Table 3.3 Defining Planetary Boundaries
Earth-system
process
Control variable
Boundary
value
Current
value
Boundary
crossed
Preindustrial
value
1. Climate change Atmospheric
carbon dioxide
concentration (ppm
by volume) [25]
See also: Tipping
point (climatology)
350
387
Yes
280
Alternatively:
Increase in radiative
forcing (W/m
2
)
since the start of the
industrial
revolution (*1750)
1.0
1.5
Yes
0
2. Biodiversity
loss
Extinction rate
(number of species
per million per
year)
10
>100
Yes
0.1–1
3. Biogeochemical (a) anthropogenic
nitrogen removed
from the
atmosphere
(millions of tonnes
per year)
35
121
Yes
0
(b) anthropogenic
phosphorus going
into the oceans
(millions of tonnes
per year)
11
8.5–9.5 No
−1
4. Ocean
acidification
Global mean
saturation state of
aragonite in surface
seawater (omega
units)
2.75
2.90
No
3.44
5. Land use
Land surface
converted to
cropland (%)
15
11.7
No
Low
6. Freshwater
Global human
consumption of
water (3 km/year)
4000
2600
No
415
7. Ozone depletion Stratospheric ozone
concentration
(Dobson units)
276
283
No
290
8. Atmospheric
aerosols
Overall particulate
concentration in the
atmosphere, on a
regional basis
Not yet quantified
(continued)
3.2 How Mainstream Economics Views Nature and Its Governance
91