Global map of tree density
These two maps initially appeared in Crowther et al (2015), with the biome map
being featured more prominently. Explicit publication of the data is associated with Glick et al (2016). As they are produced, updated versions of
these datasets, as well as alternative formats, will be made available under
Additional Versions (see below).
Methods: We collected over 420,000 ground-sources estimates of tree density
from around the world. We then constructed linear regression models using
vegetative, climatic, topographic, and anthropogenic variables to produce
forest tree density estimates for all locations globally. All modeling was done in R. Mapping was done using R and ArcGIS 10.1.
Viewing Instructions: Load the files into an appropriate geographic information
system (GIS). For the original download (ArcGIS geodatabase files), load the
files into ArcGIS to view or export the data to other formats. Because these
datasets are large and have a unique coordinate system that is not read by many
GIS, we suggest loading them into an ArcGIS dataframe whose coordinate system
matches that of the data (see File Format). For GeoTiff files (see Additional
Versions), load them into any compatible GIS or image management program.
Comments: The original download provides a zipped folder that contains (1) an
ArcGIS File Geodatabase (.gdb) containing one raster file for each of the two
global models of tree density – one based on biomes and one based on ecoregions;
(2) a layer file (.lyr) for each of the global models with the symbology used
for each respective model in Crowther et al (2015); and an ArcGIS Map Document
(.mxd) that contains the layers and symbology for each map in the paper. The data is
delivered in the Goode homolosine interrupted projected coordinate system that
was used to compute biome, ecoregion, and global estimates of the number and
density of trees presented in Crowther et al (2015). To obtain maps like those presented in
the official publication, raster files will need to be reprojected to the
Eckert III projected coordinate system. Details on subsequent revisions and
alternative file formats are list below under Additional Versions.
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Additional Versions:
Crowther_Nature_Files_Revision_01.zip contains tree density predictions
for small islands that are not included in the data available in the original dataset. These predictions were not taken into consideration in
production of maps and figures presented in Crowther et al (2015), with the
exception of the values presented in Supplemental Table 2. The file structure follows that of the original data and includes both biome- and ecoregion-level models.
Crowther_Nature_Files_Revision_01_WGS84_GeoTiff.zip contains Revision_01 of the biome-level model, but stored in WGS84 and GeoTiff format. This file was produced by reprojecting the original Goode homolosine files to WGS84 using nearest neighbor resampling in ArcMap. All areal computations presented in the manuscript were computed using the Goode homolosine projection. This means that comparable computations made with projected versions of this WGS84 data are likely to differ (substantially at greater latitudes) as a product of the resampling. Included in this .zip file are the primary .tif and its visualization support files.
References:
Crowther, T. W., Glick, H. B., Covey, K. R., Bettigole, C., Maynard, D. S., Thomas, S. M., Smith, J. R., Hintler, G., Duguid, M. C., Amatulli, G., Tuanmu, M. N., Jetz, W., Salas, C., Stam, C., Piotto, D., Tavani, R., Green, S., Bruce, G., Williams, S. J., Wiser, S. K., Huber, M. O., Hengeveld, G. M., Nabuurs, G. J., Tikhonova, E., Borchardt, P., Li, C. F., Powrie, L. W., Fischer, M., Hemp, A., Homeier, J., Cho, P., Vibrans, A. C., Umunay, P. M., Piao, S. L., Rowe, C. W., Ashton, M. S., Crane, P. R., and Bradford, M. A. 2015. Mapping tree density at a global scale. Nature, 525(7568): 201-205. DOI: http://doi.org/10.1038/nature14967
Glick, H. B., Bettigole, C. B., Maynard, D. S., Covey, K. R., Smith, J. R., and Crowther, T. W. 2016. Spatially explicit models of global tree density. Scientific Data, 3(160069), doi:10.1038/sdata.2016.69.