Global 1.0 degree. Time Series, Snapshot. Annual, Snapshot

Transcription

1 Spatial Extent: Spatial Resolution: Temporal Characteristics: Date Classes Represented: Time Steps Available: Dates represented: Global 1.0 degree Time Series, Snapshot Annual, Snapshot These data products are being distributed free of charge. Recipients have a responsibility to: 1. Cite the following reference: Hurtt, G.C., S. Frolking, M.G. Fearon, B. Moore III, E. Shevliakova, S. Malyshev, S. Pacala, R.A. Houghton The underpinnings of land-use history: three centuries of global gridded land-use transitions, wood harvest activity, and resulting secondary lands. Global Change Biology, 12, Acknowledge the University of New Hampshire, EOS-WEBSTER Earth Science Information Partner (ESIP) as the data distributor for this dataset. In addition, it is recommended that users of these data contact George Hurtt (gchurtt@umd.edu) to ensure proper data use and interpretation. Summary: To accurately assess the impacts of human land-use on the Earth System, information is needed on the current and historical patterns of land-use activities. Previous global studies have focused on developing reconstructions of the spatial patterns of agriculture. The Global Landuse Modeling (GLM) Data collection provides the first global gridded estimates of the underlying land conversions (land-use transitions), wood harvesting, and resulting secondary lands annually, for the period Using data-based historical scenarios, our results suggest that 42-68% of the land surface was impacted by land-use activities (crop, pasture, wood harvest) during this period, some multiple times. Secondary land area increased 10,000,000 44,000,000 km 2 ; about half of this was forested. Wood harvest and shifting cultivation generated 70-90% of the secondary land by 2000; permanent abandonment and relocation of agricultural land accounted for the rest. This study provides important estimates of global land-use activities for studies attempting to assess the consequences of changes to the Earth's surface over time. For this study, six major factors were evaluated that influence land-use transitions and the resulting amount, distribution, and age of secondary lands. Because the details of each of these factors are important but generally not well known historically, a scenario approach was performed to bracket the uncertainty of model estimates. Each case was designated with a 12-digit code to identify the specific assumptions made for each factor. The code consists of an alternating sequence of a letter and a number; each letter designates one of the six factors, and each number designates the case implemented for that factor (see Table 1). H1T1P1W1Z1L1 is an example of the global 12 digit code for a particular scenario. There are 216 total scenarios. Two of these cases were chosen as land-use scenarios, and have been identified as reasonable case studies for potential use in subsequent applications. The two land-use scenarios chosen for detailed analyses were based on three criteria: quantity of data inputs, the reasonableness of model assumptions, and comparisons of estimates of secondary land area to independent estimates published by the Food and Agriculture Organization (FAO 1998). One scenario was based the detailed land-use history reconstruction of Hyde (H1), and the second on Sage-Hyde (H2). Both scenarios were driven with the FAO-based wood harvest reconstruction (L1). Both concentrated wood harvesting activities in gridcells with land use (Z1); a recent FAO study on forest accessibility found that about half the world's forest was with 10 km of major transportation infrastructure (roads, railways, rivers), and about three-quarters within 40 km (FAO, 2001). Both scenarios applied minimum transitions outside the tropics and non-minimum transitions (e.g. shifting agriculture) in the tropics (T3), roughly corresponding to the distribution of shifting cultivation in the mid-late 1900s (Butler, 1980; Lanly, 1985).

