At the World Economic Forum in Davos last month, President Donald Trump declared that “the United States will join One Trillion Trees Initiative.” He reaffirmed this commitment during the State of the Union address, calling the initiative “an ambitious effort to bring together government and private sector to plant new trees in America and all around the world.”

The people behind the initiative argue that planting vast numbers of trees is “an important part of solving the global climate crisis.” By absorbing globe-warming carbon dioxide from the air, these trees will help slow down man-made climate change. This is the chief rationale for pursuing the initiative, yet the president has so far failed to acknowledge it. There’s a puzzle for you.

At any rate, this week Rep. Bruce Westerman (R–Ark.) introduced the Trillion Trees Act. This legislation forthrightly notes that “one trillion new trees globally would sequester a significant amount of atmospheric carbon and constitute a pragmatic step towards addressing global carbon emissions.” In the press release promoting the bill, Westerman states, “I challenge anyone to find a better climate solution than taking care of our forests.” Bill co-sponsor Rep. Steve Stivers (R-Ohio) hailed the Act as offering “a powerful solution to combat our changing climate.”

The inspiration for the initiative was a July 2019 study in Science by a team of Swiss researchers. They calculated that there is enough land in the world to accommodate 1.2 trillion more trees. (The current total is about 3 trillion.) Planting that many new trees would significantly cool the earth by taking about 25 percent of the carbon dioxide that is currently in the atmosphere and sequestering it in growing trees.

How much would Westerman’s bill actually contribute to the global initiative? Not much. Notably, Westerman’s bill sets no time limit on achieving the trillion-tree goal, but the press release describes the act as “legislation would plant 1 trillion trees globally by 2050.”

The act explicitly incorporates carbon sequestration goals into several existing federal forest management programs, such as the Healthy Forests Restoration Act of 2003 and the National Forest Foundation. The only funding explicitly mentioned in the bill is a boost to the annual appropriations for the Reforestation Trust Fund (moving it from $30 million to $60 million) and an extra $25 million for carbon sequestration activities under the Cooperative Forestry Assistance Act. The bill also offers an unspecified tax credit as an incentive to sequester carbon by using wood as a building material.

With respect to meeting global goals, the bill urges the administrator of the United States Agency for International Development to consider creating an International Forest Foundation. This nonprofit would accept and administer private donations for reforestation and forest preservation efforts that seek to sequester carbon dioxide emissions. Just why the federal government should be involved in creating such a nonprofit when scores of private organizations are already working on international forestry projects is not immediately evident. Basically, the idea amounts to a bit of handwaving toward what the bill refers to as “international engagement.”

If we charitably assume that our representatives are serious about meeting the trillion-tree goal, what amount of land and funding would be necessary? A January report from the World Resources Institute (WRI) calculates that as many as 330 million acres of American land (an area roughly three times the size of California) could be devoted to planting 60 billion additional trees over the next 20 years or so. That would involve reforesting 53 million acres by planting 21 billion trees; increasing tree density in existing forests with 24 billion new trees on 165 million acres; and integrating 16 billion trees into croplands, pastures, and urban areas comprising 113 million acres. By 2050, these renewed forests would be sequestering about 540 megatons of carbon dioxide annually, which is a bit more than a tenth of current U.S. emissions.

The WRI analysts estimate that the cost (in tax credits or direct payments) of planting 60 billion trees in the U.S. over the next 20 years would amount to $4 to $4.5 billion per year. Reforestation costs by one estimate range between $100 to $450 per acre, which would yield annual costs of $1.5 to $6.75 billion for planting trees on 15 million acres, so WRI’s figures are in the ballpark. In comparison, the total funding of $55 million mentioned in the Trillion Trees Act would be enough to plant between 125,000 to 555,000 acres annually. Assuming 400 trees per acre, the level of funding contemplated in the Trillion Trees Act would, at maximum, be enough to plant 220 million trees each year. That sounds like a lot, but at that rate it would take more than 250 years to plant 60 billion trees.

The American Energy Alliance, a pro-market energy advocacy group, has dismissed Westerman’s proposal as a Republican “climate messaging exercise.” That sounds about right. As written, the bill certainly does not amount to a “powerful solution to combat our changing climate.”