FORGET CLIMATE CHANGE...:

Early environmentalism in the 1970s helped focus societies on priorities such as polluted rivers - the Cuyahoga River in the United States famously caught fire in 1969 - and fouled air, with soot and smog killing millions.

Here, we have made great strides. Most bodies of water in rich countries are much cleaner, since we are prosperous enough to clean up our domestic messes. In the U.S., for instance, a recent comprehensive study showed that "water pollution concentrations have fallen substantially" over the past 50 years. And a stunning 3.8 billion people around the world have gained access to clean drinking water since 1970.

Air pollution, the world's biggest environmental killer, has seen even greater improvements. Outdoor air pollution has declined dramatically in rich countries, due in no small measure to attention from 1970's Earth Day and subsequent actions such as the landmark U.S. Clean Air Act later that year.

For the world's poor, the most deadly air pollution is indoors. Almost three billion of the world's poorest people still cook and keep warm with dirty fuels such as dung, cardboard and wood, and the World Health Organization estimates the effects are equivalent to smoking two packs of cigarettes each day.

But since 1970, the death risk across the world from indoor air pollution has been cut by more than half.

Despite the amazing progress, both indoor and outdoor air pollution still kill seven million people each year. At least two billion people still use drinking water sources contaminated by feces. So, for the next 50 years, we still have our work cut out for us. Things are far better, but they are still not okay.

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