Thursday 14 November 2013

The myth of the dense wildwood!

George Monbiot’s excellent book “Feral” has re-opened an interesting discussion on the idea of rewilding in the British landscape.  Included within it, however, is the myth of the dense wildwood – the idea that a dense forest once clothed the British landscape from coast to coast such that a squirrel could have covered the whole of the country without ever having to tread on the ground.

An attractive idea maybe – after all if you leave an area alone it develops, eventually, into a wood.  So, natural equals dense forest.  Or so the story goes.  But it is just a story.

The story, however, appears to be backed up by some science.  Pollen deposited in soils can be dated and identified so it should be possible to build up a picture of the species that were present at given times throughout history.  And, hey-presto, we have the answer.  Tree pollen takes over after the ice age finishes and non-tree pollen does not become common again until humans clear the forest for agriculture.  What is more, if you look at evidence from remains of beetles, which again can be identified and dated, then you get a supporting picture – woodland beetles, apparently, dominated throughout the wildwood period “proving” that ours was a land of dense trees before humans interfered.

Fundamental problems start to appear if you dig a little deeper though.  If dense forest was the natural habitat then how come about 50% of our plants and animals need open habitat, and about half of the rest need forest edges?  The traditional answer has it that these species were limited to small, transient patches where they struggled for existence only to emerge when human clearance gave them an opportunity.  A feeble answer but it seems to satisfy some, so, the closed canopy model is often unquestioningly adopted.  Britain should be dense with trees and anyone who tries to do otherwise is simple fighting nature.

Having accepted this model, conservationists then fall in to two camps.  One has it that these open habitat species are just a human artefact and we can do without them.  The other has it that humans have so influenced the natural environment that any emphasis on natural processes is miss-placed and it is human management that is the key tool for nature conservation.  The first is an argument against nature the second is an argument against natural processes. 

I disagree with both as I disagree with the model they both assume for wild nature.

If you look again at the evidence then all is not as it seems.  Indeed wild nature is far more complex, interesting and wonderful than is ever likely to be covered by some simplistic human model.

Look at the pollen evidence.  First there is a history of “fiddle factors” being put into the interpretation.  This is necessary because some plants are insect pollinated so produce little pollen; others are wind pollinated so produce vast amounts.  Understandable, but small changes here can make big differences to the interpretation.

More importantly, however, is the abundance of both hazel and oak throughout the pollen record.  The standard model ignores the fact that neither of these can regenerate under a tree canopy.  Indeed hazel does not flower, so does not produce pollen, even if it does manage to grow in a dense woodland. So we are missing something – how did all that oak and hazel manage to grow if there was very little open habitat for their seeds to germinate in?

How about those woodland beetles?  Well most of these are associated with trees, not woods, and the richest tree for beetles is oak.  Furthermore, when you look at the requirements of the individual beetle species you find that they require not just any oak, but oak that has grown in open conditions – indeed some need sunlight right down to the forest floor.  A similar picture emerges if you examine fly species that are specific to oak.  Today, old open-grown oak trees that get surrounded by dense forest loose all their specialist species and eventually die themselves.   So, in the wildwood we have a picture of common trees that need open habitat in order to regenerate, and their associated insect species that will only survive if those trees grow in the open.  A very different picture to the dense carpet of dark woodland that is constantly promoted.

The only sensible conclusion is that open habitat was present, probably quite common, in the wildwood. 

This is not to say that the wildwood was only open habitat.  Other shade tolerant species (such as lime, hornbeam, elm etc) were also common.  So dense forest would also have been there, probably abundant.  My guess is that the wildwood would have included far more complexity and diversity than we could possibly imagine today. 

How could this be possible?  It is pretty clear that the simplistic “closed canopy” model, which assumes the only significant natural process is the growth of trees, has major problems.  In particular the model ignores the role of natural disturbance; indeed some take it so far as to assume that disturbance is an unnatural, bad thing that should be avoided.  The 1987 storm, however, gave us a clue on the beneficial role of natural disturbance.  Dense tree canopies were opened up, flowers, trees and shrubs were able to regenerate and more species were attracted into a forest.  On top of that is flooding, erosion, insect damage, fungal disease, the effects of grazers and browsers and also the effects of predators on grazers and browsers.

Natural disturbance is not a bad thing that is imposed on an otherwise peaceful nature – on the contrary it is a main driving force within nature.

Any rewilding suggestions that do not consider the role of natural disturbance should not be considered rewilding at all – merely the construction of another human artifact.

There is a huge and fascinating agenda relating to rewilding; this will include the reintroduction (or mimicking) of natural processes – a range of processes not just a selected few.  Rewilding is not the same thing as neglect.

There are flaws in his argument but we owe George Monbiot a great debt of gratitude.  He has succeeded where many of us have failed – he has brought the subject of rewilding into the public consciousness and stimulated a fruitful discussion.  Something that I aim to continue in future blogs.

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