When I recently returned from a trip to California I took something with me that is very precious to that state, something that is causing all kinds of problems for California, but is absolutely essential to everyone and everything in California. I filled my water bottle in the airport and took it with me. Chances are the water actually came from Nevada, but that is beside the point. The point is that California is in a debilitating drought. Green things are hard to find now in California: grey and brown dominate the landscape. Flying over California is flying over a desert.
The drought affects everybody in California and is developing into a threat for society. Other parts of the country look to California for policies because they experience equally dramatic conditions. The southwest of Oklahoma is one of these areas.
Arguably, the drought is being caused by Global Change, is at least partly human induced. Another effect the water crisis has is a lot less visible: the lack of water on the surface and in the ground is changing the geology of California. Just like the melting of the glaciers removed so much weight from the land that it uplifted after the last ice age, California is now showing crustal uplift as shown in a recent study that appeared in the journal Science (http://www.sciencemag.org/content/345/6204/1587.full). Truly humans are changing their environment here!
Another aspect of the drought may have even more dramatic effects later: as we deplete the drinkable surface water, more and more water is pumped out of the ground. A depleted pond will fill up again after a good rain, but it takes a very long time to replenish our aquifers. What we are doing is not sustainable and at the cost of future generations. We are drinking the water of future generations and by doing so we may render the land uninhabitable.
flying over Southern California
Inhabiting the Anthropocene 
What a sobering photo . . .
This post highlighted two things for me. First, it is important (but still amazing to me) to see the connection between biology and geology, as shown by the way that human activity changes something as fundamental as the height of the Earth’s crust. We are used to thinking of interconnectedness in the biological sphere; in an ecosystem everything is connected to everything else. Here there seems to be a systemic connection between biological activity (fossil fuel use by people), which affects atmospheric processes leading to drought, which affects water usage, which raises the level of the ground.
Second, what you say about the impact on future generations (and maybe not the distant future!) makes a point about habitability. That is that, as with sustainability, habitability should be understood as a temporal concept. In my contributions here I’ve tried to stress the idea that habitability is in key ways a product of human activity–i.e. that a place is made habitable by the activities of its inhabitants. But as the drought case vividly shows, when we say a place is habitable, we have to consider this: given the full impacts of the activities that make it habitable (in the way it is being inhabited), what is the time scale over which that habitability can be sustained? This points to a (perhaps obvious) answer to a big question about the sustainability idea: sustainability of what? I think it is helpful to say that the object of sustainability is habitability–in the full sense of the term we’ve begun to explore here on this blog.