For much of human history, the way to make money from a tree was to chop it down. Now, with companies rushing to offset their carbon emissions, there is value in leaving them standing. The good news for trees is that the going rate for intact forests has become competitive with what mills pay for logs in corners of Alaska and Appalachia, the Adirondacks and up toward Acadia. That is spurring landowners to make century-long conservation deals with fossil-fuel companies, which help the latter comply with regulatory demands to reduce their carbon emissions.

For now, California is the only U.S. state with a so-called cap-and-trade system that aims to reduce greenhouse gasses by making it more expensive over time for firms operating in the state to pollute. Preserving trees is rewarded with carbon-offset credits, a climate-change currency that companies can purchase and apply toward a tiny portion of their tab. But lately, big energy companies, betting that the idea will spread, are looking to preserve vast tracts of forest beyond what they need for California, as part of a burgeoning, speculative market in so-called voluntary offsets.

One of the most enthusiastic, BP PLC, has already bought more than 40 million California offset credits since 2016 at a cost of hundreds of millions of dollars. In 2019, the energy giant invested $5 million in Pennsylvania’s Finite Carbon, a pioneer in the business of helping landowners create and sell credits. The investment is aimed at helping Finite hire more foresters, begin using satellites to measure biomass and drum up more credits for use in the voluntary market.  BP has asked Finite to produce voluntary credits ASAP so they can be available for its own carbon ledger and to trade among other companies eager to improve their emissions math. As part of its shift into non-fossil-fuel markets, BP expects to trade offset credits the way it presently does oil and gas.“The investment is to grow a new market,” said Nacho Gimenez, a managing director at the oil company’s venture-capital arm. “BP wants to live in this space.”

Skeptics contend the practice does little to reduce greenhouse gases: that the trees are already sequestering carbon and shouldn’t be counted to let companies off the hook for emissions. They argue that a lot of forest protected by offsets wasn’t at high risk of being clear-cut, because doing so isn’t the usual business of its owners, like land trusts, or because the timber was remote or otherwise not particularly valuable.

If other governments join California and institute cap-and-trade markets, voluntary offsets could shoot up in value. It could be like holding hot tech shares ahead of an overbought IPO. Like unlisted stock, voluntary credits trade infrequently and in a wide price range, lately averaging about $6 a ton, Mr. Carney said. California credits changed hands at an average of $14.15 in 2019 and were up to $15 before the coronavirus lockdown drove them lower. They have lately traded for about $13.

These days, voluntary offsets are mostly good for meeting companies’ self-set carbon-reduction goals. BP is targeting carbon neutrality by 2050. Between operations and the burning of its oil-and-gas output by motorists and power plants, the British company says it is annually responsible for 415 million metric tons of carbon emissions.

Excerpts from Emissions Rules Turn Saving Trees into Big Business, WSJ, Aug. 24, 2020