Great revolutions

The idea that humans have the potential to shape the world around them is nothing new. People alter their surroundings directly to suit their perceived needs and those actions have indirect effects on still other environmental systems. Look up from the computer and gaze around you right now. What do you see? Our species is remarkably effective at creating new spaces, new worlds, to suit our purposes. We have known this for a long time.

Geographers familiar with the work of George Perkins Marsh would recognize this as one of the oldest refrains echoing throughout the history of the discipline. In the middle of the nineteenth century he warned of the dangerous ways in which people altered the physical environment around them.

“...man is everywhere a disturbing agent. Wherever he plants his foot, the harmonies of nature are turned to discords. The proportions and accommodations which insured the stability of existing arrangements are overthrown... These intentional changes and substitutions constitute, indeed, great revolutions; but vast as is their magnitude and importance, they are, as we shall see, insignificant in comparison with the contingent and unsought results which have flowed from them.”

The historian Felipe Fernandez-Armesto echoes this idea of humans as environmental forces by describing civilization itself as a process whereby societies shape the environment around them to suit their real or perceived needs. In short, the drive to shape the environment is civilizing. There is no moral imperative associated with this, it is not necessarily good or bad, it just is.

Cities accordingly, represent the pinnacle of civilization in that they are the locations where the most intense and complete modification of the surrounding environment has taken place to serve its inhabitants. Not only do cities rearrange the metropolis itself but this civilizing impulse has far-reaching effects into the spaces beyond. Montgomery also looks at relationships between the physical environment and civilization, only he focuses on the downside of intensive settlement, the degradation of soils, and the resulting impacts on society.

Back in 1873 Antonio Stoppani suggested the creation of a new geologic era called the anthropozoic recognizing human activities as having enormous power and universality compared to the physical and chemical forces exerted by environmental processes. In the view of Nobel laurate chemist Paul Crutzen, these historical ideas have matured into something he refers to as the Anthropocene Era. What is the difference between the 1873 version and the 2000 version? Climate.

For a century and half, we have understood the power people have to alter vegetation, ecosystems, hydrology, and land cover. Until recently, this human control has not been extended to the atmosphere. Crutzen points to the growing concentrations of atmospheric CO2 and methane beginning in the mid-18th century and corresponding environmental changes in atmospheric composition and heat retention we are just now beginning to confront.

Climate changes the game. Long-term changes in temperature and precipitation will indirectly affect vegetation, ecosystems, hydrology, and land cover to an extent we have not seen previously. Our intentional reshaping of the world has caused "great revolutions" in the physical environment around us. But these effects will seem insignificant compared to the indirect effects of these changes. Marsh recognized this in 1864.