Environmental Engineering Reference
In-Depth Information
These concerns have found their most extreme expressions in the works of
Martin Rees and James Lovelock. Rees (2003) details in
Our Final Hour: A Scien-
tist's Warning
how “terror, error and environmental disasters” threaten the very
survival of humankind during the twenty-i rst century. And Lovelock (2009), in
another “i nal warning,” foresees the vanishing face of Gaia, a planetary goddess of
his anthropomorphic constructs. Perhaps the two most radical expressions of these
concerns in less catastrophically inclined academic publications have been the pro-
posal to use a new label for the era we live in and to discard the traditional clas-
sii cation of biomes in favor of new human-dominated entities.
Crutzen (2002) has argued that the escalating effects of humans on the global
environment—above all in the form of anthropogenic emissions of CO
2
, whose
atmospheric perseverance may change climate for millennia to come, but also in the
form of tropical deforestation, ocean exploitation, and the mobilization of reactive
nitrogen—are overwhelming the great forces of nature and that this process warrants
labeling the period that began during the late eighteenth century the Anthropocene.
His arguments were subsequently elaborated (Steffen, Crutzen, and McNeill 2007),
and the i rst steps have been taken by the International Commission on Stratigraphy
to formalize the new classii cation (Zalasiewicz, Williams, and Crutzen 2010); in
2016 the International Geological Congress will consider whether the changes have
been distinctive and enduring enough to add a new epoch (Vince 2011).
Ruddiman ( 2005) supports the concept of an anthropogenic era but argues that
it began 8,000 years ago, when CO
2
began its “anomalous increase,” followed by
the rise CH
4
concentrations that began some 5,000 years ago, driven i rst by forest
clearance for farming and then by rice cultivation. Even that backdating is not
enough for Smith, Elliott, and Lyons (2010), who assume that about 100 million
North American herbivores were killed by hunting and claim that the resulting
decline in CH
4
emissions could explain the observed decrease of atmospheric CH
4
concentrations dated to the beginning of the Younger Dryas, and that this presumed
connection justii es a recalibration of the onset of the Anthropocene to 13,400 years
before the present. Given the enormous uncertainties in estimating CH
4
emissions
from modern cattle, it is not surprising that the range of their estimate for methane
production by America's megafauna could explain as little as 10% or as much
as 100% of the recorded decline, making their claim (already based on dubious
assumptions of 100 million carcasses) a matter of arbitrary choice.
Approaching the problem in a different way, Ellis and Ramankutty (2008) believe
that the conventional biome classii cation that sees ecosystem processes as a function
of macroclimate is unrealistic because the biosphere is now dominated by anthromes
