Picture gallery: Future dim for threatened species

"Highly endangered" is only the intermediate classification on the Red List. The criteria for deciding to which degree a species is endangered are based on a number of factors. Are numbers shrinking, growing, or remaining stable? Is the natural habitat being destroyed? To what extent?

In the majority of cases, humans are primarily responsible for dwindling numbers. Through the destruction of the rainforests, agricultural practices, pollution, and climate change, we are transforming the world around us.

While the relationship between the hunter and the hunted is carefully regulated in nature, humans have proven incapable of preserving this fine balance and often drive their prey to near or total extinction. But even those animals above us in the food chain are not safe. There are estimated to be only 270 remaining Sumatran tigers in the wild and these surviving animals are considered to be "threatened by extinction."