Planetary Boundaries and Life on Earth: what are we going to do about it?

The entire article on planetary boundaries can be read by visiting the below website.

Please be part of the Sunday, June 6 biodiversity symposium that is listed under events at local motive project.

http://www.ecoearth.info/shared/docfeed/planetary_boundaries.pdf

Here is the introduction:

Planetary Boundaries: Exploring the Safe Operating Space for Humanity

Johan Rockström 1,2, Will Steffen 1,3, Kevin Noone 1,4, Åsa Persson 1,2, F. Stuart III Chapin 5, Eric Lambin 6,

Timothy M. Lenton 7, Marten Scheffer 8, Carl Folke 1,9, Hans Joachim Schellnhuber 10,11, Björn Nykvist 1,2,

Cynthia A. de Wit 4, Terry Hughes 12, Sander van der Leeuw 13, Henning Rodhe 14, Sverker Sörlin 1,15,

Peter K. Snyder 16, Robert Costanza 1,17, Uno Svedin 1, Malin Falkenmark 1,18, Louise Karlberg 1,2,

Robert W. Corell 19, Victoria J. Fabry 20, James Hansen 21, Brian Walker 1,22, Diana Liverman 23,24,

Katherine Richardson 25, Paul Crutzen 26, and Jonathan Foley 27

ABSTRACT. Anthropogenic pressures on the Earth System have reached a scale where abrupt global

environmental change can no longer be excluded. We propose a new approach to global sustainability in

which we define planetary boundaries within which we expect that humanity can operate safely.

Transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of

crossing thresholds that will trigger non-linear, abrupt environmental change within continental- to

planetary-scale systems. We have identified nine planetary boundaries and, drawing upon current scientific

understanding, we propose quantifications for seven of them. These seven are climate change (CO2

concentration in the atmosphere <350 ppm and/or a maximum change of +1 W m-2 in radiative forcing);

ocean acidification (mean surface seawater saturation state with respect to aragonite ³ 80% of pre-industrial

levels); stratospheric ozone (<5% reduction in O3 concentration from pre-industrial level of 290 Dobson

Units); biogeochemical nitrogen (N) cycle (limit industrial and agricultural fixation of N2 to 35 Tg N yr-1)

and phosphorus (P) cycle (annual P inflow to oceans not to exceed 10 times the natural background

weathering of P); global freshwater use (<4000 km3 yr-1 of consumptive use of runoff resources); land

system change (<15% of the ice-free land surface under cropland); and the rate at which biological diversity

is lost (annual rate of <10 extinctions per million species). The two additional planetary boundaries for

which we have not yet been able to determine a boundary level are chemical pollution and atmospheric

aerosol loading. We estimate that humanity has already transgressed three planetary boundaries: for climate

change, rate of biodiversity loss, and changes to the global nitrogen cycle. Planetary boundaries are

interdependent, because transgressing one may both shift the position of other boundaries or cause them

to be transgressed. The social impacts of transgressing boundaries will be a function of the social–ecological

resilience of the affected societies. Our proposed boundaries are rough, first estimates only, surrounded by

large uncertainties and knowledge gaps. Filling these gaps will require major advancements in Earth System

and resilience science. The proposed concept of “planetary boundaries” lays the groundwork for shifting

our approach to governance and management, away from the essentially sectoral analyses of limits to

growth aimed at minimizing negative externalities, toward the estimation of the safe space for human

development. Planetary boundaries define, as it were, the boundaries of the “planetary playing field” for

humanity if we want to be sure of avoiding major human-induced environmental change on a global scale.

Key Words: atmospheric aerosol loading; biogeochemical nitrogen cycle; biological diversity; chemical

pollution; climate change; Earth; global freshwater use; land system change; ocean acidification;

phosphorus cycle; planetary boundaries; stratospheric ozone; sustainability

1Stockholm Resilience Centre, Stockholm University, 2Stockholm Environment Institute, 3Australian National University, Australia, 4Department of Applied

Environmental Science, Stockholm University, 5Institute of Arctic Biology, University of Alaska Fairbanks, 6Department of Geography, University of

Louvain, 7School of Environmental Sciences, University of East Anglia, 8Aquatic Ecology and Water Quality Management Group, Wageningen University, 9The Beijer Institute of Ecological Economics, Royal Swedish Academy of Sciences, 10Potsdam Institute for Climate Impact Research, 11Environmental

Change Institute and Tyndall Centre, Oxford University, 12ARC Centre of Excellence for Coral Reef Studies, James Cook University, 13School of Human

Evolution and Social Change, Arizona State University, 14Department of Meteorology, Stockholm University, 15Division of History of Science and

