Horse meat sold as beef has made headlines and provoked consumer outrage in the UK, but the contribution of global food production—and particularly meat—to climate change is the larger scandal, according to experts who spoke to The Lancet Respiratory Medicine.

“Meat and dairy are a hotspot for ecological public health”, notes Timothy Lang (Centre for Food Policy, City University London, London, UK). “About half the world’s grain is fed to animals. The land and water use for such production systems are enormous. But this has created a situation where supposedly efficient modern agricultural systems have turned domestic animals as sources of cheap meat into direct competitors with humans for dominance in the ecological space.”

Although many people understand the threats that are posed to food systems by rising temperatures, extreme weather, and changing precipitation patterns, few seem to appreciate the degree to which human food production contributes to global climate change and the resulting health risks.

“It is bizarre that so many people in public health seem barely aware of food’s massive contribution to climate change”, remarks Lang. “This is not just unfortunate but downright irresponsible.”

An estimated 14% of greenhouse gas emissions come directly from agriculture (putting it on par with transportation emissions). Increasing transportation distances to market worsens food’s carbon footprint—a factor for which Lang coined the term “food miles.”

“A policy shift toward horticulture rather than animal-oriented agriculture is long overdue and is set to be a key challenge for the 21st century”, Lang believes. Public education campaigns to encourage people to eat less meat would seem to be the obvious direction for public health and environmental interventions meant to mitigate climate change. But public education is more easily advocated than implemented.

“In the past few years, several attempts to generate sustainable dietary advice for populations have come up against some big food-industry vested interests”, Lang says, citing recent controversies in Sweden, the UK, and Australia over proposed consumer advisories and nutritional guidelines. “Powerful interests will fight hard not to address the challenge of sustainability.”

Food production and agricultural and trade policies have been hijacked by a small number of large corporations in recent decades, agrees Wenonah Hauter (Food & Water Watch, Washington, DC, USA), whose father fled Oklahoma in the 1930s because of the so-called Dust Bowl—severe dust storms largely driven by agriculture.

In the USA, “20 large food processors own most brands on retail shelves”, notes Hauter. “Our political system is set up to allow companies to become larger and larger. During the Reagan administration, antitrust law was one of the main targets of the deregulatory agenda. They cut staff and enforcement budgets at regulatory agencies, and narrowed the definition of what constitutes an antitrust violation. Predictably, these companies became so large they’re able to dictate food and farm policy on everything from what pesticides we’re exposed to, to the way that food is made and labelled.”

US agriculture policy was further deregulated under the Clinton administration in the mid 1990s “to get in line with trade policy”, Hauter says. Deregulation of grain commodities during the 1990s saw increased corporate consolidation of corporate meat production, with the “factory farms” proportion of pork production, for example, rising from 30% in 1995 to 95% by 2005.

Under President Obama, efforts to curb junk food advertisements aimed at children yielded only “very weak voluntary guidelines”, Hauter says, which is testament to food industry lobbyists’ sway in Washington DC.

“Governments don’t govern; they follow”, cautions Lang. “Too often they are timid with regard to health and environment. The neoliberal perspective dominates: leave it to the consumer. But consumers are in the dark about the impact their food has on the planet, and the avalanche of cheap calories [in developed countries] acts as the model for what consumerism aspires to. But increasingly, scientists are aware that we need a new direction for food. We have to link human and environmental health.”

The interactions between abundant cheap calories, obesity, and the environment can generate complex feedback loops between climate, food, and epidemiology. The industrial production and global transportation of food contributes to global climate change, which affects agriculture through changes in precipitation and temperature, and extreme weather events. The effects will be felt unevenly around the planet, further impoverishing Africa’s agricultural base, for example. Overweight and obese people consume more food than others and rely disproportionately on travel by car, which together increases their carbon footprint to make obesity itself a serious global environmental problem, according to a 2009 study by scientists at the London School of Hygiene & Tropical Medicine.

The burden of respiratory disease is expected to increase with global temperatures, and the link between respiratory disorders, such as asthma and sleep apnoea, could be compounded by the environmental consequences of climate change. Extreme heat, air pollutants such as ozone and particulate matter, and increased production of plant and fungal allergens, will all conspire to drive up respiratory morbidity and mortality rates.

Early modelling studies predict that concentrations of pollen from common tree species such as oak and birch, and weeds such as the highly-allergenic ragweed, will increase by 20—30% by 2020, and will continue climbing for decades to follow, notes Leonard Bielory (Center for Environmental Prediction, Rutgers University, Springfield, NJ, USA). The US Environmental Protection Agency is funding research at Rutgers University to assess the effect of climate change on allergenic airway disease, says Bielory.

Respiratory syncytial virus infections are more common when temperatures are higher. Prolonged drought and increased airborne levels of particulate matter from wildfire smoke and dust—including the intercontinental movement of dust from growing expanses of African desert—are expected to exacerbate asthma and COPD symptoms.

Concentrations of ground-level ozone, a highly oxidative air pollutant, are expected to rise in some regions and drop in others, leading to increased rates of respiratory distress, exacerbated airway diseases such as asthma, and respiratory infection risks, adds Hans Orru (Department of Public Health, University of Tartu, Estonia). Predicted increases in ground-level ozone will hit central and southern Europe harder than northern Europe, which is likely to see declines in ozone, Orru says.

“There are a number of interactions between plant biology, which will certainly be affected by rising CO2 and increased temperature, and public health concerns. These interactions can run the gamut from aeroallergens to nutrition to pesticide use”, says Lewis H Ziska (Crop Systems and Global Change Laboratory, US Department of Agriculture, Beltsville, MD, USA). “There is initial evidence that all of these issues are already being affected.”

Recent and projected changes in atmospheric CO2 have been shown to change yields of plant food proteins, antioxidants, and omega-3 fatty acids, Ziska points out. “One key question we have is whether or not rising CO2 will also affect food allergies.” Ragweed pollen season has increased by as much as 13—27 days at higher latitudes since 1995, according to a 2011 study by Ziska, Bielory, and colleagues. Increased pollen seasons correspond to an increased number of frost-free days, Bielory notes.

Another key question is whether or not plant pollen might become more allergenic with changing temperatures or CO2 levels. The effects of air pollutants on respiratory health can be compounded by the presence of respiratory allergens, Ziska notes. Pollen sticks to larger particulate matter associated, for example, with diesel fumes. “The particulate matter can act as a platform that attracts pollen and drives it further into the lungs”, Ziska explains. Sensitisation to common seasonal allergens has doubled over the past 20 years along with symptoms, Bielory has found.

In addition to airborne allergens, the effect of climate change on plant communities might lead to larger populations of disease vectors such as mosquitoes, whose larvae can feed on pollen.

AJ McMichael (National Centre for Epidemiology and Population Health, Australian National University, ACT, Australia) and others believe that major civilisational shifts, resulting in starvation, warfare, migration, and revolution, have accompanied abrupt climatic change in the past. A recent report even links droughts in wheat-producing regions of the globe with the Arab Spring uprisings in countries that are among the largest wheat importers.

Climate change will unveil complex interactions between plants and human physiology, Ziska concludes. “We are getting a sense of what some of those interactions are, and how significant they are, but we have a great deal more yet to do”. Untangling these interactions will be a major interdisciplinary endeavour.

Source: lancet