Ecosystem Integrity

Intact forests do work. They filter water through layers of duff and root structure, releasing it to streams cold, clear, and slowly. They cool the ground beneath them and the air above. They store carbon in living trees, fallen logs, and the deep organic soils that take centuries to develop. They support food webs that depend on the relationships between predators and prey, fungi and roots, pollinators and plants — relationships that exist only when all the components are present. Roadless areas across the National Forest System are among the last large places in the contiguous United States where these systems still function with relatively little human modification. Researchers describe primary forests — those with the least disturbance history — as having "the most developed dissipative structures, the highest levels of ecosystem processes, greater stability and recovery, and thus greater resilience and the lowest risk of loss and damage" (Rogers et al. 2022).

Fragmentation breaks these systems apart. A synthesis of habitat fragmentation studies spanning multiple biomes and continents found that fragmentation reduces biodiversity by 13 to 75 percent across studied ecosystems, with effects strongest in the smallest and most isolated fragments and intensifying over time. Globally, 70 percent of remaining forest is now within one kilometer of an edge — close enough that the buffering, cooling, and habitat-providing functions of intact interior forest are compromised. Fragmentation also impairs core ecosystem functions: reduced biomass, altered nutrient cycles, less carbon storage, less water retention (Haddad et al. 2015; Pardini et al. 2010). What's lost in a fragmented forest is not just species — it is the functioning of the system that the species were part of.

Roadless areas matter to ecosystem integrity in two ways. They retain the functioning systems that fragmented landscapes have lost. And they serve as reference landscapes — places where researchers can observe what intact systems actually do, providing the baseline against which degradation elsewhere is measured. Watersheds with the highest ecological integrity scores in the National Forest System tend to be dominated by wilderness and roadless area; watersheds with the lowest scores tend to have moderate road density and little roadless cover. Roadless areas also enhance the broader protected-area network by buffering existing protected areas from external disturbance and connecting them to each other across the landscape (Talty et al. 2020; USDA Forest Service 2000).