2026-07-15 ワシントン大学（UW）
State-level estimates of river length protected by roadless areas where the roadless rule is either the primary (blue) or a contributing (orange) measure of protection. Photo: PLOS/Olden et al.
＜関連情報＞
- https://www.washington.edu/news/2026/07/15/roadless-rule-helps-protect-clean-drinking-water-new-study-shows/
- https://journals.plos.org/water/article?id=10.1371/journal.pwat.0000538
米国における道路建設禁止規則が人々と自然にとって持つ価値を評価する Assessing the value of the U.S. Roadless Rule for people and nature
Julian D. Olden,Sandra L. Postel,Michael P. Dombeck,Helen Kesting,Patrick Freeman,Lise Comte
PLOS Water Published: July 15, 2026
DOI:https://doi.org/10.1371/journal.pwat.0000538
Abstract
For more than a century, forest policy in the United States has recognized the importance of protecting forested watersheds to safeguard water resources. The 2001 U.S. Forest Service Roadless Area Conservation Rule (Roadless Rule) established Inventoried Roadless Areas (IRAs) across approximately 60 million acres of National Forest System lands to sustain high-quality soil, water, biodiversity, and recreational values by restricting road building and commercial timber harvest. Because IRAs are administratively designated rather than legislatively protected, they remain vulnerable to policy reversals. Recent efforts to rescind the Roadless Rule have renewed concerns about potential ecological and economic consequences. Here, we assess vulnerabilities to weakened protections under the Roadless Rule by quantifying the benefits IRAs provide for river protection, clean water provisioning, recreational opportunities, and aquatic biodiversity across the conterminous United States. We find that IRAs protect over 130,000 kms of streams and rivers, representing 2.5% of total river length, and serve as the primary protection mechanism for more than 100,000 kms of rivers (1.9%) when accounting for other regulatory and conservation frameworks. These protections are geographically widespread and particularly important in regions with limited alternative safeguards. IRA-influenced watersheds supply drinking water to at least 25 million Americans, with several states sourcing water for over one-third of their populations from these areas. Proximity of National Forests to urban centers amplifies these benefits, even in states with relatively small IRA extents. In addition, IRA-protected watersheds overlap substantially with high-demand hunting and fishing areas and support diverse aquatic biodiversity. Our results demonstrate that rescinding the Roadless Rule would diminish protections for rivers, and may compromise drinking water quality and affordability, reduce recreational opportunities, and threaten freshwater biodiversity. Safeguarding Roadless Rule protections is therefore essential for sustaining ecosystem services, supporting human well-being, and advancing broader conservation and resilience goals under increasing climatic and land-use pressures.
