Predicting the Presence of Groundwater-Influenced Ecosystems in the Northeastern United States with Ensembled Models

Globally, groundwater-influenced ecosystems (GIEs) are increasingly vulnerable to groundwater extraction and land use practices. Groundwater supports these ecosystems by providing inflow, which can maintain water levels, water temperature, and the chemistry necessary to sustain the biodiversity that they support. Many aquatic systems receive groundwater as a portion of baseflow, and in some systems, the connection with groundwater is significant and important to the system's integrity and persistence. There is a lack of information about where these systems are found and their relationships with environmental conditions in the surrounding landscape. Additionally, groundwater management for human use often does not address maintaining the ecological functions of GIEs. We used correlative distribution modeling methods (GLM, GAM, MaxEnt, Random Forest) to predict landscape-scale habitat suitability for GIEs in two ecologically distinct ecoregions (EPA Level II ecoregions: Atlantic Highlands and Mixed Wood Plains) in the northeastern United States. We evaluated and combined the predictions to create ensemble models for each ecoregion. The accuracy of the ensemble models was 75% in the Atlantic Highlands and 86% in the Mixed Wood Plains. In the Mixed Wood Plains, hydric soil, surface materials, and soil permeability were the best predictors of GIE presence, whereas hydric soil, topographic wetness index, and elevation were the best predictors of GIE presence in the Atlantic Highlands. Approximately 1% of the total land area in each ecoregion was predicted to be suitable for GIEs, highlighting that there likely is a small proportion of the landscape occupied by these systems.