Agriculture is a significant source of GHG emissions, as a result of both land-use change and considerable growth in livestock inventories, which rose by almost 40% between 1990 and 2010 in cattle equivalents, among the most important increases globally (USDA, 2013). The expansion of inventory doubled livestock density, from 3 heads per hectare of agricultural land in 1990 to 6 heads in 2011. These levels are comparable with those in New Zealand where a pastoral system prevails, but are low compared to world regions with more intensive livestock production (e.g. the European Union with an average total cattle number per hectare of 9.6 heads).