Think Green Rewards Earned
82,945,966
Total LBs of WMRA Recycled
55,670,185
Recovered by Greenopolis
28,771,615

Encourage

How should we encourage people who don't care about our envirorment, to care about it? 

Somewhat Mute Point

You lead by example. Most of what helps change things is for people to start something. Start a park trail clean up. Have fun while doing it. Smile and tell the people who've you've deemed as not caring what a super time you had and would they like to come along next time.

But in the end, your actions are your actions. Why feel the need to make others think as you do?

Speak about the kids

and the world they will inherit. Only the most selfish or psychopathic don't care about the next generation. We don't inherit the earth from our parents , we borrow it from our children.

...

The best way to encourage anything is through education and example. Instead of “You shouldn’t do that!” try “This is what I did today!”

Applause

Todays landfills are tommorrows archaeological digs! 
Encourage is the key word here. Scare tactics I see posted on this site are over used and under proven. Scare tactics only anger people. So I applaud your choice of words.