Abstract
Land degradation is a global environment and development issue. Up-to-date, quantitative information is needed to support policy and action for food and water security, economic development, environmental integrity and resource conservation. To meet this need, the Global Assessment of Land Degradation and Improvement (GLADA) uses remote sensing to identify degrading areas and areas where degradation has been arrested or reversed. This screening has been investigated within the parent LADA program at global scale (Bai et al., 2008a & b), and country level (Bai & Dent, 2006; Bai, 2007; Bai et al., 2007a-f, Bai & Dent, 2009, Bai et al., 2010).
Links have been established between land degradation and a decline in biomass or vegetation cover, which may be measured in terms of biomass productivity. Since the early 1980s, consistent, remotely sensed global normalized difference vegetation index (NDVI) data, and detailed studies of the relationship between NDVI and leaf area index and net primary productivity (Running & Nemani, 1988; Diallo et al., 1991; Carlson & Ripley, 1997) have prompted the use of NDVI trends as a proxy for land degradation (Wessels et al., 2004, 2007; Metternicht et al., 2010). The difficulty is to discount false alarms raised by other factors, notably fluctuations in rainfall, rising temperatures, atmospheric CO2 concentration, nitrate precipitation, and land use change, which may not be accompanied by land degradation as commonly understood (Bai et al., 2008a).
The current report is an addendum to the “international” GLADA report (Bai et al., 2008a) summarizing the 'evolution' of the GLADA approach and progress made since then.
Bai, Z G