Tropical Forests in a 4 oC+ World · 1 Tropical Forests in a 4 oC+ World Yadvinder Malhi Environmental Change Institute School of Geography and the Environment Oxford University,

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Tropical Forests in a 4oC+ World

Yadvinder MalhiEnvironmental Change Institute

School of Geography and the EnvironmentOxford University, UK

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Projected temperature change under A2 emissions scenario

IPCC 2007

2020-2029 2090-2099

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-0.5

0

0.5

1

1.5

2

-90-75-60-45-30-150153045607590

Tem

pe

ratu

re C

ha

ng

e 1

97

5-2

00

5

(oC

)

Latitude (o)

N Temperate Tropical S Temperate

0.40 0.31 0.09 oC decade-1

Rate of warming of land regions, 1975-2005

Projected warming in land regions by late 21st

century under A2 emissions scenario

Mean of 15 IPCC Global Climate Models

0

2

4

6

8

10

12

-90-75-60-45-30-150153045607590

Tem

pe

ratu

re a

no

ma

ly

oC

)

Latitude (o)

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Modelled and observed rates of change

Modelled rates: late 20th to late 21st century, A2 emissions scenario

Observed rates: 1975-2005

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

-90-75-60-45-30-150153045607590

Ra

te o

f ch

an

ge

(oC

/de

cad

e)

Latitude (o)

Mean rate of warming of Amazonia at end of last ice age

0.01 oC decade-1

Bush et al. 2004, Science

The warmest parts of the planet are warming and

will continue to warm fast

How will tropical organisms and ecosystems

respond to this warming?

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Tropical species have narrower current thermal tolerances

Deutsch C. A. et.al. PNAS 2008 Tewksbury et.al. Science 2008

Insects Lizards

Predicted impact of warming on the thermal performance of ectotherms in 2100

Deutsch C. A. et.al. PNAS 2008;105:6668-6672

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All these changes in fitness will be imposed with varying intensityon nodes of the “tangled web”

Phillips et al. 2002, Nature

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Responses to potential decline in performance

Responses of organisms , species and ecosystems will be

complex – do not simply map onto decline in performance.

• Plasticity of physiological thresholds and acclimation of

physiology

• Rapid evolutionary adaptation

• Behavioural change – timing and spatial distribution of

activities

• Migration and dispersal

In all cases the RATE of change is probably the greatest challenge

0

0.5

1

1.5

2

2.5

3

3.5

-90-75-60-45-30-150153045607590

Lati

tud

ina

l Te

mp

era

ture

Gra

die

nt

(oC

/o)

Latitude (o)

N Temperate Tropical S Temperate

135 380 140 km oC-1

Spatial gradients in temperature are shallow in the tropics

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Horizontal temperature gradient ~ 380 km oC-1

Vertical temperature gradient ~ 0.18 km oC-1

On current rates of warming, the required

rates of migration to remain in the same

temperature regime are

Horizontal migration rate ~ 116 km decade-1

(32 m day-1)

Vertical migration distance ~ 55 m decade-1

Observed tree migration rate in Andes ~ 25-35 m decade-1

Feeley et al., submitted to Global Change Biology

1122

33

55

66

Species responses to climatic warmingSpecies responses to climatic warming

44

Mountains may beMountains may be refugia refugia (2, 4)(2, 4)

traps (3, 5)traps (3, 5)

or a chance (6)or a chance (6)

Ch KörnerCh Körner

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Soares et al. 2006. Nature

The greatest threat

climate change and deforestation

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2050 Business-as-Usual Scenario:

Deforested 2.7 million km2

Forest 3.3 million km2

Non-forest 1.5 million km2

Soares et al. 2006 Nature32 Pg C

2050 Governance Scenario:

Deforested 1.7 million km2

Forest 4.4 million km2

Non-forest 1.5 million km2

17 Pg CSoares et al. 2006 Nature

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Precipitation

IPCC Fourth Assessment Report

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Savanna

Seasonal

Forest

Rainforest

Malhi et al., 2009 Exploring the likelihood and mechanism of a climate-change induced dieback of the

Amazon rainforest, Proceedings of the National Academy of Sciences.

