It is estimated that there are anywhere from 30,000 to 40,000 sloths left in the world in early 2013. There are six different species of sloths. They are all medium in size and a type of mammal. Most ground sloths are already extinct. Sloths are very good for the environment because they may house any number of fungi, beetles, algae, cockroaches, and moths. Sloths have been around for about 60 million years, though they have changed in many ways to adapt to the environment.