Population Viability Analysis
Population Viability Analysis
Uses computer simulation models to assess threats to wildlife population persistence and to evaluate the likely impact of creative management options.
A scientifically rigorous population viability analysis (PVA) helps wildlife biologists and managers better understand the mechanisms and impacts of human activities that threaten the future of endangered species. When our knowledge about the linked human-wildlife system improves, we have a much greater ability to properly manage that system. Our collaborative approach to designing and implementing a PVA uses effective methods for organizing and critically evaluating information across a broad range of disciplines and perspectives.
Our Process
We believe that creating detailed computer models of wildlife population dynamics is the best method for performing a PVA. These models realistically simulate the essential demographic processes that drive population change over time: reproduction, survival, movement of individuals into and/or out of a population via dispersal, etc.
We typically use the well-known software package Vortex for our PVAs. Each Vortex modeling project is customized for the specific biology and ecology of the species of interest, and demographic information collected from wild populations through time is used to derive input parameters for the analysis. Starting with a given set of initial conditions, a model scenario can then be projected forward in time to predict the likely outcome for a population under a unique set of assumptions about the threats impacting demographic performance. These underlying conditions can be explored in more detail to determine the primary drivers of population growth or decline, and a range of different population management scenarios can be tested to determine the best options for population management to minimize risk of extinction. Detailed simulation of ex situ (captive) population management is now a key feature of Vortex, providing considerable flexibility in designing and testing management strategies linking ex situ and in situ populations under the One Plan Approach.
The PVA project is ideally integrated into our more comprehensive Species Conservation Planning workshop process. Experts with detailed knowledge of species biology and the threats impacting population persistence take a leading role in this effort which is initiated in the early stages of a longer planning process. With a completed PVA in hand, planning workshop participants have the information they need to develop sound, evidence-based conservation actions for species that also take into account the social, cultural, and economic needs of local people.
A PVA for the greater one-horned rhino in northeast India highlighted the dire consequences of poaching just one to two animals each year from the small population inhabiting Manas National Park. These analyses mobilized government resources for more effective management of these animals, which has contributed to a substantial increase in the Park’s rhino population.
