Satellite Supported Estimates of Human Rate of NPP Carbon Use on Land: Challenges AheadM. Imhoff1, L. Bounoua1, P. Zhang1 and Rama Nemani2 - NASA’s Goddard Space Flight Center1 and Ames ResearchCenter2 2010 Fall AGU Meeting, Dec. 13-17, San Francisco, CA
Key Findings• Global requirement for land-based photosynthetic plant material rose from 20 to 25 percent from 1995 to 2005• First measurement of this trend shows both population growth and per capita consumption are driving increase.• By 2050 humans will require more than 55% of the photosynthetic production on land if people consume as much per person as N. Americans do now.• Trend has huge implications for food security regionally and may require land management at planetary scale.• Satellite-supported approach provides an updatable wall- to-wall assessment of human demands on Earth’s annual photosynthetic production on land.
Why NPP? Net Primary Production (NPP) NPP is the “Common Currency” for Climate Change, Ecological, & Economic Assessment.NPP is the amount plant material produced on Earth.It is Earth’s “Bio-Engine” - the primary fuel for Earth’s food web.NPP can be measured in terms of Carbon Photosynthesis withdraws CO2 from the atmosphere and fixes it in planttissue. Photosynthesis and fate of vegetation biomass are important incarbon exchange between atmosphere and biosphere (global climatechange).Demand for NPP strongly influences land use/land coverchange and land management policy.Agricultural versus ‘natural systems’ - Conflicting needs; energy productionversus conservation of biodiversity
Definitions for this Study• NPP “supply” is the annual amount of vegetation produced on land in terms of elemental carbon.• NPP “demand” is the mount of NPP required on the landscape to generate the food, fiber, and bio-fuels reported by the UN Food and Agriculture Organization on an annual basis.These two definitions are matched so that they are comparable using a satellite supported estimate of global NPP (supply).
Creating the Balance Sheet: Can the Earth Keep Up? Land-based Vegetation Carbon Balance (NPP) Planetary NPP Satellite Data Supply (Annual and multi- year NPP averages) –Human NPP Demand UN Food and Agriculture Data (annual) = Balance Result (global and regional balances) M. L. Imhoff et al., Nature 429, 870, 2004 M. L. Imhoff et. al., JGR, VOL. 111, 2006
NPP “Supply” Earth’s Current Terrestrial Production Vegetation biomass in terms of carbon (Above and Below Ground)28 years of Satellite Observations AVHRR (1982-2009) at (0.25x0.25 degree horizontal resolution) MODIS 1km 2000 - 2009Vegetation Indices from satellite estimate leaf area over timeTerrestrial Carbon ModelsCarnegie Ames Stanford Approach – CASABiome BGC Models combine satellite vegetation indices and climate data to calculate NPP in gC/m2 [above & below ground]. NDVI + vegetation map FPAR (0.4-0.7mm) FPAR + solar surf. Irradiance IPAR IPAR + light use efficiency NPP rates (g m-2) Climate drivers (Temperature, Precipitation, etc.)
Planetary NPP “Supply” on Land 20052005 MODIS Derived NPP in Log10 Grams Carbon per year (Total = 51.6 PgC)
NPP Global “Demand” “Demand” “Demand” = the amount of NPP Required to generate the food, fiber, and wood-fuels wood- reported in FAO annually.• Source: UN-FAOSTATS (United Nations Food and Agriculture Statistical Database) – Country level - spatially constrained – Product Specific • Vegetal Foods, Livestock-based Products, Wood, Paper, and Fiber. • Domestic Supply = Production + Imports – Exports• Bio-agronomic modules estimate landscape NPP from data – Back-calculate the NPP required “in the field” in grams Carbon. – Separate parameterization for Developing and Industrialized countries• Applied to global map of population distribution on a Per Capita basis (source: CIESIN -Center for International Earth Science Information Network)
NPP Required by Humans as % of Supply (2005)Supply estimated using MODIS NPP - Demand From UNFAO and models W. Europe North 86%America 29% 300% S. Central Asia 96% South America 8%
We are growing and consuming more per person Population and Affluence Drive Demand 50% % Increase in Population 1995 to 2005 45% % Per Capita increase in Demand 1995 to 2005 40% 35% 30% 25% 20% 15% 10% 5% 0% Africa Eastern South South Western North World Asia America Central Europe America AsiaDemand – NPP Carbon (land vegetation)
NPP (no trend) - HANPP is rising1982-1998 baseline NPP from AVHRRNPP for 2000-2005 from MODISHANPP (all years) UN FAO and models (Imhoff et al. 2004)
ConclusionsWe use a satellite-supported methodology to estimate the amount of Earth’s land-basedNPP (carbon from land vegetation) that is required for food, fiber, and fuel.Previous work showed that - as of 1995 - humans required 11.5 Pg of NPP Carbon -approximately 20% of the total generated on land.The same methodology applied to 2005 data shows that the human NPP demand hasincreased to 14.6 Pg C – about 25% of the amount generated on land that year.Increases are due to both population growth and larger per capita demand for productsof photosynthesis.Globally Earth’s production capacity in the form of NPP-Carbon shows no trend varyingonly slightly year to year due to climate and weatherRegionally, NPP varies widely putting some populations at higher riskPopulation growth and increases in per capita demand could result in the human needfor 55% of the NPP carbon on land by 2050 with major implications for landmanagement policy.
10 Years of Changes in Regional NPP Carbon Supply & Demand (Intermediate Estimate of Demand – Land NPP only) 1995 / 2005 1995 / 2005 1995 / 2005 BASELINE 1995 / 2005 REGION Population Per capita NPP NPP demand NPP Supply Demand (millions) (MTC) (Pg C) (Pg C) (% Supply) Africa 742 / 882 2.08 / 2.51 1.55 / 2.21 12.50 12.4% / 17.7%Eastern Asia 1400 / 1520 1.37 / 1.78 1.91 / 2.71 3.02 63.2% / 89.7% South America 316 / 366 3.11 / 3.59 0.98 / 1.31 16.10 6.1% / 8.1% South 1360 / 1603 1.21 / 1.23 1.64 / 1.97 2.04 80.4% / 96.6%Central Asia Western Europe 181 / 183 2.86 / 3.38 0.52 / 0.62 0.72 72.2% / 86.1% North America 293 / 323 5.4 / 5.94 1.58 / 1.92 6.67 23.7% / 28.8% World 5690 / 6378 1.58 / 2.28 11.54 / 14.55 56.80 20.3% / 25.6%
Foundations for Earth System Stewardship Session B31 Wed AM 2006 (Moscone West)8:20 Earth-System Resilience and Thresholds I. Fung8:40 Changing Climate for River Systems D. P. Lettenmaier9:00 to 9:15 PANEL DISCUSSION9:15 Feeding 9 Billion While Sustaining the Earth System J. A. Foley9:30 Human Rate of NPP Carbon Use on Land: M. L. Imhoff; L.Bounoua; P. Zhang; R. E. Wolfe9:45 Sustainability in a Rapidly Changing World F. S. Chapin; M. E.Power; S. Pickett; R. B. Jackson; D. Carter; J. W. HardenPoster Session B43B Thursday Afternoon Moscone South
Planetary NPP “Supply” on Land18 Year AVHRR Baseline (Average) 56.8 Pg Carbon AVHRR Average (1982 – 1999)
So, what do we do?Don’t PanicAvoid the extremes - Doomsday and Denial are poor choicesUse our best tools - address the issue.Past attempts failed because the system could not be “closed”Treat Earth as a systemSatellite technology enables this perspective for the 1st time inhuman history