Statistical inference for extinction rates based on last sightings.

Rates of extinction can be estimated from sighting records and are assumed to be implicitly constant by many data analysis methods. However, historical sightings are scarce. Frequently, the only information available for inferring extinction is the date of the last sighting. In this study, we developed a probabilistic model and a corresponding statistical inference procedure based on last sightings. We applied this procedure to data on recent marine extirpations and extinctions, seeking to test the null hypothesis of a constant extinction rate. We found that over the past 500 years extirpations in the ocean have been increasing but at an uncertain rate, whereas a constant rate of global marine extinctions is statistically plausible. The small sample sizes of marine extinction records generate such high uncertainty that different combinations of model inputs can yield different outputs that fit the observed data equally well. Thus, current marine extinction trends may be idiosyncratic.