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Planetary Boundaries: Exploring the safe operating space for humanity in the Anthropocene ( Nature , 461 : 472 – 475, Sept 24 - 2009) Johan Rockström, Will Steffen, Kevin Noone, Åsa Persson, F. Stuart Chapin, Eric F. Lambin, Timothy M. Lenton, Marten Scheffer, Carl Folke, Hans Joachim Schellnhuber, Björn Nykvist, Cynthia A. de Wit, Terry Hughes, Sander van der Leeuw, Henning Rodhe, Sverker Sörlin, Peter K. Snyder, Robert Costanza, Uno Svedin, Malin Falkenmark, Louise Karlberg, Robert W. Corell, Victoria J. Fabry, James Hansen, Brian Walker, Diana Liverman, Katherine Richardson, Paul Crutzen, Jonathan A. Foley
Humanity’s period of grace – the last 10000 years Aborigines arrive in Australia Beginning of agriculture Great European civilisations: Greek, Roman Source: GRIP ice core data (Greenland) and S. Oppenheimer, ”Out of Eden”, 2004 First migration of fully modern humans out of Africa Migrations of fully modern humans from South Asia to Europe
Humanity in the Anthropocene Steffen, W., et al. 2004 Kaufman, Darrell S., et al. 2009. Recent Warming Reverses Long-Term Arctic Cooling. Science , September 4, 2009
From: ” Limits to growth” ” Carrying capacity” ” Guardrails” ” Tipping Elements” To: ” Planetary Boundaries”
PB concept rests on three branches of Scientific inquiry
Earth System and sustainability science (Understanding Earth System processes; ICSU, IGBP, ESSP, IPCC, MEA, evolution of sustainability science…)
Scale of human action in relation to the capacity of the planet to sustain it (Kenneth Boulding Spaceship Earth, Herman Daly, Club of Rome, Ecological Economics reserach agenda, Ecological Footprint...)
Shocks and Abrupt change in Social-Ecological systems from local to global scales
Should constitute an unacceptable human-induced global environmental change.
The position of a planetary boundary is a function of the degree of risk the global community is willing to take, and/or for how long a boundary can be transgressed before a threshold is crossed.
The position is furthermore a function of the social and ecological resilience of the impacted societies (e.g., the ability of coastal communities to cope with sea level rise later this century if a climate change boundary is transgressed for too long).
Boundaries are identified for processes where the time needed to trigger an abrupt or irreversible change is within an “ethical time horizon” - a timeframe (i) short enough to influence today’s decisions while long enough to provide the basis for sustainability over many generations to come, and (ii) within which decisions taken can influence whether or not the estimated threshold is crossed.
A variable that is universally applicable for the sub-systems linked to the same boundary
Can function as a robust indicator of process change
Available and reliable data.
“… we have taken a pragmatic approach, sometimes choosing a parameter of ultimate ecological impact (e.g., rate of extinction of species for biodiversity loss), a proxy indicator (e.g., aragonite saturation state for ocean acidification), or a human driving force variable (e.g., P load in the oceans)”.
Climate Change Ocean acidification Ozone depletion Global Freshwater Use Rate of Biodiversity Loss Biogeochemical loading: Global N & P Cycles Atmospheric Aerosol Loading Land System Change Chemical Pollution Planetary Boundaries
Climate Change < 350 ppm CO 2 < 1W m 2 (350 – 500 ppm CO 2 ; 1-1.5 W m 2 ) Ocean acidification Aragonite saturation ratio > 80 % above pre-industrial levels (> 80% - > 70 %) Ozone depletion < 5 % of Pre-Industrial 290 DU (5 - 10%) Global Freshwater Use <4000 km 3 /yr (4000 – 6000 km 3 /yr) Rate of Biodiversity Loss < 10 E/MSY (< 10 - < 1000 E/MSY) Biogeochemical loading: Global N & P Cycles Limit industrial fixation of N 2 to 35 Tg N yr -1 (25 % of natural fixation) (25%-35%) P < 10× natural weathering inflow to Oceans (10× – 100×) Atmospheric Aerosol Loading To be determined Land System Change ≤ 15 % of land under crops (15-20%) Chemical Pollution Plastics, Endocrine Desruptors, Nuclear Waste Emitted globally To be determined Planetary Boundaries
Nitrogen flow Agricultural land use Ocean acidity Freshwater consumption Phosphorus flow Climate Change Atmospheric aerosol load Chemical pollution Ozone depletion Biodiversity loss ? ? 50-60 70-80 Latest data 90-00 Pre- Ind. ? ? ? ?
