A generation before David Brower started raising hell at the Sierra Club, a similarly militant scientist named Victor Ernest Shelford organized the Ecological Society of America, becoming its first president in 1916. Shelford stepped down from that position when the Ecological Society of America shied away from taking controversial stands. With a small group of other activist scientists, he formed the Committee for the Preservation of Natural Conditions (1917) and later the Ecologists Union (1946) with the objective of taking "direct action" to protect threatened areas.

For Shelford’s Ecologists Union, "direct action" meant buying threatened areas. The approach proved wildly popular. Today, the Ecologists Union, renamed the Nature Conservancy, spends hundreds of millions of dollars every year putting land under protected status.

But for all its success, the Nature Conservancy is sitting on the sidelines as the biggest ecological catastrophe in human history — runaway global warming — threatens to undo all the progress that the organization has made in its history. That’s tragic, because the Nature Conservancy has both the resources and the expertise to make a difference.

Until now, most efforts to stop global warming have targeted greenhouse gas emissions, in particular emissions from coal, the most carbon-intense and abundant fossil fuel. Some groups have stressed the need for carbon capture and storage technology; others have advocated phasing out coal plants. But another approach that deserves attention is to limit coal at the supply end by placing reserves into some kind of trust.

Logically, limiting coal at the source has one big advantage over controlling emissions. In terms of climate change, it’s not the yearly releases of carbon dioxide that matter, but rather the ultimate amount of carbon dioxide to accumulate in the atmosphere. Merely slowing down emissions is irrelevant if those emissions end up being released over a longer period.

So why hasn’t a "coal conservancy" strategy been developed? One possible reason is that the world’s coal reserves may seem too massive for such an approach to make any difference. After all, conventional wisdom holds that the U.S. alone has a "250-year supply of coal." If that’s true, then moving some coal reserves into trust status would be a fruitless game of Whack-a-Mole in which industry simply shifted to other locations.

At first glance, official reserve figures confirm the conventional wisdom. Such numbers largely originate from the World Energy Council, which provides the data used by other authorities including the International Energy Agency, the U.S. Energy Information Administration, and British Petroleum’s "Statistical Review of World Energy." According to the WEC, the U.S. and Canada indeed have 249.3 billion metric tons of recoverable coal — approximately a 250-year supply at the U.S.’s current rate of consumption of roughly 1 billion metric tons per year. The rest of the world consumes an additional 4 billion tons per year (China accounts for over half of that) and has another 600 billion metric tons of reserves.

A growing body of evidence, however, suggests that the WEC’s estimates of worldwide coal reserves are too high. In 2004, after Germany undertook a close review of its hard coal reserves, official estimates showed an astonishing drop [PDF] from 23 billion tons to 183 million tons, a 99 percent reduction. Similarly, between 1980 and 2004 the United Kingdom reduced its "proved recoverable coal reserves" [PDF] from 45 billion tons to 220 million tons, another 99 percent downgrade.

In 2007, Energy Watch Group, a private research effort initiated by German member of parliament Hans-Josef Fell, completed an analysis of worldwide reserve figures [PDF]. The study concluded that "data quality of coal reserves and resources is poor, both on global and national levels."

A similar conclusion was reported by a blue ribbon panel [PDF] organized under the auspices of the National Research Council and funded by the Office of Surface Mining. The panel concluded that “it is not possible to confirm the often-quoted assertion that there is a sufficient supply of coal for the next 250 years,” noting that “the data that are publicly available for such projections are outdated, fragmentary, or inaccurate.”

A separate analysis by Cal Tech professor Dave Rutledge, borrowing techniques from peak oil analysis, also concluded that official reserve figures are overstated. Rutledge estimated that actual worldwide reserves are 382 billion metric tons, less than half the 847 billion metric tons figure reported by the World Energy Council.

Some climate activists have worried that reports of lowered reserves could encourage complacency on climate. But the implication of this new analysis is really the opposite. Despite the downward revisions, coal reserves are still large enough to push carbon dioxide levels into the danger zone. What changes with the new analysis is the possibility that taking some portion of reserves off the table could actually make a difference on climate change. In other words, the lower the reserves, the more a coal conservancy starts to make sense.

Currently, scores of coal projects in the United States are stymied due to financing problems, lawsuits, and other hangups. For developers who have assembled a package of coal rights only to be thwarted in developing those rights, a fall-back of "donate the coal, take the tax break, and run" might in some cases be a sensible financial strategy.

Private initiatives to place coal in trust status could also help spur a debate over the appropriate disposition of federal coal, which dominates much of coal production in the West, including the massive Powder River Basin mines that produce 37 percent of the nation’s coal. Currently, federal policy encourages coal use by pricing leases very cheaply. From a climate perspective that encouragement is entirely counterproductive, but with the details hidden behind arcane and complex leasing arrangements, the entire issue has remained hidden from view. The attention to reserves that a coal conservancy might generate could lead to a fresh look at federal leasing policy.

A hint at what the federal government could do to protect the climate is shown in Bill Clinton’s executive order creating the Grand Staircase-Escalante National Monument in 1996. At the time, few people realized that the area contained 11 billion tons of economically mineable coal, enough to provide a lifetime fuel supply for 165 coal plants of 500 megawatts each. Now this particular deposit of coal can never threaten to tip the planet into runaway warming.

As the recent "drill, baby, drill" hysteria shows, energy price spikes can lead to rapid loosening of environmental standards. One can imagine a time in the coming decades when regions of coal not currently being mined suddenly become the focus of intense development. For that reason, a smart climate protection strategy would involve placing those areas in trust before the pressure to develop them becomes intense.

Is it certain that a coal conservancy would make a difference? Of course not. But trying it would be a vastly safer and cheaper insurance policy than any of the Buck Rogers geoengineering schemes being floated. Strangely, there’s no evidence that the approach has been even casually studied by those with the capability to make it happen.