Ecosystem Service
Benefits people derive from ecosystem. Ecosystem services are typically grouped in four broad categories: provisioning, such as the production of food and water; regulating, such as the control of climate and disease; supporting, such as nutrient cycles and crop pollination; and cultural, such as spiritual and recreational benefits. (Source: Wikipedia)
Elastic (goods and services)
Elastic goods and services generally have plenty of substitutes. Inelastic goods have fewer substitutes and price change doesn't affect quantity demanded as much. Some inelastic goods include gas, electricity, water, drinks, clothing, tobacco, food, and oil.
Payment for Environmental Services (PES)
Payments to farmers or landowners who have agreed to take certain actions to manage their land or watersheds to provide an ecological service. As the payments provide incentives to land owners and managers, PES is a market-based mechanism, similar to subsidies and taxes, to encourage the conservation of natural resources.