Analysing, Quantifying and Understanding Land Use Impacts on the Biomass State of Ecosystems

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of Economics and Social Sciences Institute of Social Ecology Karlheinz Erb Institute of Social Ecology Vienna Biomass CCI,

1 Analysing, Quantifying and Understanding Land Use Impacts on the Biomass State of Ecosystems University of Natural Resources and Life Sciences, Vienna Dept. of Economics and Social Sciences Institute of Social Ecology Karlheinz Erb Institute of Social Ecology Vienna Biomass CCI, ERC Start Grant LUISE European Union's Horizon 2020 research and innovation programme under grant agreement Land-use impacts on biomass state I Biomass CCI I No Karlheinz Erb I

2 Land, a Socio-Ecological System Managed Untouched Erb et al., 2007, 2018 Attribution: Land use and natural factors IPCC AR5, Chapter 6 Biomass is at the heart of the system: stocks and flows of carbon, a key resource for humans and all (other) heterotropic species, fundamental to ecosystem functioning and ecosystem services

Conceptual approach: isolating land-use impacts Comparison of potential and actual vegetation Potential vegetation:

changes are factored out à isolates LU impacts Is NOT equivalent to the prehistoric vegetation (environmental

3 Conceptual approach: isolating land-use impacts Comparison of potential and actual vegetation Potential vegetation: (hypothetical) vegetation that would be present in the absence of land-use, but with current climate Environmental changes are factored out à isolates LU impacts Is NOT equivalent to the prehistoric vegetation (environmental parameters have change since then) Biomass stock [PgC] Same for - NPP [Pg/yr] - τ b [a] - etc. Land-cover changes: Change of land-cover types (e.g. forestà agricultural field) [relatively well quantified and mapped] Management: Change within landcover types (e.g. thinning of forests, grazing-induced changes of natural grasslands) [largely overlooked in the literature]

4 Uncertainties and ambiguities in the current state of knowledge on global biomass stocks Potential biomass stocks Actual biomass stocks Difference: ~80 PgC (both, inventory derived; Remote sensing does not really help in understanding the difference) Erb et al. 2018, doi: /nature25138

Seven actual biomass stocks mapsbased on land-use data, bottom-up A FRA-based FRA: Forest Ressource Assessment B Pan-based Pan. Y. et al. A Large and Persistent Carbon Sink in the World s Forests.

5 Seven actual biomass stocks mapsbased on land-use data, bottom-up A FRA-based FRA: Forest Ressource Assessment B Pan-based Pan. Y. et al. A Large and Persistent Carbon Sink in the World s Forests. Science (2011). C Saatchi+Thurner-based D Baccini+Thurner-based E Cell-based minima F Cell-based maxima Remote sensing based, composites G Ruesch & Gibbs Ruesch. A. & Gibbs. H. K. New IPCC Tier-1 global biomass carbon map for the year (2008) Erb et al. 2018, doi: /nature25138

6 A IPCC-based. FRA-adjusted B IPCC-based. PAN-adjusted Six potential biomass stocks maps C Biomass stock density, cell-based minimum of classical ecological values D Biomass stock density cell-based maximum of classical ecological values E Remote sensing based F West et al. West. P. C. et al. Trading carbon for food: Global comparison of carbon stocks vs. crop yields on agricultural land. PNAS (2010) Based on land-use data, bottom-up Erb et al. 2018, doi: /nature25138

actual biomass stock [kgc m -2 ] Human impact on global biomass stocks 800 700 600 500 400 300 200 100 Mean of all 42 estimates 0 PgC FRA-based Pan-based * Actual biomass stock: mean (n=7) 450 PgC

7 actual biomass stock [kgc m -2 ] Human impact on global biomass stocks Mean of all 42 estimates 0 PgC FRA-based Pan-based * Actual biomass stock: mean (n=7) 450 PgC ( ) * Potential biomass stock: mean (n=6) 916 PgC ( ) à Reduction / all permutations: median (n=42): 447 (inner quartiles: ) à An equivalent of ~50 years of current anthropogenic C-emissions Land-cover conversions and land management effects are of similar magnitude. Management: harvest of wood, but also: secondary uses of forests/owls: forest grazing, litter raking, pollarding, etc... Erb et al. 2018, doi: /nature Unused forests Used boreal forest Wildnerness, no trees Used temperate forest Used tropical forest Used subtropical forest Natural grassland with trees 0 Artificial grassland Natural grassland, no Cropland trees Infrastructure Land-use impacts on biomass state I Biomass potential CCI biomass I Karlheinz stock Erb [kgc I m -2 ]

