Pilot Analysis of Global Ecosystems: Freshwater Systems

Abstract

The constant cycle of water between the oceans, atmosphere, and land sustains life on Earth. All organisms on the planet need water to survive. Without water, microorganisms that decompose organic matter could not exist, interrupting the ecological loops of matter and energy and shutting down all ecosystems. Freshwater systems are created by water that enters the terrestrial environment as precipitation and flows both above and below ground toward the sea. These systems encompass a wide range of habitats, including rivers, lakes, and wetlands, and the riparian zones associated with them. Their boundaries are constantly changing with the seasonality in the hydrological cycle. Their environmental benefits and costs are distributed widely across time and space, because of the complex interactions between climate, surface water and groundwater, and coastal marine areas. This analysis concentrates on the terrestrial water that is most accessible to humans: the water in rivers, lakes, and wetlands. Humans also rely heavily on groundwater, which is the only source of fresh water in some parts of the world. However, this paper will not focus as extensively on groundwater, in part because the data on this resource are scarce.