Are we bigger than the ? An examination of our human‐dominated planet

Yadvinder Malhi Environmental Change Institute School of Geography and the Environment

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 Pre‐industrial humanity

Extended metabolism: 2000 W/person

Population density: 40 persons/km2 Per unit area: 80 kW/km2

5% of natural 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 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, 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?”,