The quotation is from Edward Abbey. The longer quotation is:

"Leave your dens, abandon your cars and walk out into the great mountains, the deserts, the forests, the seashores. Those treasures still belong to all of us. Enjoy them to the full, stretch your legs, expand your lungs, enliven your hearts -- and we will outlive the greedy swine who want to destroy it all in the name of what they call GROWTH.
God bless America -- let's save some of it.
Long live the weeds and the wilderness yet!”