---
id: articles/why-no-one-knows-old-growth
about:
  label: Why no one knows exactly how much old-growth forest we have left
  description: >-
    Columbia Insight report by Nathan Gilles on the US Forest Service's first
    national inventory of mature and old-growth forest, and why its maps are too
    coarse to find a single stand.
  tags:
    - forests
    - old growth
    - inventory
    - lidar
    - mapping
    - resolution
article:
  url: >-
    https://columbiainsight.org/why-no-one-knows-how-much-old-growth-forest-we-have-left/
  published: '2024-04-18'
  publisher: Columbia Insight
  authors:
    - Nathan Gilles
domains:
  - ecology
  - places
provenance:
  origin: agent
  sources:
    - title: >-
        Why no one knows exactly how much old-growth forest we have left -
        Columbia Insight
      url: >-
        https://columbiainsight.org/why-no-one-knows-how-much-old-growth-forest-we-have-left/
    - title: >-
        Why no one knows exactly how much old-growth forest we have left - Wild
        Heritage
      url: >-
        https://wild-heritage.org/why-no-one-knows-exactly-how-much-old-growth-forest-we-have-left/
  created: '2026-10-20'
  reviewed: '2026-10-20'
  reviewed_by: 'Claude, from the sources listed'
  status: draft
---
The report appeared in 2024. The inventory covered federal land.[^1] An executive order from the Biden administration in April 2022 directed it, and the agency completed it in April 2023.[^1] It was meant to support a plan to leave older trees standing as carbon stores.[^1] The maps show the forest but not the trees. They give one classification per "fireshed" of about 250,000 acres.[^1] As the conservation director of Oregon Wild puts it in the piece, they give a total picture of the volume but cannot identify any particular stand of old growth anywhere.[^1]

The inventory rests on the Forest Inventory and Analysis program, a long-running set of about 355,000 field plots across the country. Each is around two and a half acres, spaced roughly one per 6,000 acres of forest.[^1] A retired Forest Service scientist now at the Woodwell Climate Research Center says those plots are adequate for a state or a group of national forests. For a typical old-growth stand they are too sparse.[^1]

The Forest Service official whose team oversaw the inventory says the agency did not want to create the impression that it knew exactly where the clumps of old forest were. Being wrong about a specific small area could lead to disputes, the official says, and fine-grained mapping should happen locally.[^1] The agency estimates that old growth covers 17 percent of the federal land inventoried and mature forest 45 percent.[^1]

The open question is where the old growth is, stand by stand, inside each 390-square-mile block. The Forest Service says it is exploring GEDI to close that gap.[^1] GEDI is a NASA-led lidar instrument on the International Space Station; lidar measures distance with laser pulses, which can give the height of a forest canopy. Its project lead is a professor at the University of Maryland.[^1] It had been used to map old growth in Australia but not in this inventory.[^1] At the time of writing, according to the Forest Service official, it was being stowed to make room for a Department of Defense project.[^1] Whether and when the Forest Service would use it was unclear.[^1]

Wild Heritage, a project of the Earth Island Institute, reposted a summary of the article on 12 December 2024 under its mapping and mature-and-old-growth tags.[^2] The summary repeats that the coarse maps cannot identify specific stands and that GEDI remained inactive.[^2]