Vegetation Distribution
and Climate Change in
the West
Ronald P. Neilson
USDA Forest Service
Pacific Northwest Research Station
Corvallis, OR, USA
(and a cast of many)
Challenges for Restoration
Under Rapid Climate Change
• Function – Services?
– Wetter or Drier?
•
•
•
•
Woody Expansion?
Dieback?
Infestation
Loss of Water Resources
• Diversity – Services?
– A Superstructure to maintain Function
– Functional Types – Functional Groups
– Species and Community Assembly Rules
– Migration
• Invasion
• Establishment
1988-89
1940-47
1972-77
Ocean-Climate Regime Shifts
Source: OSTP
Variations of the Earth’s Surface Temperature:
1000 to 2100
Similar to Glacial –
Interglacial
Temperature Change
High Warming
Moderate Warming
Small Warming
• 1000 to 1861, N.
Hemisphere, proxy data;
• 1861 to 2000 Global,
Instrumental;
• 2000 to 2100, SRES
projections
Climate Scenario Uncertainties
Model Uncertainty versus Emissions Uncertainty
(IPCC – Fourth Assessment Report Scenarios)
Change in Mean Monthly Temperature
(Degrees C)
2070-2099 vs 1961-1990
A2
MIROC
HAD
CSIRO
A1B
B1
Regional Precipitation Uncertainty:
North Wetter, South Drier
Percent Change in Precipitation
2070-2099 vs 1961-1990
A2
MIROC
HAD
CSIRO
A1B
B1
Long-Term
Changes in Distribution
and
Structure
Major Biome Boundaries
Ecotones in Space – Ecotones in Time (Threshold, Tipping Point)
Communities and Ecosystems:
MacMillan
RH Whittaker - New York, 1975
Water Limited
Leaf Area
Carrying Capacity
All else follows!
Current Climate
Thermal Zones
MAPSS Simulations
Boreal
Temperate
Future Thermal Impacts
• Longer Growing Season
• Migration
• Natives Invade Natives
• Release of Frost Limitations
• Loss of Alpine
• Expansion of Subtropics
• Great Basin Thresholds
• Expansion of Tropics
Subtropical
Tropical
GFDL Future Climate
MAPSS Simulated Vegetation Distribution
Ecotones in Space
Emergent Properties LAI, Ecotones, Runoff
Water Limited
Leaf Area
Carrying Capacity
All else follows!
To my Knowledge
Only three
Process-based
Biogeography
Models Published!
DGVM (Full Structure)
MAPSS  MC1, BIOMAP
DOLY  SDGVM
BIOME  LPJ
Neilson,R.P. 1995. A model for predicting continental-scale vegetation
distribution and water balance. Ecological Applications 5:362-385.
Woodland Expansion
MAPSS Simulation
Current Climate
Future Climate
(CGCM1)
Forest
(Green)
Woodland
Savanna
(Brown)
Grassland
Shrubland
Desert
Future Woody and Grass Expansion in the West
Enhance Carbon Storage, and
Catastrophic Wildfire, But…
Bachelet,D., R.P.Neilson, J.M.Lenihan, and R.J.Drapek. 2001. Climate change effects on
vegetation distribution and carbon budget in the U.S. Ecosystems 4:164-185.
Natives Invading Natives
MAPSS Simulation
Current Climate
Future Climate
(CGCM1)
Explosive Great Basin Diversity
Bachelet,D., R.P.Neilson, J.M.Lenihan, and R.J.Drapek. 2001. Climate change effects on
vegetation distribution and carbon budget in the U.S. Ecosystems 4:164-185.
MC1 Simulate Historical Vegetation Distribution
Mode Vegetation Type (1961 -1990)
MC1 Simulate Future Vegetation Distribution
Mode Vegetation Type CSIRO_a2
MC1 Simulate Future Vegetation Distribution
Mode Vegetation Type HADLEY_a2
MC1 Simulate Future Vegetation Distribution
Mode Vegetation Type MIROC_a2
Vegetation Carbon (Percent Change) CSIRO_a2
Vegetation Carbon (Percent Change) HADCM3_a2
Vegetation Carbon (Percent Change) MIROC_a2
Biomass Consumed by Fire (Percent Change) CSIRO_a2
Biomass Consumed by Fire (Percent Change) HADCM3_a2
Biomass Consumed by Fire (Percent Change) MIROC_a2
Near -Term
Changes in Variability
and
Disturbance
Some areas are projected to become wetter,
others drier with an overall increase projected
Annual mean precipitation change: 2071 to 2100 Relative to 1990
August 6, 2008
The Water Cycle moves most of the energy from the Tropics to the Poles!
