1. February 19 Land Use and Cover Change and the Global Carbon Cycle Ecological Disturbance on a Global Scale

3. Global Change / Climate Change Global Climate change which results from human activities is one of the most contentious topics in environmental science and policy There is growing agreement that: There is a climate change occurring That humans are the cause The global carbon cycle is a keystone topic

4. The carbon cycle The carbon cycle is the canonical global change issue, especially when we want to “go beyond climate change” think: is it the most important, in our time? I want to use this as a good overview issue for human impacts on the planetary scale strong geographical component strong human component, many leads and connections to human dimensions strong policy component it’s a big mystery but something important to find answers to if we cant understand something this basic we wont be able to do much else points to all the classical issues of inquiry: measurement, models, evidence, inference, uncertainty,etc social science needs to know this stuff

5. The greenhouse effect Based only on our distance from the sun, the earth should be colder by 33 degrees C. Our planet should be a chunk of ice But natural greenhouse gases – primarily carbon dioxide and water vapor provide for heating of the planet to a normal temperature. But we are now introducing MORE greenhouse gases, and we don’t know what affect this will have

6. 78% Nitrogen 21% Oxygen < 0.04% Carbon Dioxide Atmospheric Gases

7. Carbon dioxide in the atmosphere Exists in trace quantities This means doubling or halving can be important Consider oxygen: if all trees were removed the oxygen concentration would decline by 300 ppm – from 209,480 to 209,180. But an increase of 300 ppm for carbon dioxide would double it.

8. Other Greenhouse Gases And Sources Water vapor Methane Nitrous oxide CFC’s and other halocarbons Hydrological cycle Animal husbandry Chemical fertilizers* Refrigerants* * = Long residence times and contribute to ozone depletion

9. The greenhouse effect

10. Global Surface Temperatures

13. NOAA Global Flask Sampling Network

17. Years before present Petit et al. (1999) CO 2 -concentration (ppm) 200 240 280 320360160 1750 20000100,000200,000300,000400,000 Atmospheric [CO2] over the last 400,000 years

20. Historically Total emissions of C [deforestation and fossil-fuel burning] 450 PgC From 1850 to 1990 Houghton et al. 1999, Houghton 1999, Defries et al. 1999, IPCC-TAR 2001 Global Emissions from Land Use Change [ 180-200 PgC from land use change] + 90 ppm CO 2 in the atmosphere [ 40 ppm due to changes in land use] 90% due to deforestation [20% descrease Forest Area] 124 Pg emitted due to land use change 60% in tropical areas %40 in temperate areas 1 Pg C = 1,000,000,000,000,000 g C (a billion tones)

21. 7.9 Pg C/yr (6.3 Pg Fossil Fuel) (1.6 Pg Land Use) 2.9 PgC/yr - Oceans 1.3 PgC/yr - Terrestrial Ecosystems 3.7 PgC/yr - Atmosphere Global Carbon Budget - The fate of CO 2 Period 1990-1996 After IPCC, TAR 2001

22. Global CO 2 Budgets (Pg/yr) Atmospheric Increase+3.3±0.1+2.9 ±0.1 1980’s 1990-95 IPCC, TAR 2001 Land-Use Change(80’s)+1.6 (0.5 to 2.4) Land-Atmosphere Flux-0.2 ±0.7-1.0 ±0.6 Ocean-Atmosphere Flux-2.0 ±0.6-2.4 ±0.5 Emissions (fossil fuel, cement) +5.5 ±0.3+6.3 ±0.4 Residual Terrestrial Sink- 1.8 (-3.7 to +0.4)

23. dA = F + B - O - b 1980s 3.7 = 6.3 + 1.6 - 2.9 3.7  5.0 ( Difference is 1.3 -- The Missing Sink) 1990s 2.9 = 6.3 + 1.6 – 2.4 2.9   Difference is 2.6)

24. 1840 1860 1880 1900 1920 1940 1960 1980 2000 Annual Net Flux of Carbon (Pg) Net Annual Flux of Carbon from Changes in Land Use Year 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 China Africa Latin America Tropical Asia Houghton 1999 North America 6.3 Fossil Fuel

