Fire-climate-vegetation-topography-land use

1
Fire-climate-vegetation-topography-land use
What drives and determines fire patterns across
time and space? What are the implications of
global climate change?
2
Global climate change

• Avg. surface T increased by 0.6C in 20th century
• 1990s were warmest decade and 1998 was warmest
  year since 1861, and probably the warmest of the
  last 1000 yr
• Freeze-free season longer in mid and high
  latitudes
• Less snow and ice, higher sea levels

3
Global temperatures

• Mean global temperatures in 2000 were 0.39C
  (0.7F) above the long-term (1880-1999) average
• 2000 was the sixth warmest year on record
• The only years warmer were 1998, 1997, 1995, 1990
  and 1999

4
Earths surface temperature, 140 yr
IPCC 2000
5
Earths surface temperature, 1000 yr
IPCC 2000
6
Global changes in atmosphere

• CO2 content has increased by 31 since 1750
• Higher concentration now than at any time in last
  420,000 yr, and probably more than at any time in
  last 20 million yr
• Rate of increase in concentration is
  unprecedented in the last 20,000 yr

7
Greenhouse gasses
IPCC 2000
8
Future changes

• Global surface temperature increase by 1.4 to
  5.8C between 1990 and 2000
• Land areas will warm more than the oceans,
  especially northern North America
• Larger and faster changes than at any time in
  last 10,000 yr

9
Future climate extremes
IPCC 2000
10
Climate change and fires

• What are the implications for fires and their
  ecological effects?
• The answer depends in part on the role of climate
  vs topography or local fuel conditions in
  determining fire patterns
• Well also look at some of the tools people are
  using to answer these questions

11
Example hypotheses

• There are linkages among fire-climate-vegetation-l
  and use-topography across temporal and spatial
  scales
• Regional climate entrains fire patterns at fine
  spatial scales, overriding the influence of local
  topography and vegetation, leading to synchrony
  at widely separated sites and across regions
• Fires will mediate the effects of climate change

12
Approaches

• Cross-regional studies
• Comparative case studies thoughtful comparisons
  across time and space, and in different climates
  will be informative of general theory
• Simulation models
• Long-term climate-fire-vegetation reconstructions
• Combined approaches

13
(No Transcript)
14
Drought
Swetnam, TW
15
Fire along environmental gradients
Swetnam, TW
16

• Fire frequency
• Fires of some size every few yrs
• Larger fires once or twice per decade
• Regional fire yrs 2 to 5 times per century
• Synchrony
• Variable
• Factors controlling fire regimes varied through
  time
• Climate important in controlling landscape
  conditions and ignitions
• Wet conditions favored increased fuel production
  and accumulation
• Dry conditions favored effective ignition and
  spread.
• Cool/moist decreased fire frequency, but
  increased fire size and intensity.
• Long-term warm/dry conditions more frequent
  fires, but less spatial continuity of fuels and,
  consequently smaller fires.

17
Implications for the future

• Fire regimes will continue to change in response
  to changing forest conditions and climate
• A warmer climate with more frequent burning could
  change species composition
• Wet, warm climate could increase fuel production,
  with corresponding increases in fire intensity
  and size
• Warmer-drier conditions might lead to intense
  fires followed by a decrease in fire severity as
  fuel production declined.
• The forest-climate-fire system is dynamic

18
Area burned

• Selway-Bitterroot Wilderness Area
• 474,237 ha burned in 437 fires from 1880 to 1996
• 7 yrs of extensive fire, 72 of all area burned
• 1889, 1910, 1919, 1929, 1934, and 1988
• Gila-Aldo Leopold Wilderness Complex
• 147,356 ha burned in 232 fires from 1909 to 1993
• 6 yrs of extensive fire, 71 of all area burned
• 1909, 1946, 1951, 1985, 1992, 1993

19
(No Transcript)
20
Area burned during three different eras of fire
management
21
Area burned and Palmer Drought Severity Index
(PDSI)
22
Fire frequency

• Derived from the fire atlases
• Fires gt50 ha

23
Gila/Aldo Leopold Wilderness Complex Mogollon
Baldy - Langstroth Mesa Transect
1904
9
1965
15
5
1968
5
1953
5
1992
5
37
1953
1904
10
1989
1938
1992
1986 - 1997 fires per 100 ha
Lightning Ignitions
Human Ignitions
24
Lightning, fires, topography and
vegetationGALWC, fires/100 ha,1986 - 1997
Lightning ignitions
Human ignitions
25
Climate from tree rings

• Cross-dating is used to identify missing and
  false rings, and therefore to get accurate dates

Old trees give longer records
26
Changing fire patterns
27
Complex interactions

• Fires influence global C
• Fires release CO2
• Fire-killed vegetation decomposes
• Recovering vegetation may absorb less C
• Fires will increase under climate change
• Canada may experience a 50 increase in annual
  area burned (Amiro et al. 2001, Flannigan et al.
  1998)
• The number of lightning fires could increase by
  30 (Price and Rind 1994)
• Extended fire seasons

Canadian Forest Service. 2001. Forest fire
context for the Canadian Forest Services science
program. 2001. Available Online
lthttp//www.nrcan-rncan.gc.ca/cfs-scf/science/cont
ext_fire/index_e.htmlgt. Accessed November 2001.
28
Drivers

• Local site productivity
• Topography
• Climate
• Fire exclusion policies
• Land use
• Exotic plants

29
Climate-vegetation-land use linkages

• Climate is a major driver of fire occurrence in
  all fire regimes, but
• Climate and climate variability only partially
  explains changes in fire regimes through time
• Land use has altered fire regimes grazing (where
  fine fuels carry fires), roads (limit fire
  spread), fire suppression, logging, mining,
  exotics, etc.
• Intensive grazing in dry forests (Swetnam and
  Baisan 1996 Swetnam and Betancourt 1990, 1998)
• Fire suppression (Rollins et al. in press)
• Less influential where infrequent,
  stand-replacing fires were the norm
• Fire size has not changed in 20th century in
  chaparral of CA (Keeley et al. 1999)

30
What have we learned

• Climate has an overriding importance at both
  broad and fine scales (Swetnam and Betancourt
  1998 Heyerdahl et al. 2001), particularly for
  extreme events.
• Human impacts are ubiquitous as well, but more
  pronounced in altering fire regimes where fires
  were historically frequent (Hardy et al. 2001),
  and where human population density is high and
  land use is intense (e.g. chaparral in
  California, Keeley et al. 1999).

31
Challis National Forest, Idaho, Photo from Amy
Haak
Salmon R. in Idaho, Photo from Amy Haak