Chemical Pollution Steer away from irreversible impacts on living organisms
Global, ubiquitous impact on the physiological development and demography of humans and other organisms with ultimate impacts on ecosystem functioning and structure
By acting as a slow variable that affects other planetary boundaries (e.g., rate of biodiversity loss)
2 complementary approaches: amounts of persistent pollutants with global distribution (e.g., mercury); Effects of chemical pollution on living organisms
Difficult to find an appropriate aggregate control variable. Close interactions with Aerosol loading; may require sub-boundaries based on sub-impacts/categories of chemicals
Land System Change Avoid unsustainable land system change predominantly from intensive agricultural use
Contributes to global environmental change with the risk of undermining human well-being and long term sustainability
Threat to biodiversity and undermining of regulatory capacity of ecosystems
Complex global aggregate where the spatial distribution and intensity of land system change is critically important
Concentrate agricultural land use to most productive land.
No more than 15 % of the global ice-free land surface should be converted to cropland
Biogeochemical flows: Human interference with global N cycle
Local to regional scale interference with N and P flows has pushed aquatic and marine systems across thresholds generating abrupt non-linear change
Human modification of the nitrogen cycle is now profound (converting more N 2 from the atmosphere into reactive forms than all of the Earth’s terrestrial processes combined)
N and P slow variables eroding resilience of important sub-systems of the Earth system
First guess of boundary level; return to 25 % of the current human fixation of N 2 from the atmosphere
Biogeochemical flows: Human interference with global P cycle
The crossing of a critical threshold of P inflow to the oceans could explain global-scale ocean anoxic events (OAE), and past mass extinctions of marine life
A boundary level should be set that (with current knowledge) allows humanity to safely steer away from the risk of triggering an OAE even over longer time horizons (> 1,000 yrs)
May require that anthropogenic P inflow to the ocean is not allowed to exceed a human induced level of ~10 times the natural background rate of ~1 Mt P yr -1 . This is higher than the proposed trigger rate of past OAEs
There are very large uncertainties in these analyses, due to the complex interactions between oxic-anoxic states
In the Anthropocene Humanity is, for the first time, influencing hard-wired processes at the Earth System scale
We define the Holocene as the desired stable state providing necessary environmental pre-conditions for human development
We need a new approach to global sustainability and development. Scientific insights from research on resilience and complex systems, and Earth System Science, on the risks of human induced tipping points in a multitude of Earth system processes and sub-systems
We propose that a Planetary Boundary framework may provide one step towards this necessary redefinition
The Planetary Boundaries analysis presented in Nature is a “proof-of-concept” analysis , with many of the proposed boundaries being first best guesses. Many uncertainties remain, and will continue to remain.
What we suggest is a challenge to the Earth System Science community to advance further research on Earth system interactions and non-linear dynamics
Large Knowledge gaps remain
Understanding of threshold dynamics
Boundary interactions and feedbacks
Spatial variability and patchiness may require global and regional boundaries
No doubt, a Planetary Boundaries approach to sustainable development would have profound implications for governance and policy across scales . Large scientific challenges to address the human dimensions and governance implications of development within Planetary Boundaries
Despite uncertainties on allowed overshoot before large discontinuities, we have enough evidence to act now . Time is running out on several of the Planetary Boundaries, and the momentum of driving forces tremendous. This is a first attempt to define the safe space for human development, which may prove critical in turbulent times ahead.