The Iditarod features around 50 teams which each have 12-16 dogs. That's at least 800 dogs. Many mushers also have extensive kennels back home with more dogs that are breeding, in training, or retired. Let's just round it off and call it a thousand huskies, which is probably low-balling it. That means that the Iditarod race is apparently the same as running a luxury SUV for 10,000,000 miles, if this article is to be believed.
The race itself is 1,049 miles in length. That means that for the same carbon footprint our 50 dog teams produce, you could apparently make 9532 trips in a luxury SUV (assuming, of course, there were roads--which there are not).
Using the logic of this article, the Iron Dog is significantly more eco-friendly than the Iditarod. A snow machine is probably within the same magnitude of carbon footprint as a luxury SUV. You could run the Iron Dog for dozens of years before hitting the level of carbon impact that the dog teams do. Clearly, we should just switch to eco-friendly sports like snowmachine racing instead of dog mushing to solve global warming!
I don't think that's the answer the greenies would want you to come up with, though. If you haven't realized it yet, I'm pretty skeptical of this so-called news article. I'm kind of worried about what these people would do if given political power--I think their policies would be terrible for Alaska. As an outdoorsman, I honestly care about preservation of the environment and wild places. However, the carbon neutral people would want to shut down TAPS, eliminate snow machining, and make Lance Mackey be a vegetarian. Honestly, I don't know that there are many "greener" sports than dog mushing, and even that is apparently unacceptable to them.