Posted on behalf of Ewen Callaway.
Humans’ growing hunger for meat and dairy will gobble up natural resources and produce unsustainable amounts of greenhouse gases and nitrogen without changes in consumption, concludes a new projection of the global impacts of livestock in 2050.
Though lacking in geographical resolution and precision, the study, published this week in PNAS (doi: 10.1073/pnas.1004659107) underscores growing concerns over the worldwide growth in livestock production, say its authors.
According to the Food and Agriculture Organization (FAO), humans are on track to eat 465 million tonnes of meat and more than 1 billion tonnes of milk in 2050, up from 229 million and 580 million tonnes, respectively, in 2000.
Unlike most previous estimates on the environmental impacts of booming livestock production, the new study couches its projections in terms of their contribution to overall human impacts on the environment deemed to be sustainable.
Starting with the FAO projections for livestock production levels in 2050, a team led by Nathan Pelletier, an ecological economist at Dalhousie University in Halifax, Canada, estimated their environmental impacts along three broad criteria: greenhouse gases emitted, nitrogen mobilized in the form of chemical fertilizer and naturally fixed nitrogen, and biomass consumed.
Greenhouse gases contribute to climate change, nitrogen can cause eutrophication and other environmental problems, while devoting biomass to livestock production leaves less to support natural food webs, Pelletier says.
His team also assumed that future growth in livestock production would start at the efficiency of Western livestock production, and that the process would become even more efficient by 2050.
Even with those rosy assumptions, livestock production is still on track to exceed sustainable levels of nitrogen mobilization by 294% by 2050, up from 125% in 2000, Pelletier’s team calculates. At the same time, livestock production will account for 70% of greenhouse gases, up from 52%, and 88% of biomass appropriated by humans, up from 72%, assumed by Pelletier’s team to be sustainable levels.
“For me, it’s not a big surprise, but the novel thing about this paper is that it tries to relate everything to sustainability thresholds,” says Helmut Haberl a human ecologist at the Institute of Social Ecology in Vienna, Austria. However, such thresholds are not set in stone, he adds.
Nonetheless, Pelletier calls for broad changes in patterns of food consumption, particularly in the West. Replacing the protein gained from livestock with less resource hungry animals such as chickens or with soya would lessen the environmental footprint of our diets, his team calculates.
“We have to think about how we can change consumption patterns,” says Pelletier, “It doesn’t necessarily mean we stop producing livestock. I don’t think that’s realistic, but it’s equally unrealistic to expect that we can bring the entire planet up to the level of meat consumption of North Americans.”