Q: What is the single most effective thing I can do for the environment?
New Scientist's answer: Over a 75-year lifespan, the average European will be responsible for about 900 tonnes of CO2 emissions. For Americans and Australians, the figure is more like 1500 tonnes. Add to that all of humanity's other environmentally damaging activities and, draconian as it may sound, the answer must surely be to avoid reproducing.
Cheng's evil answer: DIE.
You have to concede, my inner demon isn't actually all that far off. I mean, die vs don't live, there isn't all that big a gap between them, eh? Eh?