4: Natural Resources and Environmental Systems Last updated Save as PDF Page ID 46887 Nicholas M. Holden, Mary Leigh Wolfe, Jactone Arogo Ogejo, & Enda J. Cummins University College Dublin and Virginia Tech via Virginia Tech Libraries' Open Education Initiative 4.1: Water Budgets for Sustainable Water Management 4.2: Water Quality as a Driver of Ecological System Health 4.3: Quantifying and Managing Soil Erosion on Cropland 4.4: Anaerobic Digestion of Agri-Food By-Products 4.5: Measurement of Gaseous Emissions from Animal Housing