2 To specify the remaining model assumptions, we consulted FAO (1998) estimates of secondary forest area, and chose model assumptions that yielded reconstruction estimates of secondary forest area most comparable to FAO estimates. Based on these considerations, we assumed primary land was the dominant source for land conversion (P1) on all continents, except Eurasia, where secondary land was used as the main land conversion source (P2). In addition, wood harvesting from land conversion was not counted towards fulfilling national wood harvest demand (W1), except in Eurasia for the Sage-Hyde input data (H2,W2). Since the model settings for the land-use scenarios are sub global, we chose to refer to them simply as Hyde and Sage-Hyde. All other scenarios are referenced by their 12 digit code according to Table 1. Currently, only the two land-use scenarios are available for beta testing. (Please contact User Support if you are interested in obtaining data for the other scenarios.) Available Data Sets: A. Land-use scenarios using Hyde or Sage-Hyde B. Basemaps (single layers) C. Selected movies: Decadal snapshots from 1700 to 2000 for the following: a) harvested trees b) forest cover c) primary (virgin) forest d) secondary forest e) land in crops f) land for pasture g) land for agriculture (both pasture and cropland) h) secondary land mean age -darkest color indicates >120 yrs old i) primary land j) secondary land Movies can be downloaded and range in size from about 9.5 MB to 24MB. They will play in Quicktime, stand alone, or within a browser plugin. Spatial Scale: The Hyde scenario, Sage-Hyde scenario, and Basemaps (single layers) datasets are gridded in the geographic projection with 1.0 degree by 1.0 degree cell sizes. The spatial extent of the data is global with an upper right hand corner of 90 N latitude and W longitude. Data Format The full dataset contains 360 cells in the x-dimension (longitude) and 180 cells in the y-dimension (latitude) of floating point data. The fill value for missing data and non-land/sea mask is -1. Variable Description: Land-use scenarios using Hyde or Sage-Hyde a) land-use states (fraction of the grid cell) Estimates of the fraction of land-use area per grid cell are provided for each of six land-use categories: crop, pasture, primary land, secondary land, water, and ice. For a single gridcell at a single point in time, the sum of the fractions will be 1. For the land-use scenario using Hyde, crop and pasture are taken from Hyde database (Klein Goldewijk, 2001). Primary land is also taken from the Hyde database, but it is an aggregate of 13 non-agricultural land-cover states, and its amount decreases through time due to land use (agricultural and or logging). Secondary land, calculated by GLM, is land that has experienced some amount of land-use and is in a state of recovery. Water and ice area were assumed to stay constant over For the land-use scenario using Sage-Hyde, the same methods were used, except cropland from Ramankutty and Foley, 1999 was used and supplemented with the Hyde database. See reference for more details.

3 b) land-use transitions (fraction of the grid cell) Land-use transitions describe the underlying changes to the use of land that result in changes in land-use states (e.g. which type of land was converted to what use). Explicit knowledge of these transitions is important because changes to the use of the land often directly alter land surface properties (e.g. felling trees for agriculture, etc.), the condition of agricultural land (e.g soil quality, nutrient stocks, etc.), and the amount and age-structure of secondary recovering lands. There are 13 possible land-use transitions variables calculated by GLM: primary to pasture (t_vp) primary to crop (t_vc) secondary to pasture (t_sp) secondary to crop (t_sc) crop to pasture (t_cp) pasture to crop (t_pc) pasture to secondary (t_ps) crop to secondary (t_cs) wood harvest on primary forested land (t_vs1) wood harvest on primary non-forested land (t_vs2) wood harvest on mature secondary forested land (t_ss1) wood harvest on young secondary forested land (t_ss2) wood harvest on secondary non-forested land (t_ss3); available in updates after version c) statistics on secondary land (mean grid cell) Secondary mean age (years) and secondary mean biomass (kg C/m 2 ). For any particular year and grid cell, secondary land can be gained or lost due to land use or logging. Some amount may also remain from previous years due to land abandonment. Therefore, each of these land-use transitions causes the age of secondary land to be in the form of a distribution; some parcels may be younger or older than others. For model simplicity, we compute and track the mean age of this distribution. From mean age, mean biomass is also computed and tracked. d) Basemaps (single layers) There are four static variables that complement each scenario. The first two complement the land-use state variables; ice covered land and ocean/water (fraction of the grid cell). Other variables include a forested/nonforested grid (binary values of 1/0), and a grid of cell area (km 2 ). Model Inputs Land-use categories of cropland, pastureland, and primary land were aggregated from the Hyde database (Klein Goldewijk, 2001) or a modified version of the Hyde database with substituted cropland from Ramankutty and Foley, Grids for 1700, 1750, 1800, 1850, 1900, 1950, 1970, and 1990 were interpolated to an annual resolution. Grids were also extrapolated from 1990 to 2000 using national statistics for crop and pasture area from FAO (FAOSTAT, 2004). National statistics from Houghton and Hackler (2003) from were used and extended to 2000 using annual FAO data (FAOSTAT, 2004). Input for biomass density was based on a global extension of the Miami-LU ecosystem model (Hurtt et al., 2002). Miami-LU is driven by the empirically-based Miami Model of net primary production (Leith, 1975). See Reference for more details on inputs.

