Tag Archives: politics

What trees would we plant to maximise carbon uptake?


Fangorn Forest as represented in Lord of the Rings: The Fellowship of the Ring. This is fantasy fiction, not the type of habitat that we should expect to find or create in the real world.

One of the reasons often put forward for growing more trees is that it’s a method to draw down carbon from the atmosphere and lock it up in wood. Afforestation is far more efficient and straightforward than any currently imagined ‘carbon capture technology’. Photosynthesis is the original carbon uptake mechanism, evolved and perfected over more than a billion years, and human ingenuity isn’t going to design anything better, at least not on the scales required by rapid climate change. Trees have done it all before.

Before going much further, and for the avoidance of doubt, planting trees (even a trillion of them) isn’t going to solve the climate crisis. It’s one potential tool but no substitute for massive reductions in emissions. At its very best, tree-planting would only remove the carbon which has been released from land-use change, not that from the burning of fossil fuels, which represent stores of carbon generated hundreds of millions of years ago. That’s even before we get to the contentious question of where we might plant the trees, which usually turns out to be someone else’s country.

The other problem with tree-planting is that it assumes the trees either stay in place or are continuously replenished. Forest fires, logging, land clearance, droughts, pest outbreaks… all the potential causes of tree mortality will eventually lead to this carbon returning to the atmosphere. A tree is at best a temporary carbon store, albeit one that can last a few centuries. We’re not laying down any new coal deposits, they just don’t make it any more. I’m therefore sceptical of any off-setting program which justifies current emissions on the basis of anticipated long-term carbon storage through tree planting. It’s not something we can rely on.

All these caveats accepted, we can begin to ask the question: if we really were planting forests with the primary objective of taking up carbon, and we planned to do it in the temperate countries which are overwhelmingly responsible for global change, what should we plant?

A recent newspaper article asked this question with the UK in mind*. By coincidence I had a Twitter exchange on the same subject shortly before the article came out. As a thought experiment it’s a reasonable discussion to have, and by doing so publicly it forces people to contemplate the implications of the arguments that are so often made for planting trees.

The right tree species should be (a) fast-growing under local conditions, (b) tall, preferably forming dense forests with as little space between the trees as possible, and (c) of high wood density, maximising the amount of carbon for a given volume of trunk. Ideally they should also be long-lived and relatively resistant to the many forms of disturbance that kill trees, including extreme weather and diseases. There’s no single species of tree that satisfies all these conditions, not least because high wood density leads to slower growth rates. Some compromise is necessary.

The conclusion of the article, taking into account the assumption that carbon uptake was the sine qua non, was that plantations of fast-growing non-native conifers were the best way forward.** The backlash to this suggestion was immediate, predictable and justified. Such tree species are not only hopeless for conservation (and therefore would lead to a net loss of biodiversity) but also aesthetically undesirable as they would transform familiar landscapes. Yes, say the public, we want more forests, but surely not like this.

I don’t disagree with any of the objections to such a scheme, but it does highlight the inherent problem with making so many claims for the benefits of tree planting that are logically incompatible. It is impossible to design a forest which maximises all the potential functions we want from them: promoting native species, boosting biodiversity, storing carbon, amenity value, aligning with our aesthetic preferences, and maybe also providing some economic benefit to the landowners who are being asked to turn over their productive estates to trees. If we pick just one of these factors to emphasise — in this case carbon — then inevitably we will have to lose out on the others.

Every response to climate change presents us with difficult choices. The trite maxim that we should plant more trees puts people in mind of a sylvan idyll of sun-dappled glades beneath the bowers of mighty broad-leaved giants. Such forests exist in Europe only in the imagination. If real trees are to be used to solve our problems then real forests will be necessary, and they might not be the ones that everyone expected. Be careful what you wish for.



* Full disclosure: the academic whose views the article reports, Prof. John Healey of Bangor University, is also a collaborator of mine (we co-supervise a PhD student). We haven’t shared our opinions on this topic though.

** My pick, if we’re playing tree Top Trumps, is the Nordmann fir, Abies nordmanniana, which is so much more than just a great Christmas tree. It’s also the tallest-growing native tree in Europe and as a montane species tolerates a wide range of challenging environments.


Stop the eco-triumphalism now


There is no excuse for this. Image taken from the Twitter feed of XR East (@xr_east)*. Note that Extinction Rebellion UK have disavowed both this group and the sentiments expressed in the post. Similar opinions have been circulating on social media for some time though.

I’m angry. I was reluctant to write anything on this blog about COVID-19, pandemics or epidemiology, given that none of them are among my specialisms*. But lately I’ve been appalled by a subset of ecologists and environmental campaigners — admittedly small — who have used this crisis to score points for their personal obsessions.

