afforestation and global climate
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Afforestation and global climate. Yadvinder Malhi Environmental Change Instiuuk School of Geography and the Environment University of Oxford. GPP. The Carbon Cycle of a Forest. NPP VOC. NPP leaves,flowers,fruit . R leaf. NPP wood (Branch + Stem). D Fine litterfall. R stem. - PowerPoint PPT PresentationTRANSCRIPT
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Afforestation and global climate
Yadvinder MalhiEnvironmental Change Instiuuk School of
Geography and the EnvironmentUniversity of Oxford
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GPP The Carbon Cycle of a Forest
R leaf
R stem
R CWD
Fdoc
DFine litterfall
DCWD
R roots
R soil
DRoot
R soil het
NPP coarse roots
NPP fine roots
NPP VOCNPP leaves,flowers,fruit
NPP wood (Branch + Stem)
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Intact forest Converted to grassland
Carbon stocks in mature and converted forests (Mg C ha-1)
House and Prentice 2002
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The global carbon cycle
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Foley et al (2003)
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Dense forest: 0.05-0.20
Pasture and croplands: 0.3-0.4
Snow albedo: 0.8
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Bala et al 2007, Proceedings of the National Academy of Sciences
Surface Albedo
Net AlbedoCloudiness
Evaporation
Modelled effects of global deforestation on albedo
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9
CO2 emissions from Land Use Change (1850-2009)
R.A. Houghton 2010, personal communication; GFRA 2010
-400-200
0200400600800
10001200140016001800
1850
1860
1870
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
Tropical
Temperate
CO2 e
miss
ions
(TgC
y-1)
Time (y)
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Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
Human Perturbation of the Global Carbon Budget
Sink
Sour
ce
Time (y)
5
10
10
5
1850 1900 1950 2000
1.1±0.7deforestation
CO2 f
lux
(PgC
y-1)
2000-2009(PgC)
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Human Perturbation of the Global Carbon Budget
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
5
10
10
5
1850 1900 1950 2000
7.7±0.5
deforestation
fossil fuel emissions
Sink
Sour
ce
Time (y)
CO2 f
lux
(PgC
y-1)
1.1±0.7
2000-2009(PgC)
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Human Perturbation of the Global Carbon Budget
Time (y)
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
5
10
10
5
1850 1900 1950 2000
deforestation
fossil fuel emissions
Sink
Sour
ce
CO2 f
lux
(PgC
y-1) 7.7±0.5
1.1±0.7
2000-2009(PgC)
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Human Perturbation of the Global Carbon Budget
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
5
10
10
5
1850 1900 1950 2000
4.1±0.1
fossil fuel emissions
deforestation
atmospheric CO2
Sink
Sour
ce
Time (y)
CO2 f
lux
(PgC
y-1) 7.7±0.5
1.1±0.7
2000-2009(PgC)
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Human Perturbation of the Global Carbon Budget
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
5
10
10
5
1850 1900 1950 2000
atmospheric CO2
fossil fuel emissions
deforestation
ocean2.3±0.4
oceanSink
Sour
ce
Time (y)
CO2 f
lux
(PgC
y-1)
(5 models)
4.1±0.1
7.7±0.5
1.1±0.7
2000-2009(PgC)
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Human Perturbation of the Global Carbon Budget
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
5
10
10
5
1850 1900 1950 2000
2000-2009(PgC)
atmospheric CO2
oceanland
fossil fuel emissions
deforestation
(Residual)
Sink
Sour
ce
Time (y)
CO2 f
lux
(PgC
y-1)
2.3±0.4(5 models)
4.1±0.1
7.7±0.5
1.1±0.7
2.4
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Fate of Anthropogenic CO2 Emissions (2000-2009)
1.1±0.7 PgC y-1
+7.7±0.5 PgC y-1
2.4 PgC y-1
27%Calculated as the residual of
all other flux components
4.1±0.1 PgC y-1
47%
26%2.3±0.4 PgC y-1
Average of 5 models
Global Carbon Project 2010; Updated from Le Quéré et al. 2009, Nature Geoscience; Canadell et al. 2007, PNAS
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Carbon sources and sinks over the last two centuries (Pg C)
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How much can afforestation contribute to climate change mitigation?
Carbon and biophysical effects of an extreme afforestation scenario
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Carbon sources and sinks over the last two centuries (Pg C)
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Arora and Montenegro 2011
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Arora and Montenegro 2011
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Global average temperature rise under A2 emissions scenario
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Arora and Montenegro 2011 Nature Geoscience
Global mean: -0. 11 oC; Global land mean: -0.16 oC
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Arora and Montenegro 2011 Nature Geoscience
Global mean: -0.04 oC; Global land mean: +0.01 oC
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Arora and Montenegro 2011 Nature Geoscience
Global mean: -0. 16 oC; Global land mean: -0.25 oC
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Climate effectiveness of afforestation per unit area
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100% global afforestation of croplands
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100% global afforestation of croplands
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100% global afforestation of croplands
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But can we afford to regrow forests in a world on 9+ billion?Would afforestation compete with food supply?
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New England 1900 New England 2000
Many temperate regions have already been undergoing afforestation
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Other regions lock out afforestation for cultural reasons, not resource supply ones
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Or for historical legacies and minority interests…
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In many tropical regions cultural factors also dominate over food economics
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Conclusions
Afforestation can be a relatively low component of a climate mitigation strategy (except in regions with substantial winter snow)
If appropriately done, it brings many co-benefits including biodiversity, watershed protection and soil protection.
Tropical afforestation (and avoided deforestation) is particularly effective.
It is possible to afforest and reforest in a food-demanding world.