrates for each class of hedge, within the area of study:
1. Control hedges, which have not been conservation hedge laid (CHL) had 67 individual invertebrates.
2. Hedges which have been CHL in the past 1 / 2 years had 90 individual invertebrates.
3. Hedges which have been CHL in the past 3 / 4 years had 110 individual invertebrates with highest 113.
For me part B is the most astonishing - levels of abundance explodes once the hedge gets beyond year 1 / 2.
It is highly likely that Harry’s research dissertation will be published in an academic journal. And get this, Harry hasn’t graduated yet!
This is all very big news! Our Operation Moonshot worked!
A bit of crucial background stuff…Once we had 500,000 miles of hedgerows in the UK – today we have close to 300,000. Too many of the hedgerows which dissect our terrestrial environment are very poorly managed – they are too often subjected to annual flailing, leaving them damaged and dying. Poor habitat for fauna. As the Peoples Trust for Endangered Species state, in their online document about hedges; ‘Today, neglect and incorrect management, such as too-frequent trimming, are responsible for more hedgerow loss than outright removal’.
And why do hedgerows matter…Ben MacDonald unravels this for us in Rebirding, page 36; ‘Our native (pre-historic) scrub mosaic, where seed-eating birds foraged in disturbed grassland, and nested in dense bushes, was reincarnated in the hedgerow’.
So there we have it - rare, rambling, dense and tall mixed hedges are proxies for the wild scrubland that was a feature of our prehistoric land. It was a land that supported species like turtle doves and nightingales.
More broadly why do invertebrates matter. Dave Goulson (Professor of Biology at the University of Sussex), in his most recent book Silent Earth states (p 3); ‘...it seems likely that insects have declined in abundance by 75 per cent or more since I was five years old’. (He was five years old in 1970). So why does this matter…more from Dave Goulson (p21); ‘…insects are intimately involved in all terrestrial and freshwater food chains and food webs’. ‘The loss of insect life from the food chain would not just be catastrophic for wildlife. It would also have direct consequences for human food supply.’
There is clearly more research to be done around CHL. What effect might this management have on bird and mammal numbers…I have a hunch….
On the wildlife front at UWNR…
Last winter was the season of migratory redwings, blackbirds and fieldfares - they arrived in October / November and dispersed as early spring began to show itself. They all merrily plundered the fruit rich holly, bramble and blackthorn. Each evening this wonderful mob would roost in the dense and substantial thicket which runs behind the lake. They numbered 100’s.
This season no sign of them - instead we have migratory woodcock. They (I cant be certain, but think there are 3 - 5 birds) arrive at the lake shore at dusk and probably feed late into the night. I love this species with its high-speed, darting, zig-zag flight and angular body form. Just this week I disturbed one individual buried deep, hunkering down in a stand of hazel and holly. They will head north as we head into early spring. As UWNR rewilds, perhaps it is increasingly attractive to species like woodcock….