I will mark Brainliest to best answer!
At what generation did the environment start to go downhill?

Baby boomers and Generation X

Explanation:

Pollution started in the 1950's through 1970's

Boomers where born in 1946-1964

Generation X where born in 1965-1979

Also The Silent Generation helped start the idea of pollution, but generations after that continued to pollute and that's when the environment went down hill.

b.

developed countries have tended to improve the environment, while developing countries have tended to damage it.