Fire and Climate Change in Washington

1. Fire and Climate Change in Washington Jeremy S. Littell JISAO CSES Climate Impacts Group University of Washington

2. Water balance and fire • Water balance deficit is the difference between atmospheric demand for water and the water available to satisfy that demand • As deficit increases, fuel moisture typically decreases • Different fuel types respond differently: dead and fine fuels vs. foliage WACCIA 12 Feb 2009

3. Area burned in 11 Western states, 1916-2007* Littell et al. in press WACCIA 12 Feb 2009

4. As temperature increases, the atmosphere evaporates more water from the landscape, plant tissues, and fine fuels This produces larger than normal, and more connected areas of depleted fuel moisture during the fire season Regional synchronization of fuel availability occurs Fire “blowups” are driven by extreme weather, but are contingent on climatically-driven fuel moisture. Regional fire and climate change MODIS, Northern Rockies, July 2003 WACCIA 12 Feb 2009

5. Different fuel types respond differently to climate Two mechanisms: drying of fuels and production of fuels Fuel (moisture) - limited systems Climate (energy) - limited systems Fuels and ecosystem pattern influence how climate affects fire Littell, McKenzie, Peterson, and Westerling. In press. WACCIA 12 Feb 2009

6. 20th century climate and fire: build a model Regional: precip. and temp. (1916-2006) Sub-regional: precip., temp., water balance deficit variables (1980 - 2006) Projected climate for the 2020s, 2040s, and 2080s Use model to project fire into future given future climate Projecting future area burned WACCIA 12 Feb 2009

7. Historical average: 425,000 acres 2020s: 0.8 million 2040s: 1.1 million 2080s: 2.0 million Probability of a year >> 2 million acres: Historical: 5% 2020s: 5% (1 in 20) 2040s: 17% (~1 in 6) 2080s: 47% (~1 in 2) Projections of future regional area burned Best model (tie): summer precip + summer temp OR summer water balance deficit WACCIA 12 Feb 2009

8. Future area burned: Bailey’s ecosections WACCIA 12 Feb 2009

9. Ecosection fire results All models had important “water limitation” terms: summer water demand, maximum temperature, or water deficit. Okanogan highlands, Columbia basin, and Palouse prairie all show some evidence of climatic facilitation (wetter seasons prior to fire lead to more area burned) Coast range/Olympics and Puget/Willamette did not yield models, but big fires have occurred in last several hundred years.

10. Uncertainties and implications Uncertainties: Disturbance synergies, interactions with and limitations of vegetation West-side sensitivity is possibly “threshold”, and statistical fire models do a poor job Implications: Rate of vegetation and landscape change would potentially be much faster than species change alone. Large fires are destructive, but potentially an opportunity to affect ecosystem trajectories too - if new varieties or new species are planned, conversion can be faster.

11. Summary: HB1303 Forest Ecosystems Increased summer temperatures lead to increased water deficit and increased climatic stress for trees. This leads to changes in species distribution, but more importantly, to: Increases in pine beetle host vulnerability Shifts to higher elevations of pine beetle range Increases in regional area burned Increases in area burned in WA ecosections Implications are that “stress complexes” will be strong agents of landscape change by midcentury