■ Abstract Ecological indicators have widespread appeal to scientists, environmental managers, and the general public. Indicators have long been used to detect changes in nature, but the scientific maturation in indicator development primarily has occurred in the past 40 years. Currently, indicators are mainly used to assess the condition of the environment, as early-warning signals of ecological problems, and as barometers for trends in ecological resources. Use of ecological indicators requires clearly stated objectives; the recognition of spatial and temporal scales; assessments of statistical variability, precision, and accuracy; linkages with specific stressors; and coupling with economic and social indicators. Legislatively mandated use of ecological indicators occurs in many countries worldwide and is included in international accords. As scientific advancements and innovation in the development and use of ecological indicators continue through applications of molecular biology, computer technology such as geographic information systems, data management such as bioinformatics, and remote sensing, our ability to apply ecological indicators to detect signals of environmental change will be substantially enhanced.

The order of authorship was determined alphabetically. We are grateful to Andrew Henderson, Monica Higgins, Timothy Pollock, Gerard Sanders, and seminar participants at the University of Texas at Austin for providing valuable comments on earlier drafts of this paper. We also thank Linda Johanson, Joseph Porac, and the anonymous ASO reviewers for their constructive feedback and suggestions. This paper theorizes that relatively poor firm performance can prompt chief executive officers (CEOs) to seek more advice from executives of other firms who are their friends or similar to them and less advice from acquaintances or dissimilar others and suggests how and why this pattern of advice seeking could reduce firms' propensity to change corporate strategy in response to poor performance. We test our hypotheses with large-sample survey data on the identities of CEOs' advice contacts and archival data on firm performance and corporate strategy. The results confirm our hypotheses and show that executives' social network ties can influence firms' responses to economic adversity, in particular by inhibiting strategic change in response to relatively poor firm performance. Additional findings indicate that CEOs' advice seeking in response to low performance may ultimately have negative consequences for subsequent performance, suggesting how CEOs' social network ties could play an indirect role in organizational decline and downward spirals in firm performance.0 A number of interconnected literatures have sought to explain the robust finding from research in organization studies and strategic management that top executives often do not initiate significant changes in corporate strategy in response to poor firm performance and, paradoxically, may adhere even more firmly to current strategies in response to performance problems. A central theme in much of this literature is that systematic biases or "perceptual distortions" among top managers are at least partly responsible for strategic inertia in the face of poor performance (Starbuck, Greve,

Region 2 comprises arctic and subarctic North America and is underlain by continuous or discontinuous permafrost. Its freshwater systems are dominated by a low energy environment and cold region processes. Central northern areas are almost totally in¯uenced by arctic air masses while Paci®c air becomes more prominent in the west, Atlantic air in the east and southern air masses at the lower latitudes. Air mass changes will play an important role in precipitation changes associated with climate warming. The snow season in the region is prolonged resulting in long-term storage of water so that the spring¯ood is often the major hydrological event of the year, even though, annual rainfall usually exceeds annual snowfall. The unique character of ponds and lakes is a result of the long frozen period, which aects nutrient status and gas exchange during the cold season and during thaw. GCM models are in close agreement for this region and predict temperature increases as large as 48C in summer and 98C in winter for a 2 Â CO 2 scenario. Palaeoclimate indicators support the probability that substantial temperature increases have occurred previously during the Holocene. The historical record indicates a temperature increase of 418C in parts of the region during the last century. GCM predictions of precipitation change indicate an increase, but there is little agreement amongst the various models on regional disposition or magnitude. Precipitation change is as important as temperature change in determining the water balance. The water balance is critical to every aspect of hydrology and limnology in the far north. Permafrost close to the surface plays a major role in freshwater systems because it often maintains lakes and wetlands above an impermeable frost table, which limits the water storage capabilities of the subsurface. Thawing associated with climate change would, particularly in areas of massive ice, stimulate landscape changes, which can aect every aspect of the environment. The normal spring¯ooding of ice-jammed north-¯owing rivers, such as the Mackenzie, is a major event, which renews the water supply of lakes in delta regions and which determines the availability of habitat for aquatic organisms. Climate warming or river damming and diversion would probably lead to the complete drying of many delta lakes. Climate warming would also change the characteristics of ponds that presently freeze to the bottom and result in fundamental changes in their limnological characteristics. At present, the food chain is rather simple usually culminating in lake trout or arctic char. A lengthening of the growing season and warmer water temperature would aect the chemical, mineral and nutrient status of lakes and most likely have deleterious eects on the food chain. Peatlands are extensive in region 2. They would move northwards at their southern boundaries, and, with sustained drying, many would change form or become inactive. Extensive wetlands and peatlands are an important component of the global carbon budget, and warm...

This article contributes to the literature on board effectiveness by being perhaps the first to systematically examine how the nature of outside directors' prior experience, and resulting expertise, will influence the performance of a focal firm's strategic initiatives. Our theoretical model is grounded in the psychological literature on expertise and its role in group decision making effectiveness. We focus on outside director expertise in acquisition decision making, and its implications for the performance of the acquisitions of a focal firm. Our conceptual framework indicates that directors will develop expertise in making particular kinds of acquisition decisions (e.g., related or unrelated acquisitions or acquisitions in specific industries or product markets) through their past experiences at other firms with decisions about those specific types of acquisitions, and we predict that this experience and expertise will have positive effects on the performance of a focal firm's acquisitions. We extend our theoretical model to consider the conditions under which relevant director experience will prove most beneficial. Our model predicts that outside director acquisition expertise will deliver the greatest benefits when the focal firm's board is independent from management. We find empirical support for all of our hypotheses. In considering how and when director experience and resulting expertise may influence the performance of corporate acquisitions, our theory and results help to highlight a potential second main focus for research on the long-standing question of what factors render boards of directors effective.

This article contributes to the social networks literature by examining how corporate governance factors influence CEOs' external advice-seeking behaviors. We incorporate insights from social networks research into an agency theory perspective to predict, and demonstrate empirically, that governance factors recommended by agency theory increase CEOs' tendencies to seek out advice contacts who are likely to offer perspectives on strategic issues that differ from their own; these advice-seeking behaviors ultimately enhance firm performance. Accordingly, this article also contributes to the corporate governance literature by describing how and why CEOs' advice networks mediate the effects of governance factors on firm performance.