Lewis and Clark Bridge Bill to be introduced

It’s said that the map is not the territory.

This statement, say critics, is especially true of the maps created by the U.S. Forest Service to inventory the nation’s largest carbon sinks: its mature and old-growth forests.

In April 2023, under pressure from the Biden administration, the Forest Service completed its first-ever nationwide inventory of mature and old-growth forests found on federal lands. This inventory of older trees is part of an ambitious Biden administration plan to harness the power of our nation’s forests as a nature-based solution to the climate crisis.

The idea is simple: rather than cut older trees down, the Biden administration is proposing we leave many of them standing, allowing them to do what years of scientific research has shown older trees do very well: take climate change-causing carbon out of the atmosphere and store it for long periods of time.

Announced in December 2023, the awkwardly named “Land Management Plan Direction for Old-Growth Forest Conditions Across the National Forest System” has been widely lauded by environmentalists and many scientists as a long-overdue step to help address the nation’s over-sized carbon footprint. The nationwide forest plan is expected to lead to revisions of local forest plans throughout the country, including the Northwest Forest Plan governing Washington, Oregon and sections of northern California.

But whether the nation’s older trees will be enlisted in the fight against climate change and spared the chainsaw could depend on knowing where those trees are.

And that, according to both critics of the Forest Service and the Forest Service itself, is not something the Forest Service’s inventory and mapping can do, because these maps are just not detailed enough to be used for management purposes on a stand-by-stand basis.

A study written by Forest Service scientists and published in August 2023 in the journal Forest Ecology and Management hints at this fact.

The study’s authors write that although the maps they created contain “a high degree of accuracy. … Identifying mature and old-growth forests in a stand management context will likely require additional measurements, adjustments to criteria at local scales, and incorporation of social and traditional knowledge within a consistent definition framework.” In other words, the maps show the forest but not the trees.

The Forest Service’s mature and old-growth inventory used data on trees collected at individual forest plots that are part of the agency’s Forest Inventory and Analysis, a long-term scientific monitoring effort designed by the Forest Service to assess the health of the nation’s forests.

Data from the FIA program goes back decades. These data, and the FIA program generally, are widely respected and used by scientists both in and out of the Forest Service.

Nonetheless, FIA has its limitations, according to Richard Birdsey, retired Forest Service scientist turned senior scientist at the nonprofit Woodwell Climate Research Center. Based in Massachusetts, the Woodwell Climate Research Center funds scientific research related to climate change. Many of its scientists have been critical of the Forest Service and its practices.

“[FIA is] a terrific program and really is a backbone for policies,” says Birdsey. “But it’s a little less effective when trying to monitor what’s happening at smaller scales or at the project scale. And that’s where a lot of public interest is.”

Here’s the problem. While the Forest service has 355,000 FIA plots (on public and private lands) in forests across the United States, the FIA plots themselves are small, covering approximately two-and-half acres each. The plots are also miles away from each other, with one plot every 6,000 acres, or nine square miles, of forested land.

This leaves big gaps in the available data set, gaps that need to be filled with scientific guesswork that has to come from other sources of data.What you get from this is a big picture look at the forest, but not a detailed one. And this, says Birdsey, is exactly what the Forest Service ended up producing in 2023.