Indicators of the effects of climate change on freshwater ecosystems

Abstract

Freshwater ecosystems, including lakes, streams, and wetlands, are responsive to climate change and other natural and anthropogenic stresses. These ecosystems are frequently hydrologically and ecologically connected with one another and their surrounding landscapes, thereby integrating changes throughout 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 difficult to predict a priori. We present a conceptual model to elucidate how freshwater ecosystems are altered by climate change. We identify eleven indicators that describe the response of freshwater ecosystems to climate change, discuss their potential value and limitations, and describe supporting measurements. Indicators are organized in three inter-related categories: hydrologic, water quality, and ecosystem structure and function. The indicators are supported by data sets with a wide range of temporal and spatial coverage, and they inform important scientific and management needs. Together, these indicators improve the understanding and management of the effects of climate change on freshwater ecosystems.

Figure 1.

Conceptual model highlighting how freshwater ecosystems are impacted by climate change. Indicators of the effects of climate change are organized into three categories: hydrologic, water quality, and ecosystem structure and function indicators. Climate-driven changes in these indicators, in turn, have implications for various sectors of society. Note all effects have associated feedbacks represented by the double-ended arrows.

Figure 2.

Data availability (K, thousands of sites) and geographic coverage through the USGS and EPA Water Quality Portal (https://www.waterqualitydata.us/). Orange and blue lines and mapped locations indicate sites with at least 10 and 25 years of data, respectively as of August, 2021. See text for more details on data availability, including data availability from other sources.