Simulating the impacts of

Large Scale Insect- and Disease- Driven Tree Mortality

on atmospheric chemistry

Colette Heald, Sam SilvaDepartment of Civil &

Environmental EngineeringMassachusetts Institute of Technology

Jeffrey Geddes, Randall MartinDepartment of Physics & Atmospheric Science

Dalhousie University, Canada

AGU Fall Meeting 2015 Abstract A41R-07 jeff.geddes@dal.ca

Human-Driven Land Use and Land Cover Change

Ramenkutty et al. (2008)

Global Croplands

Global Pastures

Croplands

Grasslands

Forests

Area

(106

km

2 )

Lawrence et al. (2012)

http://www.fws.gov/news/blog/index.cfm/2011/5/18/

“Natural” Land Cover Change

http://www.fws.gov/news/blog/index.cfm/2011/5/18/

“Beetle-Battle”http://www.climate.org/

“Unprecedented Assault”http://www.ucsusa.org/

“Perfect Storm” http://www.fws.gov/

“Zombie Trees” http://www.king5.com/

“The West’s Hurricane Katrina”

http://e360.yale.edu/

“Natural” Land Cover Change

Land System Impacts on Atmospheric Chemistry ??

DEPOSITION

BVOC NOx

Terrestrial Ecosystems

NOxOH OH CH4

BVOC

O3, SOA O3, PAN, HNO3 …

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)

http://www.fs.fed.us/foresthealth/technology/nidrm.shtml

2013 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 RegionsNeedleleaf 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%Iso

pren

eTo

tal

Mon

oter

pene

s

Tota

l Se

squi

terp

enes Δ

Emiss

ions

(μm

ol m

-2

hr-1)

Emiss

ions

(μm

ol m

-2

hr-1)

Slower Deposition Velocity (~10%) over Affected Regions

DRY DEPO

SITION

𝐹 𝑖=𝑣 𝑑×[𝐶 ]

Ozone Deposition Velocity

Lower vegetation density decreases grid-average deposition velocity (vd)

Important for species whose depositional losses are competitive

with chemistry

Spatial Variability in O3 Impacts Depend on Chemistry/Deposition

O 3 (p

pb)

Base Simulation

Changing Emissions

Only

Changing Emissions

& Depositio

n

O3 (

ppb)

Decrease in concentrations (~0.6

ppb) due to lower BVOC emissions

Net increase in concentrations (~1.2 ppb) due to slower

deposition velocities

Largelycounteracted by…

Spatial Variability in O3 Impacts Depend on Chemistry/Deposition

Base Simulation

Changing Emissions

& Depositio

n

Mitigates high O3 in polluted regions

Exacerbates high O3 in clean regions

Changing Emissions

Only

O 3 (p

pb)

O3 (

ppb)

Organic Aerosol Decreased by ~10%; Locally up to ~25%

Biogenic-derived Secondary Organic Aerosol (ug/m3)

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, 29303-29345.

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 SilvaA43G-0392 13:40

O3 (ppb)

Acknowledgements

…and Thanks for your attention

A41R: Tropospheric Chemistry-Climate-Biosphere InteractionsConveners, Chairs, and PresentersFunding:Natural Sciences and Engineering Research Council of Canadaand the NSERC CREATE IACPES ProgramNational Science Foundation (AFC-1238109)