The One Trillion Trees Project and Increasing US Forest Cover

The World Economic Forum launched the One Trillion Trees project in January.

As it noted in a press release (January 22, 2020): "Nature-based solutions – locking-up carbon in the world’s forests, grasslands and wetlands – can provide up to one-third of the emissions reductions required by 2030 to meet the Paris Agreement targets." On one side, I like trees. On the other side, I'm by nature skeptical. 

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As a piece of short-form writing, I've long been a fan of George Orwell's tribute to trees in his 1946 newspaper essay ("A Good Word for the Vicar of Bray," Tribune, April 26, 1946) where he wrote:

The planting of a tree, especially one of the long-living hardwood trees, is a gift which you can make to posterity at almost no cost and with almost no trouble, and if the tree takes root it will far outlive the visible effect of any of your other actions, good or evil. ...

Recently, I spent a day at the cottage where I used to live, and noted with a pleased surprise--to be exact, it was a feeling of having done good unconsciously--the progress of the things I had planted nearly ten years ago ... This job lot consisted of six fruit trees, three rose bushes and two gooseberry bushes, all for ten shillings. One of the fruit trees and one of the rose bushes died, but the rest are all flourishing. The sum total is five fruit trees, seven roses and two gooseberry bushes, all for twelve and sixpence. These plants have not entailed much work, and have had nothing spent on them beyond the original amount. They never even received any manure, except what I occasionally collected in a bucket when one of the farm horses happened to have halted outside the gate.

Between them, in nine years, those seven rose bushes will have given what would add up to a hundred or a hundred and fifty months of bloom. The fruit trees, which were mere saplings when I put them in, are now just about getting in their stride. Last week one them, a plum, was a mass of blossom, and the apples looked as if they were going to do fairly well. What had originally been the weakling of the family, a Cox's Orange Pippin--it would hardly have been included in the job lot if it had been a good plant--had grown into a sturdy tree with plenty of fruit spurs on it. I maintain that it was a public-spirited action to plant that Cox, for these trees do not fruit quickly and I did not expect to stay there long. ...

A thing which I regret, and which I will try to remedy some time, is that I have never in my life planted a walnut. Nobody does plant them nowadays--when you see a walnut it is almost invariably an old tree. If you plant a walnut you are planting it for your grandchildren, and who cares a damn for his grandchildren? ... Even an apple tree is liable to live for about 100 years, so that the Cox I planted in 1936 may still be bearing fruit well into the twenty-first century. An oak or a beech may live for hundreds of years and be a pleasure to thousands or tens of thousands of people before it is finally sawn up into timber. I am not suggesting that one can discharge all one's obligations towards society by means of a private re-afforestation scheme. Still, it might not be a bad idea, every time you commit an antisocial act, to make a note of it in your diary, and then, at the appropriate season, push an acorn into the ground.

But when a skeptic like me reads that opening comment from the World Economic Forum, my brain spits out questions like: How practical is such an increase? How much land will it take? How much are the benefits likely to be overstated? What would it look like in the United States? In short, I need some outside expert input.

David Wear has written a short overview "Tree Planting as Climate Policy" for Resources for the Future (May 2020, RFF Issue Brief 20-07). Wear offers a thoughtful discussion of US forest patterns in recent decades--and what policies are most likely to increase the number of trees substantially. He also makes a case that they way to get more trees planted may be demand-side policies to find more uses for wood, not supply-side policies to put more acorns in the ground. Wear writes (citations and footnotes omitted):  

In 1950, planted forests were rare in the United States, but they now account for 68 million acres (8 percent) of forests, and tree planting is an integral component of the timber-growing sector. Between 2011 and 2015, roughly 11.4 million acres were planted ... Given average planting densities, an annual average of 1 billion to 1.5 billion trees were planted over this period. Most (75 percent) of these trees were planted in the US Southeast, where returns to forestry are high relative to other rural land uses because of good growing conditions, genetically improved trees, and widespread access to markets for timber. At times, planting by noncommercial private landowners has been subsidized through various costshare programs addressing reduced crop production, increased timber supply, or conservation benefits, but the lion’s share, and nearly all planting since 2000, has relied exclusively on private-sector capital. ...

Forest investment in the United States has driven an orderly transition of the forest sector from harvests of old-growth forests to a near-exclusive focus on managing second-growth forests. ... Remarkably, forest investment fully offset the loss of 17.1 million forested acres to development between 1982 and 2012 by establishing new forests on pasture- and croplands. These land use and forest dynamics resulted in a vast and growing reservoir of land-based carbon sequestered from the atmosphere—US forests capture more than 600 teragrams per year of carbon dioxide equivalents and more than 10 percent of economywide emissions ... Near-term prospects for expanding forest area and forest carbon capture seem limited, given these market changes. Indeed, recent projections suggest a slowing of forest carbon sequestration in the United States as forest area peaks and forests age. Parts of the western United States are expected to soon reach a carbon stasis and then become a carbon source ...

When it comes to incentives for planting more trees, Wear emphasizes several themes that bear repeating.

First, additional subsidies to plant large numbers of trees are likely to displace the existing private capital that has been planting trees,without much net growth in forest cover.

Policies that grow timber inventories ... face the prospect of amplifying downward pressure on timber prices and returns to forest management. Coupled with stable to increasing agricultural prices, the result would likely be a displacement of private investment capital from the forest sector and land switching from forest to agricultural uses.  ... This is a classic leakage problem where market forces offset the policy instrument through substitution. ... Ultimately, tree-planting initiatives will have limited effects on forest area because they are supply-side interventions in a private market with growing supplies and stagnant prices. They “swim against the current” of expected landowner responses.

Second, Wear acknowledges a bunch of options like more trees in urban areas, suburbs, near riverbanks, park areas, and when re-establishing habitat. But he writes: "These examples simultaneously provide cobenefits arising from watershed protection, enhanced biodiversity, and human health benefits, but such targeted approaches are unlikely to result in substantial carbon benefits.

Third, if the policy goal is to increase forest cover quite substantially, a more plausible if somewhat counterintuitive option may be to increase demand for wood products. He writes:

Policies that address the demand side of the forest sector are likely to be more effective. Policy-driven demand growth is an alternative approach to increasing carbon sequestration that would raise prices and incentivize forest retention and private investment in tree planting and management. Forest bioenergy has the most potential for policy-determined demand growth, and recent studies show its strong potential for reducing the carbon density of US energy production while expanding forest carbon sequestration (see Faveroet al. 2020). The use of mass timber in commercial construction is another avenue for growing timber demand, while also providing additional long-term carbon storage in wood products. Market fundamentals suggest that demand-side policies would outperform tree-planting programs in affording climate benefits.

Wear's comments suggest some issues the Trillion Tree Project will need to face. Overall forestland has been growing in high-income countries, including the United States, for some decades now. There may be situations where preserving habitat will prevent forests from being reduced in size, like preservation of mangrove forests or parts of the Amazon rain forest. But the policy goal here is not just to preserve forests, but to add to them extensively. It may be that if the goal is substantial growth in the size of global forests to increase their function as a carbon sink, thinking about market demand for wood products may be even more important than thinking about preservation and parks.

A version of this article first appeared on Conversable Economist.