This is not to criticise those who seek positive messages to cling onto when there is so much to mourn or fear. Some of this desire is misdirected, including numerous stories of nature returning to areas which have seen dramatic reductions in human activity. Whether it’s drunk elephants in Chinese villages or dolphins in Venice, these have usually turned out to be false reports. Does it matter that many people share stories that are quickly disproven if they offer a brief cheering distraction? Perhaps not so much. There are more dangerous lies out there.

Yet linked to many of these stories is an agenda, sometimes implicit, other times actively advanced, which has at its core a desire to show that something good has come of the pandemic. Few would say so with quite that lack of subtlety, but there is no other way to interpret many of the articles on declines in air pollution, clear skies or the potential for advancing a green agenda during the anticipated recovery. I’m more sympathetic to those who point out that the international response shows that we have the ability to pull together for the collective good that could be harnessed again. There may be opportunities to be taken once we can see the light at the end of the tunnel, but that still seems a long way off.

Others are even less subtle, for example the assertion by the European Agroforestry Federation that all this wouldn’t have happened if we’d had more agroforestry. Even if true, and despite being a longstanding advocate of agroforestry I’d struggle to make an evidence-based case for it***, now is surely not the time.

The most pernicious narrative, one which lurks in the fringes of the Deep Green movement and other more mainstream environmentalist groups, is that anything that reduces human populations and activities can only be a good thing for the environment. I have even seen it argued (and I refuse to link to it) that COVID-19 is an expression of Gaia immunity, the Earth fighting back against the infestation of humans that is taking it out of some mythical balance****. The refrain ‘we are the virus’ has been expressed repeatedly on social media. The sentiment at the top of this article is not a isolated incident. Nor is it a new idea; in 1988 Prince Philip told a German interviewer that he was ‘tempted to ask for reincarnation as a particularly deadly virus’ so as to aid in population control. Yes, he really did say that.

To believe that a catastrophe causing widespread mortality is somehow beneficial is simple eco-fascism. Privileged people in the Global North, living in splendid isolation whilst delighting (even indirectly) in the death, privation and suffering of others, is not morally acceptable on any grounds. There is no positive side to a pandemic.

There are two strands to eco-fascism. One has a long history in the belief that restricted national resources compel populations to resist immigration in the name of supposed sustainability. This narrative has already inspired acts of terrorism, but also been made in more mainstream settings by France’s National Rally (Rassemblement national) among others. Most reasonable, compassionate people would disavow this set of arguments.

The other narrative, however, holds that any reduction in human population can only help the natural world. This is sometimes expressed as the suggestion that not having (so many) children is the best way of combating climate change, an argument which is both logically and morally suspect. Any case for global population control always ends up being anti-female, racist and ultimately anti-human. Even if we might agree on a ‘sustainable’ human population level — and that’s not an easy figure to decide upon — the process of reaching it is unconscionable by any means, and certainly with the speed required for it to be an effective measure. As Jenny Turner put it, “How can a planet lose seven or eight billion humans… without events of indiscriminate devastation? When people start thinking about getting rid of other people, which sorts of people does history suggest are usually got rid of first?”

On this point, in which countries do you expect the death rate from COVID-19 to be the highest? It will almost certainly be in the Global South where access to medical care, nutrition and government support is most lacking. They are not the ones who bear the greatest responsibility for global change, and once again they will carry the heaviest burden. This pandemic is first and foremost a tragedy. It will not in itself be of any lasting benefit to the environment.

We are rightly offended when politicians use disasters to advance their own partisan agendas. As scientists, including ecologists, we need to step back from the campaigns that are usually at the forefront of our minds and accept that this situation is a distinct crisis of its own. Yes climate change remains a pressing issue; yes extinctions continue apace; yes the international wildlife trade is abhorrent. But these are separate problems which the world’s attention will return to again. For now simple compassion and decency requires us to stand back and accept that for once it isn’t about us.



* I suspect (and rather hope) that the post will be taken down, but here’s the evidence. There is a dispute going on about whether this represents a genuine faction of XR, or ‘infiltrators’, which are difficult for an autonomous movement with no central leadership to protect themselves against. It wouldn’t be the first time that someone associated with XR has said something offensive though. For the record, I continue to be a strong supporter of XR and their core principles.


** Not that this has stopped quite a number of people.

*** The only relevant project I’ve been involved with, on mosquito-borne diseases in Northern Thailand, actually implicated orchard expansion as a likely cause of greater risk of infection. But this is a complicated subject and no single study can tell the whole story, particularly one which wasn’t designed to test that hypothesis.

***** I don’t have time here to explain in detail why Gaia theory is nonsense and has been rejected by the majority of ecologists. For more see pages 175–176 in my textbook and the papers it refers to. I’m also writing another book about it.

