humans and fire in prehistoric landscapes: legacies …
TRANSCRIPT
HUMANS AND FIRE IN PREHISTORIC LANDSCAPES:
LEGACIES THAT INFLUENCE CONTEMPORARY
ECOLOGY AND MANAGEMENTRachel Loehman, USGS
Linn Gassaway, USFS
1909 1948
1968 1989
What is naturalness?
Competing hypothesis:
Predominance
Lightning or Human ignitions
“Lightning fires, including onsite ignitions and lightning fires spreading from
other areas, were well capable of maintaining most fire regimes in the West.”
(Barrett, et. al. 2005)
One authority on fire history, while conceding “significant Indian
influence” refers to nineteenth-century forests as “unmanaged” and
“natural” environments. (Robbins 1999)
Did Native Americans change vegetation to a “condition outside of the natural realm of historical variability”? (Parker 2002:237)
Was it the intent of Native Americans to change the vegetation?
How did they live, use and interact with fire?
Geographic and Ecological View Point
Anthropological View Point
Outside of “Natural Fire Regime”
• “Unnatural” Fire Return Interval
• Seasonality
• Asynchronous fire
• Fire in wet years
• No fire in dry years
Assumed
Anthropogenic Fire Signatures
Finding Human Ignitions in the Past:
At a national scale lightning strikes appear to be able to account for all
ignitions.
Is it a question of scale?
⁻ Complex ecological problems require complex approaches!
⁻ Detect human influences on landscapes, including persistent legacies that are not detectable by other disciplines
⁻ Augment other data sources - fading record in fire history
⁻ Extend spatial and temporal scales of inference in traditional ecology
⁻ Re-imagine baseline conditions and best practices in land management
Why study ancient human-environment interactions?
Limitations
• Inability to distinguish between human induced fire and
lightning fire in tree rings
• Failure to take into account the wide variety of uses
Native Americans had for fire
• Use of broad regional histories
• Failure to accurately take into account the ethnographic
and archaeological data in the study areas
Does the use of multiple comparable data sets at a similar scale
change the interpretation?
Known prehistoric
archaeological sites
MODIS
2000-2007
Two examples of pre-historic human impacts on landscapes and fire patterns
California –anthropogenic use of fire
Jemez Mountains, New Mexico –alteration of fuelscapes
Who lived there?
• Hunter-Gatherers
•Non-agriculturalist
• Seasonal rounds
•Few permanent villages
•Large numbers of seasonal camps
• “triblets” - 100-500 people
Southern Sierra Miwok
Ahwah’-nee
Proposed Cultural Chronology Moratto 1999
DATES
A.D. 1945-
A.D. 1891-1944
A.D. 1864-1890
A.D. 1848-1863
A.D. 1800-1847
A.D. 1350-1800
A.D. 650-1350
1200 B.C. - A.D. 650
3500-1200 B.C.
6000-3500 B.C.
7500-6000 B.C.
8500-7500 B.C.
9500-8500 B.C.
>9500 B.C.
PERIODS
Historic 4
Historic 3
Historic 2
Historic 1
Protohistoric
Late Prehistoric 3
Late Prehistoric 2
Late Prehistoric 1
Intermediate Prehistoric 2
Intermediate Prehistoric 1
Early Prehistoric 4
Early Prehistoric 3
Early Prehistoric 2
Early Prehistoric 1
COMPLEXES/PHASES
Rancheria
Tenaya
Yosemite
Mariposa
Tamarack (?)
Crane Flat
Merced, Wawona,
?
El Portal
?
?
?
The
Physical evidence
Archaeology
• Not all sites inhabited at same time
• Best correlation of occupation and fire use
FIRE
How often?
Where?
When?
Relationship of fire scarred trees
to
Habitation and Gathering
Fire Return Interval –
how often fire occurs in a selected location over a period of time
FRI = >70
Yosemite Dendrochronological Fire History
1552-2004
Study area Sample Area Sample
Size (hectares) 30 1.5-11 Tree
Samples 57 5-14
MFI
(Weibull Median)
1.92
(1.61)
4.69 - 17.83
(3.33 - 16.5)
17.7
Interval Range 1-11 1-43 2-56
Is it Human or Lightning?
