############################################################################## # Global Historical Land Cover and Land Use Estimates (1700-1990) # ############################################################################## The files in this directory were provided by Dr. Kees Klein Goldewijk from the National Institute of Public Health and the Environment (RIVM) in the Netherlands. These are global, gridded, coarse resolution (1/2 and 1 degree spatial resolutions) data sets with historical estimates of land cover and land use over the past 300 years. Data layers are provided for every 50 years from 1700 to 1950 and then every 20 years to 1990. The original 0.5 degree files are available from RIVM at http://www.rivm.nl/env/int/hyde/ Testing against historical data is an important step for validating integrated models of global environmental change. Owing to long time lags in the climate and biogeochemical systems, these models should aim to simulate the land use dynamics for long periods, i.e., spanning decades to centuries. Developing such models requires an understanding of past and current trends and is therefore strongly data dependent. For this purpose, a historical database of the global environment has been developed: the History Database of the Global Environment (HYDE) (Klein Goldewijk 2001). Historical statistical inventories on agricultural land (census data, tax records, land surveys, etc.) and different spatial analysis techniques were used to create a geographically-explicit data set of land use change, with a regular time interval. The data set can be used to test integrated models of global change. The original 0.5 degree data set has been modified by the staff of the International Satellite Land Surface Climatology Project (ISLSCP) Initiative II data collection in order to match the land/water boundaries used in the collection. A separate file that shows the differences between the original 0.5 degree land/water boundaries and the ISLSCP II land/water mask is provided. Finally, the ISLSCP II staff has created a 1 degree version of the data set by aggregating the 0.5 degree data set to the coarser resolution. This 1 degree version was produced so that all data sets within the ISLSCP II collection contained 1 degree versions of all data sets and should be considered a 'browse' product. Users should always refer to the full data set documentation or the reference below for more details on data set production. ############################################################################## File Name Convention --------------------- The files in this data set are named "historic_landcover_XX_YYYY.asc", where XX can be either hd or 1d, meaning a spatial resolution of 0.5 and 1 degree in both latitude and longitude, respectively and YYYY is the year from 1700 to 1990. For each spatial resolution, 8 files with global estimates of historical land cover and land use are provided for every 50 years from 1700 to 1950, and then every 20 years to 1990. An additional file called "historic_landcover_hd_chngm.asc" is also provided that shows the differences between the original 0.5 degree land/water mask and the 0.5 degree land/water mask used in this collection. Note that the land/water mask difference file is only available at a 0.5 degree spatial resolution. ############################################################################## ASCII File Format ------------------ All of the files in the ISLSCP Initiative II data collection are in the ASCII, or text format. The file format consists of numerical fields of varying length, which are delimited by a single space and arranged in columns and rows. The files in this data set contain 720 columns by 360 rows for the 0.5 degree data sets, and 360 columns and 180 rows for the 1 degree data sets. All values are written as integer numbers. Land cover/use classes are assigned the values below (note that values 3 and 4 are non-existent): 0 Water Bodies 1 Cultivated land 2 Pasture/land used for grazing 5 Ice 6 Tundra 7 Wooded tundra 8 Boreal forest 9 Cool conifer forest 10 Temperate mixed forest 11 Temperate deciduous forest 12 Warm mixed forest 13 Grassland/Steppe 14 Hot desert 15 Scrubland 16 Savanna 17 Tropical woodland 18 Tropical forest 19 No data over land (e.g. Antarctica) The values in the "historic_landcover_diffs_hd.asc" file represent the differences between the 0.5 degree ISLSCP II land/water mask and the original land/water mask and mean the following: -1 = ISLSCP II mask is water and original data is land (data removed) 0 = Data sets agree over land or water (data unchanged) 1 = ISLSCP II mask is land or water and original data is missing (fill value used). The files are gridded to a common equal-angle lat/long grid with spatial resolutions of 0.5 x 0.5 and 1 x 1 degree in latitude and longitude, where the coordinates of the upper left corner of the files are located at 180 degrees W, 90 degrees N and the lower right corner coordinates are located at 180 degrees E, 90 degrees S. Data in the files are ordered from North to South and from West to East beginning at 180 degrees West and 90 degrees North.