Lost on the Pacific Crest Trail: a 4,270 km survey of wilderness waste distribution and characteristics

Mismanaged waste threatens the environment and human health. To better understand waste sources and impacts along recreation trails, we surveyed the entire 4,270 km Pacific Crest Trail, conducting 251 waste surveys (1 km every 16 km). Surveys counted and classified waste within 2 m of the trail. We estimated that there were 53,000 pieces (12,000-130,000) of waste along the trail in 2023, based on a mean count of 12.5 pieces per km. Waste count had a negative log-log linear relationship with distance to the nearest road. Far in the backcountry (survey start 10 km from a road), waste was sparse (0.4 pieces per km), but close to roads (10 m from a road), waste increased to 13 pieces per km. The most common material types were soft plastic (36 %), metal (11 %), and sanitary waste (10 %). The most common morphologies were fragments (47 %), package ends (7 %), and wipes (6 %). Brands visible on waste were rare (48 pieces). We assessed the bias of this survey method, showing that it underestimated waste counts by 50 % compared to conducting the survey twice or with twice the number of surveyors. Surveying trail sections with snow cover or at night also reduced observed counts. These findings suggest that cleanup near roads, waste handling education, reduced plastic use, and innovation from outdoor consumer product producers could reduce trail waste. We propose that a baseline value of 0.4 pieces per km should be a waste management target to achieve for all spaces.