State of knowledge: Quantifying Forest C capacity and potential Tara Hudiburg NAS Terrestrial Carbon Workshop September 19 th, 2017
Global Forest Cover http://www.wri.org/resource/state-worlds-forests Half of terrestrial carbon is in forests Forests can be substantial carbon sinks (30% offset of global FFE emissions) Climate, disturbance, and land use change
The Goal: Reliable Carbon Storage
Questions 1. What is known about the carbon storage potential of forests/forest management practices? 2. What do we need to know about the field-level and landscape-level processes that impact forest C sequestration and loss? 3. What is the impact of changing forest management practices on carbon sequestration, GHG emissions? 4. What are the significant gaps that limit our ability to assess how changing land management alters the terrestrial and atmospheric carbon budget?
What do we know: Carbon sinks and sources (Pg C year 1) in the world s forests. Yude Pan et al. Science 2011;333:988-993 Published by AAAS
Driving Factors controlling Forest C 1. Climate 2. Natural Disturbance 3. Management (e.g. Harvest) 4. Policy (REDD+)
elevated CO2 Global Forest Cover, Deforestation, 2000 2000-2012 changing aridity warming Figure 11.10: CMIP5 multi-model ensemble mean of projected changes in DJF and JJA surface air temperature for the period 2016 2035 relative to 1986 2005 under RCP4.5 scenario (left panels). The right panels show an estimate of the model-estimated internal variability (standard deviation of 20-year means). Hatching in left-hand panels indicates areas where projected changes are small compared to the internal variability (i.e., smaller than one standard deviation of estimated internal variability), and stippling indicates regions where the multi-model mean projections deviate significantly from the simulated 1986 2005 period (by at least two standard deviations of internal variability) and where at least 90% of the models agree on the sign of change. The number of models considered in the analysis is listed in the top-right portion of the panels; from each model one ensemble member is used. See Box 12.1 in Chapter 12 for further details and discussion. Technical details are in Annex I. Figure 11.14: CMIP5 multi-model annual mean projected changes for the period 2016 2035 relative to 1986 2005 under RCP4.5 for: (a) evaporation (%), (b) evaporation minus precipitation (E-P, mm day 1), (c) total runoff (%), (d) soil moisture in the top 10 cm (%), (e) relative change in specific humidity (%), and (f) absolute change in relative humidity (%). The number of CMIP5 models used is indicated in the upper-right corner of each panel. Hatching and stippling as in Figure 11.10. N deposition deforestation Do Not Cite, Quote or Distribute beetle mortality 11-107 Hansen Hansen et et al. al. 2013 2013 wildfire Total pages: 123
Environmental change impacts on forests 1. Rates of recovery generally increase with CO2, temperature, and water availability 2. Varies with age and species composition 3. Age and species dependent responses provide a mechanism by which climate change may push forests past critical thresholds Global Change Biology Volume 19, Issue 7, pages 2001-2021, 3 APR 2013 DOI: 10.1111/gcb.12194 http://onlinelibrary.wiley.com/doi/10.1111/gcb.12194/full#gcb12194-fig-0003
Western US Tree mortality from fire, beetles, and harvest (cumulative 2003-2012) Berner, LT, et al. 2017.Tree mortality from fires, bark beetles, and timber harvest during a hot and dry decade in the western United States (2003 2012), Env Res Lett Mg Aboveground C ha -1 Tg Aboveground C per state Average 8 Tg AGC yr -1 0.20% yr -1 Average 15 Tg AGC yr -1 0.35% yr -1 Average 23 Tg AGC yr -1 0.55% yr -1
Mortality Immediate C loss Beetles: No immediate loss. Slow decomposition. Regeneration is fast. Fire: Fire severity affects C loss, but even in the most severe fire, only 30% of aboveground C is consumed. Slow decomposition. Harvest: About 60% of losses are recouped in wood products (40% is lost to the atmosphere). All wood products decay.
