Citation:

Fergus, E., J. Lapierre, S. Oliver, N. Skaff, K. Cheruvelil, P. Soranno, K. Webster, AND C. Scott. The Freshwater Landscape: Lake, Wetland, and Stream Abundance and Connectivity at Macroscales. To be Presented at American Water Resources Association, Snowbird, UT, April 30 - May 03, 2017.

Impact/Purpose:

It is recognized that inland water bodies and their surface water connections are active components in the landscape that facilitate both internal processes within systems and the movement of nutrients, contaminants, and organisms across space. But to bring freshwater systems into landscape-level studies, we need to first quantify the abundance of lakes, wetlands, and streams and their surface connectivity characteristics at broad spatial extents. We measured lake, wetland, and stream abundance and surface connectivity attributes at a subcontinental extent in the Midwest and Northeast U.S. to characterize the macroscale patterns of the freshwater landscape. We found that there were distinct spatial patterns among lake, wetland, and stream connectivity that revealed a layer of complexity that abundance measures alone did not capture. The distinct freshwater connectivity spatial patterns observed suggest that ignoring connectivity characteristics in landscape studies would omit unique information on the structural attributes of freshwater systems that are critical to a number of ecological processes and ecosystem health. This study presents a method of quantifying lake, wetland, and stream connectivity over broad spatial extents that does not rely on fine-scale, hydrologic data that are rarely available. In addition, it describes the distribution of freshwater systems based on their surface connectivity characteristics, which can help inform freshwater management and conservation by identifying where system types are found at spatial scales aligned with state and regional management units.

Description:

It is becoming increasingly recognized that inland waterbodies and their surface hydrologic connections are active components in the landscape, influencing multiple ecological processes that can propagate to broad-scale phenomena such as regional nutrient and carbon cycles and metapopulation dynamics. Quantifying the abundance of lakes, wetlands, and streams and their surface connectivity characteristics at broad spatial extents is critical to integrate freshwater systems into macroscale processes. While freshwater abundance of lakes, wetlands, and streams have been estimated separately at regional and global extents, freshwater connectivity attributes have been largely ignored at macroscales, and scientists have a poor understanding of regional to continental patterns of freshwater abundance and connectivity. We measured lake, wetland, and stream abundance and surface connectivity attributes at a subcontinental extent in the Midwest and Northeast U.S. to characterize macroscale spatial patterns of the freshwater landscape. We applied freshwater connectivity metrics that captured aspects of landscape position of freshwater bodies within stream networks to national-scale, freshwater geographic data layers – National Hydrology Dataset and National Wetlands Inventory data. We found that freshwater abundance of lakes and wetlands exhibited spatial patterns that were opposite from stream density and generally followed glaciation extent boundaries. In addition, we found distinct spatial patterns among lake, wetland, and stream connectivity that revealed a layer of complexity that abundance measures alone did not capture. Patterns of freshwater abundance and connectivity in the study extent were associated with underlying hydrogeomorphic, climate, and land use variables, providing insight about potential drivers of freshwater composition and distribution. The distinct freshwater connectivity spatial patterns observed suggest that ignoring connectivity characteristics and only relying on freshwater abundance measures in macroscale analyses omits unique information on the structural attributes of freshwater systems that can be critical to key ecological processes. Understanding patterns of the integrated freshwater landscape including abundance and connectivity measures will further our understanding and management of these systems.

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