Surely among the most predictable questions asked about the Hudson River are: what is its current state? And, given its historical reputation for being polluted, is it improving?
To provide answers, we face the question of which metrics to use, i.e., how do we establish a scoring system that reliably characterizes the Hudson's environmental condition and trajectory? This is not a trivial problem. The indicators chosen should represent the system in question and not geographically broader effects, should encompass its full breadth at numerous physical and biological levels, and should be sensitive to both gradual and episodic environmental impacts.
The New York-New Jersey Harbor Estuary Program tackled this issue with a report issued in 2003
that found nine of twenty-four proposed environmental indices showing improvement, including sedimentloading, benthic communityhealth, contaminant loadings, and the areal extent of shellfish beds. But meanwhile, harmful algal blooms were on the rise and abundances of some important resource species were on the decline. Other indicators, such as abundances of striped bass, forage fish, and winter flounder revealed no appreciable changes. On the whole, the weight of the evidence is positive, particularly indicators of toxic substances,butbiologicalresources are stillinneed of upgrading.
Perhaps the most exciting results reported in this volume involve the great progress made in relating ecosystem processes to environmental change and human efforts at environmental restoration. The chapter on the benthic communities of New York Harbor (Chapter 18) shows a clear recovery over decades in response to reductions of contaminant inputs. The clean up of Foundry Cove has removed the major source of metal pollution to the Hudson, which will decrease trophic transfer of metals through food webs (Chapter 30). Follow through on current plans to dredge PCB hotspots should have similar effects for this contaminant (Chapters 24, 25), the limiting factor for unfettered consumption of Hudson River finfish.
Radically improved sewage treatment in the 1900s, particularly since the Clean Water Act of 1972, has led to major improvements in water quality throughout the estuary (Chapter 23). Indeed, a focus on this baseline issue has generated considerable new knowledge of how the system functions ecologically from nutrients upward to the watershed level (Chapters 9, 10). It may be argued that successes achieved in the water quality arena have allowed the recent focus in the estuary on habitat evaluation and restoration - an initiative that would not merit serious attention in the absence of adequate dissolved oxygen levels.
But all is not well and vigilance is required to prevent environmental backsliding. The recent invasion of zebra mussels (Chapter 21) has resulted in major declines in freshwater phytoplankton and noticeable decreases in oxygen. Much earlier misguided introductions of organisms such as water chestnut, common carp, and others (Chapter 21) have had profound effects in portions of the estuary and are reminders that such mistakes usually are irreversible. Pollution inputs have been lowered dramatically (Chapter 22), but intermittent episodes may still occur, such as oil spills. And nonpoint sources of contaminants still leach into the system.
Do we know all we need to know about the Hudson? No, although we've made great strides. Despite a volume filled with exciting progress and results, we still require more knowledge of the River's flow patterns and how they distribute sediments and contaminants. We still are in need of comprehensive modeling approaches to fisheries that relate physical variables and human impacts to fish production, and to how species abundances are affected by interactions with other species. We still know relatively little about the importance of tributaries to Hudson River fishes, sediment transport, and water quality. These and many other realms of study can only benefit from periodic syntheses, such as this one, of what we continue to learn about this great river, which will help steer future research efforts.
Geological, Physical, and Chemical Setting of the Hudson
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