Indicators of the effects of climate change on freshwater ecosystems
Freshwater ecosystems, including lakes, streams, and wetlands, are responsive to climate change and other natural and anthropogenic stresses. These ecosystems are generally hydrologically connected with one another and with the landscapes around them, integrating changes that occur in their watersheds. The responses of any given freshwater ecosystem to climate change depend on the magnitude of climate forcing, interactions with other anthropogenic and natural changes, and the characteristics of the ecosystem itself. Therefore, the magnitude and manner in which freshwater ecosystems respond to climate change is not straightforward. Here, we present a conceptual framework describing how freshwater ecosystems are altered by climate change. Using this framework, we identify a suite of potentially valuable indicators of the response of freshwater ecosystems to climate change, discuss their potential value and limitations, and identify the availability of associated measurements. Indicators are organized in three inter-related categories: hydrologic, water quality, and biological structure and function. The compiled suite of indicators includes both those with substantial high quality records as well as those for which only limited data exist; all represent metrics that will address important scientific and management needs. Together, these indicators provide input for the 4th National Climate Assessment report and enable more informed decision making on how climate change is altering freshwater ecosystems.