As most people on the planet aren't Christian this probably won't mean something to everybody. However, if you live in the western world it's hard not to get caught up in the consumerism that surrounds Christmas, no matter what your beliefs are. As we in the west are responsible for most of the worlds pollution, due largely to our appetite for things we don't need, which we buy more of at Christmas than any other time of the year, why not try something different this year?
Buy fewer presents or even none at all. If you must buy presents do Chris Kringle amongst your family and friends and buy one inexpensive present (under $20) each for someone else.
Also, if you do buy presents buy ones that have less impact on the environment.
Buy less food for Christmas dinner. Have a simple Christmas meal and don't pig out on the Christmas pud.