ABSTRACT
Previous chapters of this book have focused on various strategies for sampling ecological populations to estimate parameters such as the population size or density. Often, environmental managers require information not only on the current status of a population but also on the changes in the population over time. For example, interest may be in monitoring a special area such as national parks (e.g., Fancy et al., 2009), monitoring for biodiversity (Nielsen et al., 2009), monitoring to detect the spread of invasive species (Byers et al., 2002), or monitoring of pollution or contamination levels (Wiener et al., 2012). Monitoring for changes over time helps discern whether management actions are needed for a vulnerable species or ecosystem and for assessing whether management actions have been effective. For example, the Convention on Biological Diversity, which aimed to reduce the rate of loss of biological diversity, referred to indicators to assess progress toward the 2010 target (https:// www.biodiv.org/2010-target). Included in these indicators was monitoring the changing abundance and distribution of selected species, as well as measuring changes in the status of rare or threatened species.
