Are we bigger than the biosphere? An examination of our human‐dominated planet
Yadvinder Malhi Environmental Change Institute School of Geography and the Environment University of Oxford
How do we measure how “big” humanity is relative to the Earth? Global Land Net Primary Productivity
g C m‐2 year‐1 www.globalcarbonproject.org Global Ocean Net Primary Productivity
earthobservatory.nasa.gov 6 Biological metabolism Social or extended metabolism 60 Watts Pre‐agricultural humanity
Extended metabolism: 300 W
Human metabolism: 120 W
Population density: 0.1 person/km2 Metabolism per unit area: 30 W km‐2
Janegrok.wordpress.com Biological metabolism of tropical savanna: 30 MW km‐2 Early human social metabolism: 30 W km‐2 (0.0001% of savanna)
Multiple independent origins of agriculture
Jared Diamond 2002, Nature12 Agriculture is the “colonization” of ecosystems Pre‐industrial humanity
Extended metabolism: 2000 W/person
Population density: 40 persons/km2 Per unit area: 80 kW/km2
5% of natural ecosystem metabolism
Breugel, the Harvesters, Wikipedia Commons Human extended metabolism throughout history
2500
2000 person) per
1500 (W
West 1000 East metabolism
Social 500
0 ‐14000 ‐12000 ‐10000 ‐8000 ‐6000 ‐4000 ‐2000 0 2000 Year Derived from Morris (2012) Extended metabolism of key civilizations throughout history
4000
3500
3000
person) Roman Empire 2500 per
Song Dynasty (W
2000 West East 1500 Han Dynasty metabolism
Social 1000
500
0 ‐2000 ‐1500 ‐1000 ‐500 0 500 1000 1500 2000 Year Derived from Morris (2012) 17 18 The forces that have brought about the Anthropocene have brought much that is good to humanity England, 2010
Social metabolism: 8,000 W
Population density: 407 persons/km2
Natural ecosystem metabolism: 200 GW
Extended social metabolism: 400 GW
200% of ecosystem metabolism The industrial metabolism of humanity
www.globalcarbonproject.org How much of our metabolism is directly drawing from the (contemporary) biosphere? Global human socioeconomic metabolism, 1800‐2000
Haberl, 2006, Energy Human appropriation of land biosphere production
Haberl et al. (2009) The scaling of metabolism in animals Kleiber’s Law
25 Consequences of metabolic scaling
Whole organism B ~ M3/4 Metabolism per unit mass = B/M : ~ M‐1/4 Rates (e.g. heartbeat, reproduction rate) ~ M‐1/4 Times (lifetime, gestation time, gut residence time) ~ M1/4
Number of heartbeats in a lifetime ~ Heartbeat rate x lifetime M‐1/4 . M1/4 = M0 = constant
26 Metabolism of different‐sized animals
100000
10000
Elephant (W)
Rhino Use 1000 Bull
Human 100
Dog Metabolism/Energy
10
1 1 10 100 1000 10000 100000 Mass (kg)
Malhi, 2014., the metabolism of a human‐dominated planet27 How metabolically “large” are humans?
100000
North American 10000 Industrial Mean
Elephant (W)
Agriculturalist Rhino Use 1000 Bull Hunter gather
Human 100
Dog Metabolism/Energy
10
1 The average 1industrial 10 human 100 has the 1000 resource 10000 consumption 100000 of a 15 tonneEquivalent primate. Mass (kg)
(in North America this increases up to 30 tonnes) 28 29 Global Land Biosphere metabolism: 150 TW
Pre‐agricultural human extended metabolism: 0.003 TW (0.002% of biosphere)
Pre‐industrial human extended metabolism: 3 TW (2% of biosphere)
Modern human extended metabolism: 25 TW (17% of biosphere)
Global UN Projection (2050): 48 TW (32% of biosphere)
“Global China”: 60 TW (40% of biosphere)
“Global US” : 180 TW (120% of biosphere) All of human history
12000
10000 person) 8000 per
(W
6000 West East
4000 metabolism
Social 2000
0 ‐14000 ‐12000 ‐10000 ‐8000 ‐6000 ‐4000 ‐2000 0 2000 Year A new challenge for humanity: approaching planetary boundaries
Steffen et al. 2015, Science Planetary Boundaries: Guiding human development on a changing planet Many pre‐industrial societies were “full”.
The industrial revolution opened up access to previously unavailable energy from deep time ecosystems.
We are still in a period of “metabolic inflation” that we have come to regard as normal, but is only a few generations deep.
This period is now hitting constraints of both resource supply and waste production, constrained by the size of the planet’s systems. Urban humanity
34 More than half of humanity is urban
Wikipedia Commons35 Cities as superorganisms?
Manhattan, New York, USA 36 The scaling of metabolism in super‐ organisms – insect societies
37 The scaling of metabolism in super‐ organisms – insect societies
Hou et al 2010, PNAS Energetic basis of colonial living in social insects 38 An example of metabolic scaling in cities –the speed of walking
Bettencourt et al 2009, PNAS 39 Growth, innovation, scaling, and the pace of life in cities Cities get faster with increased size
Bettencourt et al 2009, PNAS 40 Growth, innovation, scaling, and the pace of life in cities In some ways cities are not like social insect colonies … they are more like stars
Bettencourt 2013, Science The origin of scaling in cities 41 Bettencourt et al 2009, PNAS 42 Growth, innovation, scaling, and the pace of life in cities Successive cycles of superlinear innovation reset the singularity and postpone instability and subsequent collapse.
Bettencourt et al 2009, PNAS 43 Growth, innovation, scaling, and the pace of life in cities Population relative growth rates in New York City
Bettencourt et al 2009, PNAS 44 Growth, innovation, scaling, and the pace of life in cities Thomas Malthus Ester Boserup The socio‐metabolic challenge
Perhaps the fundamental environmental challenge of our time, the defining characteristic of the Anthropocene, is that global human industrial metabolism is of similar size to the natural planetary metabolism. This leads to resource depletion, overharvesting, natural habitat loss, accumulation of metabolic waste products and atmospheric change.
46 A state of metabolic inflation cannot persist indefinitely on a finite planet.
Our challenge in the 21st century is to navigate a transition from endless metabolic inflation to a sustainable global state while providing well being for humanity and living space for the rest of the biosphere.
This will require innovation, both in technology and in governance. This presentation will be available at www.yadvindermalhi.org
48 Malhi (2014) The metabolism of a human‐dominated planet, in “Is the Planet Full?”, Oxford University Press