OOS 64-2 - Lichen and moss bioindicators of air quality in the U.S. Forest Inventory: from forests to high elevation wilderness and urban neighborhoods

Air monitoring networks are too widely spaced to capture air quality at sub-regional scales, creating demand for higher resolution data to inform land and air management decisions. Lichens and mosses absorb their water and nutrients from the atmosphere, leading to the accumulation of pollutants in their tissues as well as predictable shifts in species composition, making them effective bioindicators for understanding air quality at finer spatial scales. Since 1989, the U.S. Forest Service’s Forest Inventory and Analysis and Air Resources Management Programs have collected over 10,000 standardized epiphytic lichen community surveys across the U.S., making it the largest such inventory in the world. These surveys are widely used by federal land managers and others to monitor how nitrogen and sulfur-based pollutants affect forest health. Even small enhancements of these pollutants can harm ecologically important lichen functional groups linked to wildlife use and nutrient cycling. Management tools based on the community surveys, such as ‘critical loads’, are increasingly utilized in environmental planning and decision-making on forest land. However, the core lichen inventory didn’t support inquiries about other pollutants or areas where epiphytic communities are poor or non-existent, like high elevation wilderness or urban forests. To address this, we report on two case studies exploring the use of low-cost chemical assays of lichen and moss tissue as alternatives, including: 1) a pilot using saxicolous (rock-dwelling) lichens to map levels of nitrogen, sulfur, and heavy metals, in the high Sierra Nevada range in California, and 2) a study using a stress-tolerant moss to map heavy metals in industrial-adjacent neighborhoods in Seattle, Washington, with known environmental justice concerns. We discuss new opportunities and challenges created by this research, including a role for civic science and community engagement in data collection and, potentially, broader participation in the research process itself.