8 May 2013

Green and Pleasant Land: hard times for Britain’s trees

Channel 4 News is examining the alarming changes taking place in the British countryside. Science Editor Tom Clarke takes a look at trees – and why they have never had it so tough.

Green and Pleasant Land: hard times for Britain's trees

The rolling, wooded hills of Britain have fuelled, fed and sheltered us for generations and remain the green lungs of the country.

Last year we learned one of our most iconic trees could be wiped out by a new disease. But ash dieback is not the only invader we face. Our entire tree-scape is under attack like never before, as an unprecedented number of new pests and diseases arrive in Britain. And its climate change that is creating the conditions for them to take hold.

Channel 4 News can reveal Defra is launching the largest ever trial to try and contain Oak Processionary Moth (OPM). The department is giving £1.5m to the Forestry Commission to spray an organic insecticide in a pilot project to see if they can halt the spread of OPM.

We have also gained exclusive access to the first major project to combat ash dieback. We have also spoken to the scientists who want your help to find out just how sick the rest of our woodlands are. And we visit what could be the forests of the future – planted to withstand our fast changing climate.

Fighting back ash dieback

Together the Woodland Trust, Defra and the Forestry Commission are embarking on the largest ever field trial to find natural resistance to ash dieback in our native trees. They are planting 25,000 ash saplings from across the UK to see if any have the ability to fight off the infection.

“We want to get a good mix of the genetic types, which are naturally here in the UK. But lay them out in a very strict pattern so we can monitor them closely and see which ones might hold the key to resistance for ash for the future,” said Austin Brady, head of conservation at the Woodland Trust.

The disease was first spotted at the Pound Farm wood in Suffolk making it the ideal location for the trial. “Really this is the best place to put these trees. Right in the eye of the storm, in terms of putting them where the spores are going to be present,” said Brady.

Over the coming months they will be intensively monitoring the saplings. Evidence from mainland Europe is that one or two per cent of them may be resistant to ash dieback. A few of the saplings at Pound Farm may hold the key to the future survival of all Britain’s ash.

A changing climate

But as they race to find resistance to ash dieback in the rest of our trees are facing an unprecedented onslaught.

When Dutch elm disease wiped out 25 million trees in the 1970s, it was one of just a handful of imported pests diseases. A few more arrived before the new millennium. But in the last 10 years the floodgates opened to 16 more.

Horse chestnuts are struggling with the leaf miner, now spread across half the UK. Mysterious acute oak decline is attacking our most enduring tree. The oak processionary moth is doing the same while also threatening human health. Tiny spines from the moth’s caterpillars can cause severe allergic reaction in some people. New strains of the pathogen Phytopthera are also threatening native and commercial trees such as larch.

Read more: Your questions on ash dieback answered

The science suggests climate change is creating the conditions for more of these invaders to take hold. Higher temperatures, droughts, floods, wet summers; all of those can stress trees making them more susceptible to pests and diseases.

“Trees are like people, if we stay healthy and we’re fit and we have all the nutrients that we want then we can overcome flu and cold,” said Tony Kirkham head of the arboretum at the Royal Botanic Gardens in Kew.

“Temperate trees, these that are growing around us, need those four seasons. They need to shut down, they need to know what’s happening, and they are confused.”

Citizen science

But we still face a major problem. No one really knows how healthy Britain’s trees are. And that’s where you come in.

Tomorrow Open Air Laboratories (Opal), led by the Natural History Museum and Imperial College London, is launching the first ever citizen-led survey of our nation’s tree health. Their survey pack guides volunteers though a tree health check.

“We can’t cover the whole country ourselves. There are many places that are not accessible to us, for example peoples back gardens,” said Dr Linda Davies, director of Opal. “The information the public provide will be really important in helping us understand the distribution of these pests and diseases, but also the general condition of our trees,” she said.

Future forests

With pests, diseases and climate putting the squeeze on our trees, the experts are trying to plant resilience into the forests of the future.

This year the Forestry Commission has changed its policy on what trees are best for Britain. It has begun planting of coast redwoods in the Forest of Dean in Gloucestershire. Their preference for hot summers and lots of rain could make them an ideal commercial species in future. More drought tolerant coast redwoods are being dug in the east of Britain.

Our woods are small and fragmented, they are more vulnerable, because they are quite narrow in terms of the nature of them and the number of species. Austin Brady, Woodland Trust

“For the last 20 years successive organizations have talked about using native trees, of local origin, on local spots,” said John Weir, advisor for woodland resilience at the Forestry Commission. “That assumes a stable climate; that assumption no longer applies. So we’re now saying local is not always best.”

And in the Forest of Dean even England’s heart of oak is getting a transfusion of French blood. They are planting oak samplings reared from acorns brought from the Loire Valley in the hope they are better able to cope with warmer temperatures in future.

So if our trees and their, pests and diseases, are on the move because of a change in climate and the demands of people, is it time to accept that what we perceive as traditional British woodland is actually a thing of the past?

Those who care about woods say it would be too easy to just accept change and walk away. Our woods, they argue, are currently too sensitive to change: “Our woods are small and fragmented, they are more vulnerable, because they are quite narrow in terms of the nature of them and the number of species,” said the Woodland Trust’s Austin Brady.

“What we need to think about is having more woodlands, more diverse native species, and having those woods better connected.”

So the current onslaught has the potential to irreversibly alter Britain’s forests. But it has also raised new awareness about the importance of our trees and their vulnerabilities. Some good may come of the current crisis, but we’re not out of the woods yet.