The Earth System: Sustaining Planetary Life-Support Systems

Abstract

The Earth as a whole can be viewed as a social-ecological system; in fact, the largest such system that can exist. The increasing evidence that human activities are now interacting with the natural environment of the Earth at the scale of the planet lends credence to this perspective. The scientific understanding of the human imprint on the planet is well recognized throughout the policy and management sectors and is raising severe challenges to governance structures. Never before has humanity had to devise and implement governance structures at the planetary scale, crossing national boundaries, continents and large biogeographic regions. Responsible stewardship of the global social-ecological system is the ultimate challenge facing humanity, as it entails safeguarding our own life-support system. The Earth as a social-ecological system is a very recent phenomenon. For nearly all of its existence, Earth has operated as a biophysical system, without the social component, as fully modern Homo sapiens arose only about 200,000–250,000 years ago. This long evolution of Earth as a biophysical system provides the canvas on which the human enterprise has exploded with exponentially growing impact in the last micro-instant of Earth’s existence. A full understanding of the implications of this phenomenon requires an understanding of Earth as a system, and particularly the natural envelope of environmental variability that provides the conditions for human life on the planet.