Changes in nitrogen (N) levels in soils, air, and water affect the benefits people derive from ecosystems. These benefits, known as ecosystem services, fall into the four categories of provisioning, regulating, cultural, and supporting services. In this chapter we examine ecosystem services that are known to be affected by nitrogen levels and management activities, with a focus on those that are relevant to California. The five sections of this chapter address the central role of N in food production and agriculture (Section 5.1); how N affects the ecosystem goods of clean drinking water and clean air (Sections 5.2 and 5.3); the regulating service that N provides in maintaining a stable climate (Section 5.4); and the cultural and spiritual values that N affects, most notably how excess N alters biodiversity in terrestrial and aquatic ecosystems, changing the way humans interact with and enjoy nature (Section 5.5).