Revolutions that made the Earth

Tim Lenton University of Exeter

(with thanks to Jim Lovelock, Richard Boyle, Stuart Daines, Colin Goldblatt, Hywel Williams and especially Andy Watson)

• Driven by rare evolutionary events

• Increasing energy and material flows

• Causing dramatic planetary changes

• Each contingent on the previous one

• We wouldn’t be here without them

Evolutionary regime shifts

Williams & Lenton (2010) Oikos 119: 1887-1899

Population

Nutrients

Recycling

Environment

time

‘Tree of life’

T. M. Lenton et al. (Working Group 1) 91st Dahlem Workshop on Earth System Analysis for Sustainability (2003)

Ages in Ga (109 yr BP)

Environment

Life

T. M. Lenton et al. (Working Group 1) 91st Dahlem Workshop on Earth System Analysis for Sustainability (2003)

Ages in Ga (109 yr BP)

Environment

Life

Inception

T. M. Lenton et al. (Working Group 1) 91st Dahlem Workshop on Earth System Analysis for Sustainability (2003)

Ages in Ga (109 yr BP)

Environment

Life

Oxygen RevolutionInception

T. M. Lenton et al. (Working Group 1) 91st Dahlem Workshop on Earth System Analysis for Sustainability (2003)

Ages in Ga (109 yr BP)

Environment

Life

Complexity RevolutionOxygen RevolutionInception

The carbon cycle over Earth history

Shields and Veizer (2002) G3 3: 1-12

The Oxygen revolution

Oxygenic photosynthesis (~2.7 Ga)

Image of a colony of the cyanobacteria Trichodesmium from Annette Hynes’ website

Why use water?• General equation for photosynthesis:

CO2 + 2 H2A + hv → (CH2O)n + H2O + 2Acarbon dioxide + electron donor + light energy → carbohydrate + water + oxidized donor

• Many anoxygenic forms:– Electron donors: H2, H2S, S0, SO3

2-, S2O32-, Fe2+

– All easier to extract electrons from than H2O

• Need to exhaust these electron donors– Requires an unusual environment

• Need to capture sufficient energy to split H2O– Requires very complex biochemistry

Evolution’s solution

Allen & Martin (2007) Nature 445: 610-612

Origin of oxygenic photosynthesis

Evidence becomes

compelling

Multiple stages of oxygenation

Reducing

O2 < 10-12 atm

Anoxic

Anoxic

Atm

osph

ere

Surfa

ceO

cean

Dee

p O

cean

>2.7 Ga

Reducing

O2 < 10-12 atm

Anoxic

Anoxic

Reducing

O2 ~ 10-6 atm

Oxygenated

Anoxic

Atm

osph

ere

Surfa

ceO

cean

Dee

p O

cean

Oxygenicphotosynthesis

>2.7 Ga ~2.7-2.4 Ga

Multiple stages of oxygenation

Reducing

O2 < 10-12 atm

Anoxic

Anoxic

Reducing

O2 ~ 10-6 atm

Oxygenated

Anoxic

Oxidising

O2 > 10-3 atm

Oxygenated

Anoxic

Atm

osph

ere

Surfa

ceO

cean

Dee

p O

cean

Oxygenicphotosynthesis

GreatOxidation

>2.7 Ga ~2.7-2.4 Ga ~2.3-1.0 Ga?

Multiple stages of oxygenation

History of atmospheric oxygenPAL = Present Atmospheric Level

Goldblatt, Lenton, Watson (2006) Nature 443: 683-686

Oxygenicphotosynthesis

Greatoxidation

Mass Independent Fractionation (MIF) of sulphur isotopes

Great Oxidation

Ozone layer present

Oxygenicphotosynthesis

Goldblatt, Lenton, Watson (2006) Nature 443: 683-686

Long-term oxygen balance

H2

O2

Hydrogen escape

O2

PhotosynthesisO2

Respiration + Methanotrophy

Oxidative weathering

Organic carbon burial

O2

O2

O2

CH4

Space

Crust

Mantle

Atmosphere

Reducingvolcanic material

Photochemical reaction

Mantle oxidation?

O2

Fe2+

O2

Photochemical methane oxidationCH4 + 2O2 → CO2 + 2H2O

Data are published results from Jim Kasting's 1D photochemical model

Why the delayed oxygen rise?

Two stable states for O2 are separated by formation / loss of an ozone layer

Goldblatt, Lenton, Watson (2006) Nature 443: 683-686

Bi-stability of atmospheric oxygen

Oxidised soils <2.2 Ga

MIF of Sulphur>2.4 Ga

Goldblatt, Lenton, Watson (2006) Nature 443: 683-686

What triggered oxygen rise?

