Measures of species richness are one of the most straightforward ways to indicate how important an area is for biodiversity. The number of small plants and animals is usually estimated by sampling of plots. It is also important to know which aspects are under most immediate threat. This, however, requires a large amount of data and time-consuming analysis. For this reason, global analyses of threatened species status have been carried out for only a few groups of organisms.
Birds are the only species for which the status of all members has been assessed.
Mammals approach birds in this respect, but an estimated 45 percent of mammal species remain to be assessed. The table shows information on protected areas, numbers of certain species, and numbers of those species under threat. Because of differences in definitions and reporting practices, cross-country comparability is limited. Compounding these problems, available data cover different periods. Natural monuments and natural landscapes with unique aspects.