variables estimate the associated impacts at the global as well as the basin levels [2],
and inform the impacts at the pressure point of the DPSIR impact pathway (see
Fig. 1). Likewise, SDG Indicator 6.4.1 evaluates the same problem at the pressure
point in the impact pathway (in terms of water use efficiency). Consequently, at the
state point, SDG Indicator 6.4.2 accounts for the effects of excessive water withdrawals (i.e. the level of water stress), which is similar to the PB control variable
[12]. However, the proposed SDG indicators do not include any absolute limits.
We, therefore, recommend deploying the thresholds proposed for the freshwater use
PB because the control variables and the SDG indicators largely overlap; and both
inform the impacts at the pressure or state point in the impact pathway.
Increasing atmospheric CO 2 concentration and the associated CO 2 uptake by the
oceans have resulted in ocean acidification problems [2]. As a consequence, a PB
called “ocean acidification” was introduced with a control variable (state point)
and a threshold for carbonate ion concentration in terms of aragonite [2].
Meanwhile, the SDGs advanced an indicator (SDG Indicator 14.3.1) that estimates
the pH level of the oceans [12]. Although the control variable and the SDG
Indicator apply different units to track the ocean acidification effects, the objective
and the point of assessment in the DPSIR framework are the same. Moreover, both
the SDG indicator and the control variable evaluate the impacts on an absolute
scale. We, therefore, comprehend that the ocean acidification impacts can be
measured in terms of either aragonite or pH level of the oceans.
The “changes in biosphere integrity” PB adopts two control variables to assess
the two components of the biosphere: genetic and functional diversity [1, 2]. The
first component evaluates the extinction of species due to human pressures, whereas
the second estimates the loss of biodiversity at different ecosystem levels.
According to Fig. 1, the impacts pertaining to the both components are expressed at
the impact point of the DPSIR impact pathway. In this regard, the SDGs also
propose a set of indicators for protecting terrestrial, marine and freshwater
ecosystems [12]. SDG Indicators 14.4.1 and 14.5.1 estimate the proportion of fish
stocks existing within the biologically sustainable levels and the coverage of protected marine areas, respectively. Moreover, SDG Indicator 6.6.1 tracks the changes
occurring in both marine and freshwater ecosystems due to water quality degradation. Although these SDG indicators implicitly underpin the significance of
operating within the Earth’s carrying capacity, no relevant boundaries have been
reported. However, given that the objectives of these control variables overlap with
the SDG indicators, it makes sense to supplement the SDG indicators with the
thresholds proposed for the “changes in biosphere integrity” PB to inform the
environmental impacts in terms of genetic and functional diversities on an absolute
scale.
Considering the intensive use of nutrients and the associated eutrophication
effects in major ecosystems, Steffen et al. proposed the so-called “biogeochemical
flows” PB and two associated control variables [2]. These control variables evaluate
the eutrophication effects in oceanic, freshwater and terrestrial ecosystems. Given
that the major eutrophication problems arise from N and P fertiliser use and the
control variables evaluate the impacts at the pressure point (as shown in Fig. 1),
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C. Chandrakumar and S. J. McLaren
and inform the impacts at the pressure point of the DPSIR impact pathway (see
Fig. 1). Likewise, SDG Indicator 6.4.1 evaluates the same problem at the pressure
point in the impact pathway (in terms of water use efficiency). Consequently, at the
state point, SDG Indicator 6.4.2 accounts for the effects of excessive water withdrawals (i.e. the level of water stress), which is similar to the PB control variable
[12]. However, the proposed SDG indicators do not include any absolute limits.
We, therefore, recommend deploying the thresholds proposed for the freshwater use
PB because the control variables and the SDG indicators largely overlap; and both
inform the impacts at the pressure or state point in the impact pathway.
Increasing atmospheric CO 2 concentration and the associated CO 2 uptake by the
oceans have resulted in ocean acidification problems [2]. As a consequence, a PB
called “ocean acidification” was introduced with a control variable (state point)
and a threshold for carbonate ion concentration in terms of aragonite [2].
Meanwhile, the SDGs advanced an indicator (SDG Indicator 14.3.1) that estimates
the pH level of the oceans [12]. Although the control variable and the SDG
Indicator apply different units to track the ocean acidification effects, the objective
and the point of assessment in the DPSIR framework are the same. Moreover, both
the SDG indicator and the control variable evaluate the impacts on an absolute
scale. We, therefore, comprehend that the ocean acidification impacts can be
measured in terms of either aragonite or pH level of the oceans.
The “changes in biosphere integrity” PB adopts two control variables to assess
the two components of the biosphere: genetic and functional diversity [1, 2]. The
first component evaluates the extinction of species due to human pressures, whereas
the second estimates the loss of biodiversity at different ecosystem levels.
According to Fig. 1, the impacts pertaining to the both components are expressed at
the impact point of the DPSIR impact pathway. In this regard, the SDGs also
propose a set of indicators for protecting terrestrial, marine and freshwater
ecosystems [12]. SDG Indicators 14.4.1 and 14.5.1 estimate the proportion of fish
stocks existing within the biologically sustainable levels and the coverage of protected marine areas, respectively. Moreover, SDG Indicator 6.6.1 tracks the changes
occurring in both marine and freshwater ecosystems due to water quality degradation. Although these SDG indicators implicitly underpin the significance of
operating within the Earth’s carrying capacity, no relevant boundaries have been
reported. However, given that the objectives of these control variables overlap with
the SDG indicators, it makes sense to supplement the SDG indicators with the
thresholds proposed for the “changes in biosphere integrity” PB to inform the
environmental impacts in terms of genetic and functional diversities on an absolute
scale.
Considering the intensive use of nutrients and the associated eutrophication
effects in major ecosystems, Steffen et al. proposed the so-called “biogeochemical
flows” PB and two associated control variables [2]. These control variables evaluate
the eutrophication effects in oceanic, freshwater and terrestrial ecosystems. Given
that the major eutrophication problems arise from N and P fertiliser use and the
control variables evaluate the impacts at the pressure point (as shown in Fig. 1),
418
C. Chandrakumar and S. J. McLaren