Presence-absence versus abundance data for monitoring threatened species

Effective detection of population trend is crucial for managing threatened species. Little theory exists, however, to assist managers in choosing the most cost-effective monitoring techniques for diagnosing trend. We present a framework for determining the optimal monitoring strategy by simulating a manager collecting data on a declining species, the Chestnut-rumped Hylacola (Hylacola pyrrhopygia parkeri), to determine whether the species should be listed under the IUCN (World Conservation Union) Red List. We compared the efficiencies of two strategies for detecting trend, abundance, and presence-absence surveys, underfinancial constraints. One might expect the abundance surveys to be superior under all circumstances because more information is collected at each site. Nevertheless, the presence-absence data can be collected at more sites because the surveyor is not obliged to spend a fixed amount of time at each site. The optimal strategy for monitoring was very dependent on the budget available. Under some circumstances, presence-absence surveys outperformed abundance surveys for diagnosing the IUCN Red List categories cost-effectively. Abundance surveys were best if the species was expected to be recorded more than 16 times/year; otherwise, presence-absence surveys were best. The relationship between the strategies we investigated is likely to be relevant for many comparisons of presence-absence or abundance data. Managers of any cryptic or low-density species who hope to maximize their success of estimating trend should find an application for our results.

Enabling change for corporate sustainability: An integrated perspective

This article explores the processes of change that enable corporations to move towards sustainable practices, focusing on the human resource and business strategies that support rather than diminish global ecology and human/social capabilities. We argue that this unified approach is necessary to bring about a change in the interpretation of corporate sustainability and to support the activities of change agents (managers, consultants, and community activists) in managing the massive corporate change needed to move corporations toward sustainable practices in a systematic way. We propose a schema in the form of an integrated phase model for understanding how corporations move from compliance modes to the attainment of strategic sustainability and beyond to the ‘ideal’ or sustaining corporation. We discuss the leadership of change and the roles and strategies that corporate change agents can employ to bring about both incremental and transformational change for sustainability.