When my wife and I got married, we asked for no gifts and instead provided a list of non-profits (focused on advocating for marriage equality) that we invited guests to donate to in our name.
Other things you can do to limit consumption at your wedding: Our church was partnered with a men's shelter, and residents at the shelter were the ones getting paid to set up the space and then rearrange it for the reception while we were outside taking pictures. All the leftovers from the reception buffet went immediately next door to the shelter as well. I don't know how practical the first will be for you, but making sure the extra food (and flowers, if any) get donated is a great way to offset the consumptive footprint of a traditional wedding.