I know there are a lot of ways artists can contribute to the environment by use of "green" materials. Most artists by nature are into recycling and conserving, and many artists contribute percentages of their sales to worthy causes. I support coral reef conservation organizations in this manner. Another way to contribute is by refusing to use materials derived from threatened species.
One of the organizations I donate to, The Coral Reef Alliance recently published a newsletter article about the huge market for red coral jewelry worldwide depleting the species. There has been a movement to put red coral on the threatened species list, but the proposal on the table has been blocked by nations who are benefiting financially from the sales of red coral (and guess what, the US is the biggest buyer of red coral!). If jewelers would simply refuse to use this material, the threat would go away.
For more information, visit http://www.coral.org
I am sure there are many other ways artist's can help the environment. Fee free to contribute your ideas in this thread.