A climatic driver for abrupt mid-Holocene vegetation dynamics and the hemlock decline in New England

The mid-Holocene decline of eastern hemlock is widely viewed as the sole prehistorical example of an insect- or pathogen-mediated collapse of a North American tree species and has been extensively studied for insights into pest-host dynamics and the consequences to terrestrial and aquatic ecosystems of dominant-species removal. We report paleoecological evidence implicating climate as a major driver of this episode. Data drawn from sites across a gradient in hemlock abundance from dominant to absent demonstrate: a synchronous, dramatic decline in a contrasting taxon (oak); changes in lake sediments and aquatic taxa indicating low water levels; and one or more intervals of intense drought at regional to continental scales. These results, which accord well with emerging climate reconstructions, challenge the interpretation of a biotically driven hemlock decline and highlight the potential for climate change to generate major, abrupt dynamics in forest ecosystems.     

Plant facilitation of a belowground predator

Interest in facilitative predator plant interactions has focused upon above-ground systems. Underground physical conditions are distinctive, however, and we provide evidence that bush lupine, Lupinus arboreus, facilitates the survival of the predatory nematode Heterorhabditis marelatus. Because H. marelatus is prone to desiccation and lupines maintain a zone of moist soil around their taproots even during dry periods, we hypothesized that dry-season nematode survival under lupines might be higher than in the surrounding grasslands. We performed field surveys and measured nematode survival in lupine and grassland rhizospheres under wet- and dry-season conditions. Nematodes survived the crucial summer period better under lupines than in grasslands; however, this advantage disappeared in wet, winter soils. Modeling the probability of nematode population extinction showed that, while even large nematode cohorts were likely to go extinct in grasslands, even small cohorts in lupine rhizospheres were likely to survive until the arrival of the next prey generation. Because this nematode predator has a strong top-down effect on lupine survival via its effect on root-boring larvae of the ghost moth Hepialus californicus, this facilitative interaction may enable a belowground trophic cascade. Similar cases of predator facilitation in seasonally stressful environments are probably common in nature.     

Air quality measurements for the aerosol research and inhalation epidemiology study

Measurements of pollutant gases, airborne particulate matter mass and composition, and meteorology have been made at a core site near downtown Atlanta, GA, since August 1998 in support of the Aerosol Research and Inhalation Epidemiology Study (ARIES). This site is one of eight in the Southeastern Aerosol Research and Characterization network. The measurement objective is to provide a long-term, multivariate dataset suitable for investigating statistical associations of respiratory and cardiovascular disease with airborne particulate matter composition, meteorology, and copollutant gases through epidemiologic modeling. Measurements are expected to continue through 2010. Ancillary multiyear measurements at additional sites in the Atlanta metropolitan area and in short-term exposure assessments have been used to estimate the exposure/measurement error associated with using data from a central site to approximate human exposures for the entire area. To date, 13-, 25-, and 53-month air quality datasets have been used in epidemiologic analyses.     

Water and sustainability

This inquiry summarizes global water resources and patterns of use, applies indicators of water sustainability in order to identify areas of water stress, and examines prospects for water sustainability in the list century. A long-range conventional development scenario is introduced based on a vision of the future in which the values, consumption patterns and dynamics of the Western industrial society will be progressively played out on a global scale. The scenario is driven by commonly cited projections of population and economic growth, assumes no major changes in water policy and, following historic trends, incorporates progressive improvements in the efficiency of water use. The scenario helps clarify the constraints of a conventional picture of water development, and provides a useful point of departure for examining alternative long-range scenarios and their implications for water and development policy. In the conventional development scenario, there is growing pressure on water resources, particularly in developing regions. Strategies for beginning a transition to a sustainable water development path are summarized .     

Waiting for Peace: Perspectives from Action-oriented Research on the Humanitarian Impasse in the Caucasus

Cease-fires in the Caucasus during the past five years have prevented large-scale life-threatening emergencies and created space for peace negotiations. Yet genuine conflict resolution and normalisation have proven elusive, frustrating the return of uprooted populations and constraining reconstruction. This paper reviews a series of seven strategy sessions held in Moscow and the Caucasus in late 1998 to reflect upon the performance of humanitarian agencies and stimulate greater synergies with diplomatic actors. An experiment in promoting discussion of recently conducted independent policy research throughout the north and south Caucasus, the series resulted in a fresh look at the issues in the region and at agency headquarters. The generic nature of the policy challenges gives the experience potential relevance well beyond the region.     

