“Green infrastructure” is the umbrella phrase for describing the natural features - river corridors, vegetation, open space areas - that provide us with important services such as water supply, water filtration, flood control, erosion control, carbon sequestration, air quality improvement, and more. These services are often referred to as “ecosystem services” or “environmental services.” The green infrastructure concept highlights the fact that these services have real value to us both in economic and ecological terms. They are as much a part of our infrastructure needs as the built infrastructure that we create, such as sewage treatment plants.