1. Assessing the Influences of Urbanization on Terrestrial Carbon Pools and Fluxes Andy B. Reinmann and Lucy R. Hutyra Boston University, Department of Earth & Environment

2. View of the Terrestrial Carbon Cycle Carbon cycle research has centered on quantifying and understanding the controls on the terrestrial carbon sink in undeveloped landscapes

3. Global urban expansion occurring at twice the rate of population growth Tripling of urban land cover from 2000-2030 Developed land covers ~6% of contiguous U.S. land area Twice the extent of northern hardwood forest Doubling of urban extent from 2000-2030 Urbanization is new face of land cover change View of the Terrestrial Carbon Cycle Seto et al. 2012 ; Nickerson et al. 2011

4. Projecting Land Cover Change from Urbanization Projects housing development 1 ha resolution across U.S. 13 housing density categories 5 population growth scenarios EPA Integrated Climate and Land Use Scenarios (ICLUS) ICLUS Bierwagen et al. 2010

5. Projecting Land Cover Change from Urbanization Combine ICLUS with National Land Cover Database (NLCD) products Composition of each housing density category Proportions used to infer land cover change from ICLUS projections ICLUSNLCD

6. Projecting Changes in Carbon Storage and Fluxes USFS Forest Inventory and Analysis Forest growth curves Forest biomass Harvesting patterns Biomass removed from harvesting and development divided into 9 carbon turnover pools Published urban biomass values (Raciti et al. 2012)

7. Massachusetts-Specific Parameters Forest and Urban are most common land cover types Inversely related Approach is an empirically informed, bookkeeping and scenario analysis NOT a process-based model Proportion of Total Area Housing Density Category

8. Historical Changes in MA Forest Cover Agricultural Expansion Reforestation Urban Expansion

9. Projected Changes in MA Forest Cover 1971-2010 (observed) 0.22% yr -1 decline 2010-2050 (projected) 0.07 to 0.27% yr -1 decline

10. Projected Changes in MA Forest Cover 1971-2010 (observed) 0.22% yr -1 decline 2010-2050 (projected) 0.07 to 0.27% yr -1 decline MA pop. growth rate is 0.31% yr -1 US mean is 0.97% yr -1 Global mean is 1.29% yr -1 US Census; UN Population Division

11. Forest cover decreases west to east (Inverse of population patterns) Lowest forest losses in most rural counties, losses increase from west to east Projected Spatial Distribution of Forest Cover 20-30% 40-50% 50-60% 60-70% 70-80% 80-90% 2010 Forest Cover B1 (Low Pop. Growth) 2010-50 A2 (High Pop. Growth) 2010-50 <10% 10-20% 20-30% 30-40% Forest Loss <10% 10-20% 20-30% 30-40% Forest Loss Boston

12. Conserved/Undevelopable Stable > 50% Forest Cover Stable Urban > 25% Loss of Forest Cover Changes in Spatial Distribution of Forest Cover 2010 to 2050

13. Terrestrial Carbon Fluxes 2010 to 2050 B1 (Low pop. growth) Forest carbon sink offsets emissions from land conversion A2 (High pop. growth) Land conversion becomes net source in rapidly urbanizing counties Land conversion reduces forest C sink by up to 28% Loss to atmosphere Uptake by veg.

14. Briber et al. (in review) Urban growing conditions in aggregate favor vegetation growth (at least in MA) Terrestrial Carbon Fluxes 2010 to 2050

15. Urban biomass accrual up to 75% of terrestrial C sink in rapidly developing landscapes Potential to offset reductions in C storage from forest loss Importance increases with urbanization Loss to atmosphere Uptake by veg. Terrestrial Carbon Fluxes 2010 to 2050 ? ? ? ? ? ?

16. Assuming constant per capita rate of emissions Emissions from land cover change < 2% of total emissions Rural emissions offset by terrestrial carbon sink MA terrestrial carbon sink projected to offset 10 to 12% of fossil fuel emissions Loss to atmosphere See Gately et al. poster on fossil fuel emissions Terrestrial Carbon Fluxes 2010 to 2050

17. Summary Urbanization has a profound affect on the terrestrial C cycle Rapid decline in MA forest cover; urban biomass can comprise a large proportion of the terrestrial C sink Terrestrial C sink will offset emissions associated with urbanization, but will be less than 12% of MA fossil fuel emissions Most of our future urban area does not yet exist, we can actively shape the patterns in C fluxes through development choices Urban biosphere fluxes also vital for atmospheric inversions and GHG verification Ongoing & Future directions Process-based modeling (e.g., Hardiman et al. poster) Albedo and latent heat flux Quantify uncertainty Export to other states (Gradient of land cover types and urbanization trajectories)

18. Acknowledgements Special Thanks to: Britt Briber, Tori Dearborn, Conor Gately, Jackie Getson, Brady Hardiman Funding Sources: