You would get an array of answers: The Mayor, The City Council, The President, etc...
The one person you need to add to that list is you !
Safeguard and Improve Your Environment is The Way To Happiness precept #12. If you feel like you can't do anything about the environment (not true), You can always keep your block, community or city in good order. Most organizations have an Adopt a Street program in the part of town. So when you go through some of the unsightly parts of town where there's trash, unkempt buildings or whatever, The main reason is not because of the government. the main reason is that the people in that community agreed that nothing can be done. You don't have to agree with that.
Planet-wide, There are many Organizations that concern themselves with protecting the planet. Greenpeace and the Sierra Club are a couple of them. But it starts in your area. It starts with you!