Why are extinction rates highest for birds and mammals?
Perhaps attributes of birds and mammals, such as higher energetic requirements due to being endothermic, make them more susceptible to extinction. Alternatively, these data may reflect insufficient information. Other groups are less well studied than are birds and mammals. We simply are unaware of many extinctions in these groups. FIGURE 57.5 Human populations in hotspots. The rich biodiversity in many hotspots is under pressure from (a) dense and (b) rapidly growing human populations. Why do population density and growth rates differ among hotspots? Answer: Many factors affect human population trends, including resource availability, governmental support for settlement in new areas or for protecting natural areas, and the extent to which governments attempt to manage population growth. FIGURE 57.7 The economic value of maintaining habitats. (a) Mangroves in Thailand and (b) rainforests in Cameroon provide more economic benefits left standing than if they are destroyed and the land use
