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Why tree planting touted as a panacea for global warming is in fact the opposite

Trees, don't you just love them?

It is time that everybody calmed down. Anyone who engages with the media, or listens to politicians and lobbyists, and whose brain has not been so profoundly damaged by the experience, will be alarmed about trees.

Of course, we like trees. It would be hard to find someone who doesn't. But what is going on now is frankly mad and it will have catastrophic consequences if it carries on the way it is going.

It is widely, and reasonably accepted, that climate change is driven by excessive levels of carbon dioxide (CO2) and methane (CH4). It is obvious that one of these – CO2 – is absorbed by green plants, including trees, during daylight hours. As trees are larger than most other plants they absorb more CO2 than, say, petunias. Thus when casting about for a solution to the climate crisis, planting trees is an obvious choice.

There are however problems with this approach. The first is that trees are part of the “Carbon Cycle”. Peat or limestone are, or should be, materials that permanently remove CO2 and lock it up for ever or at least for millennia. Most trees do nothing of the sort. They shed needles, leaves, and branches throughout their lives, these are broken down by natural processes releasing CO2. They may be eaten by birds, insects and mammals, who release more CO2 and sometimes CH4. Many, such as birch, can live shorter lives than we do, and are completely broken down yielding yet more CO2.

Furthermore, the act of planting them often releases more green house gases than would have been released if they had not been planted at all. This is particularly the case on peat or peat rich soils. These are often too wet for trees to thrive, so the first task is to drain the ground, with serious adverse environmental impacts. The disturbance of the soil exposes stored soil carbon to the air and it is oxidised releasing CO2. As they grow the shade of the trees kills the mosses that are essential to peat formation, so the tree is likely to store less carbon than the original vegetation would have done. The tree roots dry the peat allowing yet more oxidation and carbon loss. And as well, disasters do happen. Just this weekend a wildfire at Dove Stone Reservoir on Marsden Moor destroyed "two and a half football pitches worth" of trees that had been newly planted by volunteers. "This is a blow to carbon sequestration, biodiversity and also to the community", said a spokesman. Indeed; far from sequestering carbon, quite the opposite has happened.

So, if the point is to permanently sequester carbon, a lot of the tree planting currently being touted as a panacea for global warming is in fact the opposite of what is claimed. The land that is planted with ill-considered trees, in an ill-considered manner, may produce more carbon dioxide than if it had been left alone.

Trees can of course be planted in such a way that they enhance the environment and biodiversity, whilst assisting in some relatively small way in ameliorating the impact of rising CO2 levels. But this takes careful planning based on developing science and existing skill, and will only succeed if sufficient resource and skill are available to manage them throughout their lives. Unfortunately this brings us to another unfortunate element in the current craze for tree planting: its conflation with what is called re-wilding.

The popularity of re-wilding may have much to do with the feelings of people, some of them very influential, that we can return to an imagined golden age, far from the dystopian mess that they live in, and which their own demands for an unsustainable life style ensure must only get worse. Re-wilding has the advantage of being whatever you want it to be, although the most quoted successful example at Knepp Castle is actually an example of sensible and sensitive land management, rather than the abandonment of all management dear to the hearts of the more fundamentalist re-wilders.

If you add to this conflation of re-wilding and tree planting the concept of tradeable 'Carbon Credits' and the idea that the 'public purse' (obviously something distinct from taxpayers hard earned money) will provide huge sums for eco-system services, you end up with a toxic mixture of pseudo-science, guilt, hubris and greed that virtually guarantees yet another environmental car crash.

Rewilding at Oostvaardersplassen hasn't been the success it was touted as

There are now so many organisations and individuals trying to exploit the situation for financial gain that it is not possible to keep count, and equally difficult to separate the schemes and scams.

At its cheapest it costs less than a pound to plant a tree. But that is a very small tree, with a slender chance of survival, and planting a tree that cheaply is only possible if you are planting thousands in the same place at the same time and expect most of them to be harvested or dead very quickly. Yet you can now buy toilet paper sold on the basis that every roll you buy plants a tree. You can buy a t-shirt made of cotton grown in Asia, manufactured in the Far East and transported by lorry and ship, and as a result of your purchase, trees will somehow be planted somewhere.

Planting the right tree in the right place is not cheap. Making sure it survives is more expensive. The people who run the uplands are well aware of that because they have been doing it for a long time and, as they were using their own money, they fully understood the cost.

It should be borne in mind that most of the tree planting by carbon off-setters will be conifer plantations. Whatever anyone says or promises, no one will ever make a living out of mountain ash, hawthorn and holly. The money is in Sitka spruce planted densely enough to make them grow straight with few side branches. Not only that, scattering small, non-commercial native trees across the landscape isn't going to capture much carbon, so it will not get the requisite carbon credits. Unfortunately, the inevitable miles of dark and silent conifer plantations are about as natural as a supermarket car park. Nothing like them exists in nature and their contribution to the existing biodiversity of the uplands is almost entirely negative.

If they are planted on what is laughably being referred to as 'unused farmland', which is what they are calling pasture of any sort, as though grazing sheep and cattle was not farming, they will still be a more artificial landscape than the one they replace. Trees may be natural, plantations are not. Of course there will be assurances but we all know what weight can be attached to them. A Welsh or Scottish hill farm bought to plant trees to offset the carbon footprint of a multinational fuel guzzling conglomerate! What's not to like? What could possibly go wrong?

But wait a bit. There can't be a problem with all this. Our concerns are obviously unfounded. If they weren't surely the RSPB, the Green Party, and celebrity conservationists who can't pass a mirror without practising a sound bite would be up in arms. But instead they are silent. As silent as the dark rows of Sitka spruce will be as they march across our upland farms and moors.


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