Inferring extinctions II: A practical, iterative model based on records and surveys

Extinctions are difficult to observe. Estimating the probability that a taxon has gone extinct using data from the field aids prioritisation of conservation interventions and environmental monitoring. There have been recent advances in approaches to estimating this probability from records. However, complete assessment requires consideration of the type, timing and certainty of records, the timing, scope and severity of threats, and the timing, extent and reliability of surveys. Until recently, no single method could integrate these different sources and qualities of data into a single measure. Here we describe a new, accessible method for estimating the probability that a taxon is extinct based on different kinds of both record and survey data, and accounting for data quality. The model takes into account uncertainties in input parameter estimates and provides bounds on estimates of the extinction probability. We illustrate application of the model using information for the Alaotra Grebe Tachybaptus rufolavatus. Application of this approach should facilitate more efficient allocation of conservation resources by enabling scenario analyses that inform investments in searches and management interventions for potentially extinct taxa. It should also provide more reliable estimates of recent extinction rates.