I have just read this article about green eating. I am pleased that the author address the issue of eating less meat. As you may be able to tell I am vegan, and believe that it is one of the simplest and easiest ways to reduce your environmental impact . But let's face it, many people for a variety of reasons will never go vegan, and therefore from an environmental point of view, being a Lessmeatatarian - eating less meat - is a good alternative. A typical Western diet consists of far more meat than our bodies require. This has many adverse effects from being bad for one's health to the obvious problems involved in the intensive rearing of animals, from the sometimes obscene cruelty that is nowadays simply a part of the industry  to the breeding and promotion of disease.
Therefore, if you want to do one thing that can make a difference on numerous levels, all of them important, eat less meat.
 Of course this only applies if you eat sensibly, cook most of your veggies, grains etc from scratch (or even better, have them raw in a nice salad) and don't live off only polystyrene-packaged take-aways and factory-produced substitutes.
 Don't believe the PETA link? See the movie Earthlings. It will tell you more than you ever wanted to know about whether the animals that end up on dinner plates really frolic happily on wide open fields until they are humanely and painlessly killed, or whether the reality is slightly darker.