8 Potential & prehistoric biomass stocks The effect of land use consists of two components cumulative land-use emissions land-use-induced reductions in carbon sequestration that would result from environmental changes. Interpretation of the difference of 447 ( ) PgC: If PgC are emitted in the industrial period due to LULUCF, PgC must have been emitted in the pre-industrial period (~Ruddiman~) or the industrial period emissions are larger, entailing the residual sink strength is underestimated (e.g. Arneth et al., 2017), (or both..) Erb et al. 2018, doi: /nature

Another, related, KEY variable: Human acceleration of biomass turnover time Key variable integrating stocks and flows: turnover of biomass τ b = SC / NPP Key ecosystem parameter, determines the size

9 Another, related, KEY variable: Human acceleration of biomass turnover time Key variable integrating stocks and flows: turnover of biomass τ b = SC / NPP Key ecosystem parameter, determines the size of the carbon pool Determinants of ecosystem carbon turnover time Temperature Precipitation Carvalhais et al., 2014 doi: /nature13731 Responsible for morst of the uncertainty in global vegetation models (Friend et al. PNAS 2014) 9

Land-use induced acceleration of biomass turnover time Potential vegetation: 13.

9 All biomes affected about equally Impact on stocks much stronger than on NPP (NPP,

expected to increasemost biomass comes from fast ecosystems Key: understand

10 Land-use induced acceleration of biomass turnover time Potential vegetation: 13.7 yrs Actual vegetation: 7.1 yrs Global Acceleration factor: 1.9 All biomes affected about equally Impact on stocks much stronger than on NPP (NPP, SC ) High biomass harvests result in larger τ b acceleration Demand for biomass is expected to increasemost biomass comes from fast ecosystems Key: understand tradeoffs, between increasing harvest and increasing stocks; e.g. related to degradation Erb et al doi: /ngeo

Uncertainties, and their meaning Pot. NPP Act. NPP Pot. biomass stock Act.

1038/ngeo2782 Actual biomass stocks uncertainty is particularly pronounced, and massive, in (sub)tropical forests outside

detection limits in the tropcial zones (changes below 750gC/m²/yr remain undetected) BIOMASS CCI should narrow the

11 Uncertainties, and their meaning Pot. NPP Act. NPP Pot. biomass stock Act. biomass stock Uncertainty of τb: contribution of components Erb et al doi: /ngeo2782 Actual biomass stocks uncertainty is particularly pronounced, and massive, in (sub)tropical forests outside the tropical cores If translated into a detection limit of stock changes, these uncertainties result in extremely large detection limits in the tropcial zones (changes below 750gC/m²/yr remain undetected) BIOMASS CCI should narrow the uncertainties Question: how much progress can be expected in the other wooded land zones? Detection limit of annual changes in actual biomass stocks, based on 7 SCact maps Erb et al. 2018, doi: /nature25138

12 Conclusions Land management effects are large - and (still) largely under-researched in the literature. (Good! and better!) BIOMASS data has a high potential to help here! à Biomass stocks integrates all fluxes and flows (changes) over time. Large datagaps/uncertainties prevail, in particular in sensitive regions (e.g. savanna, non-humid tropics, regions of social vulnerability and large knowledge gaps on the social systems). Can / will BIOMASS data help here? Understanding mosaics/dynamics will be key. In reply: Spatial resolution = Yes, of course... key for small-scale applications, but not so important for global approaches. Thjje social system is not organized in grids. Robustness is much more important, AND thematic resolution. Temporal frequency of biomass and biomass change maps (epochs): the longer (backwards) the better (easy); temporal resolution = two-bladed sword, allows for unprecedented assessments (temporal dimensions of human activities ~ land use mapping, degradation, etc.), but data handling becomes expert job, needs (not existing) handling capacities Accuracy and uncertainty documentation: key! The use of biomass data within the climate change community: extremely useful, attribution/separation of land-use and climate impacts, strength of residual sink, etc. 12