Historically observed Lightning
1930-2002
2 villages
1 permanent year round
1 seasonal camp
2 gathering areas
2 “controls” - no known use
When -
0
1
2
3
4
5
6
7
8
1520-2004 1520-1800 1800-1847 1848-1863 1864-1890 1891-1944
All time periods Late Prehistoric 3 Protohistoric Historic 1 Historic 2 Historic 3
Mean
Fir
e R
etu
rn
In
terval
Changes in MFI by archaeological time period
Time Period Statistical Difference P
Prehistoric vs. Protohistoric
(A.D. 1520-1800) (1800-1847) Significant 0.0000
Protohistoric vs. Historic 1
(A.D. 1800-1847) (1848-1863) Not Significant 0.1929
Historic 1 vs. Historic 2
(A.D. 1848-1863) (1864-1890) Not Significant 0.9610
Historic 2 vs. Historic 3
(A.D. 1864-1890) (1891-1944) Significant 0.0001
2 Tail T-Test (P < 0.025)
1.922.4
1.091.5 1.47
5.0
Location Study
area
(ha)
# of trees
sampled
MFI
Study
Area
MFI
Range
Source
Blodgett 5 46 4.7 4-28 Stephens and
Collins 2004
Pilot Creek 15 15 5.7 3-18 Stephens and
Collins 2004
South fork
of
Tuolumne
2100 209 1.5 1-16 Scholl
Unpublished
Yosemite
Valley
30 57 1.92 1-11 Gassaway
2005
South fork
of Merced
1625 69 2.13 1-28 Scholl
Unpublished
Southern-
central
Sierra
Nevada
50 2-3 1-25 Swetnam et al
1998
SEKI –
Redwood
Creek
1030 37 2.1 1.73-
2.35
Kilgore and
Taylor 1979
Bearskin
Creek
770 183 1.7 1.55-
1.86
Kilgore and
Taylor 1979
SeasonalityLocation Fire Seas on Source
Blodgett 21% Dormant 79% Late wood
Stephens an d Colli ns 2004
Pilot Creek 21% Dormant 79% Late wood
Stephens an d Colli ns 2004
South fork of Tuolumne 51% Dormant 24% Late wood
Scholl Unpub lished
Yosemite Valle y 48% Dormant 31.5% Latewood 7.3% Early Earlywood 5.2% Middle Earlywood 7.3% Late Earlywood
Gassawa y 2005
South fork of Merced 38% Dormant 32% Late wood,
Scholl Unpub lished
Southern -central Sierra Nevada
23% Dormant 54% Late wood 18% Late Ear lywood 4% Middle Earlywood 1% Early Earlywood
Swetnam et al 1998
Mt. Home State Forest 20% Dormant 61% Late wood 16% Late Ear lywood 1% Middle Earlywood
Swetnam et al 1998
Fire Return Intervals and
Seasonality
can not be used alone
to determine
the source of ignition.
Testing competing hypothesis: Predominance: Lightning or Human ignitions
Minimum datasets needed
• Modern lightning fire return interval
• Location specific Human occupation
• Cultural chronology
• Fire History
Lightning ignited fires since 1878 and currently
recorded prehistoric sites
(Gray = no archaeological survey)
IMPLICATIONS
Major indicator is MFI change
corresponds to Culture Change
From an anthropological
standpoint the Southern Sierra
Miwok culture is not anomalous.
Archaeological data show no
major difference between the
material culture of the Ahwah’-nee
and other groups in the Sierra
Nevada
“Hunter-gatherers are necessarily responsive to
local environmental fluctuations and
perturbations, whether natural or man-made. Like
men everywhere, hunter-gatherers cannot long
ignore disruptions which adversely effect their
day-to-day subsistence. However, because their
subsistence strategies are more directly and
immediately linked to environmental imperatives,
they must soon make accommodations or else
become one more evolutionary failure” (Lewis
1993:56).