September 14, 2008
The Water Cycle moves most of the energy from the Tropics to the Poles!
June 4, 2009
The Water Cycle moves most of the energy from the Tropics to the Poles!
June 6, 2009
The Water Cycle moves most of the energy from the Tropics to the Poles!
July 12, 2009
The Water Cycle moves most of the energy from the Tropics to the Poles!
Drought and Fire in the West
(Simulated Fire, no Fire Suppression)
-4
60
50
-2
PDSI
40
0
30
20
Wet
2
10
4
0
1900
1910
1920
1930
1940
1950
Palmer Drought Severity Index
(5 year running average)
1960
1970
1980
1983
Simulated Area Burned (MC1 Model)
(5 year running average)
Spearman Rank Correlation Coefficient -0.59***
1990
Simulated Area Burned
(millions of acres)
Dry
Western Regions
2000
1998
El Niño
The MAPSS Team, unpublished
Precipitation (Red Transect)
Moisture Zones
Global Cooling
Global Warming
Wet vs. Dry Winter
Global Warming
Global Cooling
Polar Front
Tentative Changes
Arizona Monsoon
(July – August
Summer
Humidity
Gradient
• Winter Cyclonic Storms
• Wetter North, Drier South
• Seasonality Shifts
•Expansion of Arizona Monsoon
Mitchell,V.L. 1976. Journal of Applied Meteorology 15:920-927.
Neilson & Wullstein. 1983. Journal of Biogeography 10:275-297.
Variation in Leaf Carbon (g/m2)
OR / WA / ID (SRES A2 Scenarios)
200
150
100
50
0
-50
4K-hist
8K-hist
8K-Miroc
8K-Had
8K-CSIRO
2100
2090
2080
2070
2060
2050
2040
2030
2020
2010
2000
1990
1980
1970
1960
1950
1940
1930
1920
1910
1900
1890
-100
Variation in Leaf Carbon (g/m2)
CA / NV / UT (SRES A2 Scenarios)
50
25
0
4K-hist
8K-hist
8K-Miroc
8K-Had
8K-CSIRO
2100
2090
2080
2070
2060
2050
2040
2030
2020
2010
2000
1990
1980
1970
1960
1950
1940
1930
1920
1910
1900
1890
-25
Variation in Leaf Carbon (g/m2)
AZ / NM / CO (SRES A2 Scenarios)
50
25
0
4K-hist
8K-hist
8K-Miroc
8K-Had
8K-CSIRO
2100
2090
2080
2070
2060
2050
2040
2030
2020
2010
2000
1990
1980
1970
1960
1950
1940
1930
1920
1910
1900
1890
-25
Summary
• Warmer temperatures will push alpine and
subalpine communities off the tops of the mountains
• Wetter winters in the north, drier in the south with
great uncertainty and variability inbetween
• The Arizona Monsoon will very likely be enhanced,
although the GCMs are very weak in simulating this
• Thus, lower elevational forest ecotones could go
down at southern latitudes (within the Monsoon
region), even while deserts could become hotter and
either more or less xeric.
• Huge Uncertainties:
– CO2 effect on enhanced woody expansion.
– Near-Term Variability, Establishment and Disturbance
Management Implications
(personal musings)
• Management Goals face an uncertain Future
– The Future will NOT echo the Past
• Instead,… Manage Change, per se
– Desired function may supercede ‘Desired future condition’
• Improve resilience of ecosystems to rapid change,
e.g.
– Keep forest density below water-limited carrying capacity
– Plant diversity rather than homogeneous monocultures
• Restoration efforts confront:
– a) establishment bottlenecks,
– b) invasions,
– c) functional communities
Acknowledgements
Pacific Northwest Research Station
Managing Disturbance Regimes Program
Oregon State University
Colorado State University
University of Montana
National Center for Atmospheric Research
IRI, International Research Institute for
Climate Prediction
CEFA/DRI Program for Climate, Ecosystem
And Fire Applications
National Fire Plan
USFS Climate Change Program
NSF, EPA, DOE, EPRI, USGS-BRD
Variation in Leaf Carbon (g/m2)
Western States (SRES A2 Scenarios)
100
75
50
25
0
4K-hist
8K-hist
8K-Miroc
8K-Had
8K-CSIRO
2100
2090
2080
2070
2060
2050
2040
2030
2020
2010
2000
1990
1980
1970
1960
1950
1940
1930
1920
1910
1900
1890
-25