13 The End Thank you very much for your attention! ERC Start Grant LUISE European Union's Horizon 2020 research and innovation programme under grant agreement No Detecting changes in essential ecosystem and biodiversity properties towards a Biosphere Atmosphere Change Index: BACI (lead: MPG Jena) 13

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17 Land use Pongratz et al., /gcb

18 Conclusions & the future Land management effects are large - and largely overlooked in the literature Large datagaps/uncertainties prevail, in particular in sensitive regions (e.g. savanna, non-humid tropics) Need to improve systemic understanding of land use biosphere interaction: Demand for biomass is expected to increase substantially: population growth, diet changes, bioenergy Most biomass harvest for humans are taken from fast systems (humans replace slow with fast systems to raise harvest) Erb et al doi: /ngeo2782 Challenge: Trade-offs between increasing biomass supply and conserving carbon stocks 18

Comparison with other studies Land-use impact calculated here is much larger than cumulative emissions calculated in modelling studies BUT: potential vegetation prehistoric vegetation Cumulative

19 Comparison with other studies Land-use impact calculated here is much larger than cumulative emissions calculated in modelling studies BUT: potential vegetation prehistoric vegetation Cumulative emissions most probably smaller. Kaplan et al., 2010: -100PgC due to environmental (non-land use) changes à EITHER the residual sink is larger OR A key aspect of land use is underappreciated in the literature Mean Includes crop harvest Includes shifiting cultivation, land use intensity This study Erb et al. 2018, doi: /nature25138 Includes wood and crop harvest, tillage, shifting cultivation

20 actual biomass stock [kgc m -2 ] Land conversions vs. management * Infrastructure Artificial grassland Ambigious * Cropland Used tropical forest (forest management) Used subtropical, temperate & boreal forest (forest management) Natural grassland, with and without trees (grazing) Unused forests Used boreal forest Wildnerness, no trees Used temperate forest Used tropical forest Used subtropical forest Natural grassland with trees Artificial grassland Natural grassland, no Cropland trees Infrastructure potential biomass stock [kgc m -2 ] Land cover change (52-58% -small area, huge impact) and land management (42-47% -large area, medium/low impact) are of similar proportion * Ambiguous denotes cases attributed differently in the two assessments. Erb et al. 2018, doi: /nature25138

feed 8,4% Grazing land 29% Cropland 49% Fuelwood 9,8% Grazing, fodder 50,0% HANPP%: Aggregated effect of land use and harvest

21 Global Human Appropriation of NPP in 2000 HANPP LUC %: Productivity changes due to land coversions << -10% >> Forest 11% Built-up land 4% HANPP Human induced fires 7% Consumption Industrial Wood 6,2% Other uses 11,1% Food 13,7% Seed 0,7% Market feed 8,4% Grazing land 29% Cropland 49% Fuelwood 9,8% Grazing, fodder 50,0% HANPP%: Aggregated effect of land use and harvest << -24% >> : 13% à 25% factor 2 Population: factor 4 GDP: factor 17 Haberl et al

22 Interpreting the 450 PgC difference This study Land-use impact calculated here is much larger than cumulative emissions calculated in modelling studies BUT: potential vegetation prehistoric vegetation Cumulative emissions most probably smaller. Kaplan et al., 2010: -100PgC due to environmental changes. à not large enough à EITHER the residual sink is larger, OR a key aspect of land use is underappreciated in the literature: management Effects of management (42-47%) similar to effects of deforestation (52-58%) Infrastructure Ambigious Used tropical forest (forest management) Artificial grassland Used subtropical, temperate & boreal forest (forest management) Cropland Natural grassland, with and without trees (grazing) Erb et al. 2018, doi: /nature25138 Erb et al. 2018, doi: /nature25138

Carbon accounting related to Bioenergy: Where do we stand?

Carbon accounting related to Bioenergy: Where do we stand? Helmut Haberl, 1 Karl-Heinz Erb, 1 Tim Beringer, 2 Wilfried Winiwarter 3 1 Institute of Social Ecology, Alpen-Adria Universitaet Schottenfeldgasse