Environmentalists are typically viewed as seeking to protect human life from such health hazards as dirty air and polluted water. But that's a superficial assessment. The essence of environmentalism is the belief that nature must be protected, not for man, but from man.
One of the more recent illustrations of this philosophy is provided by the current drought in California, where the government has imposed severe water-rationing measures. Not only have environmentalists opposed the construction of new reservoirs—none have been built in that state in the last 35 years—but they are diverting water from human use to the preservation of fish. Federal regulators have ruled that channeling some 1.2 million acre-feet of water to California farmers would have endangered the three-inch smelt. So the water, enough for more than three million households to live on for a year, went unused.
The premise of environmentalism is that the reshaping of nature to fulfill human needs is an evil that must be stopped. Think of that as you enjoy your home with its indoor plumbing and electrical appliances, or when you drive your car along paved highways, or when you go to work in a high-rise office building—and ponder the alternative of life in pre-industrial, "unspoiled" nature.
(For more on environmentalism, see my chapter "The Philosophy of Privation" in Ayn Rand's Return of the Primitive: The Anti-Industrial Revolution—http://amzn.to/1JQrxtv.)