Livestock production and the global environment: Consume less or produce better?

Whereas the Green Revolution was a concerted political and scientific response to rapidly growing populations, the Livestock Revolution currently underway in developing countries is driven by growing incomes or the world’s emerging middle class (1). Recently, a number of studies have underscored the impact of livestock on the global environment, including anthropogenic climate change (2), nitrogen cycles (3), and phytomass appropriation (4). In a paper published in PNAS, Pelletier and Tyedmers argue that the livestock sector will soon reach, or exceed, recently published sustainability thresholds in the areas of climate change, reactive nitrogen mobilization, and anthropogenic biomass appropriation and that curbing livestock sector growth should be a major focus in environmental governance (5). We agree that the current environmental impact of livestock is large, but it can be significantly attenuated. We show that some countervailing trends are already in place that have the potential to reduce environmental impact drastically, notably the shift to monogastrics and continued efficiency gains in the production of feed and livestock. These tendencies will help mitigate livestock’s global environmental impact to a larger extent than suggested by Pelletier and Tyedmers (5). Although addressing excessive levels of consumption will help reduce environmental impact, there is a vast mitigation potential on the production side. We argue that addressing environmental impacts of livestock on the production side may also carry important benefits for socially and economically disadvantaged livestock producers in developing countries.

Demand projections point to increases of global meat consumption of 68% and of global milk consumption of 57% over the 2000 base period by 2030 (6). Livestock are used to appropriate the majority of global phytomass captured by human activity, mostly by converting vegetal material of no immediate other use by way of ruminant production. Biomass appropriation does not necessarily imply a negative impact on the environment. In properly managed grass-based systems, grazing and mowing contribute to increased ecosystem productivity and biodiversity. The continuation of ruminant-based meat production systems into modern days, however, implies significant resource use and low resource-use efficiencies when high-value feed is used. This is because of the inherently low feed conversion rates of ruminants and their long reproduction intervals, which entail that more than one-half of dietary energy requirements in cattle production systems are for maintenance (2). In addition, because of the specifics of the digestive system of cattle, sheep, and goats (foreguts), their production is associated with high levels of methane emissions, substantially contributing to climate change. The production of monogastric meat and eggs is associated with much lower emission intensities, phytomass appropriation, and reactive nitrogen. Global monogastric meat production has increased by 103% over the 1987–2007 period as opposed to an increase of 28% in ruminant meat production (7); these trends are expected to continue into the future (6).

Productivity growth, triggered by demand growth and resource scarcity, also has the potential to reduce phytomass appropriation per unit of product and emission intensity. Measured in global protein output per standing livestock biomass, the productivity of ruminant species (beef and sheep) has been stable over the past two decades, whereas productivity of monogastrics (pig and poultry) grew at an annual rate of 2.3% (8). Productivity increases in livestock have been brought about by the broad application of science and advanced technology in feeding and nutrition, genetics and reproduction, and animal health control as well as general improvements in animal husbandry. Because livestock production relies increasingly on products of arable land, productivity increases in crop production also help in reducing the environmental impact that can be attributed to livestock. Close to 90% of total crop production increase is the result of productivity increase as opposed to area expansion (9). This is indicative of the large role that advanced technology can play in reducing environmental impact, particularly in developing country agriculture and livestock production where there are large productivity gaps. Closing these gaps could substantially reduce aggregate environmental impact of livestock. Fig. 1 describes the aggregate of the land use of livestock between 1961 and 2001. Globally, meat and milk production increased by 245% and 70%, respectively, whereas total use of arable land increased by 30% and grazing land by less than 10% (2).

Fig. 1.

Expansion of livestock production and supporting land.

Following current trends, the shift to monogastric species and continued productivity growth has the potential to considerably reduce environmental impact per unit of product (10), but given the projected increases in demand, aggregate impact is poised to grow further. For a more drastic reduction, livestock production needs to be intensified in a responsible way (i.e., be made more efficient in the way that it uses natural resources and generates harmful emissions, drawing from accelerated technological change and alignment of agricultural policies to global environmental objectives). For example, effective area protection and certification of origin can reduce deforestation and subsequent greenhouse gas emissions from land use change that is attributable to livestock. Deforestation is not necessary for meeting meat demand, and the required marginal growth can be easily achieved by intensification of current production, given the low-intensity levels of production in much of Latin America where most of the livestock-associated deforestation occurs. Another example is methane emission from anaerobic storage of waste (lagoons); regulatory change, perhaps combined with positive incentives, could avoid the majority of emissions from this source. A third example is methane emissions in the form of enteric methane. Regional average methane emission intensity ranges from 1.2 to 7.5 kg CO₂-eq./kg of milk (11). These differences reflect the vast intensity and productivity spectrum of global livestock production. Productivity increases in traditional dairy systems in places like India (the world’s largest dairy producer) can allow for meeting additional demand for dairy products and may also be a powerful tool for raising small producers’ income if avoided greenhouse gas emissions could be marketed.

Forms of responsible intensification and incentives that are realigned to global environmental objectives are needed to drive accelerated technological change. Given the large scope of mitigation and the presence of social/environmental win–win situations, we argue that there is a larger scope in altering production to reduce livestock’s environmental impact than suggested by Pelletier and Tyedmers (5), who only assume efficiency gains in production above 2000 levels. Similar trends have been observed in crop production, where land intensification has contributed to reducing emissions (12).

Calling for reining in livestock sector growth as a priority in environmental policy also carries the risk that such efforts target those countries and population segments that currently have low levels of consumption and where food intakes need to grow as opposed to those countries where they are currently high and where a reduction may also be desirable from a nutritional perspective. Average consumption levels of meat in sub-Saharan Africa are still only about one eighth of those in industrialized countries. Most of

Addressing environmental impacts of livestock on the production side may also carry important benefits.

the consumption growth is, however, taking place in emerging countries, rapidly approaching consumption levels observed in the most affluent parts of the world. Addressing the dietary convergence and putting in place environmental and public health policies to reorient consumption patterns on more sustainable paths would effectively reduce the sector’s impact. Policies directly targeting dietary patterns are often resented as interfering with very personal choices of how and what to eat; educational and awareness programs which promote healthy food choices have been shown to work in some places (13) but are likely to be slow in yielding the desired impact.

The extent and form of global environmental impact of livestock production, like in the form of climate gas emissions, have developed in the absence of environmental policies; in the livestock sector, such policies have mostly targeted water pollution and odor issues in industrialized countries and, to a certain extent, in emerging countries. Livestock production and consumption issues have not been a major focus of environmental policies thus far, and it can be argued that such policies could correct for many of the environmental externalities through regulatory and market-based instruments (14). Such policies could alter production modes to much higher efficiencies and shift prices to levels that reflect a social value of resources and emissions. Given the large gaps between attainable and actually attained efficiencies and the vast consumption growth potential in industrializing countries, a dual approach, targeting both production systems and consumption trends, should be pursued to effectively bring down the environmental impact of livestock.