Because the human population is
growing so rapidly, we are crowding out
other species. As people take up more
space and use more resources, we destroy
the habitats of other species. More species
are going extinct because of habitat
destruction today than ever before. Global
warming is a threat that is causing a
change of climate for animals, such as the
polar bear. The polar bear is a threatened
species. This means that it will become
endangered if something is not done to
protect it. An endangered species is one
whose numbers are so low that it is likely to
become extinct.