Biogeochemical Causes and Consequences of Land Use Change Christoph Müller, Alberte Bondeau, Hermann Lotze-Campen, Dieter Gerten, Wolfgang Lucht, Pascalle Smith, Sönke Zaehle

Outline Introduction LPJ-DGVM Causes of land use change Consequences of land use change Outlook

Causes and Consequences Biogeochemical causes Climate Atmospheric CO2 concentration Water availability Soil fertility Biogeochemical consequences Impacts on water cycle Impacts on carbon cycle

LPJ-DGVM space and time loops competition differentiation climate CO2 AET COi space and time loops metabolism soil water supply mean structure of an individual yearly NPP allometric conditions old structure new crown area height fine roots leaves LAI sapwood heartwood 0-50 cm 50-150 cm stem diameter biochemistry functional relationships differentiation allometry competition APAR = PAR · [1  exp( k · LAI )] LPJ-DGVM climate CO2 soil C budget H20 budget biogeography

Crops in LPJ Better representation of biogeochemical stocks and fluxes Assessment of agricultural production in global change context Climate change Socioeconomic changes just fine too dry too wet

Crops in LPJ Adaptation of LPJ to simulate the carbon and water fluxes for crops: each CFT on a distinct stand with access to a separate soil water pool Sowing date estimation: for 4 temperate CFTs = f(T), for 4 tropical CFTs = f(P) Adaptation of heat sum and vernalization requirement Oct Jul LAI, ~ 6 Total biomass, ~ 20 tDM/ha Grain harvested, ~ 6 tDM/ha Daily coupled growth and development simulation: Phenology, LAI change, carbon allocation to leaves, roots, storage organs, ... Estimation of the harvesting period Winter wheat New input needed: Land Use For grasses, several cuts (f(LAI)), or regular grazing No water stress for irrigated crops, computation of the water requirement and of the effective irrigation Possibility of multiple cropping (e.g. rice) Grass during the intercrop season Harvested biomass removed, residues sent to the litter pool or removed (fodder, biofuel, ...)

Crops in LPJ Phenological variations for the European temperate zone [10°W-32°E; 34°N-72°N] period 1982-1998

Biogeochemical Causes of Land Use Change Causes: Climate <-3.5 0.0 >3.5 Changed yield potentials due to climate change +2°C -10% prec. Biogeochemical Causes of Land Use Change

Causes: Socio-economy Drivers of world food demand Population Dietary habits World GDP growth (1991-2000) 2.8 % p.a. (per capita: 1.4 % p.a.) Income Causes: Socio-economy

Mind games: Settings Demography: 5.6 billion vs. 12 billion Lifestyles: diet of 1995 vs. meat*2 vs. meat/2 Market structures: perfect global market

Mind games: Land Use Patterns Early 1990s Leff et al. 2004 Mind games: Land Use Patterns Scenario pop12, meat*2

Consequences of Land Use Change 80-100% 60-80% 45-60% 30-45% 20-30% 10-20% 0-10% Harvested NPP/NPP Biogeochemical Consequences of Land Use Change

Consequences of Land Use Change

Consequences of Land Use Change Difference in transpiration (mm yr–1) 1961–90 without irrigation yr–1 < Global totals (change): Transpiration: – 7.3 % Runoff: + 2.2 % Gerten et al. (2004)

Mind games: Consequences Agricultural area (b) Harvested crop biomass (c) (a)

Outlook: MAgPIE Generating Land Use Patterns for LPJ Optimization algorithm (Linear Programming) Minimize total costs of production, subject to economic and environmental constraints Other model outputs total crop & livestock production total input use (labor, fertilizer) shadow prices (land, water) Model structure (global) [i] economic regions (~10 - 100) [j] spatial cells ( 59 000 ~ LPJ resolution) [k] activities (~20): crops, livestock, irrigation, biofuels [m] constraints: physical limits, rotational, internal balances Biophysical constraints (LPJ) land, water Socio-economic constraints (GTAP, FAO) demand, cost structures, prices Crop yields (LPJ) Land use shares in LPJ cells (%) Cereals Oilseeds Pulses Sugar beets Generating Land Use Patterns for LPJ

Thank you for your attention.