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5 Understanding the Complementarities of Environmental …
We illustrate this with two brief examples. On climate change, for instance, atmospheric concentration of CO 2 and radiative forcing have been chosen as two control
variables for setting climate boundary, but also for measuring current climate state
(Rockström et al. 2009a). The concurrent use of the two variables represents an
unnecessary dual-objective trade-off and thus may compromise the usefulness of
setting carbon boundary. By using carbon footprint—a consensus impact indicator
of climate change (Hellweg and I Canals2014; Minx et al. 2013), a convergence of
these two independent variables is harmoniously achieved. According to Hoekstra
and Wiedmann (2014), global carbon footprint is amounted to 46–55 Gt CO 2 -eq./yr
for 2011.
In the case of freshwater use, Rockström et al. pose that at present the annual global
water consumption is approximately 2600 Gm
3 /yr. Apart from the uncertainty of this
approximation, the value only accounts for the evaporation and transpiration from
surface and ground water—a small fraction of total freshwater usage (Molden 2009),
ignoring green water that is estimated to be 6700 Gm
3 /yr (Hoekstra and Mekonnen
2012). The serious underestimate of human freshwater consumption should have
been overcome by aggregating the blue and green water footprints using existing
water footprint models with high degrees of scientific certainty.
The two cases as referred to demonstrate the necessity of standardized and reproducible footprint models to support the assessment of actual human-induced environmental pressure or impact. One may extrapolate that the scientific foundation of the
PBF will be consolidated by the substitution of well-grounded footprint models for
rough current estimates. However, this does not justify the incorporation of capacity
thresholds into footprint indicators within the existing footprint discussions. Ambiguity and confusion may occur, as proven by the ecological footprint which sometimes refers to the footprint itself, and at other times refers to both the footprint
indicator and biocapacity. As a result, the purpose of the remainder of this chapter is
not to consider boundaries as a part of footprints, nor to consider footprints as a part
of boundaries. Instead, we keep the footprint metric and boundary metric separate,
while taking the two as complements in assessing environmental sustainability.
5.4 Complementary Use of Environmental Footprints
and Planetary Boundaries for Environmental
Sustainability Assessment
5.4.1 The Root of the Environmental Sustainability Concept
Responding to the increasing challenge of finding ways to maintain the carrying
capacity of the global ecosystem, the significance of the boundary concept in making
sense of environmental sustainability had already been underlined in the late twentieth century. For example, Daly (1990) presented an operational principle of sustainable development; that is, the regenerative and absorptive capacity must be treated as
5 Understanding the Complementarities of Environmental …
We illustrate this with two brief examples. On climate change, for instance, atmospheric concentration of CO 2 and radiative forcing have been chosen as two control
variables for setting climate boundary, but also for measuring current climate state
(Rockström et al. 2009a). The concurrent use of the two variables represents an
unnecessary dual-objective trade-off and thus may compromise the usefulness of
setting carbon boundary. By using carbon footprint—a consensus impact indicator
of climate change (Hellweg and I Canals2014; Minx et al. 2013), a convergence of
these two independent variables is harmoniously achieved. According to Hoekstra
and Wiedmann (2014), global carbon footprint is amounted to 46–55 Gt CO 2 -eq./yr
for 2011.
In the case of freshwater use, Rockström et al. pose that at present the annual global
water consumption is approximately 2600 Gm
3 /yr. Apart from the uncertainty of this
approximation, the value only accounts for the evaporation and transpiration from
surface and ground water—a small fraction of total freshwater usage (Molden 2009),
ignoring green water that is estimated to be 6700 Gm
3 /yr (Hoekstra and Mekonnen
2012). The serious underestimate of human freshwater consumption should have
been overcome by aggregating the blue and green water footprints using existing
water footprint models with high degrees of scientific certainty.
The two cases as referred to demonstrate the necessity of standardized and reproducible footprint models to support the assessment of actual human-induced environmental pressure or impact. One may extrapolate that the scientific foundation of the
PBF will be consolidated by the substitution of well-grounded footprint models for
rough current estimates. However, this does not justify the incorporation of capacity
thresholds into footprint indicators within the existing footprint discussions. Ambiguity and confusion may occur, as proven by the ecological footprint which sometimes refers to the footprint itself, and at other times refers to both the footprint
indicator and biocapacity. As a result, the purpose of the remainder of this chapter is
not to consider boundaries as a part of footprints, nor to consider footprints as a part
of boundaries. Instead, we keep the footprint metric and boundary metric separate,
while taking the two as complements in assessing environmental sustainability.
5.4 Complementary Use of Environmental Footprints
and Planetary Boundaries for Environmental
Sustainability Assessment
5.4.1 The Root of the Environmental Sustainability Concept
Responding to the increasing challenge of finding ways to maintain the carrying
capacity of the global ecosystem, the significance of the boundary concept in making
sense of environmental sustainability had already been underlined in the late twentieth century. For example, Daly (1990) presented an operational principle of sustainable development; that is, the regenerative and absorptive capacity must be treated as