There is a pressing need for developing and testing a general set of theories in order to provide a confident basis for prediction of multiple stressor effects. Confident prediction is central to confident decision making in water pollution control. Consequently, WERF commissioned this study, which has as its goal to provide a study design based on good science that helps establish a general, conceptual approach to multiple stressors. The objectives addressed in this report are: (1) review and critique the existing body of knowledge for multiple stressors; (2) develop a searchable, annotated bibliography of multiple stressor research; and, (3) identify gaps in the body of knowledge. A rigorous, theoretical basis for the prediction of multiple stressor effects could not be developed from the literature on experimental studies of multiple stressor effects in aquatic ecosystems. Despite the wealth of observational data, the existence of several useful tools for interpretation of cause/effect relationships (including formal Stressor Identification methods), and the studies reviewed in this report, there are no tools that allow a confident, a priori, prediction of ecosystem response to multiple stressors. The current literature provides, at best, a series of site-specific glimpses of the response of ecological communities and ecosystems to multiple stressors. There is seldom, if ever, any reference to a more generalized model of multiple stressor effects apart from the discussion of the expectations regarding additivity versus synergism. Many articles that purport to be multiple stressor studies do not go beyond an inventory of the various stresses and upsets affecting the ecosystem, without attempting to assess the interactions among them.

Multiple Stressors in River Ecosystems: Status, Impacts and Prospects for the Future provides a comprehensive and current overview on the topic as written by leading river scientists who discuss the relevance of co-occurring stressors for river ecosystems. River ecosystems are subject to multiple stressors that threaten their ecological status and the ecosystem services they provide. This book updates the reader's knowledge on the response and management of river ecosystems to multi-stress situations occurring under global change. Detailing the risk for biodiversity and functioning in a case-study approach, it provides insight into methodological issues, also including the socioeconomic implications. - Presents a case study approach and geographic description on the relevance of multiple stressors on river ecosystems in different biomes - Gives a uniquely integrated perspective on different stressors, including their interactions and joint effects, as opposed to the traditional one-by-one approach - Compiles state-of-the-art methods and technologies in monitoring, modeling and analyzing river ecosystems under multiple stress conditions

Ecotoxiclogical risk from multiple stressors covers any situation where org- isms are exposed to a combination of environmental stressors. These include physical and chemical pollutants as well as other stressors such as parasites and environmental impact (e. g. , climate change or habitat loss). The combi- tion of stressors can result in increased risk to organisms (either additive or synergistic effects) or decreased effects (protective or antagonistic effects). The multiple stressor challenge is an international, multi-disciplinary problem requiring an international, multi-disciplinary approach. The c- rent approach to multiple stressors is to examine one stressor at a time and assume additivity. Little work has been done on combinations of stressors such that potential interactions can be determined. The problem is very complex. Multiple stressors pose a whole spectrum of challenges that range from basic science to regulation, policy and gove- ance. The challenges raise fundamental questions about our understanding of the basic biological response to stressors, as well as the implications of those uncertainties in environmental risk assessment and management. In addition to the great breadth, there is also great depth in the research ch- lenges, largely due to the complexity of the issues. From a basic science point of view, many of the mechanisms and processes under investigation are at the cutting edge of science — involving new paradigms such as genomic ins- bility and bystander effects.

The science of ecotoxicology and the practice of ecological risk assessment are evolving rapidly. Ecotoxicology as a subject area came into prominence in the 1960s after the publication of Rachel Carson's book on the impact of pesticides on the environment. The rise of public and scientific concern for the effects of chemical pollutants on the environment in the 1960s and 1970s led to the development of the discipline of ecotoxicology, a science that takes into account the effects of chemicals in the context of ecology. Until the early 1980s, in spite of public concern and interest among scientists, the assessment of ecological risks associated with natural or synthetic pollutants was not considered a priority issue by most government. However, as the years passed, a better understanding of the importance of ecotoxicology emerged and with it, in some countries, the progressive formalization of an ecological risk assessment process. Ecological risk assessment is a conceptual tool for organizing and analyzing data and information to evaluate the likelihood that one or more stressors are causing or will cause adverse ecological effects. Ecological risk assessment allows risk managers to consider available scientific information when selecting a course of action, in addition to other factors that may affect their decision (e. g. , social, legal, political, or economic). Ecological risk assessment includes three phases (problem formulation, analysis, and risk characterization).

This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.

The research of the last decade has demonstrated that ecosystems and human systems are influenced by multiple factors, including climate, land use, and the by-products of resource use. Understanding the net impact of a suite of simultaneously occurring environmental changes is essential for developing effective response strategies. Using case studies on drought and a wide range of atmosphere-ecosystem interactions, a workshop was held in September 2005 to gather different perspectives on multiple stress scenarios. The overarching lesson of the workshop is that society will require new and improved strategies for coping with multiple stresses and their impacts on natural socioeconomic systems. Improved communication among stakeholders; increased observations (especially at regional scales); improved model and information systems; and increased infrastructure to provide better environmental monitoring, vulnerability assessment, and response analysis are all important parts of moving toward better understanding of and response to situations involving multiple stresses. During the workshop, seven near-term opportunities for research and infrastructure that could help advance understanding of multiple stresses were also identified.