James Fenton writes to the New Scientist, questioning whether planting trees will mitigate climate change:When scientists can't be certain about relationship between tree planting and atmospheric levels of carbon dioxide, we need a climate change policy that allows for such uncertainty. For many years I've been advocating that we need clarity over what we are trying to achieve. Let's assume that we are trying now to slow down and stop the climate changing by reducing the level of greenhouse gases in the atmosphere. (That sidesteps the question of whether we should be concentrating on reducing climate change, or reducing the negative impacts of climate change - see here.) Planting trees might have an important, even crucial role, in determining climate outcomes. But we don't have a policymaking system that allows for the uncertainties that Mr Fenton cites, nor for any other massive uncertainties such as the effects of certain sorts of cloud - see my post here.
It may not always work. Planting trees on open ground may change the reflectivity, or albedo, of land. At higher latitudes this can cause a warming effect, as three-dimensional woodland absorbs more radiation than the essentially two-dimensional open ground that it replaces. In many places new planting is likely to be targeted at upland areas, which generally possess stratified soils with a high organic carbon content. In the UK there is an order of magnitude more carbon stored in soil carbon than plant biomass. Tree planting on such soils can oxidise this carbon, potentially releasing more than the amount taken up by the trees. And practices such as ploughing land before planting can dry out the soil, causing carbon release. At the other end of the forestry cycle, modern tree extracting machines can similarly churn up the soil. So it isn’t clear to me whether tree planting will benefit the climate. Can planting trees combat climate change very much?, James Fenton, letter published in New Scientist, 8 February
Our policymaking system relies on our being able to identify with reasonable certainty the relationship between cause and effect. But our society and environment are now too complex for that blithe assumption to work. We just don't know whether planting trees will mitigate or accelerate climate change, but we cannot currently make policy in any other way. l.
Which is why I suggest we target the goal we want to achieve, and reward the people who find the best ways of achieving them: ways that we cannot now identify with any certainty. Any efforts, then, must be long-term in nature, and they must encourage research, experimentation and, finally, implementation, all of which means that policy must be consistent over time. We cannot at this point convincingly advocate, say, tree planting, but what we can do is provide a system of incentives that will reward tree planting (more accurately: the right sort of tree planting) to the degree that it helps achieve society's climate change goal. We reward the outcome, and let investors work out the best ways of achieving it, giving assurances that their successful long-term efforts, which will doubtless entail many failed experiments, will be rewarded.
Long time readers will know that, of course, I'm advocating the application of the Social Policy Bond concept to climate change. We urgently need to reward people who (1) are investigating exactly the sort of relationships about which Mr Fenton writes and (2) are implementing the most successful of their activities and terminating those that are less promising. We need to encourage a wide range of diverse, adaptive approaches and we need to reward the most useful of these. Our current policymaking system is too sclerotic to contemplate such a flexible approach.
It's not just climate change, where at least we think we can identify many of the likeliest explanatory variables. There are just as urgent, big issues, such as nuclear peace, or disaster reduction, where the complexities are so obvious even to policymakers that any activities now being undertaken to address them are half hearted, scattered, incoherent, and too poorly-financed to achieve anything useful. The Social Policy Bond concept can be applied to those issues too.
Climate change, conflict reduction, nuclear peace: these are huge, urgent problems whose causes we cannot identify with any certainty, and vary with time and geographic area. Conventional policy cannot cope with the diverse, dynamic nature of these problems, which are going to be solved only with an array of diverse, adaptive approaches. Social Policy Bonds, by targeting outcomes rather than the supposed ways of achieving them, can deal with uncertain, complex relationships between cause and effect. Current politics can't.
See here for links to my papers on Climate Stability Bonds, and here for my work on conflict reduction.