4 Table 1: Model Factor and Scenarios Model Factor H: Historical land-use reconstruction T: Land-use transition algorithm L: Wood harvest history reconstruction W: Land-conversion wood clearing tallied as harvest to satisfy annual logging P: Priority for land-use transitions Z: Spatial distribution of wood harvest Scenarios H0: No data : linear interpolation in each grid cell from zero agricultural land use in 1700 to 2000 values. H1: Hyde crop and pasture land-use history. H2: Sage crop land-use history + Hyde pasture land-use history. T1: minimum transitions. T2: minimum transitions plus fractional abandonment of crop and pasture (6.7% yr -1 ), applied globally. T3: minimum transitions plus fractional abandonment of crop and pasture (6.7% yr -1 ), applied to the tropics (23 S to 23 N). L0: No harvest: wood harvest set to zero. L1: Historical reconstruction from FAO and population data (see 2.2). L2: No data: linear interpolation in each grid cell from zero wood harvest in 1700 to 2000 values. W1: 0% W2: 100% P1: land needed for crop, pasture, or logging taken first from primary lands, then, as needed, from secondary lands. P2: land needed for crop, pasture, or logging taken first from secondary lands, then, as needed, from primary lands. Z1: priority to grid cells with land use, then to adjacent grid cells. Z2: uniform harvest across all forested grid cells in a country. Table 2: GLM Version Summary Version Description GLM version (March 2007) An update from version GLM version (March 2006) Corresponds with Hurtt et al 2006 GLM version (March 2007) modifications In version (Hurtt et al 2006), wood carbon bulk density values (0.325 Mg C/m3 for non-coniferous, Mg C/m3 for coniferous) were inadvertently reversed when converting FAO wood harvest values (reported in m3/y for coniferous and non-confierous wood) to carbon units (Mg C/y). Here in version 3.3.1, we have corrected this error. National wood harvest estimates were recalculated for using corrected carbon bulk density values. We have recalculated all the land-use transitions and derived land-use states globally for the two land-use cases in Hurtt et al The error in version did not affect the qualitative results of Hurtt et al 2006, but did affect some of the quantitative results. In summary, because global wood harvest is approximately 60% non-coniferous by volume (FAO data for , the non-coniferous fraction increased over that time period from ~55% to ~65%), and the global wood harvest increased by about 10% from the originally reported values. The corrected global wood harvest excluding slash ( ) is 95 Pg C (reported as 86 Pg C in Hurtt et al 2006). The correction also shifted the harvest more towards the tropics (typically non-coniferous) and away from the temperate/boreal regions (more coniferous wood harvest). The corrected fraction of total wood harvest by continent are (old values in parenthesis) Africa: 7% (6%); South America: 5% (4%); North and Central America: 24% (27%); Oceania: 1% (1%); Eurasia: 63% (62%). The correction also made small changes (usually < 5%) in continental and global aggregate land-use transition rates (land area converted per year), area of secondary land, and mean age of secondary land.

5 Acknowledgement: This research was made possible through grants from the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA). Reference: Hurtt, G.C., S. Frolking, M.G. Fearon, B. Moore III, E. Shevliakova, S. Malyshev, S. Pacala, R.A. Houghton The underpinnings of landuse history: three centuries of global gridded land-use transitions, wood harvest activity, and resulting secondary lands. Global Change Biology,12,1-22. Data Providers: Dr. George C. Hurtt, Department of Geography; 1149 LeFrak Hall, University of Maryland, College Park, MD ; Ph: ; Dr. Steve Frolking, Complex Systems Research Center, Institute for the Study of Earth, Oceans, and Space, Morse Hall, University of New Hampshire, Durham, New Hampshire, USA. Ph: , Fax: , Latest Data Update: 2/28/2007 Last Doc. Updated: 2/28/2007 Doc. Updated By: Rita Freuder Matt Fearon This Data Guide was created by EOS-WEBSTER for the EOS-EarthData website that you can view here.