Download - Afforestation and global climate
Afforestation and global climate
Yadvinder MalhiEnvironmental Change Instiuuk School of
Geography and the EnvironmentUniversity of Oxford
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)
Intact forest Converted to grassland
Carbon stocks in mature and converted forests (Mg C ha-1)
House and Prentice 2002
The global carbon cycle
Foley et al (2003)
Dense forest: 0.05-0.20
Pasture and croplands: 0.3-0.4
Snow albedo: 0.8
Bala et al 2007, Proceedings of the National Academy of Sciences
Surface Albedo
Net AlbedoCloudiness
Evaporation
Modelled effects of global deforestation on albedo
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)
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)
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)
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)
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)
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)
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
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
Carbon sources and sinks over the last two centuries (Pg C)
How much can afforestation contribute to climate change mitigation?
Carbon and biophysical effects of an extreme afforestation scenario
Carbon sources and sinks over the last two centuries (Pg C)
Arora and Montenegro 2011
Arora and Montenegro 2011
Global average temperature rise under A2 emissions scenario
Arora and Montenegro 2011 Nature Geoscience
Global mean: -0. 11 oC; Global land mean: -0.16 oC
Arora and Montenegro 2011 Nature Geoscience
Global mean: -0.04 oC; Global land mean: +0.01 oC
Arora and Montenegro 2011 Nature Geoscience
Global mean: -0. 16 oC; Global land mean: -0.25 oC
Climate effectiveness of afforestation per unit area
100% global afforestation of croplands
100% global afforestation of croplands
100% global afforestation of croplands
But can we afford to regrow forests in a world on 9+ billion?Would afforestation compete with food supply?
New England 1900 New England 2000
Many temperate regions have already been undergoing afforestation
Other regions lock out afforestation for cultural reasons, not resource supply ones
Or for historical legacies and minority interests…
In many tropical regions cultural factors also dominate over food economics
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.