Environmental tipping points are in part determined by how humans react

Environmental tipping points are, according to a paper in the Proceedings of the National Academy of Sciences sometimes dependent on whether humans are indifferent, or prepared to accept the runaway consequences of environmental change or are sufficiently enlightened or motivated to do something to control or reverse the change.

http://www.eurekalert.org/pub_releases/2011-04/uond-hrm041511.php

The historical pattern seems to be one of government by crisis: of political action that follows extreme and unacceptable circumstances such as major environmental damage or actual impact on public health.  But there may loom in the future threats  that cause irreversible environmental damage and where there is no remedy.  It is here that political systems must act in anticipation rather than in arreas, when it will be too late.