A simple rainfall biogeography of Amazonia

Savanna

Seasonal Forest

Rainforest

Malhi et al. 2009, Exploring the likelihood and mechanism of a climate-change induced dieback of the Amazon

rainforest, Proceedings of the National Academy of Sciences,

Adjusted climate model predictions for Amazonia (A2 Scenario)

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0

1

2

3

4

5

6

Low T Low CO2 Low T High CO2 High T Low CO2 High T High CO2

Eva

po

tra

ns

pir

ati

on

(mm

da

y-1

)

UK MOSES-TRIFFID Model

Low CO2 = 280 ppm, High CO2 = 850 ppm

Change in T = +4.5 oC

Effects of temperature and CO2 on water use by forests

Malhi et al. 2009, Exploring the likelihood and mechanism of a climate-change induced dieback of the Amazon

rainforest, Proceedings of the National Academy of Sciences,

0

1

2

3

4

5

6

Low T Low CO2 Low T High CO2 High T Low CO2 High T High CO2

Eva

po

tra

ns

pir

ati

on

(mm

da

y-1

)

Savanna

Savanna ? Rainforest

Seasonal Forest

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The role of fire

Forest fires in eastern Acre State (Brazil)

during the 2005 Amazonian drought

Aragão et al, Spatial patterns and fire response of recent Amazonian

droughts, Geophysical Research Letters. (2007)

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No burn

First burn

Second or third

burn

Barlow J & Peres CA (2008)

Fire-mediated dieback and

compositional cascade in

an Amazonian forest.

Philos Trans R Soc London

0

1

2

3

4

5

6

Low T Low CO2 Low T High CO2 High T Low CO2 High T High CO2

Eva

po

tra

ns

pir

ati

on

(mm

da

y-1

)

Savanna

Rainforest

Seasonal Forest

Fire-prone forests

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Interactions between potential deforestation and climate change

“Business as usual” deforestation

by 2050“High governance” deforestation

by 2050

Malhi et al. (2008)

Climate change, deforestation, and the

fate of the Amazon, Science.

0.6

0.7

0.8

0.9

1.0

1.1

1.2

0% 20% 40% 60% 80% 100%

Re

lati

ve

Pre

cip

ita

tio

n (

p/p

0)

Deforestation Area (%)

Amazonia - SOYBEANArea: East/Northeast

DJF

MAM

JJA

SON

Sampaio et al. 2008

Journal of Geophysical Research

Modelled effect of conversion to soybean on rainfall in Eastern Amazonia

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Eastern Amazonia 2100

Deforestation warming: + 5 oC

Greenhouse warming: + 4.5 oC

Eastern Amazonia 2100

Deforestation warming: + 1 oC

Greenhouse warming: + 4.5 oC

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Maintaining tropical forest area is a

strategy for adapting to climate change

• Minimise contact points between forest fragments

and fire zones

• Lower surface temperatures because of evaporative

cooling of near-surface area

• Maintenance of shade habitats

• Maintenance of dry season rainfall

• Maintain connectivity for species migration to cooler

or wetter refugia

Forest protection is also a component strategy for mitigation of

global climate change.

This presents an opportunity

Reduced Emissions from

Deforestation and Forest

Degradation (REDD)

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Rapid change is coming to tropical forests – climate change and

deforestation present a dangerous synergy.

We are only beginning to comprehend the impacts of this change

Rapid climate change is reweaving the web of life. We do not yet

know what this implies for risk of extinction or ecosystem shift

New opportunities for tropical forest conservation are emerging

through recognition of their value in climate change mitigation

and adaptation – we are only beginning to grasp the challenge

that these opportunities will bring.

Conclusions