The chief scientific adviser to the United Nations’ Trillion Tree Campaign, Thomas Crowther, is urging an end to the planting. The promised green revolution turns out to be more complicated than sowing new forests and may be better advanced by lumberjacks firing up their chainsaws.

Mr. Crowther headlined a study in 2019 estimating that the earth had room for another 1.2 trillion trees. Its authors called “global tree restoration” the “most effective climate change solution to date.” But the promised reduction of CO2 has failed to materialize. Instead, emissions have risen.

In his 1971 book, “The Lorax,” Dr. Seuss’s titular character presumes to “speak for the trees” and promoted a message of childlike simplicity: Trees are good; so, more trees are better. Oaks, maples, and spruce soon stopped being seen as a crop to be nurtured and harvested like any other.

One example will emerge over the coming weeks as Americans begin hauling to the curb the 25 to 30 million natural Christmas trees they trimmed. The ritual often comes with pangs of guilt of the sort that led President Theodore Roosevelt to ban pines from the White House yuletide.

Upon deeper analysis, the Christmas tradition rests on an industry of farms nurturing 350 million trees in America alone. Once discarded, the trees serve ecological purposes, such as strengthening eroding coastlines. Each year, New Jersey’s Island Beach State Park collects hundreds of trees to build up dunes by trapping sand.

“Increased electric car adoption” and “large-scale solar and wind farms,” the Wall Street Journal reported in November, will also require more felling of trees, because America is “going to need a whole lot more power poles in the near future” to upgrade power grids.

Despite these realities, Joyce Kilmer’s poem beginning, “I think I shall never see a poem as beautiful as a tree” was written about the living variety, not dead ones. When Mr. Crowther promised that planting more could save the earth, his solution was just too romantic — and easy — to dismiss.

Those who warned in 2019 that the Trillion Tree Campaign was a waste of money that would fall far short of promised carbon capture were ignored. Across the globe, people started digging and oil companies funded forestry to offset their emissions.

The Tesla chief executive, Elon Musk, donated $1 million to plant 20 million saplings. Politicians from Vice President Gore to President Trump supported the idea. In November, the New York City Council pledged to plant 250,000 trees by 2035. 

Now, Mr. Crowther, an ecologist, is asking everyone to put their shovels and spades back in the shed. “If no one had ever said, ‘Plant a trillion trees,’” he told the UN’s COP28 Climate Change Conference in Dubai last month, “I think we’d have been in a lot better space.”  

Mr. Crowther’s latest study, published by Nature in November, pruned the hopes of all those modern Johnny Appleseeds. “Forests are a substantial terrestrial carbon sink,” though not a permanent solution, it said, and “anthropogenic changes in land use and climate have considerably reduced the scale of this system.” 

Indeed, the global climate has complex dynamics, influenced by the wildcard of human activity. By giving companies and governments a way to “greenwash” their emissions, the Trillion Tree Campaign has become, Mr. Crowther said, “an excuse to avoid cutting emissions.”

Last January, an investigation by the Guardian, Die Zeit, and SourceMaterial, found “more than 90 percent of rainforest carbon offsets by biggest certifier are worthless.” The company awarding the credits, Verra, is used by Shell, Disney, and others to bolster their green credentials.

Mr. Crowther said at Dubai that without the UN scheme, “maybe there wouldn’t have been so much noise and attention on nature, so that all the very responsible scientists who are here could correct it and turn it into something that is good.”

Like Mr. Crowther, doing good for the earth was the aim of Roosevelt, Kilmer, and Seuss. Now it turns out that the goal of a more sustainable future may be best served by ignoring the Loraxes who claim to speak for the trees and shouting, “Timber!”