Is there an obligation to help? No. Would it be in everyone's best interest for wealthy nations to aid poorer nations? Absolutely. How best to aid them? Trade. How best to improve environmental issues? Once again, trade. Currently Japan is aiding China in pollution control, to the benefit of both -- Japan exports its technology, China improves its citizen's health. The toxic toy problem a while back is another example -- Citizens in the US will not buy lead painted toys (Although to be fair, the US had lead paint on its toys for many years. But we have since learned better, and raised the standard of children's health in doing so. ) If China wants to trade toys, it had better change its manufacturing process. Healthy trade will do more good for more people more quickly than any government incentive or program. On a more local level, the same can be said of putting your money where your mouth is regarding environmental issues by consciously purchasing the more expensive, but less polluting products. "Charity begins at home."