Climate & Refugia

Forests cool the ground beneath them. Under an intact forest canopy, ground-level temperatures during the hottest part of the day average roughly 4°C cooler than in open areas — and during heatwaves, the difference can exceed 5°C, with peak differences as high as 11°C documented in some studies. The cooling effect comes from canopy shade, transpiration, and the deep, moist soils that intact forests build over centuries. This is not metaphor: forests function as physical air conditioners for the species and ecosystems beneath them, including for streams that stay cold because the forest above them blocks the sun (Schnabel et al. 2025; Wang et al. 2025; Xu et al. 2022).

The cooling matters because the species and ecosystems that depend on it are already under climate pressure. Cold-water fish — bull trout, native cutthroat, salmon — depend on cold headwater streams that are becoming rarer as overall stream temperatures rise. Studies of the western U.S. show that under modest warming scenarios, the cold-water habitat that salmonids need could be reduced to less than 13 percent of current stream networks (Isaak & Young 2023). Species also need to move — northward, upslope, upstream — to track shifting climate conditions. Roadless areas, with intact forest cover, unbroken elevation gradients, and headwater streams that remain cold, function as climate refugia: the places where species can persist while the broader landscape warms. Researchers describe these refugia as one of the largest hopes for population persistence under climate warming (Morelli et al. 2016; Gibson et al. 2026).

The Notice of Intent that proposed rescinding the Roadless Rule cites "growing impacts of extreme wildfire, drought, and insect and disease infestations" as justification for increased road access and active management. The research points the other way. Intact forests buffer microclimate temperatures — the buffering capacity is highest in warm and dry years, precisely when species need it most (Thom et al. 2020). Protected forests warm at rates up to 20 percent slower than the surrounding landscape (Xu et al. 2022). Once forests are fragmented by roads, that buffering capacity declines: clearcuts can take 30 years to recover their pre-harvest cooling effect, and edge effects penetrate 20 meters or more into adjacent forest (Starck et al. 2025; Ewers & Banks-Leite 2013). The roadless condition is not what makes these lands vulnerable to climate stress. It is what makes them resilient to it.