Travel costs, adapted from Nelson (2008), were 72 min per grid cell for natural land cover, 12 for tracks,

6 for rivers or sea, 4 for artificial surfaces, 3 for shipping lanes, 2 for major roads and 1 min for highways. The economic pressure on each grid cell k is thus equal to the nearest centre’s economic pressure (EPnc) divided by the Selleck JNK inhibitor square-rooted travel cost (in minutes) between them (tcknc): $$ \textEPL_\textk = \text EP_\textnc / \sqrt \texttc_\textknc $$ (2)Here, we defined market centres as cities with more than 50,000 people, yielding 8,518 centres [definition adopted from Nelson (2008)]. We then used a database of gridded world population for the year 2000 (CIESIN 2005) to assign the entire world’s population to their nearest market selleck chemicals centre (in kilometres). We multiplied the resulting combined urban and rural population by the average calorific intake of each market centre’s country (Food and Agriculture Organisation 2006). In order to estimate the effect of trade between centres, we created a 8,518 × 8,518 matrix containing the distance between

all market centres. For each cell, we effectively factored the pressure from all human individuals in the world, weighted by their consumption patterns and channelled by their respective market centres. The global economic pressure on land for the year 2000 is shown in Fig. 1. Fig. 1 selleck chemicals llc Economic pressure for year 2000. Economic pressure on land index, resulting from population, consumption and distance to markets patterns. Different colour scales are applied for forests and non-forest areas. Deserts are shaded grey In order to avoid distortion arising from using financial units in a global, long-term

analysis, we used physical quantities for consumption (calorific intake), distance (kilometres) and travel cost (minutes per kilometre). Calorific intake is compatible with our observed variable (global land cover in 2000), as the latter relates to land converted to agriculture and cattle ranching, primarily food producing land uses (see also Goldewijk and Ramankutty 2004). Agriculture and cattle ranching comprise most of the historically converted land globally (Goldewijk and Ramankutty 2004) and our analysis does not include land converted to timber production or urban settlements. Protected areas When projecting the likelihood of land-cover change until 2050, we incorporated the effect of PAs into the analysis, by combining data from the World Database on Protected Areas (IUCN and UNEP 2009) and data from Joppa and Pfaff (2010) that estimate the effectiveness of PAs in each country.