Abstract
Abstract. Land-use and land-cover change (LULCC) impacts local energy and water balance and contributes on global scale to a net carbon emission to the atmosphere. The newly released annual ESA CCI (climate change initiative) land cover maps provide continuous land cover changes at 300 m resolution from 1992 to 2015, and can be used in land surface models (LSMs) to simulate LULCC effects on carbon stocks and on surface energy budgets. Here we investigate the absolute areas and gross and net changes in different plant functional types (PFTs) derived from ESA CCI products. The results are compared with other datasets. Global areas of forest, cropland and grassland PFTs from ESA are 30.4, 19.3 and 35.7 million km2 in the year 2000. The global forest area is lower than that from LUH2v2h (Hurtt et al., 2011), Hansen et al. (2013) or Houghton and Nassikas (2017) while cropland area is higher than LUH2v2h (Hurtt et al., 2011), in which cropland area is from HYDE 3.2 (Klein Goldewijk et al., 2016). Gross forest loss and gain during 1992–2015 are 1.5 and 0.9 million km2 respectively, resulting in a net forest loss of 0.6 million km2, mainly occurring in South and Central America. The magnitudes of gross changes in forest, cropland and grassland PFTs in the ESA CCI are smaller than those in other datasets. The magnitude of global net cropland gain for the whole period is consistent with HYDE 3.2 (Klein Goldewijk et al., 2016), but most of the increases happened before 2004 in ESA and after 2007 in HYDE 3.2. Brazil, Bolivia and Indonesia are the countries with the largest net forest loss from 1992 to 2015, and the decreased areas are generally consistent with those from Hansen et al. (2013) based on Landsat 30 m resolution images. Despite discrepancies compared to other datasets, and uncertainties in converting into PFTs, the new ESA CCI products provide the first detailed long-term time series of land-cover change and can be implemented in LSMs to characterize recent carbon dynamics, and in climate models to simulate land-cover change feedbacks on climate. The annual ESA CCI land cover products can be downloaded from http://maps.elie.ucl.ac.be/CCI/viewer/download.php (Land Cover Maps – v2.0.7; see details in Sect. 5). The PFT map translation protocol and an example in 2000 can be downloaded from https://doi.org/10.5281/zenodo.834229. The annual ESA CCI PFT maps from 1992 to 2015 at 0.5∘×0.5∘ resolution can also be downloaded from https://doi.org/10.5281/zenodo.1048163.
Highlights
LULCC (Land-use and land-cover change) is the essential human perturbation on natural ecosystems (Klein Goldewijk et al, 2016) and one of the main drivers of climate change (Alkama and Cescatti, 2016; Bonan, 2008) through biophysical and biogeochemical effects
Well defined and spatially explicit gridded LULCC data are a prerequisite for calculating ELUC in models, either under the form of annual area change in bookkeeping models or converted to changes in plant functional type (PFT) areas in land surface models (LSMs)
Global satellite data include the Global Land Cover 2000 (GLC2000) map based on SPOT VEGETATION (SPOT-VGT; 1 km resolution; Bartholomé and Belward, 2005), the MODIS Collection 5 Land Cover Product (500 m resolution; Friedl et al, 2010), forest cover maps based on Landsat (30 m resolution; Hansen et al, 2013), the GlobCover 2005 and 2009 products (300 m resolution; Bontemps et al, 2011; Defourny et al, 2012) and the European Space Agency Climate Change Initiative (ESA CCI) epoch maps based on MERIS (300 m resolution; Bontemps et al, 2013)
Summary
LULCC (Land-use and land-cover change) is the essential human perturbation on natural ecosystems (Klein Goldewijk et al, 2016) and one of the main drivers of climate change (Alkama and Cescatti, 2016; Bonan, 2008) through biophysical (e.g. albedo and transpiration change; Peng et al, 2014; Zhao and Jackson, 2014) and biogeochemical effects (e.g. carbon emissions from gross deforestation and carbon sinks in secondary forest regrowth; Houghton and Nassikas, 2017). Global satellite data include the Global Land Cover 2000 (GLC2000) map based on SPOT VEGETATION (SPOT-VGT; 1 km resolution; Bartholomé and Belward, 2005), the MODIS Collection 5 Land Cover Product (500 m resolution; Friedl et al, 2010), forest cover maps based on Landsat (30 m resolution; Hansen et al, 2013), the GlobCover 2005 and 2009 products (300 m resolution; Bontemps et al, 2011; Defourny et al, 2012) and the European Space Agency Climate Change Initiative (ESA CCI) epoch maps based on MERIS (300 m resolution; Bontemps et al, 2013) These satellite land cover products, differ in terms of land cover type, spatial resolution, time span, stability and accuracy due to the different sensor designs, classification procedures and validation methods (Bontemps et al, 2012). The previous ESA CCI epoch maps contain all LC types (Bontemps et al, 2013) but the LC transitions are not appropriate to be used in LSMs because these epoch products represent 5-year composite maps and do not allow us to assess annual LC change dynamics; only transitions to or from forest cover were considered at that time (Li et al, 2016)
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