Climate change and the Watchmen hypothesis

The climax of Alan Moore’s famous graphic novel (warning: spoilers*) plays out around a moral dilemma. In a world of conflict and discord, maybe the only thing that can bring humanity together is a shared enemy. If you accept that proposition, then could it ever be morally defensible to create such an enemy? And if you discovered that the enemy was a sham then would it better to reveal the truth or join the conspiracy? Part of the reason the conclusion to the book is so chilling is that your heart wants to side with the uncompromising truth-seekers while your head makes rational calculations that lead to unpalatable conclusions.


Selected panels from p.19 of WATCHMEN 12 (1987) by Alan Moore and Dave Gibbons, published by DC Comics.

Why am I invoking an old comic? In climate change we face a common enemy which is undeniably real, whose approach can be measured, predicted and increasingly experienced in real time, and which has been created entirely by ourselves. It may not have the same dramatic impact as a surprise alien invasion; think of it more like spotting the aliens while their ships are still some distance from reaching Earth, but they’re already sending trash-talk transmissions in which they detail exactly how they’re going to render the planet uninhabitable to humans and frying a few interstellar objects just to prove the point. And we invited them, knowing exactly what would happen.

In this case there is no conspiracy. The stream of scientific studies demonstrating the perils of allowing global temperatures to increase further is so continuous and consistent as to be almost background**. We want to stick our heads in the sand and ignore climate change because we enjoy our short-haul flights for city breaks, private cars to drive to work and occasional steaks. The individual incentives are all aligned towards apathy, ongoing consumption and deferred responsibility. Whatever is the worst that could happen, many of us in the Global North will be dead of natural causes by the time it reaches our parts of the world.

In the face of such an obvious existential threat, about which we have been forewarned by the consistent voice of the overwhelming majority of scientists, how is humanity preparing? Are we coming together as one? Have we overcome our differences and channeled our collective intellects and resources into finding a solution for all?

Like hell. America withdraws from the only international agreement with a shred of common purpose; Australia continues to mine coal while the country burns; Poland hosts a gathering of climate scientists and uses it to defend the coal industry. I know people who have stopped attending UNFCCC meetings because the emotional toll is so great. To recognise how much needs to be done and to witness how little has been achieved is a terrible burden. This is not to say that the situation is hopeless; with concerted action we can still avert the worst outcomes, and doing so remains worthwhile.

With all this in mind, I’m forced to conclude that the evidence in support of the Watchmen hypothesis is lacking. Creating a common enemy will not be enough to bring the world together. We’ve been trying it for 30 years already***.

Where does this leave the likes of Extinction Rebellion? Over the last year I’ve been amazed by the scale of the protests in London, Berlin and cities around the world, which exceed every previous effort. It feels like it a tipping point, and it ought to be, because one is long overdue. Whether it proves to be the moment the tide turns, time will tell. It has all the elements of a success story: popular support for the message, if not always the methods; an inspiring figurehead in Greta Thunberg who continues to exceed expectations; politicians scrambling to be seen on their side. Yet the background to this is the ongoing prosecution of many of the participants as states quietly assert their control. And the usual pattern of politics is for green issues to slip down the agenda as soon as an election looms****.

One of the side-effects of XR is that the disaster narrative has currently obscured other discourses and even subjected them to friendly fire. But this is not a battle which will be won on a single front. Many alternatives are available, including market mechanisms, commercial partnerships or a rebalancing of economic goals (there are good reasons why the Green New Deal isn’t quite it, but I admire its objectives). These are not exclusive of one another, nor likely to be sufficient on their own, but if we are to succeed in inspiring change then a mixture of approaches and messages will be essential.

I’m not saying that we should stop heralding the impending catclysm*****. The uncompromising truth-speakers are right. We need to keep up the drumbeat of evidence, narratives, reporting and campaigning as the climate crisis unfolds. There are positive, individual steps that we can all take. But if we hold out for the moment when humanity suddenly unites to act as one then I fear it may never come.


* It’s been out since 1987 so you really have had plenty of time to read it, but if you haven’t then perhaps you should. And no, watching the film doesn’t count. Trigger warning: contains scenes of sexual violence.

** Even in such times, this paper stands out as particularly terrifying.

*** The first IPCC report was published in 1990. The fundamental message hasn’t altered since, even if the weight of evidence and urgency of action have increased. At least half of global carbon emissions have occurred since this report.

**** A few years ago I attended a talk by a statistician from one of the major political research agencies in the UK. He showed polling data with a consistent pattern that voters placed a high priority on green issues between elections but they fall down the ranking in advance of an election. Politicians know this, which is one reason why action in democratic countries is so slow.

***** If we’re going to stick with the comic book metaphors, this makes climate scientists the Silver Surfer to climate change’s Galactus. Too geeky?