Potential to mitigate carbon emissions through forestry activities 1. Reduce emissions from deforestation and degradation 2. Increase forested land area through afforestation/reforestation 3. Increase the carbon density of existing forests at both stand and landscape scales (this includes harvest impacts) 4. To expand the use of forest products that sustainably replace fossil-fuel CO 2 emissions (conflicts with strategy #1) Canadell, Josep G., and Michael R. Raupach." Science 320.5882 (2008): 1456-1457.
Global potential of land-based biological climate mitigation activities based on current available technology is categorized by small*, medium + and high &. Ecosystem Main activity Project activities Benefits (+)/risks( ) component Sink/source management Conserve and increase biomass production Afforestation*, reforestation, deforestation avoidance &, improve forest/fire management*, set aside land*, higher use of wood products* +Biodiversity conservation, improved soil quality, improved hydrological regulations, reduced erosion Non-permanence (risk of reversal), saturation, decreased water availability for other uses. Bioenergy production Biomass Electricity and heat from forests +Industrial and domestic energy, linked to wood product industry, no waste Low efficiency and limited GHG savings, residues needed for soil fertility Canadell, Josep G., and E. Detlef Schulze. "Global potential of biospheric carbon management for climate mitigation." Nature communications 5 (2014): 5282.
#1 Priority: Avoidance of emissions from deforestation and degradation Deforestation: 13 Mha per year for the period 2000 2010 (FAO 2010) driving a deforestation gross emission flux of 2.8±0.5 PgC per year Net emissions including forest regrowth are 0.9±0.5 PgC per year (Le Quere, C. et al., 2013)
Afforestation: Albedo changes
Potential C sequestration: Wisconsin Jeanine M. Rhemtulla et al. PNAS 2009;106:6082-6087 2009 by National Academy of Sciences
Hudiburg et al., 2009. Carbon dynamics of Oregon and northern California forests and potential land-based carbon storage. Ecol. Applications, 19:163 180 Blue Mountains Carbon budget of West Coast Forests East Cascades Sierra Nevada Coast Range West Cascades 70 60 50 40 30 20 10 0 70 60 50 40 30 20 10 0 3.2 ± 0.34 Pg C 5.9 ± 1.34 Pg C Klamath Mountains 0 100 200 300 400 500 600 Stand Age (years) 70 60 50 40 30 20 10 0 Current Biomass (kg C m -2 ) Potential Biomass (kg C m -2 )
Modeling Climate and Mitigation Impacts Hudiburg, T, et al, Nature Climate Change (2011);Hudiburg, T, et al. Environmental science & technology (2013)
Europe s forest management did not mitigate climate warming Kim Naudts et al. Science 2016;351:597-600 Published by AAAS
Thinning to avoid emissions (Difficult) Carbon (C) losses incurred with fuel removal can exceed what is protected from combustion should the treated area burn Even among fire-prone forests, one must treat about ten locations to influence future fire behavior in a single location Only when treatments change the equilibrium between growth and mortality can they alter long-term C storage However, over the LONG TERM (100+ years), restoration can work, but there will be short term C losses, regardless. Campbell, J., et al., 2012. Frontiers Ecol. Environ.
What are the significant gaps that limit our ability to assess how changing land management alters the terrestrial and atmospheric carbon budget? 1. Models are still insufficient 2. LCA is wildly all over the place (for wood products and wood bioenergy) 3. Biogenic emissions need to be accounted for (over time and space) 4. Disagreement between sectors (in the literature) 5. Substitution is only real when there is a reference scenario that is real Important References: Schulze, Ernst Detlef, et al. "Large scale bioenergy from additional harvest of forest biomass is neither sustainable nor greenhouse gas neutral." Gcb Bioenergy 4.6 (2012): 611-616. Haberl, Helmut, et al. "Correcting a fundamental error in greenhouse gas accounting related to bioenergy." Energy Policy 45 (2012): 18-23. Cherubini, Francesco, et al. "CO2 emissions from biomass combustion for bioenergy: atmospheric decay and contribution to global warming." Gcb Bioenergy 3.5 (2011): 413-426.