25. Global Carbon Sinks resulting from land use/cover change

26. NOAA-CMDL 1999 Location of Global C Sources and Sinks CO 2 Flask Network and Inverse Modeling - Atmospheric constraints of Global C sources and sinks -

27. Inverse Model Estimates of CO 2 Uptake (7 Models) IPCC, TAR, 2001

28. - 0.7 to - 2.4 Pg C/yr + 1.6 Pg C/yr Biological C Sources and Sinks - 1.6 Pg C/yr 0.0 Pg C - 0.0 Pg C/yr

29. Fan et al. 1998 Inverse Modeling Calculations of C Sources and Sinks North America: 1.6 PgC/yrEuroasia: 0.5 PgC/yr

30. - 0.1 - 0.5 - 0.3 - 1.3 Ciais et al 2000 TM2 1985-1995 GlobalView-CO 2 Inverse Modeling Calculations of Terrestrial Carbon Sources and Sinks Pg C/yr

31. Current Terrestrial Sinks Potential Driving Mechanisms CO 2 fertilization Nitrogen fertilization Climate change Regrowth of previously harvested forests Reforestation / Afforestation Regrowth of previously disturbed forests Fire, wind, insects Fire suppression Decreased deforestation Improved agriculture Sediment burial Future: Terrestrial Carbon Management (e.g., Kyoto) Land Use/Cover Change

32. The Northern Hemisphere Temperate/Boreal Sink The Eastern USA sink China sink Carbon Sinks Three Examples:

33. 1. Northern Hemisphere Carbon Sink Late 80’s-Early 90’s Goodel et al 2001 (in press) - Forest Inventories and Land Use Change as constraints of C Sources and Sinks - Total Sink: 0.7 to 2.4 Pg C/yr [Inverse modeling] 30-100% 70% in Temperate Regions [Larger sink in Euroasia than in North America] [Forestry Sector] 0.7 to 0.8 Pg C/yr 0.2 Pg C yr -1 in living biomass, 0.4 Pg C yr -1 in dead organic matter 0.1 Pg C yr -1 in forest products

34. Carbon Stocks in Live Forest Vegetation Over the Last Half Century 1950 1960 1970 1980 1990 2000 30 25 20 15 10 5 0 Live Vegetation (Pg C) Canada Coterminous US Euro Russia China Asian Russia Europe Goodel et al 2001 (in press)

35. 2. Eastern United States Carbon Sink Eastern United States (5 states) 96% of the C sink attributed to land use change: Forest regrowth after crop abandonment Reduced harvesting Fire suppression Caspersen et al. 2000 4% remaining attributed to: Increasing CO 2 Nitrogen Deposition Climate Change

36. 3. Changes in Forest Biomass C storage in China 1949-1998 Fang et al. 2001 Between 1940’s and 70’s, C storage declined by 0.68 Pg C due to forest exploitation policies From late 1970’s to present, C storage has increased by 0.4 Pg C due to policies of protection and timber production [+ 0.021 Pg C/yr] 0.38 Pg C comes from planted forests

37. Nepstad et al. 1999 Landsat TM image, Paragom.,1991, classified as forest and non-forest [Brazilian Government reporting methodology] – 62% Forest Same image, classified after ranch owners interviews: only 1/10 of the above forest was Classified as undisturbed forest by human practices – 6.2% Forest Forest Conversion: Carbon Density Forest Impoverishment: - Surface fires (could be responsible for doubling C emissions during El Nino years) - Logging (4-7% of that of forest conversion)

38. Forest Structure: Carbon Sink Strength time Biomass Sink Strength

39. Carbon Source: Emissions from Forest Fires Direct C emissions from Fires in Canada (1950-1999) Amiro et al. 2000 Photo: M. Flannigan, Canada Area burned in the North America Boreal Forest Region (1940-1998) Kasischke and Stocks 2000 Annual global carbon emissions from vegetation fires 1.6 Pg C/yr  25% of the amount of fossil fuel emissions

40. Fire exclusion has increased C storage in forests [last 100 yrs] Carbon Sink: Fire suppression Photos: M. Flannigan [Canada] Total Area Burned (US) Houghton et al. 2000 Annual Flux of C (TgC yr -1 ) Eliminating fire completely, US forest could accumulated 2.6 Pg C by 2140

