I just don't see the moral obligation. The world has been constantly falling under the influence of man for close to a million years now, virtually nothing is trully "natural" or untouched by human guidance. The only thing which has seemed to have changed recently is social morality in a post industrial paradigm more than the enviromental change itself. People say the degree of change is speeding up, but to me it seems like whatever change is happening we are dealing with it fairly well. Even in a theoretical food chain collapse it would not be instantaneous, it would be a gradual decline and infrastructure would compensate or adapt in tandem. I do believe however we should switch from fossil to nuclear on materialistic grounds. It is criminal how more effective nuclear is as a fuel source and the lack of potentially harmfull waste products it produces, a good number of them even have product use.