MICHAEL WELBANK: Heath could be overrun in 50 years

No discussion about Hampstead Heath can avoid the topic of dead hedging. Why bother with it at all? Many delight in citing examples of action undertaken in the name of conservation as being just vandalism by over enthusiastic chain-saw maniacs.

The cutting down aspects are always more dramatic and visible than the building up aspects. The former always attracts criticism, in part arising from the mindset of the critics and in part from failure to provide easily assimilated information about what is being done and why.

But a 'do nothing' option is not really available. If that were followed and the Heath left to its own devices then forecasts indicate that it would be covered entirely by trees, primarily sycamore, within 50 years. The idea of 700 acres of dense secondary woodland with no glades, no grassland, no hedgerows, no open spaces and dark overshadowed lakes is to say the least unappealing and would be an abrogation of the responsibilities of the guardians of the Heath.

In all this, caring for our existing ancient trees is important and a great step forward would be for everybody to learn to love 'dead hedging'. Some consider these straggly piles of dead branches all over the place as just an indication of laziness on the part of the tree teams who have not bothered to take their rubbish away or to leave the place looking neat and tidy (something the Heath can never be; it is a heath, not a park). But 'dead hedging' has an important purpose; despite its name, it heralds new life.

Many of the major trees on the Heath sit alongside paths or mark spots where paths converge. Years of pedestrian traffic around these trees has created such severe compaction of the clay soils that a hard pavement-like surface is formed, causing water to run off away from the tree and stopping any water penetration to the sub-soil. Over time such trees have lacked adequate water and their roots fight to survive.

Remedial action for this takes a number of forms. Firstly the soil in the area around the tree can be reactivated by the use of compressed air probes which simply blow the compacted soil apart, allowing for oxygen and water penetration which restarts the whole cycle of top soil life. This process is then helped by providing a surface mulch layer around the tree and lastly to prevent the reoccurrence of soil compaction this mulched area is enclosed by 'dead hedging' to divert paths to pass further away from the tree. The advantage of doing this with 'dead hedging' rather than a fence is that the material is to hand and it is intended to be temporary until new path lines become well established.

'Dead hedging' rots down naturally, providing soil nutrients and home for myriads of invertebrates forming the bottom end of the food chain. This type of remedial action is followed wherever possible to sustain venerable trees in good health, so 'dead hedging' should be a welcome sight on the Heath.

The mighty oak at Hampstead Gate benefited from remedial action in 2005. At that time the paths around here were all focused on the entrance gate into Kenwood for which this oak served as a marker. The ground around had become like polished stone paving and the tree was suffering. Diverting the paths away from the tree was only made possible by the active co-operation of the Kenwood Estate, which made a new entrance gate some distance away. Then an area of surface mulch was formed around the tree, laid by Heath Hands.

There has been a bit of turmoil in the area but it will all settle down eventually and memories of what it was like previously will fade; the tree is reacting, you can now spot the new growth, it is much happier and can look forward to many years of life yet.

This is just one example of conservation work which is justifiably interventionist, does involve some chainsaw work, leaves lopped branches around but does achieve beneficial physical change.

Not all conservation work is like that but the conservation principles applying to the whole Heath are published and open for all to see.

q Michael Welbank is chairman of the Hampstead Heath management committee