A global map of travel time to cities to assess inequalities in accessibility in 2015. Source: Weiss, D.J., Nelson, A., Gibson, H.S., et al. (2018) License AP / CC BY 4.0 To obtain data please visit: https://map.ox.ac.uk/research-project/accessibility_to_cities

Decline in tree cover, if observed in any 30 m2 pixel contained within each 1 km2 pixel. The change in tree cover is derived from satellite observations at 30 m resolution (per year).

Aridity Index less than 0.65 (Dryland). Aridity is a measure of ‘dryness’ of the climate expressed as the ratio of precipitation to evapotranspiration; the lower the ratio the drier the climate

Livestock density > class median. Livestock is calculated in terms of livestock ‘units’ (LSU). This allows to accumulate the various types of livestock (cattle equal 0.8 LSU, sheep 0.1, goats 0.1, pigs 0.4, chicken 0.01LSU). The layer is compiled with the 2007 FAO GLW data that is improved with current statistics and the use of higher resolution predictor variables. The density of livestock is related to environmental pressures from livestock related land use change, grazing lands and fodder production, and greenhouse gas emissions. Within the broad land classes an additional subdivision between dryland and non-dryland was introduced for calculating the GCI thresholds.

Below-average biomass productivity due to drought conditions. Decline in annual plant biomass productivity (as derived from Fraction of Absorbed Photosynthetically Active Radiation –fAPAR) due to drought conditions (here, based on negative deviations from the 1901-2010 average Standardized Precipitation and Evaporation Index). Expresses the response of plant productivity to climate fluctuations.

Population density > broad land cover class median. Population density (number of people per km2) is derived from census data.

Severe or Moderate decline in land productivity. Classes 1-3 in the land productivity dynamics map (LPD). Land productivity, here calculated as the annual growing season accumulation of the above ground biomass production is a proxy for NPP. The dynamics, observed by satellite and derived from phenological analyses of a 15-year time series (1999-2013), point to long term alterations of the health and productive capacity of the land.

Irrigation occurs > 10 % of grid cell. Area equipped for irrigation, expressed as percent of total 10 × 10 km area. Obtained by combining sub-national irrigation statistics with geospatial and satellite information on the position and extend of irrigation schemes. This layer does not map the area that is actually irrigated.

Average income of a country's citizens > broad land cover class median. Computed based on the Gross National Income (the value of a country's annual income – domestic plus net income received from abroad) divided by size of its population

At least one fire over the period. The number of fires observed over the period on satellite iimages with 1 km grid cells

Change in population density > broad land cover class median. Reflects the dynamics of increasing number of people in a certain area.

Total water withdrawal is > 40 % of the total surface water plus groundwater available (per year). Total water withdrawals refer to water use from the agriculture, domestic, and industrial sectors. Water stress is a measure for chronic human induced stress, rather than drought stress

Increase in built-up area > broad land cover class median. Built up is expressed as percent of pixel (1 km2) that is observed to be covered by building construction. This is derived from high resolution satellite observations, augmented by ancillary information.

Nitrogen surplus exists. Calculated based on the N balance level remained above the fourth quantile. The nitrogen balance indicates the level at which the crop(s) uses the applied nitrogen according to local conditions. Values in the fourth quantile mean that there is more nitrogen than the crop needs. (quantiles are calculated per broad land class)

Nitrogen deficit exists. Calculated based on the N balance level remained below the first quantile. The nitrogen balance indicates the level at which the crop(s) uses the applied nitrogen according to local conditions. Values in the first quantile mean that there is less nitrogen than the crop needs. (quantiles are calculated per broad land class).

At any given place on Earth, complex human-environment interactions are at play, which include differing rates and magnitudes of drivers (e.g. overgrazing, climate change, agricultural practices) and consequences (e.g. soil erosion,changes in productivity, loss of biodiversity). Because these are tied to specific places on the ground with their own intertwined biophysical, social, economic and political environments, land degradation is not a phenomenon that can be modelled or mapped at a global scale. WAD3 builds on a systematic framework of providing a convergence of reliable,global evidence of human environment interactions to identify local or regional areas of concern where land degradation processes may be underway. Concerns can be validated or dismissed only by evaluating them within local biophysical, social, economic and political contexts. Local context provides an understanding of causes and consequences of degradation, but also offers guidance for efforts to control or reverse it.