Save the Earth?

Everybody is talking about save the earth, and don't use plastic bags. But I have one question: If we don't use plastic bags, how are we suppose to pack and throw our rubbish?

People talk about planting more trees to save our earth. I just read an article on the internet last night. There are scientist mentioned that if our global temperature increase for another 2 degree celcius, the trees may produce CO2 instead of O2. So, planting more trees doesn't guarantee to save our earth.