Carbon-water interactions with grassland to plantation conversions:
effect of vegetation cover on the production of ecosystem services
Kathleen Farley, San Diego State University, USARobert Jackson, Duke University, USA
Esteban Jobbagy, Roni Avissar, Somnath Baidkya Roy, Damien Barrett, Charles Cook, David LeMaitre, Bruce McCarl, Brian Murray
Conversion of grasslands to plantations: new policy/market incentives
• Kyoto Protocol Clean Development Mechanism– Issued first CERs (Certified
Emission Reductions) in October 2005
• EU Emission Trading Scheme– $4.5 billion in emissions
credits in 2005
• Chicago Climate Exchange
South America: plantation area and potential expansion
Source: World Forest Institute
How does afforestation alter ecosystem processes, in particular water yield
Compiled global data set on afforestation effects on water yield
Global synthesis• Annual runoff data from afforested sites
with a previous land cover of grassland or shrubland
• Included 26 data sets, most from paired catchment studies, with 504 annual observations
• Analyzed change in runoff as related to original vegetation type, plantation species, plantation age, and mean annual precipitation
Results• Runoff reductions >75% for at least one
year in 1/5 of catchments• Runoff reductions, averaged across all
plantation ages, were greater in grasslands (44 ± 3%) than shrublands (31 ± 2%) (p<0.001)
• Eucalypts had greater effect on runoff than pines in sites that were originally grasslands (75 ± 10% vs 40 ± 3%) (p<0.001)
Change in runoff with plantation age1a: afforested grasslands
plantation age (years)
3020100
chan
ge in
runo
ff (%
)20
0
-20
-40
-60
-80
-100
plantation type
other
eucalyptus
pine
all species
R2 = 0.75; p<0.001
Farley et al. 2005
Change in runoff with plantation age1c: afforested shrublands
plantation age (years)
403020100
chan
ge in
runo
ff (%
)40
20
0
-20
-40
-60
-80-100
plantation type
eucalyptus
pine
all species
R2 = 0.71; p<0.001
Farley et al. 2005
Change in runoff with plantation age
Grassland Shrubland
Age (yrs) runoff (%) n runoff (%) n
1-5 -16 ± 5 35 -15 ± 3 36
6-10 -50 ± 6 36 -35 ± 4 40
11-15 -67 ± 5 30 -39 ± 4 30
16-20 -58 ± 5 29 -43 ± 4 23
21-25 -42 ± 6 12 -35 ± 4 20
26-30 -54 ± 4 4 -32 ± 4 20
Change in runoff in wet and dry regions
-350
-300
-250
-200
-150
-100
-50
0
<1000 1000-1250 1250-1500 >1500
mean annual precipitation (mm)
chan
ge in
runo
ff (m
m)
-80
-60
-40
-20
0
chan
ge in
runo
ff (%
)
mm**
%***
Farley et al. 2005
Vegetation-climate feedbacks
• Simulations for the easterns U.S. (Forest and Agricultural Sector Optimization Model-GHG): crops and pasture replaced by hardwood and softwood plantations
• Regional Atmospheric Modelling System: in these locations, higher water use of plantations not offset by increased precipitation
Jackson et al. 2005
Vegetation-climate feedbacks
• Summer ET increased by >0.3 mm/day, summer surface air temperature decreased by up to 0.3°C, precipitation decreased by as much as 30 mm/month
• No evidence for increased rainfall from local convection in most locations
Jackson et al. 2005
Soil quality effects
Jackson et al. 2005
VEGETATION PATTERN
ECOSYSTEM PROCESS
PRODUCTION OF ECOSYSTEM SERVICES
Production of ecosystem services with grassland to plantation conversion
• There is a carbon for water tradeoff when plantations are established
• Previous land cover type affects the severity of the tradeoff– Larger, more sustained streamflow
reductions when grasslands planted than shrublands
• Plantation species affects the severity of the tradeoff– More severe streamflow reductions
with eucalypts than pines• Climatic zone affects the severity of
the tradeoff– Lower rainfall zones may be more
severely impacted
Vulnerability assessment
• How sensitive is the system to shocks, stresses, or disturbances?
• What is the current state of the system relative to the threshold of change?
• What is the system’s ability to adapt to changing conditions?
From Luers 2005
Vulnerability & water yield• How large is the change in runoff
relative to available water resources?• Change in runoff as a percent of
mean annual precipitation consistently ~14-15%
• Comparison with renewable water can guide policy in areas with limited information
0
100
200
300
400
500M
ean
annu
al re
new
able
wat
er (m
m)
200 400 600 800 1000 1200Mean annual rainfall (mm)
Namibia
Israel
Botswana South Africa
Europe
Zimbabwe Australia
Africa
Swaziland
Canada
Lesotho
USA
Asia
World
Mozambique
Angola
Malawi
30%
10%
Jackson et al. 2005
Vulnerability assessment
From Luers 2005
Land use change & ecosystem services
-15
-10
-5
0
5
10
15C H20 quantity H2O quality Soil fertility
• Vulnerability not just to change in a single service, but to a suite of ecosystem services
• Scale issues are a challenge to analysis: C vulnerability global, water vulnerability local
• Uneven markets also a challenge
-10
-5
0
5
10
15C H20 quantity H2O quality Soil fertility
-15
-10
-5
0
5C H20 quantity H2O quality Soil fertility
VEGETATION PATTERN
ECOSYSTEM PROCESS
PRODUCTION OF ECOSYSTEM
SERVICES
policy
Ecuadorian example
• Páramo grasslands are primary source of drinking water– e.g. Sistema Papallacta
provides 50% of Quito’s drinking water, estimated at $2.5 million/year
• Grassland to plantation conversions likely to reduce water supply
Ecuadorian example
• FONAG: Water fund that collects payments from water users for watershed protection
• Proposed forestry law: limit plantations above 3500 m
VEGETATION PATTERN
ECOSYSTEM PROCESS
PRODUCTION OF ECOSYSTEM
SERVICES
policy
Acknowledgements
• Duke University Center on Global Change• National Science Foundation• US Department of Energy, Southcentral
Regional Center of NIGEC
