Payments for Ecosystem Services
Ecosystems such as rivers, forests, grasslands and wetlands benefit society through the ecosystem services they provide: water purification, improving air quality, and flood protection, among other benefits. However, these services are frequently left out of resource management decisions because they aren’t easily quantified or assigned a monetary value. As a result, society undervalues the environmental benefits provided by these ecosystems and contributes to the loss of natural systems. Environmental markets can help to mitigate this by providing incentives to preserve ecosystems and the services they provide.
USDA Resources
Forests, Water and People Analysis
From Forest to Faucet: Drinking Water as an Ecosystem Service
Caring for Our Natural Assets: An Ecosystem Services Perspective
NRCS Landscape Conservation Initiatives
Conservation Effects Assessment Project (CEAP)
NRE Analysis on Natural Resources and Environment Issues
"The Use of Markets to Increase Private Investment in Environmental Stewardship"
Nitrogen in Agricultural Systems: Implications for Conservation Policy
Data and Modeling for Environmental Credit Trading
Other Resources
RFF: "Ecosystem Services: Quantification, Policy Applications, and Current Federal Capabilities" 
Draft Federal Inventory of Ecosystem Services Research and Policy
Ecosystem Services: A Guide for Decision Makers
Creating Markets for Ecosystem Services: Notes from the Field
CRS: Provisions Supporting Ecosystem Services Markets in US Farm Bill Legislation