Climate Driven Deforestation of the Coastal Forested Wetlands on the North Atlantic and Gulf of Mexico Coastal Plains

Abstract:

Coastal forested wetlands (CFWs) provide critical ecosystem services as part of the coastal wetland mosaic. CFWs are sensitive to changes in coastal hydrologic management, saltwater intrusion (SWI), and sea level rise (SLR), with synergistic effects being potentially more damaging. Prior research give insight into the area and rate of CFW loss. However, those research efforts are often field-based and lack scalability. Crucially, there is a lack of regional quantification of rate and areal loss of CFWs. Further, understanding the fate of lost CFWs is still incomplete. Here we used remotely sensed data to assess the fate and quantify the rate and areal loss of CFWs along the North Atlantic Coastal Plain (NACP) and northern Gulf of Mexico (nGOM) from 1996 to 2010. We used NOAA Coastal Change Analysis Program (C-CAP) data, which are Landsat-based classified maps, and the USGS Hydrologic Unit Code (HUC) level 2 boundaries (subregions). Google Earth Engine and R were used to process and analysis the pre-classified data.

Across the entire study region CFW totaled 151,797 km² in 1996, however 17,841 km² (12%) were lost during 1996-2010 (1,274 km²/yr). Individually, the NACP (70,722 km² in 1996) and nGOM (72,450 km² in 1996) also experience significant loss amounting to 9416 km² (673 km²/yr) and 8278 km² (591 km²/yr), respectively. The top 10 (of 50 relevant) HUC subregions, ranked by total area lost, comprised 72% (12,778 km²) of the total losses. These 10 subregions originally represent only 50% (76,225 km²) of the total area of CFWs. The fate of lost CFWs ended in either palustrine scrub/shrub or marsh 69% of the time. The similar rates of loss for the NACP and nGOM indicate that the issue is not region-specific or driven by a local phenomenon. It is likely that the combined effects of SWI and SLR (SWISLR) are driving the changes across the regions. These data also indicate that at the current rate of loss, CFW may no longer exist early into the next century. There is a significant cause for concern that the rate determined here may accelerate due to worsening SWISLR, more frequent and severe hurricanes, and anthropogenic modification of coastal hydrology and landscapes. More detailed and present-day study needs to be completed to see if the rates of loss are staying consistent and if new hotspots of change are noticeable.