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Revising the
planetary boundary for
freshwater use
Dieter Gerten
Head of Flagship Activity „Planetary Opportunities & Plan...
The concept of “planetary boundaries” (PBs)
 For nine interacting earth system processes PBs were identified,
which altog...
Four PBs already transgressed
Steffen et al.,
Science 2015
PB for human water consumption: 4,000 km3/yr
Current status: 1,...
Global discharge = maximum available freshwater: 40,700 km3 yr-1
 Minus inaccessible flow (69%): 12,500 km3 yr-1
Rockströ...
Estimated environmental flow requirements
Median estimate
from 5 methods
Maximum estimate
from 5 methods
Gerten et al., CO...
Freshwater PB may be lower than thought
Steffen et al.,
Science 2015
Regional boundaries crossed in many places
Original P...
PBs as a chance for transformation
Safe space =
Opportunity
space*
* „Planetary opportunities“ to
stay below the freshwate...
J. Jägermeyr (PIK)
 Talk tomorrow!
Food/Water Security session
Available cropland
(land-system & biosphere PB)
?...?
Incr...
PB interactions: climate change
+2°C (climate mitigation target)
Risk of lower water availability and/or more droughts (19...
 Respecting environmental flow requirements points to a
PB for consumptive freshwater use of 1,100–4,500 km3 yr-1.
 The ...
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Revising the planetary boundary for freshwater use, Dieter Gerten

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Dieter Gerten
Head of Flagship Activity „Planetary Opportunities & Planetary Boundaries“
Research Domain I: Earth System Analysis
Potsdam Institute for Climate Impact Research
Potsdam, Germany

at the Our Common Future Under Climate Change conference, July 7-10 in Paris, France.

More at http://www.commonfuture-paris2015.org/

Published in: Science
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Revising the planetary boundary for freshwater use, Dieter Gerten

  1. 1. Revising the planetary boundary for freshwater use Dieter Gerten Head of Flagship Activity „Planetary Opportunities & Planetary Boundaries“ Research Domain I: Earth System Analysis Potsdam Institute for Climate Impact Research Potsdam, Germany gerten@pik-potsdam.de
  2. 2. The concept of “planetary boundaries” (PBs)  For nine interacting earth system processes PBs were identified, which altogether demarcate the Earth‘s Holocene state Climate change | Stratospheric ozone depletion | Atmospheric aerosol loading Ocean acidification | Biogeochemical flows | Chemical pollution Land use change | Biodiversity loss | Freshwater use  Holocene is regarded as a safe operating space within which human civilization could develop and which therefore should not be left  PBs point to the risks of leaving the safe space, adopting a precautionary principle after Rockström et al., Nature 2009
  3. 3. Four PBs already transgressed Steffen et al., Science 2015 PB for human water consumption: 4,000 km3/yr Current status: 1,600–2,600 km3/yr
  4. 4. Global discharge = maximum available freshwater: 40,700 km3 yr-1  Minus inaccessible flow (69%): 12,500 km3 yr-1 Rockström et al., Nature 2009 Postel et al., Science 1996  Minus environmental flow requirements* (9%) and volumes to avoid water stress (9%): 5,000 km3 yr-1  Lower end of uncertainty range ±1,000 km3 yr-1  Planetary boundary 4,000 km3 yr-1 Original top-down calculation of freshwater PB ↔ here: Bottom-up calculation of the freshwater PB based on spatially explicit estimations of environmental flow requirements* o Using a dynamic biosphere model (LPJmL) o Using 5 methods to estimate the flow requirements o Reflecting different conservation goals and ethical considerations
  5. 5. Estimated environmental flow requirements Median estimate from 5 methods Maximum estimate from 5 methods Gerten et al., COSUST 2013 Fraction of river flow to sustain ecosystems
  6. 6. Freshwater PB may be lower than thought Steffen et al., Science 2015 Regional boundaries crossed in many places Original PB: 4,000 km3/yr New PB and range: 1,100–4,500 km3/yr (avg. 2,800 km3/yr) Current status: 1,600–2,600 km3/yr
  7. 7. PBs as a chance for transformation Safe space = Opportunity space* * „Planetary opportunities“ to stay below the freshwater PB:  Safeguard aquatic ecosystems  Improve water productivity  Reduce water-intensive diets  Optimise spatial production patterns and virtual water trade  … (water consumption)
  8. 8. J. Jägermeyr (PIK)  Talk tomorrow! Food/Water Security session Available cropland (land-system & biosphere PB) ?...? Increased future demand for food and water ?...? Global yield increase through improved on-farm water management while respecting the freshwater PB Efficient water use: one planetary opportunity
  9. 9. PB interactions: climate change +2°C (climate mitigation target) Risk of lower water availability and/or more droughts (19 climate models) Gerten et al., ERL 2013 +3.5°C (current emission reduction pledges)
  10. 10.  Respecting environmental flow requirements points to a PB for consumptive freshwater use of 1,100–4,500 km3 yr-1.  The PB is already transgressed if the lower estimate applies.  Positioning the boundary implies ethical standpoints.  Furthermore to be quantified: o Other components of the freshwater PB (accessibility) o Links with other PBs (land use!) o Pathways for society to stay within the PBs Conclusions Thank you for your attention!  Core question: Is food production for a growing world population possible while staying within all planetary boundaries?

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