Does Less Ice Mean Fewer Polar Bears?
While data on polar bear populations are relatively scarce, data on population trends are nearly nonexistent. Thus, to determine whether polar bears will be endangered by the disappearance of sea ice, trends in population are predicted using something called population viability analysis (PVA), which is statistical modeling used to predict various outcomes within animal populations. The major meta-analysis of polar bear populations is the IUCN/SSC Polar Bear Specialist Group’s 2005 report on the status of the polar bear.[23] The report uses a type of stochastic subpopulation viability analysis, meaning that it incorporates random variability terms into PVA to come up with estimates of future sizes for polar bears by region. In the IUCN/SSC models, estimated polar bear mortality rates (from tag-and-recapture studies); litter sizes; sex ratio of cubs; initial subpopulation size; and the sex, age, and family status of killed polar bears are fed into a computer program that forecasts futur