41. Woody Biomass Precipitation Water Availab. Soil toxicities Air temperature + +- Woody Encroachment: Biophysical and land management drivers After Scholes and Hall 1996 - - Fire Browsers Harvesting Overgrazing ++ + - - - NutrientsHuman population + + N deposition Increasing CO 2 Photo: S. Archer

42. Woody Encroachment Photo: Martin 1975, Arizona 1903 & 1941 Woody plant encroachment has promoted C sequestration in grassland and savanna ecosystems of N and S America, Australia, Africa, and Southeast Asia over the past century. Maximum Potential C sequestration in the absence of fire = 2 Pg C yr -1 (upper value) Scholes and Hal 1996 Estimated CO 2 sink: USA : 0.17 PgC/yr for the 1980s ( Houghton et al., 1999) Australia : 0.03 PgC/yr (Burrows, 1998)

43. Improved Agriculture Practices Donigian et al. 1994, Lal et al. 1998, Metting et al. 1999, IPCC Land Use and Forestry 2000 High yielding plant varieties Fertilisers Irrigation Residue management Reduced tillage for erosion control has contributed to the stabilisation or enhancement of carbon stocks

44. 0 10 20 30 40 50 60 70 Maximum Yearly C Mitigation Potential (Tg C y-1) 0 1 2 3 4 5 6 % Offset of 1990 European CO 2 Emissions Land Management Change Animal manure Sewage sludge Straw Incorp. No-till Bioenergy production Woodland regeneration Extensification Carbon Mitigation and Offsets due to Land Management in Europe A combination of best practices could offset 0.113 Pg C/ yr. Over 100 years this is equivalent to a C offset of 11.3 Pg.

45. In the USA: Full adoption of best management practices would be likely to restore soil organic carbon levels to about 75-90% of their pre-cultivation level, increasing 7.5-20.8 Pg C over 100 years (0.075 to 0.208 Pg C per year).

46. Example from the tropics

47. Main points Land use and management leaves a mosaic of various cover types and cover states These systems have memory Memory is manifested in long term sources, and sinks in regrowth and soil OM storage Memory is also manifested in how many cycles or transitions a landscape patch has undergone alteration Changes in stocks – changes in area, changes in density -- and changes in fluxes, which vary with time

48. Geography and timing Some important issues include geography and timing Geography in the broader context to include spatial pattern Past deforestation may currently be regenerating; in regions where current deforestation is declining and there are larger regenerating areas (reflecting a history of large deforestation rates), such asynchronies may be important. Considerable evidence for large areas of regeneration, and for considerably variable rates of clearing

49. Multiple changes in one landscape The current landscape is a mosaic, or record, of current and past land use and cover changes Variation exists at fine temporal and spatial scale Variation exists across classes of cover (from conversion) and within classes of cover (from modification or degradation) History has created a more complex landscape We know nothing about the processes which form this landscapes over time, nor do we have good measures (maps) of these landscapes themselves. Our prognostic ability is severely limited

50. Observations: extent and density We focus on making direct observations of changes in forest extent (both increase and decrease) and density This can be done using annual observations from high spatial resolution remote sensing in conjunction with a coupled land use-carbon models. This approach complements, but is more direct in determining the land use component, than use of other measures of changes in forest carbon from stand inventory data alone (Casperson et al. 2000)

51. Inter-annual Flux of Carbon

52. Inter-annual variation in rates of deforestation and regrowth

53. Carbon flux over space

54. Carbon flux over time

55. Example from North America

56. 1938 1955 1996

57. 1938 1955 1996

58. The urban-agriculture interface has grown trees as it expands (and the urban-forest interface has cut and fragmented trees)

62. Some other objectives of interest… …or confusion

63. Forest edges: biomass collapse Tropical sources from mortality Tropical sinks from regrowth Tropical and Global sinks from space Logging

64. Formation Rate Eradication Rate Total Flux (F 1999 ) Annual Flux 1999 ConstantCompoundingConstantCompoundingTg C Tg C yr -1 1x x 35.3080.693 2 xx 35.2400.701 3x x 72.8821.641 4 x x 72.7421.599