Photo: Craig Allen, USGS
Photo: NPS
Modeling the prehistoric human-ecological landscape
⁻ Ancient Jemez WUI, AD 1200-1900
⁻ Varied population levels, wood use amounts, number of ignitions, agricultural footprints
⁻ Detected thresholds, scales of impacts
Jemezreservation
Bandelier NM
Valles Caldera NPHuman
“footprint”
Annual area burned (ha)
Fire size (ha)
Scenarios:LP/HP: Low or High population
LF/HF: Low (1 cord/person/yr) or High (2 cords/person/yr) fuelwood use
EI: Elevated ignitions (+50%)
SF: Live tree harvest @ 1 tree/person/yr
MIA: elevated ignitions @ 0.15% per person/yr + 1 acre/person/yr ag land
HIA: elevated ignitions @ 0.30%/ per person/yr + 4 acre/person/yr ag land
AD 1200-1325 1326-1450 1451-1525 1526-1625 1626-1700 1701-1900
Humans and local fire regimes: altered area burned, fire size
15
0
40
00 5
00
0
50
00
50
0
50
0
70
00 8
00
0
80
00
30
00
Vallecitos Paliza Early Jemez Late Jemez Guadalupe
Low popn High popn
No people
Fewer peopleMore people
More ignitions
More ignitions, ag land, live tree harvest
Profound human impacts on fuelscapes
Scenarios:LP/HP: Low/High pop’n.LF/HF: Low/High fuelwood SF: Structural wood harvestMIA: Mod. ignitions & agric.HIA: High ignitions & agric.
Mean fire return interval, AD 1526-1625: Local and landscape-scale human impacts
Fuelwood collection fragments fuels, fewer
spreading fires
Added ignitions spread fires across landscape
HP,SF, MIA
8.5x
25x
25 times more fire
than “null” no-human scenarios
LP,SF, HIA
13x16x
----
Ecosystems respond to human activity
Ponderosa pine
Juniper spp.
Piñon pine
Grasses
Gambel oak
Scenarios:LP/HP: Low or High population
LF/HF: Low (1 cord/person/yr) or High (2 cords/person/yr) fuelwood use
EI: Elevated ignitions (+50%)
SF: Live tree harvest @ 1 tree/person/yr
MIA: elevated ignitions @ 0.15% per person/yr + 1 acre/person/yr ag land
HIA: elevated ignitions @ 0.30%/ per person/yr + 4 acre/person/yr ag land
AD 1526-1625:5000 people, 1 cord fuelwood/person/yr., 8.5x background ignitions, 1 acre ag land/person/yr., 1 live tree/person/yr.
AD 1526-1625:8000 people, 2 cords fuelwood/person/yr., 13x background ignitions, 1 acre ag land/person/yr., 1 live tree/person/yr.
AD 1200-1325 1326-1450 1451-1525 1526-1625 1626-1700 1701-1900
Po
nd
ero
sa p
ine
Gra
sse
s
No people
Fewer peopleMore people
More ignitions
More ignitions, ag land, live tree harvest
(p.181) …it is possible that prehistoric Native Americans used fire widely in the southwest, but little evidence has survived to our current day due to the ”fading record" problem. The role of people in southwestern fire regimes relates to a larger question: Were the pre-European landscapes of the Southwest in the 1500s pristine wildernesses or humanized culturescapes? …despite a variety of early human land uses, most mountains in the Southwest retained a dominantly wilderness character until the advent of Anglo-American exploitation in the late nineteenth century, as evidenced by the persistence of natural fire regimes until this time.
(p.180) Multiple lines of evidence from this region overwhelmingly suggest that in A.D. 1850, as in A.D. 1580, most mountain landscapes were "natural" and "wild'" with regard to fire regimes and associated vegetation patterns. Evidence of landscape-scale fire use by aboriginal people in the southwest is scanty to nonexistent, and most assertions of aboriginal burning are based upon anecdotal accounts or sources subject to substantial historical bias.
– Humans as fire surrogates
– Recent land use and management have destabilized forests
– Restoration can’t be achieved by natural processes alone
– Fire management includes fuel manipulation…then and now
– Archaeology highlights the complexity of land management and land use
– Biasness of older fire histories
Significance for contemporary ecology, archaeology, & management
Time
(Population density,
Period of culture conflict or cultural movement,
Changes in material culture)
Location
(topography,
fuels, weather)
Culture
(Hunter-Gatherer,
Agricultural)
“The only constant is change. Ecology is a science of place. Native influence varied by place.” James Agee