A brief history of wildfire: the past as a window to future REM 244 Guest Lecture, 17 Jan., 2012

Transcription

1 A brief history of wildfire: the past as a window to future REM 244 Guest Lecture, 17 Jan., 2012 Philip Higuera Assistant Professor "The farther backward you can look, the farther forward you are likely to see." - Winston Churchill

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3 Key Questions for Today s Class 1. What can we learn from the past? 2. How do we learn from the past? 3. What have we learned?

4 1. What can we learn from the past? A. Context and perspective

5 How old is fire?

6 What do we need for fire? 1. Fuel Flame 2. Oxygen 3. Ignition fuel

7 What do we need for fire? 1. Fuel - Terrestrial vegetation 2. Oxygen 3. Ignition - Oxygen 13-35% (today = 21%) - Lightning, volcanoes, humans

8 How old is fire? Late Silurian, 420 mya Human evolution 5 mya

9 420 million 400,000 13% 50,000-10,000 Historical precedence: (Bowman et al. 2009) Cottrell 2004

10 Context and perspective Fire is a longstanding natural process, present throughout the evolution of the life and much of the planet Fire is something that ecosystems do, not something that happens to them - D. Falk Natural phenomenon, human disaster - My high school headmaster Erickson Creek Fire, Interior Alaska, 2003

11 1. What can we learn from the past? A. Context and perspective B. How does fire respond to environmental change? Use the past as a natural experiment.

12 The past as a natural experiment Multimillennial millennial: glacial / interglacial periods Graphic: IPCC:

13 The past as a natural experiment Millennial to centennial: glacial-holocene transition Ice core temperature record from the Greenland Ice Sheet approximate temperature anomaly (degrees C) Holocene d 18 O (per mil.) Thousands of years before present (Ky bp) Data: Greenland Ice Sheet Project II (GISPII)

14 The past as a natural experiment Centennial-decadal: past 1000 years Earth s history is filled with wellunderstood environmental variability, at multiple scales Graphic: IPCC 2007: html

15 Key Questions for Today s Class 1. What can we learn from the past? a) Context and perspective b) How fire responds to environmental change 2. How do we learn from the past?

16 Reconstructing the past Proxy a stand in Biological Proxies: tree rings pollen forams diatoms Physical Proxies: charcoal isotopes glaciers boreholes Images: P. Higuera, L. Brubaker;

17 Important characteristics of all proxies: Indirect measures? Precision varies vs. Availability varies Images:

18 Fire-scarred trees: cambium killed by fire on a portion of the tree; growth around scar used to determine date of fire Fire scars Birth year of tree Fire scared ponderosa pine.

19 Fire-scarred trees: Fire scars from individual trees Heyerdahl, E. K., L. B. Brubaker, and J. K. Agee Spatial controls of historical fire regimes: A multiscale example from the interior west, USA. Ecology 82:

20 Lake-sediment records pollen: macrofossils: charcoal: cm cm

21 Higuera et al. in prep. Lake-sediment records Chickaree Lake, RMNP, CO: Charcoal peaks from past fires

22 Geomorphic Records Severe burns smooth soil surfaces reduced infiltration greatly increased surface runoff Large firerelated events Meyer et al. 1992

23 Geomorphic Records Fire-related sedimentation events 1997 deposits 197 ± ± ± ± ± 43??? Pierce, Meyer, et al. 2006

24 Accuracy of fire history proxies: Geomorphic records Modified from Gavin et al. 2007

25 Key Questions for Today s Class 1. What can we learn from the past? a) Context and perspective b) How fire responds to environmental change 2. How do we learn from the past? 3. What have we learned from the past?

26 3. What have we learned from the past? A. Climate has been a primary control of biomass burning, at multiple time scales

27 Millennial, Global Global biomass burning varies with global temperature

28 Millennial, Global Charcoal Temp. proxy 10,000 Time (yr BP) 80,000

29 Millennial, Global Climate warming Climate cooling Charcoal Temp. proxy After climate event Before climate event

30 Millennial, Hemispheric Temp. proxy Fire frequency Biomass burning proxy Arboreal pollen 15,000 10,000 Years before present

31 Millennial, Regional Fire frequ. Temp. proxy Yellowstone NP: 17,000 yr. fire history correlates with summer insolation (temp.) Fire frequencies vary with climate at millennial time scales Millspaugh, Whitlock, and Bartlein et al Geology 28 (3),

32 Centennial Extreme drought associated with above-average area burned, for past 750 yr Recon. area burned (ha x 1000) Med. area burned (ha x 1000) % CI 90% CI wet dry Higuera et al., Precipitation record: Gray et al. 2007; Tree-ring record: Romme and Despain 1989.

33 3. What have we learned from the past? A. Climate has been a primary control of biomass burning, at multiple time scales B. Humans and fire have always been tightly linked, but human impacts on large-scale fire regimes have varied

34 Cottrell 2004 Humans and fire: (Bowman et al. 2009) Years before present

35 Australian aboriginals and Firestick farming a long-standing and increasingly-relevant question.

36 Biomass burning index Years before present Temp. proxy Temp. proxy

37 Human Population density Limited evidence for human influence on regional burning prior to 200 ybp Biomass burning index Years before present (x 1000)

38 Cottrell McWethy 2004 et al Initial burning period: widespread and coincident with human arrival Humans had immediate and dramatic impacts on forest communities, via fire. Little evidence that climate change played a roll

39 Biomass burning Climate dominant until ca. mid 19 th century, then human impacts important, globally Year AD

40 Summary Fire has been a key process in the evolution of our planet, for millions of years Fire regimes have varied at multiple time scales, largely in response to direct and indirect impacts of climate change Human have existed with fire for millions of years, and impacts vary among ecosystems and time periods

41 Questions? High Fireweed severity (Epilobium 1988 fire angustifolium) in subalpine forest dominating of Yellowstone after a high National severity Park fire in boreal forest of Alaska.

42 Some Resources NOAA Paleoclimate Web Page: Information on all aspects of paleoclimate research and findings, including raw data. IPCC 2007, Working Group 2 (Scientific Basis): The Intergovernmental Panel of Climate Change s latest report. The Ultimate Tree-ring Web Page (literally): Everything you could want to know about tree-ring research. Brown University pollen viewer: nima/viewer31/webviewer.html

43 Idaho large events & Yellowstone National Park YNP all events SFP 'large events' SFP 'large events' including high elevation Medieval Climatic Anomaly: ~ yr BP sum of probabilites cal yr BP Pierce et al. 2004