I think it depends on where the yard is. A luscious green garden of non-native plants is a waste of water in desert areas. With the kinds of droughts that are becoming more common, replacing yards with rocks and low-water native plants is beneficial. And to be honest, even in areas that aren't in a drought, manicured lawns don't do much for the environment because they get loaded with pesticides and fertilizers to keep them as green and homogenous as possible. No flowers, no weeds, no bugs, no seeds, no diversity.