Ecology and Society: From LTER to LTSER: Conceptualizing the socio-economic dimension of long-term socio-ecological research

River basins provide an opportunity to understand the interactions between human activities and the state of the environment, to observe changes of stocks and flows in the environment over time, and across a range of spatial scales. The Hudson River Basin constitutes an interesting example (see Ayres and Ayres, 1988, Ayres and Tarr, 1990, Tarr and Ayres, 1990). An in-depth study was initiated in 1982 to review the history of fish catches in the Hudson and Raritan Rivers and associated Estuary. The purpose of the study, financed by NOAA, was to establish correlations between fish catches in different stretches of the river and emissions of a specified series of pollutants into the water. Three principle flow paths were considered, direct point source emissions from industrial sites along the river, sewage from urban areas and diffuse non-point pollution in the for, of run-off and leachates from the surrounding land.

One of the interesting features of this case was the radical changes in land use that took place over the period 1880 to 1980, including dramatic growth in the population of the urban area (New York city and suburbs), and changes in the patterns and intensity of agricultural in the hinterlands. Sewage treatment facilities, including those for storm run-off (storm sewers) were introduced and improved over the period, capable of treating 100% of by the end of the period. Another major change during the century was the shift from use of coal for household heating to oil and gas, and this resulted in a major change in the quantity and composition of the wastes that were generated and collected during the period. Much of the coal ash was used as landfill under Laguardia Airport. A third major change during the century could be described as de-industrialisation. At the end of the 19^th century for example the New York area boasted no less than four large copper refineries, as well as cable manufacturing facilities, other activities associated with the burgeoning market for electrical goods, and chemical products. Polychlorinated biphenols (PCBs) which are highly toxic to fish were being produced as a insulation materials for the electrical industry. Wastes simply accumulated behind a dam on the Mohawk River, a tributary of the Hudson, which circa 1980 gave way, releasing large amounts of PCBs to sediments which are to this day still moving down river. In recent years most of these industries have moved away, New York losing its primacy as an entrepot (oil refineries remained, such as that of Standard Oil). Nowadays the city is centre of finance, retail activity, publishing and consumption. All of these changes have reduced dramatically the immediate emissions burden, however the history of the region still determines the quality of the river ecosystem, its properties and patterns.

The level of copper in the lower Hudson and harbour areas is still exceptionally high due to leaching from wastes from the former copper refineries, the last one of which closed in the mid 1980s. As a result of the aforementioned accident significant levels of PCBs are still measureable. Sediments in New York Bay contain high levels of a suite of heavy metals, thanks to uncontrolled emissions from the chemical industry in the early 20^th century. The waters of the bay circulate slowly, sediments accumulate and do not move out to the sea at large. An ambitous project is underway by the Army Corps. Eng. to bury these sediment in a deep hole under the bay itself, hence avoiding issues of reoxidation and mobilisation of toxic metals.

This study illustrates one of the problems and one of the possible approaches to carrying out historical LTSER. The problem is that there is virtually no useable data on pollutants and toxic emissions prior to the 1970s. However, it is possible to make use of historical information on socio-economic activities and conditions to make reasonable estimates of emissions in earlier periods. This was done in the case of the Hudson-Raritan Basin study and a few other cases (Rhine, Danube; see Stigliani and Anderberg, 1993).