Anthropogenic climate change represents one of the greatest and swiftest transformations the earth has experienced. Some scientists argue that since the advent of the industrial era, humanity has caused enough biotic, sedimentary and geochemical changes to the planet that we have left the Holocene and entered a new geological phase: the Anthropocene. The implications of this geologic event for the future of life on earth are unclear. Understandably, some scientists have interpreted this wholesale transformation of the planet's climate and biosphere systems as a sign that humanity is reaching, or has already exceeded, the limits of the planet's carrying capacity.

In "The Planet of No Return," Ellis takes issue with this position and argues that human systems have proven resilient to all sorts of natural system transformations including climatic fluctuations. Successful adaptation to global warming, however, requires a transformation of human systems concomitant with the scale of transformation taking place in the planet's natural systems. While Ellis outlines some developments in agricultural systems, he fails to appreciate or take full account of the transformations needed on our warming planet.

Ellis simplifies humanity's agricultural prowess. Large-scale geoengineering of terrestrial ecosystems is only part of the story. Humanity's agricultural systems do not operate in a vacuum. They are embedded in complex cultural, economic and political systems whose interactions and feedbacks are impossible to disentangle. The success of Rome's agricultural systems, for example, was due less to the Roman plough than the influence of the Roman state. The same can be said of America's formidable agricultural systems. Without the large-scale intervention of the US Army Corps of Engineers during the Great Depression in Florida's natural water systems, the state would still be an impenetrable marsh rather than the agricultural powerhouse it is today. Indeed, throughout recorded history natural and human systems have often decoupled with complex consequences for carrying capacity. Witness North Korea -- a political system capable of producing the atomic bomb but incapable of feeding its population.

In fact, institutional innovation in the political and economic spheres may well be the single most important factor explaining the resilience of the most successful human systems on the planet.Daron Acemoglu, James Robinson. 2012. Why nations fail: The origins of power, prosperity and poverty. USA: Crown PublishersThe level of reorganization needed for agricultural systems to adapt to and mitigate climate change will only be achieved when it is matched by an equally large leap in humanity's political, economic, social and cultural systems. This has been the case throughout humanity's past and will continue to be so in the future.

In the 1951 science fiction film "When Worlds Collide," humanity is given a second chance, following the earth's destruction, on the planet Zyra. As the spaceship with a chosen few lands on Zyra, the survivors discover the planet is not only inhabitable but that the ruins of an ancient civilization lie semi-hidden in luxuriant vegetation. The film provides a prescient metaphor for the crossroads at which humanity stands today.

We possess an incredibly sophisticated knowledge about our past and present. We have even reached the point where, through computer models, we can catch a glimpse of our possible futures. Yet never has humanity had access to so much information and proven so incapable of reaching an imaginative conclusion about what ought to be done. It is as if the capacity to know has stunted the capacity to imagine. This is unfortunate because imagination, above all, is what we need to redesign our human systems to make it possible for the human species to thrive beyond the 21st Century.

Finally, while Ellis's point is well taken regarding the remarkable ability of human agricultural systems to adapt to change in the earth's natural systems, one wonders whether our current political systems will show identical stamina in confronting the advent of the Anthropocene. In the 1967 Star Trek episode, "Planet of No Return," Captain Kirk, the foremost political authority aboard the Starship Enterprise, orders the destruction of the planet in question. Let us work, through the exercise of political and technological imagination, to avoid a similar fate for our planet.