We do nothing, shrug and carry on as before because we are not designed to react to long term threats. Immediate problems ( a wolf jumping at us) gives us an immediate, and effective response which we inherit from out forebears. But long term? Meh, cycle, not drive? Stop smoking? Take exercise? etc We need a way of thinking and reacting that, until now we have been, by dint of out genetic past, been unable to do.