CO2 emissions from automobiles are regarded as responsible for global warming, so you can contribute something to the environment by commuting by train.
ボランティアとして、町のゴミ拾いに参加したい。
As a volunteer, I would engage in picking up litter on the street.
I make a point of buying environment-friendly goods, separating trash for recycling, and frequently adjusting the air-conditioner. I think these small steps on the individual level are most important in order to preserve the Earth's environment.