Simulating the impacts of Large Scale Insect- and Disease- Driven Tree Mortality on atmospheric chemistry Colette Heald, Sam Silva Department of Civil & Environmental Engineering Massachusetts Institute of Technology Jeffrey Geddes, Randall Martin Department of Physics & Atmospheric Science Dalhousie University, Canada AGU Fall Meeting 2015 Abstract A41R-07

Human-Driven Land Use and Land Cover Change Ramenkutty et al. (2008) Global Croplands Global Pastures Croplands Grasslands Forests Area (10 6 km 2 ) Lawrence et al. (2012)

“Natural” Land Cover Change

“Beetle-Battle” “Unprecedented Assault” “Perfect Storm” “Zombie Trees” “The West’s Hurricane Katrina” “Natural” Land Cover Change

Land System Impacts on Atmospheric Chemistry ?? DEPOSITION BVOC NO x Terrestrial Ecosystems NO x OH CH 4 BVOC O 3, SOAO 3, PAN, HNO 3 … Biosphere acts as both a source and sink of important reactive chemical species

Land-Atmosphere Exchange in a Chemical Transport Model Geddes et al. (2015) Atmos. Chem. Phys. Discuss.

Projected Insect- and Disease-driven Tree Mortality (2013 – 2027) National Insect and Disease Risk Map GEOS-Chem Land Input File Base Simulation Tree Mortality Simulation Impacts on atmospheric chemistry? Jun-Jul-Aug Geddes et al. (2015) Atmos. Chem. Phys. Discuss.

Predicted Tree Loss Exceeds 20% in Many Regions Needleleaf Trees Broadleaf Trees Pine, spruce, fir beetles; Spruce budworm Beech bark disease; Dutch elm disease; Oak wilt Tree Cover Fraction  Tree Cover

Country-wide BVOC Emissions Decrease ~5%; Locally up to 50% Isoprene Total Monoterpenes Total Sesquiterpenes Δ Emissions (μmol m -2 hr -1 ) Emissions (μmol m -2 hr -1 )

Slower Deposition Velocity (~10%) over Affected Regions DRY DEPOSITION Ozone Deposition Velocity Lower vegetation density decreases grid-average deposition velocity (v d ) Important for species whose depositional losses are competitive with chemistry

Spatial Variability in O 3 Impacts Depend on Chemistry/Deposition O 3 (ppb) Base Simulation Changing Emissions Only Changing Emissions & Deposition  O 3 (ppb) Decrease in concentrations (~0.6 ppb) due to lower BVOC emissions Net increase in concentrations (~1.2 ppb) due to slower deposition velocities Largely counteracted by…

Spatial Variability in O 3 Impacts Depend on Chemistry/Deposition Base Simulation Changing Emissions & Deposition Mitigates high O 3 in polluted regions Exacerbates high O 3 in clean regions Changing Emissions Only O 3 (ppb)  O 3 (ppb)

Organic Aerosol Decreased by ~10%; Locally up to ~25% Biogenic-derived Secondary Organic Aerosol (ug/m 3 ) Relative Impact to Total Organic Aerosol Highest impacts (~25%) in terpene-dominated regions Total OA decreases by 5-10% across large areas of south, eastern, and northwestern U.S.

Conclusions & Future Considerations Large local impacts on atmospheric chemistry due to projected tree mortality Temporal dimension of insect attack and post- disturbance succession? Insect - Fire - Climate Interactions? Geddes JA, Heald CL, Silva SJ and Martin RV (2015) Land cover change impacts on atmospheric chemistry: Simulating projected large-scale tree mortality in the US, Atmos. Chem. Phys. Discuss., 15,

Conclusions & Future Considerations Large local impacts on atmospheric chemistry due to projected tree mortality Must consider land cover change in regional chemistry and climate predictions Temporal dimension of insect attack and post- disturbance succession? Insect - Fire - Climate Interactions? Current and future oil palm expansion: Sam Silva A43G :40  O 3 (ppb)

Acknowledgements …and Thanks for your attention A41R: Tropospheric Chemistry-Climate-Biosphere Interactions Conveners, Chairs, and Presenters Funding: Natural Sciences and Engineering Research Council of Canada and the NSERC CREATE IACPES Program National Science Foundation (AFC )