ABSTRACT
Pastures and crops used for livestock production cover nearly 75% of the world’s agricultural land (~3.7 billion ha) and consume >70% of freshwater extracted annually for irrigation and livestock needs (Foley et al., 2011). The growing international food requirements will place further pressure on scarce water resources as agriculture intensifies to meet demand. However, intensification is also a significant contributor to climate change and degradation of freshwater and soil quality (Foley et al., 2011; Mackay, 2008). Traditional land use practices are also under increasing scrutiny as societal awareness, understanding and tolerance of environmental, equity and animal welfare issues evolve. For example, the majority of agriculture’s 10-12% contribution to global greenhouse gas emissions comes from ruminant livestock systems, and 19% of the global warming up to 2010 is attributed to methane and nitrous oxide emissions from livestock (Reisinger and Clark, 2017). It is hardly surprising therefore that greater environmental regulation and greater challenge to the social licence to operate our current livestock production systems has resulted (Reheul et al., 2017). This environmental and societal debate must be balanced against the need for farming systems to remain economically viable. In temperate regions, the
economic viability of grassland farming is dependent on the amount of grazed pastures and supplementary feed crops that can be produced on-farm, and the subsequent utilisation of this forage for milk, meat and fibre production. Farmers have invested in irrigation systems and higher inputs of nitrogenous fertilisers to maximise production of low-cost forage, and they have increased stocking rates to improve utilisation of the extra feed. These practices, along with increased use of supplements (e.g. palm kernel extract) brought in to fill feed and energy deficits associated with the seasonal distribution of temperate pasture production, have all contributed to the worsening environmental footprint of temperate pasture systems.
