Friday, 10 January 2020

Trees and the climate emergency (2 of 4)

In my last blog I raised the huge potential damage that could be caused to the environment if forest creation was done poorly.  This generated some excellent discussion and I am glad that it stimulated interest. 

I do not plan to respond to all points raised but there was one set of comments where some expansion is worthwhile.  This is the point that we are in a climate emergency, the priority must be to get the trees in the ground as an emergency action.

This is very reasonable.  In nature conservation we often must press forward with the best approximation of the truth so, if the overriding need is carbon sequestration then we better get on with it.  It might be said that the problems are small in comparison to the needs of the emergency.  However, the follow points should nuance this:

First, the UK is only 13% wooded.  It should be possible to double this without causing any ecological problems.  To stress this further, concern about ecological damage should not be an excuse for reducing forest creation – we must just get it right.  For example, high nature value chalk grassland occupies only 4% of the South Downs here in Sussex.  If a tree planting plan can’t restrict itself to the other 96% then it is not trying very hard!

The second point is that, done badly, tree planting can cause a net release of carbon.  Soil disturbance in ground preparation, particularly on peaty soils will release more carbon from soil than the trees will make up, at least in the short term.  This should be avoided by good planting design and good attention to local conditions.  But an attitude that any habitat without a tree on it is a wasted habitat, will be very damaging.

Third, it is not only trees that lock up carbon.  Peatland holds more carbon than all our forests. Kelp forests in the sea lock it up far quicker than trees, and wetlands are particularly good at soaking up carbon on land.  Salt marsh is so good at building up soil on the coast that it is likely to keep pace with sea level rise from climate change – if left to itself.  Even grassland, which do not appear to have the obvious standing crop of carbon that you associate with trees, are very good at pumping carbon into the soil.  As roots in grasslands die off their carbon is left in the soil.  Rewilding is turning out to be one of the best ways of getting carbon into soils.  The mixture of trees, shrubs, ground cover plants, animals, dung and dung fauna working together to build up soils almost twice as quickly as organic farming.  And most of that new soil is carbon.

A fourth point is that planting a tree, or regenerating a forest, is only the start.  This is a long-term investment.  Throughout history, woods only survived because they had a purpose in the local community.  Traditionally, this meant woods being kept and managed to provide products for local use.  Hence, managed woods were more likely to remain than unmanaged ones.  This is still true today.  One of the best ways to create and maintain forests is to demand products made of wood, not just to plant a tree.  However, a purpose for forests might be broader today.  Wild unmanaged forests may be as valuable, but in a different way, to forests providing sustainable products for human use.

Part of the same fourth point is that we should not deify trees so much that management becomes a sin!  Part of appreciating trees is to appreciate the products they provide us and therefore drive their sensitive management.  Cutting trees down as part of sustainable management is not an ecological compromise, it is part of a much-needed woodland culture.  Furthermore, cutting down trees in the right way creates diversity in woods, mimicking the natural disturbance that wild forests might once have had.  One felled tree in a well-managed wood will be replaced by hundreds of saplings – without any planting.  (This is not carte blanche for any old management though!)

As I said before, simple answers to complex problems are always wrong.  I would add now that this is not an excuse for inaction, it is more a drive to understand and celebrate complexity.  Nature is complex – and that’s just great!

1 comment:

Roderick Leslie said...

I couldn't agree more about the care needed in creating new woods and forests - the old chestnut of 'plant up the rough corners' horrifies me - there are hardly any rough corners left in our farmed landscape and they are where most of the refugee wildlife is.

On the other hand I'm sure you'd agree that much recent planting is a beacon of how careful, thoughtful design can massively benefit the environment. There is no shortage of space: so little biodiversity is left in most of the farmed lowlands that planting trees will almost invariably improve the environment, quite possibly simply because it removes the land from the murderous pesticide regimes that have decimated our insects.

Obsession with tree species is a good indicator that there'll be problems - foresters are far too over excited by a debate that's almost a hobby, and many non-foresters understanding doesn't extend beyond a crude conifer vs broadleaf. Structure is probably as important, if not more so: for biodiversity most of the game is in existing woodlands, especially ancient woodlands and its the tens of thousands of hectares of dark, stood over coppice in the SE & SW where some of our favourite woodland wildlife is dying out.

As you say, the risks are real and significant - but the benefits can be equally so.