We can say that species are "endangered," and that the gulf oil gusher threatens them, but what that means in the context of today's situation of very depleted life comes a great deal clearer with something like this, concerning the threat of this oil and chemical disaster to sperm whales in the Gulf :
"A 2009 stock assessment report by the National Oceanic and Atmospheric Administration (NOAA) estimated that the potential biological removal, or PBR, level for the Gulf of Mexico sperm whale population is three. That means the whales' long-term survival is at risk if, in addition to natural deaths, three sperm whales a year are killed or removed by human causes. The loss of a handful of whales each year can impact a population of hundreds, because sperm whales—especially females—require a very long time to reach sexual maturity. Females then give birth to just three or four calves during their entire lifetimes. "