CONSTRAINTS IN WATER MANAGEMENT ON AGRICULTURAL LANDS1

ABSTRACT Whether the goal is minimizing water quality degradation in receiving streams or maximizing agricultural production on existing croplands; the solutions are identical - improved water management practices. Technology has succeeded in developing feasible solutions to improving irrigation water management, but the law has been slow to encourage or direct implementation. The villain of the western United States water problem is the property right concept of the appropriation doctrine. Improving water management also implies organizational improvements. Also, the so-called “human factor” involves questions of inefficiency and ineffectiveness, that when examined under the criteria of efficacy, may dictate a policy of continuing present practices in certain localities or regions with little technological intervention. The present effort for improving water quality management implies, therefore, a manyfold attack aimed at increasing project irrigation efficiency and effectiveness, under the larger rubric of efficacy and the achievement of larger social goals.     

Influence of Geoengineered Climate on the Terrestrial Biosphere

Various geoengineering schemes have been proposed to counteract anthropogenically induced climate change. In a previous study, it was suggested that a 1.8% reduction in solar radiation incident on the Earths surface could noticeably reduce regional and seasonal climate change from increased atmospheric carbon dioxide (CO₂). However, the response of the terrestrial biosphere to reduced solar radiation in a CO₂-rich climate was not investigated. In this study, we hypothesized that a reduction in incident solar radiation in a Doubled CO₂ atmosphere will diminish the net primary productivity (NPP) of terrestrial ecosystems, potentially accelerating the accumulation of CO₂ in the atmosphere. We used a dynamic global ecosystem model, the Integrated Biosphere Simulator (IBIS), to investigate this hypothesis in an unperturbed climatology. While this simplified modeling framework effectively separated the influence of CO₂ and sunlight on the terrestrial biosphere, it did not consider the complex feedbacks within the Earths climate system. Our analysis indicated that compared to a Doubled CO₂ scenario, reduction in incident solar radiation by 1.8% in a double CO₂ world will have negligible impact on the NPP of terrestrial ecosystems. There were, however, spatial variations in the response of NPP-engineered solar radiation. While productivity decreased by less than 2% in the tropical and boreal forests as hypothesized, it increased by a similar percentage in the temperate deciduous forests and grasslands. This increase in productivity was attributed to a 1% reduction in evapotranspiration in the Geoengineered scenario relative to the Doubled CO₂ scenario. Our initial hypothesis was rejected because of unanticipated effects of engineered solar radiation on the hydrologic cycle. However, any geoengineering approaches that reduce incident solar radiation need to be thoroughly analyzed in view of the implications on ecosystem productivity and the hydrologic cycle.     

Assessing potential bioavailability of metals in sediments: A proposed approach

Due to anthropogenic inputs, elevated concentrations of metals frequently occur in aquatic sediments. In order to make defensible estimates of the potential risk of metals in sediments and/or develop sediment quality criteria for metals, it is essential to identify that fraction of the total metal in the sediments that is bioavailable. Studies with a variety of benthic invertebrates indicate that interstitial (pore) water concentrations of metals correspond very well with the bioavailability of metals in test sediments. Many factors may influence pore water concentrations of metals; however, in anaerobic sediments a key phase controlling partitioning of several cationic metals (cadmium, nickel, lead, zinc, copper) into pore water is acid volatile sulfide (AVS). In this paper, we present an overview of the technical basis for predicting bioavailability of cationic metals to benthic organisms based on pore water metal concentrations and metal-AVS relationships. Included are discussions of the advantages and limitations of metal bioavailability predictions based on these parameters, relative both to site-specific assessments and the development of sediment quality criteria.     

International education and sustainable development: an American experience in Bangkok,Venice and Guayaquil

Worcester Polytechnic Institute's (WPI) unique academic plan enables students to study sustainable development and the environment as part of an international educational experience. As a technological university, WPI requires students to complete an interdisciplinary project on the interaction of science or technology and society. This paper describes the environmental projects completed by WPI students, in Bangkok, Venice and Guayaquil. The lessons from WPI's experience provide a model for environmental education at other institutions. These interdisciplinary projects not only promote environmental awareness among students, but they also provide tangible assistance to regions which are developing strategies for sustainable development.