From the time that life first appeared on Earth, species have gone extinct. Extinction is a natural part of evolution. Species that are best at adapting to their environment survive. Other species are unable to adapt quickly enough – so they die off. So, why do endangered species get so much attention today? One reason is much of the extinction happening these days is unnatural. The leading reason for a species to become endangered is loss of habitat. As humans cut down forests for farmland, expand cities, or pollute waterways, to name a few ways that habitat is destroyed, animals, plants, and insects find it harder and harder to survive. Thus, the effect of humans on the natural world is causing species to become endangered, and, ultimately, go extinct. Another leading reason for a species to become endangered is climate change. For example, the lizards in this article could probably adapt to a gradual change in temperature. However, the rapid change in the climate, and the consequent decrease in lizard birthrate, threaten to doom many lizard species. If human activity is a major reason for climate change, then it would seem that we are changing our world far too rapidly for species to naturally adapt. Humans are highly adaptable, but most species need a lot of time to get used to changing conditions.