Environmental Engineering Reference
In-Depth Information
impact has reached from deep aquifers and the ocean's abyss to the stratosphere
(Foley et al. 2005).
A single-paragraph list of such notable transformations must include the follow-
ing: changes of surface albedo and hence of soil and vegetation temperatures,
evaporation, and evapotranspiration (Liang et al. 2010); altered CO
2
l uxes due to
photosynthesis and respiration and increased emissions of CO
2
from biomass com-
bustion (Houghton 2003; Bond-Lamberty and Thomson 2010; Dolman et al. 2010);
reduced or increased emissions of volatile hydrocarbons and numerous trace gases,
including CH
4
, N
2
O, NO
x
, and SO
x
(Houweling et al. 2008; Crutzen, Mosier,
and Smith 2008; Penuelas and Staudt 2010); increased generation of terrigenic dust,
lowered retention of soil moisture, enhanced soil erosion and sedimentation, and
losses of organic soil nitrogen (Kellogg and Grifi n 2006; Wilkinson and McElroy
2007; Lal 2007; Eglin et al. 2010); and declines in abundance and biodiversity
affecting species ranging from soil microfauna to the top predators, with perhaps
the outright extinction of some invertebrates and many vertebrate animals (Butchart
et al. 2010; Rands et al. 2010; IUCN 2011).
Curiously, a recent assessment of a safe operating space for humanity—one that
identii es quantii es the planetary boundaries that must not be transgressed if unac-
ceptable environmental change is to be prevented (Rockström et al. 2009)—does
not list either a minimum phytomass stock or primary productivities among its ten
concerns. Rather, these concerns are climate change, disturbances of nitrogen and
phosphorus cycles, stratospheric ozone depletion, ocean acidii cation, global fresh-
water use, atmospheric aerosol loading, and chemical pollution, and they address
phytomass stocks and productivity only indirectly, via the categories of biodiversity
loss and changes in land use (explicitly dei ned as the percentage of global land
cover converted to cropland, with a proposed limit of no more than 15%, compared
to the current 12%).
In my list the collective and cumulative impact of harvesting the biosphere would
have been included explicitly and prominently because it has been—together with
the increasing production, processing, and combustion of fossil fuels and the extrac-
tion and use of other minerals—the principal cause of the human transformation
of the biosphere. The recent pace and extent of this process have led not only to
questions about the degree of the human appropriation of the biosphere's primary
production that I analyzed in some detail in chapter 11 but also to concerns
about the “ecological overshoot” of the human economy (Wackernagel et al. 2002;
Kitzes et al. 2008) and about the perilous human domination of Earth's ecosystems
(Vitousek et al. 1997; Kareiva et al. 2007; McCarthy 2009).
