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Ecological Leftovers: food for a finite planet
by Tim Willmott : Be the first to leave a comment
It is well known that the production of livestock-based diets comes with a very large ecological footprint (livestock emits approximately 14.5% of all man-made greenhouse gas (GHG) emissions)¹. Swedish researchers have been looking at food production that remains within the global footprint which involves the ‘ecological leftovers’ principle, by raising livestock on pasture or by-products not suitable for humans. They developed three diets based on the ecological leftovers method and compared their environmental impact with current diets.
Advocated by many, meat-free diets are not necessarily the solution – some vegetarian diets use more land and have a greater climate impact than diets with a small amount of meat – but reducing livestock consumption could have significant benefits. Furthermore, livestock provides essential protein in developing countries, creates jobs for 30% of the world’s population², and delivers ecosystem services including biodiversity conservation and nutrient cycling.
The study re-evaluated the system of livestock production to balance the dietary needs of the population with environmental limits. A method was developed for designing ‘fair diets’, which do not use more than the available arable land per capita. Animals are fed with resources that are not fit for human consumption, such as grass from marginal land or by-products from crop production and food processing. These diets were compared with an average Swedish diet.
The method used to design the diets, named ‘ECOLEFT’, follows three principles:
- arable land should mainly be used for production of plant-based foods for humans;
- livestock should be fed biomass not suitable/desirable by humans;
- semi-natural grassland should be used for livestock production only if grazing can be justified by reasons other than meat and milk production (e.g. biodiversity conservation, providing livelihood).
ECOLEFT was used to develop three different dietary models, applied to Sweden.
In the first scenario (I-Milk), milk and meat were produced in intensive systems, in which high-producing dairy cows were used to maximise milk production.
In the second scenario, E-Milk, dairy cows were fed on forage (e.g. grass or hay), while the by-products (plus cereals and legumes) were fed to poultry and pigs.
In the final scenario, Suckler, the pasture was grazed by suckler herds (young animals that still draw milk from suckling cows). The number of animals needed to graze the land could then be reduced (as suckling cows can survive on semi-natural grassland to a greater extent than dairy cows). By-products were again used to feed poultry and pigs.
The researchers compared the amounts of protein-rich foods consumed in the three diets to current consumption patterns and Swedish nutrition recommendations. The I-Milk, E-Milk and Suckler diets would reduce the proportion of agricultural land used to grow feed for animals from the current level of approximately 75% to 58%, 50% and 42%, respectively.
To assess the environmental impacts of these changes, the researchers used the planetary boundaries framework³.
Land use for all ECOLEFT diets was within planetary boundaries, and lower than for the current Swedish population’s diet. After producing the food needed and energy needed for agriculture, there was ‘spare land’ available in all the ECOLEFT diets, when compared with the total currently available arable land in Sweden. Although the diets did not meet the strict climate planetary boundary of zero net emissions, their climate impact was less than half that associated with current Swedish diets and compatible with pathways for limiting global warming to 2°C.
The researchers say that it is clear that ECOLEFT techniques—which reduce climate impact and create land for other purposes—are likely to cause less overall environmental damage than techniques supporting current, established diets.
- FAO (2013) Tackling climate change through livestock. http://www.fao.org/docrep/018/i3437e/i3437e.pdf
- World Bank, 2014. World Development Indicators Table 3.2.
- Rockström, J. et al (2009). A safe operating space for humanity. Nature, 461(7263), pp.472-475.
- Steffen, W. et al (2015). Planetary Boundaries: Guiding Human Development on a Changing Planet. Science, 347 (6223).
Source: Röös, E., Patel, M., Spångberg, J., Carlsson, G. & Rydhmer, L. (2016). Limiting livestock production to pasture and by-products in a search for sustainable diets. Food Policy, 58, pp.1-13. DOI: 10.1016/j.foodpol.2015.10.008
source: Science for Environment Policy