Ecosystem Health最新文献

ABSTRACT

I contend that focusing on the “absence of health,” or what I will call “extreme cases,” provides a basis for agreement about ecosystem health in ecosystem management. An extreme case is defined where there exists (1) scientific agreement about models, (2) scientific agreement about scale, (3) policy agreement that the risks will be great and unnecessarily so. Scientific agreement requires that a link be established between biodiversity and ecosystem processes, goods, and services. I discuss recent work concerning ecosystem engineers that demonstrates such a link. Agreement about scale requires consensus about the scale of management decisions, both spatial and temporal, and reconciliation of management goals and objectives of the various stakeholders in an ecosystem. Finally, policy agreement requires that ecological risks be great and unnecessarily so. Where these extreme cases do not apply, I suggest that it will be useful to appeal to stakeholder negotiations to seek agreement concerning ecosystem health.

ABSTRACT

This article describes the development of a framework for selecting a core set of indicators suitable for an integrated ecosystem health assessment of a governed landscape. Integrated assessments are those that consider a combination of biophysical, socioeconomic, and human health considerations. Highly governed landscapes are cultural landscapes that are strictly controlled by humans to the extent that they would revert to an entirely different form were it not for continued human intervention. One example of such a landscape, which serves as the setting for this investigation, is the former wetlands of the northeastern Italian coastal zone, which have been subject to widespread land reclamation and coastal development over the past century. The science of ecosystem health has been chosen as the frame of reference because “health” is not judged by the degree of “naturalness” but instead on the ability of the ecosystem to maintain and renew itself. The framework consists of first reviewing literature and methods related to ecological and environmental monitoring, state-of-the-environment reporting, landscape ecology, and sustainability. This is followed by the definition of indicator guidelines that are designed to assist in the evaluation and selection of potential indicators. A core set of indicators are then presented based on a conceptual framework devised for this purpose. Indicators are classed as abiotic, biotic, and cultural, and selected according to the ecological districts comprising the study area. The ultimate goal is their application to an ecological monitoring and assessment program within a governed landscape such as the northeastern Italian coastal zone. Given such a commitment, the normal process of core indicator refinement can then proceed, based on such actions as further consultations with interested stakeholders and evaluation of methodological and practical constraints to their actual application.

ABSTRACT

The sensitivities of three indicators of ecosystem health were evaluated at several sites in the Jornada Basin of the Chihuahuan Desert in southern New Mexico. The size of bare patches, proportion of total grass cover contributed by long-lived perennial grasses, and soil stability are interdependent indicators of ecosystem functions related to the retention and use of water and nutrients. Sensitivity tests were chosen using data collected along disturbance gradients and then tested using independent, ungrazed exclosures and adjacent grazed pastures. The mean size of bare soil patches was sensitive to anthropogenic disturbance. When bare soil patch data were transformed using natural logarithms, the skewness of the frequency distribution weighted by mean bare patch size could be used to indicate early disturbance to the ecosystem. The proportion of total vegetation that was long lived also was sensitive to anthropogenic disturbance and appears to be a good indicator of ecosystem degradation. The slake test for soil surface stability was extremely sensitive to disturbance and may serve as an early-warning indicator of soil degradation for the coarse-textured soils that were evaluated.

ABSTRACT

Existing definitions of agroecosystem health do not address one of the most important issues, namely, how tradeoffs should be made among different components of an agroecosystem. To resolve this issue, it is important to be clear on which perspective is being taken in any health assessment. An internal perspective would focus on the health of the biophysical components of the agroecosystem, whereas an external perspective would focus on human communities. This article proposes a three-stage, transdisciplinary approach to agroecosystem health, called a Framework for Agroecosystem Health Tradeoffs, which uses internal and external perspectives at different stages. In the first stage, the type of ecosystem and the time and spatial scale of concern are identified. Once this is established, required levels of biophysical indicators are set and monitored to ensure that basic internal needs for agroecosystem survival are met. In determining levels of biophysical indicators, “positivistic” scientific analysis would be required as well as normative judgments by society on acceptable levels of risk. The third stage involves determining the potential for making tradeoffs in the agroecosystem that would be beneficial to society without affecting the required levels of biophysical indicators specified in the second stage. Economic analysis and community consultation would be used to determine which agroecosystem components or services are valued most by society so that decisions on tradeoffs could be made. Although there remain practical problems in implementing this approach, the notion of setting minimum constraints which human activity cannot violate and making the best tradeoffs possible after these constraints are met provides a useful framework to begin putting agroecosystem health into practice.

ABSTRACT

Pollution from persistent toxic substances, interpreted as downward causation from the Biosphere, was the primary factor causing the integration of human and ecosystem health in the Great Lakes Basin. Institutional measures that set the political stage for integration were the Boundary Waters Treaty of 1909 and the Great Lakes Water Quality Agreements of 1972 and 1978 (the latter with an accent on an ecosystem approach and persistent toxic substances). Fish and wildlife biologists played a crucial role as “eco-catalysts” in alerting the public and the International Joint Commission (IJC) to reproductive and developmental health problems associated with persistent toxic substances in fish, reptiles, birds, mammals, and—by implication—humans.

The rationale for the recommendation to sunset industrial chlorine stemmed from the IJC’s conclusion that persistent toxic substances, including many organochlorines, are harmful to humans and the Biosphere. It is conjectured that the focus on chlorinated chemicals arose from the fact that more than half of the 373 persistent toxic substances identified in the Great Lakes Basin Ecosystem were organochlorines; the uncontrollability of many organochlorines in the production phase, in long-range transport in air and water, in chemical transformations in the environment, and in bioaccumulation in food chains; and the need for a strategic spearhead to break the dysfunctional, after-the-fact, one-by-one approach to regulating persistent toxic substances. Generic controls are necessary whenever public health or property is threatened by environmental conversion from harmless to harmful forms (as in the case of phosphorus, lead, mercury, and PCBs).

Attention is drawn to the rarity of organochlorines in vertebrates and their general use in defense also to the bypassing of lower halogens in favor of iodine (as thyroxine) in regulating basal metabolism in vertebrates. The sunsetting of industrial chlorine is considered essential to the protection of human and biospheric health; however, because of the current requirement for proof of harm, chemical by chemical, the process is likely to take decades.

ABSTRACT

This study surveyed 10 different geographical locations on Georgian Bay, Ontario, Canada, and compared the levels of water quality indicators throughout an 11-week period in the summer of 1994. Of the four indicator microorganisms studied (fecal coliforms, Escherichia coli, fecal streptococci, and Pseudomonas aeruginosa), fecal coliforms/E. coli appeared to be the most sensitive to changes in the surrounding environment. Fecal coliforms and E. coli were deemed to be good indicators of the relationship between human health and ecosystem health. A number of environmental variables were found to affect fecal coliform/E. coli concentrations in water and in sediment, including location, objective measure of fetch values (indicating the amount of water exchange), wind velocity, wave action, percentage of organic carbon in sediment (which is related to fetch), and boat number (again related to fetch). No effect on the indicator microorganism concentration was observed for week number, number of swimmers, number of cottages, water temperature, and rainfall.