2.69-2.44 Ga Hamersley BIFFe deposition

>2.4 GaglobalFe input

Presenthydrothermal

Fe input

Time (Ma)

Oxygen and glaciations

PAL = Present Atmospheric LevelGreat

oxidation

GlobalRegional

The Complexity Revolution

~1.8 Ga possible eukaryotic alga Grypania spiralis ~2cm diameter coils

image from Phil Wilby (BGS)~0.6 Ga Ediacaran fossils

Origin of eukaryotes (~2 Ga)

Proterozoic evolution

Butterfield (2000; 2005) Paleobiology

Planavsky et al. (2011) Nature Poulton et al. (2010) Nature Geoscience

Oxic

Euxinic

Ferruginous

The Proterozoic OceanO2 (% of present level)

GENIE model reconstructionO2 = 0.1 PAL, PO4 = 0.5 x present dayMidPacific

EAtlantic

5μM μM2

0

EastAtlantic

0

0

0

30μM 30μM

Results from Stuart Daines

Oxygen and glaciations

PAL = Present Atmospheric Level

Lesseroxygenation

GlobalRegional

Reducing

O2 < 10-12 atm

Anoxic

Anoxic

Reducing

O2 ~ 10-6 atm

Oxygenated

Anoxic

Oxidising

O2 > 10-3 atm

Oxygenated

Anoxic

Atm

osph

ere

Surfa

ceO

cean

Dee

p O

cean

Oxygenicphotosynthesis

GreatOxidation

>2.7 Ga ~2.7-2.4 Ga ~2.3-1.0 Ga?

Multiple stages of oxygenation

Reducing

O2 < 10-12 atm

Anoxic

Anoxic

Reducing

O2 ~ 10-6 atm

Oxygenated

Anoxic

Oxidising

O2 > 10-3 atm

Oxygenated

Anoxic

Oxidising

O2 ~ 10-1 atm

Oxygenated

Oxygenated

Atm

osph

ere

Surfa

ceO

cean

Dee

p O

cean

Oxygenicphotosynthesis

GreatOxidation

Lesseroxygenation

>2.7 Ga <0.6 Ga~2.7-2.4 Ga ~2.3-1.0 Ga?

Multiple stages of oxygenation

Proterozoic world

Lenton, T. M. et al. (2014) Nature Geoscience 7: 257-265.

O2 ~ 1-10% of present atmospheric level (PAL)

Eukaryotic algae (~750 Ma)

Lenton, T. M. et al. (2014) Nature Geoscience 7: 257-265.

Filter-feeding animals (750?-600Ma)

Lenton, T. M. et al. (2014) Nature Geoscience 7: 257-265.

Zooplankton (~550 Ma)

Lenton, T. M. et al. (2014) Nature Geoscience 7: 257-265; Logan, G. A. et al. (1995). Nature 376: 53-56.

Bioturbation (550-520 Ma)

Boyle et al. (2014). Nature Geoscience 7: 671-676

Onsetofbioturbating animals

Less organic carbon burial

Lower C/P burial ratio

Oxygenate sediments

Long-term stabilisation of O2

Newproduction

Org-Cburial

AtmosphericO2

OceanO2

_

Bioturbation

+Oceanic

PO4

Boyle et al. (2014). Nature Geoscience 7: 671-676; Van Cappellen & Ingall (1996) Science, 271: 493-496.

Land plants (~410 Ma)

Land-based oxygen regulator

PhosphorusWeathering

LandVegetation

P toOcean and

Land

OrganicCarbonBurial

O2

Fires

_

Lenton & Watson (2000) Global Biogeochemical Cycles 14: 249-268

Common features of revolutions

• They are caused by (rare) biological innovations

• They involve step increases in information processing, complexity of organisation, energy capture and material flow through the biosphere

• They rely on the Earth system having some instability, such that new waste products can cause catastrophic upheavals in carbon cycling and climate

• They end only when the system finds a new stable state, able to close the biogeochemical cycles again, by recycling all the materials

What about us? (0 Ga)

Increased information processing

New levels of organisation

City of Ur in Iraq (Urim in Sumerian times)

Increased energy and material flows

0100,000200,000300,000400,000500,000600,000Age (yr BP)

300

500

400

600

180200220240260280

Projected Concentration After 50 More Years of Unrestricted Fossil Fuel Burning

CO2

[ppm

v]

Temperature proxy

Earth system instability

Where next?

Lenton et al. (2008) PNAS

Apocalypse?

Retreat?

Revolution?