Harvesting the Biosphere: What We Have Taken from Nature

Part I: The Earth’s Biomass: Stores, Productivity, Harvests

I The Earth’s Biomass: Stores, Productivity, Harvests 2 Part I NASA’s global map shows the intensity of the Earth’s primary (photosynthetic) productivity. The darkest shading in the Amazon and in Southeast Asia indicates net annual primary productivity approaching 1 kg C/m2 . A high-resolution image in color can be downloaded at http://earthobservatory.nasa.gov/Features/GlobalGarden/Images/npp_199912_bump_lrg.jpg. The Earth’s Biomass 3 In December 1990, the Galileo spacecraft came as close as 960 km to the Earth’s surface in order to get a gravitational assist from the planet on its way to Jupiter.This flyby was used by Sagan et al. (1993) as an experiment in the remote detection of life on Earth: just imagine that the spacecraft, equipped with assorted detection devices, belonged to another civilization, and registers what its beings could sense. The three phenomena indicating that this planet was very different from all others in its star system were a widespread distribution of a pigment, with a sharp absorption edge in the red part of the visible spectrum; an abundance of molecular oxygen in the Earth’s atmosphere; and the broadcast of narrow-band,pulsed,amplitude-modulated signals. The light-harvesting pigment absorbing in red light is chlorophyll, a key enabling agent of photosynthesis, the planet’s defining energy conversion mechanism, which releases oxygen and produces an astonishing variety of biomass, directly as plants and indirectly as the energizer of all nonphotosynthesizing organisms, from the simplest heterotrophic bacteria to humans, the species that began, at the turn of the twentieth century, sending modulated signals into space as yet another demonstration of its mental prowess.These realities circumscribe and define the subject of this book: there would be no story of human evolution and advancing civilization without a parallel story of harvesting the biomass, and the increasing intensity and extent of biomass harvests are in turn changing the very foundations of civilization’s well-being. Human harvesting of the biosphere has transformed landscapes on vast scales, altered the radiative properties of the planet, impoverished as well as improved soils, reduced biodiversity as it exterminated many species and drove others to a marginal existence, affected water supply and nutrient cycling, released trace gases and particulates into the atmosphere, and played an important role in climate change. These harvests started with our hominin ancestors hundreds of thousands of years ago, intensified during the era of Pleistocene hunters, assumed entirely new forms with the adoption of sedentary lifeways, and during the past two centuries transformed into global endeavors of unprecedented scale and intensity. The story of biomass harvests spans all of human evolution and all of our history, and its continuation will be a key determinant of our future success or failure as a civilization. And yet, comprehensive inquiries into this complex harvesting process are of surprisingly recent origin (only a few decades old), and interest still remains heavily tilted toward particulars rather than toward a global examination of this now planetwide transformation. But an important chore must be taken care of before I proceed. The careless or vague use of undefined (or poorly defined) terms is all too common in modern scientific discourse. While putting in place a fairly comprehensive foundation of accurate definitions of many relevant variables is not a captivating way to start a book, for the sake of clarity I will briefly do just that. ...