Using Land Use Change Models to Assess Biophysical and Biogeochemical Consequences: The Future is Not Like the Past

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Using Land Use Change Models to Assess
Biophysical and Biogeochemical Consequences The
Future is Not Like the Past

• R. DeFries,
• rd63_at_umail.umd.edu
• Department of Geography and Earth System Science
  Interdisciplinary Center, University of Maryland
  College Park
• L. Bounoua, Dept. of Meteorology, UMD and
  Goddard Space Flight Center

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Land Use Change Models
Biophysical/Biogeochemical Consequences of Land
Cover Change
Human Drivers of Land Use Change
Sustainability
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Consequences of Land Cover Change for Ecosystem
Services

• Net primary production global terrestrial
  carbon model (CASA)
• Surface climate coupled land surface-general
  circulation model (SiB2-CSU GCM)

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1 What are the consequences of anthropogenic
land cover change for net primary production and
surface climate at regional and global
scales? 2 How might consequences of future land
cover change differ from the past? 3 How do the
effects from land cover change compare with
interannual variability?
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Undisturbed (derived from Matthews, 1983)
Existing (DeFries and Townshend, 1994)
Broadleaf evergreen forest Broadleaf deciduous
forest Mixed forest Coniferous forest Needleleaf
deciduous forest Wooded grassland Grassland Shrubs
and bare Tundra Bare Cropland Ice
2050 Future (derived from IMAGE 2.0)
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Difference in Net Primary Production (existing
- undisturbed land cover)
NPP loss
NPP gain
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Difference in Net Primary Production (future -
existing land cover)
NPP loss
NPP gain
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IS EFFECT OF ANTHROPOGENIC LAND COVER CHANGE ON
NPP SIGNIFICANT RELATIVE TO INTERANNUAL
VARIABILITY?
Undisturbed to existing land cover
Existing to future land cover
Latitude
Land cover change
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Land cover change affects surface climate through

• Morphology albedo surface roughness
• Physiology evapotranspiration balance
  between sensible and latent heat flux

General increase in albedo (cooling) and decrease
in latent heat flux (warming) with land use change
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Hansen et al., 1995, Climate Forcings in the
Industrial Era, PNAS.
Govindasamy et al., 2001, Land use change and
Northern Hemisphere cooling, GRL. Bonan, 1999,
Frost followed the plow Impacts of deforestation
on the climate of the United States, Ecological
Applications. Shukla et al. 1990, Amazonian
deforestation and climate change, Science.
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IS EFFECT OF FUTURE ANTHROPOGENIC LAND COVER
CHANGE ON CLIMATE SIGNIFICANT RELATIVE TO
INTERANNUAL VARIABILITY?
winter
summer
future cooling
future warming
future cooling
future warming
Land cover change
Modelled interannual variability in 1980s
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1 What are the consequences of anthropogenic
land cover change for net primary production and
surface climate at regional and global scales?

• Depends on type of land cover conversion
• Large regional disparities
• Temperate conversion increase in NPP, surface
  cooling
• Tropical conversion decrease in NPP, surface
  warming
• Global averages mask regional differences

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2 How might consequences of future land cover
change differ from the past?

• Past conversions predominantly in temperate
  regions for mechanized agriculture
• Future conversion likely to be predominant in
  tropics
• Predominant effect in future likely to be
  opposite in sign to past

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3 How do the effects from land cover change
compare with interannual variability?

• Consequences of past land cover change mostly
  within decadal-scale interannual variability
• Consequences of future changes outside of
  interannual variability

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The past is not prologue to the future
1986
1996
50 km
Deforestation in Southern Bolivia