Technology, Royal Institute of Technology, 16Department of Soil, Water, and Climate, University of Minnesota, 17Gund Institute for Ecological Economics,

University of Vermont, 18Stockholm International Water Institute, 19The H. John Heinz III Center for Science, Economics and the Environment, 20Department of Biological Sciences, California State University San Marcos, 21NASA Goddard Institute for Space Studies, 22CSIRO Sustainable

Ecosystems, 23Environmental Change Institute, School of Geography and the Environment, 24Institute of the Environment, University of Arizona, 25Earth

System Science Centre, University of Copenhagen, 26Max Planck Institute for Chemistry, 27Institute on the Environment, University of Minnesota

Ecology and Society 14(2): 32

http://www.ecologyandsociety.org/vol14/iss2/art32/

NEW CHALLENGES REQUIRE NEW

THINKING ON GLOBAL SUSTAINABILITY

Human activities increasingly influence the Earth’s

climate (International Panel on Climate Change

(IPPC) 2007a) and ecosystems (Millennium

Ecosystem Assessment (MEA) 2005a). The Earth

has entered a new epoch, the Anthropocene, where

humans constitute the dominant driver of change to

the Earth Systemi (Crutzen 2002, Steffen et al.

2007). The exponential growth of human activities

is raising concern that further pressure on the Earth

System could destabilize critical biophysical

systems and trigger abrupt or irreversible

environmental changes that would be deleterious or

even catastrophic for human well-being. This is a

profound dilemma because the predominant

paradigm of social and economic development

remains largely oblivious to the risk of humaninduced

environmental disasters at continental to

planetary scales (Stern 2007).

Here, we present a novel concept, planetary

boundaries, for estimating a safe operating space for

humanity with respect to the functioning of the Earth

System. We make a first preliminary effort at

identifying key Earth System processes and attempt

to quantify for each process the boundary level that

should not be transgressed if we are to avoid

unacceptable global environmental change.

Unacceptable change is here defined in relation to

the risks humanity faces in the transition of the

planet from the Holocene to the Anthropocene. The

relatively stable environment of the Holocene, the

current interglacial period that began about 10 000

years ago, allowed agriculture and complex

societies, including the present, to develop and

flourish (Fig. 1). That stability induced humans, for

the first time, to invest in a major way in their natural

environment rather than merely exploit it (van der

Leeuw 2008). We have now become so dependent

on those investments for our way of life, and how

we have organized society, technologies, and

economies around them, that we must take the range

within which Earth System processes varied in the

Holocene as a scientific reference point for a

desirable planetary state.

Despite some natural environmental fluctuations

over the past 10 000 years (e.g., rainfall patterns,

vegetation distribution, nitrogen cycling), Earth has

remained within the Holocene stability domain. The

resilience of the planet has kept it within the range

of variation associated with the Holocene state, with

key biogeochemical and atmospheric parameters

fluctuating within a relatively narrow range (Fig. 1;

Dansgaard et al. 1993, Petit et al. 1999, Rioual et al.

2001). At the same time, marked changes in regional

system dynamics have occurred over that period.

Although the imprint of early human activities can

sometimes be seen at the regional scale (e.g., altered

fire regimes, megafauna extinctions), there is no

clear evidence that humans have affected the

functioning of the Earth System at the global scale

until very recently (Steffen et al. 2007). However,

since the industrial revolution (the advent of the

Anthropocene), humans are effectively pushing the

planet outside the Holocene range of variability for

many key Earth System processes (Steffen et al.

2004). Without such pressures, the Holocene state

may be maintained for thousands of years into the

future (Berger and Loutre 2002).

So far, science has provided warnings of planetary

risks of crossing thresholds in the areas of climate

change and stratospheric ozone (IPCC 1990, 2007a,

b, World Meteorological Organization 1990).

However, the growing human pressure on the planet

(Vitousek et al. 1997, MEA 2005a) necessitates

attention to other biophysical processes that are of

significance to the resilienceii of sub-systems of

Earth (Holling 1973, Folke et al. 2004, Gordon et

al. 2008) and the Earth System as a whole. Erosion

of resilience manifests itself when long periods of

seemingly stable conditions are followed by periods

of abrupt, non-linear change, reflected in critical

transitions from one stability domain to another

when thresholds are crossed (Scheffer et al. 2001,

Walker et al. 2004, Lenton et al. 2008, Scheffer

2009).

The Anthropocene raises a new question: “What are

the non-negotiable planetary preconditions that

humanity needs to respect in order to avoid the risk

of deleterious or even catastrophic environmental

change at continental to global scales?” We make a

first attempt at identifying planetary boundaries for

key Earth System processes associated with

dangerous thresholds, the crossing of which could

push the planet out of the desired Holocene state.