The Hackensack River Estuary is a complex tidal ecosystem in Northern New Jersey once known as one of the most polluted water course in the United States. This legacy has significantly impaired the ecological function of some 8,300 acres of remaining tidal wetlands. The main factors driving this impairment are tide restricting structures, high levels of contaminates in the sediments, the continuous influx of nutrients from sewage treatment plants and permitted combined sewer outflows, invasive species, habitat fragmentation, alterations in the hydrology and the filling of wetlands. This study measured physical and ecological impairments of seven wetlands to create an objective evaluation system to priorities the sites for wetland acquisition, wetland preservation, wetland enhancement, and natural resources management.
Results/Conclusions
The study compared minimally impacted, degraded and ecologically enhanced wetlands to test the developed impairment metrics and compare the marshlands. Plant species composition and abundance including the presence of invasive species provided excellent indicators of habitat degradation. Aspects of tidal inundation and overall hydrology acting on sites such as stage duration and frequency, flood and ebb velocities, and hydraulic duty; were deemed to be good measurable integrative factors that helped illustrate degrees of impairment. Finally, microtopography, vegetation patterns, habitat fragmentation, and connectivity, as well as proximity to legacy land uses such as landfills contributed substantially to the assessment of levels of wetland impairment. According to the developed impairment metrics the enhancement site scored highest, followed by the minimally impacted wetlands and the degraded marshlands.