I think the rotomolded boats probably make a smaller impact, simply because they might be recyclable?????? Maybe.
hmmmmm.....perhaps a biodegradable boat. Then you guys can smoke it when the hulls get delam. All kidding aside, I was reading in an automotive magazine about these two guys who were trying to get a patent on a biodegradable jeep body. I can't find an online article, but seem to recall that they had planned on using industrial hemp fibers in place of glass.
Actually, I don't think that cross-linked polyethylene plastic is recyclable.