Isolating Anthropogenic Wetland Loss by Concurrently Tracking Inundation and Land Cover Disturbance across the Mid-Atlantic Region, U.S.

Melanie K Vanderhoof,Jay Christensen,Christine Mazzarella,Megan W Lang,Yen-Ju G Beal,Nora Hwang,John W Jones,Ben Devries

doi:10.3390/rs12091464

Abstract

Global trends in wetland degradation and loss have created an urgency to monitor wetland extent, as well as track the distribution and causes of wetland loss. Satellite imagery can be used to monitor wetlands over time, but few efforts have attempted to distinguish anthropogenic wetland loss from climate-driven variability in wetland extent. We present an approach to concurrently track land cover disturbance and inundation extent across the Mid-Atlantic region, United States, using the Landsat archive in Google Earth Engine. Disturbance was identified as a change in greenness, using a harmonic linear regression approach, or as a change in growing season brightness. Inundation extent was mapped using a modified version of the U.S. Geological Survey’s Dynamic Surface Water Extent (DSWE) algorithm. Annual (2015–2018) disturbance averaged 0.32% (1095 km2 year−1) of the study area per year and was most common in forested areas. While inundation extent showed substantial interannual variability, the co-occurrence of disturbance and declines in inundation extent represented a minority of both change types, totaling 109 km2 over the four-year period, and 186 km2, using the National Wetland Inventory dataset in place of the Landsat-derived inundation extent. When the annual products were evaluated with permitted wetland and stream fill points, 95% of the fill points were detected, with most found by the disturbance product (89%) and fewer found by the inundation decline product (25%). The results suggest that mapping inundation alone is unlikely to be adequate to find and track anthropogenic wetland loss. Alternatively, remotely tracking both disturbance and inundation can potentially focus efforts to protect, manage, and restore wetlands.

Highlights

Across the globe, wetlands provide a myriad of ecosystem services including flood abatement, erosion control, hydrologic regulation, carbon sequestration, and water quality improvement [1,2,3]
The study was limited to the U.S Environmental Protection Agency (EPA) Region 3, which extends across the Mid-Atlantic region of the United States, including Pennsylvania, Delaware, Maryland, Washington, D.C., Virginia, and West Virginia
In comparing Landsat ETM+ and Operational Land Imager (OLI) inundation extent relative to the inundation extent derived from processed WorldView-2, 3 imagery, errors of omission for inundation (17.5% and 18.7%, respectively) were larger than errors of commission for inundation (0.9% and 4.3%, respectively) (Table 3)

Summary

Introduction

Wetlands provide a myriad of ecosystem services including flood abatement, erosion control, hydrologic regulation, carbon sequestration, and water quality improvement [1,2,3]. Even in countries such as the United States, which has a national policy of no net loss of wetlands, mitigating losses through wetland creation and restoration can fall short, resulting in net wetland degradation and declines in wetland area [8,9]. These trends make it essential to monitor wetland extent over time, as well as enhance our understanding of the causes and spatial distribution of wetland loss and gain

Objectives

Methods

Results

Discussion

Conclusion