Long-term monitoring to assess the status of plant and animal populations is essential for protecting endangered species, for managing fisheries and wildlife populations, and for rapidly identifying costly pest outbreaks. However, because it's impossible to directly count entire populations, resource managers have to develop ways of monitoring populations that allow them to make accurate assessments from limited data. Many of these programs are currently designed based on intuition and guesswork, and different agencies often monitor populations in very different ways. My project will use computer models to more rigorously evaluate the efficacy of a number of different approaches to monitoring plants and animal populations. This will lead to general guidelines for what types of monitoring programs are most useful in different kinds of situations, as well as software tools to assist in designing and evaluating better monitoring programs.