Zooming Out: Methods and Future Directions in Landscape-Scale Functional Assessment of Inland Wetlands

Wetlands play a vital role in supporting hydrologic, biogeochemical, and ecological processes across landscapes, yet understanding and quantifying their functional contributions at large spatial scales remains a challenge. In response to increasing demand for regional and national assessments, a growing number of methods have emerged that estimate wetland function using widely available geospatial data. This systematic review describes and evaluates currently available approaches to quantifying wetland function at landscape scales and highlights key lessons for future assessments. We identify two primary methodological categories: classification-based approaches, such as hydrogeomorphic (HGM) and LLWW (Landscape Position, Landform, Water Flow Path, Waterbody Type) frameworks, which assign functional scores based on mapped wetland class; and indicator-based approaches, which derive metrics or indices directly linked to functional processes using remote sensing and other spatial data. Across both, we find that validation against field data remains limited, habitat functions are consistently the most difficult to assess, and that many assessments estimate only the potential of wetlands to perform specific functions rather than how they are actually functioning under current landscape conditions. At the same time, advances in high-resolution remote sensing, automation, and ecological modeling are creating new opportunities for more scalable, repeatable, and functionally relevant assessments. Hybrid approaches that bridge classification and indicator methods, and that integrate land-use and disturbance metrics, represent a promising path toward national-scale functional assessments. Together, these findings point to a way forward for producing wetland functional assessments that are both scientifically rigorous and actionable for conservation and policy. This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Water and Life > Conservation, Management, and Awareness Science of Water > Water and Environmental Change.