Ian Roberts: Slim chances for a fat planet

Last week the geopolitics of the biofuel debacle looked something like this. On the left both geographically and politically, we had Evo Morales, President of the very poor and increasingly hungry Bolivia, pleading “la vida primero los autos segundos” (life first, cars second), exhorting the wealthy world to stop burning food in their cars.

On the right, we had Gordon Brown, fresh out of his food summit, calling for more agricultural research, free trade and food aid for the starving.

Apart from calling for better roads so that poor farmers can “sell their products in our markets” Brown, made no reference to transport as a protagonist in the struggle for energy between people and cars. Morales, who as a youth witnessed a cocoa farmer being doused in petrol and burned alive, understands how transportation fuel use by the rich equals suffering for the poor. Brown’s was a serious oversight.

Car use and food prices were linked long before policies on biofuels. Car use in rich countries increases the price of food because thanks to agricultural research, oil is now an essential agricultural input and rising car use drives up the oil price. In its daily communion with the sun, the earth’s surface is blessed with only about 200 watts of radiant energy per square metre. Plants raise their leaves to receive this energy and after sipping carbon dioxide from the atmosphere, carry out photosynthesis to make the food that sustains all life. For centuries, incoming solar energy set a limit on the amount of food energy that could be harvested from a given amount of land. But the discovery of seemingly limitless supplies of oil changed everything.

From the 1940s onwards, fossil fuel based fertilisers, pesticides, irrigation and mechanisation dramatically increased food yields. Modern agriculture became the use of land to turn petroleum into food. The transportation sector is almost entirely dependent on oil and without billions of barrels of this precious black sludge to lubricate them, the words roads and the global economy would grind to a halt. Petrol tanks and stomachs were competing to be filled long before biofuels were proposed to tackle climate change.

But the links between transport, food and the environment go much deeper. Try this out: car use causes obesity, obesity increases car use and rising obesity increases food consumption and worsens global warming. If that sounds like a vicious circle with dire implictions for global food security and the environment then you are on the right track. Take a non-obese seventy kilogram man of stable weight. He starts to drive rather than walk the 500 metres to the office every because he thinks buses are for losers. In just over a year he will have gained a kilogram of fat due to his use of fossil fuel energy rather than food energy for transport. The gradual accumulation of fat will continue. His increasingly heavy body will become a disincentive to physical activity and due to movement inertia he will be loathe to walk or cycle anywhere, choosing instead to use the car for even short journeys. The energy imbalance that causes obesity is small but self perpetuating. As he gets fatter back pain, arthritis and shortness of breath will add to his movement discomfort. Low self esteem from body dissatisfaction will lead to comfort eating and he will start drinking more of that deceptively energy dense anaesthetic called alcohol. The physics of human movement quickly lock the transportation system into a downward spiral of increasing vehicle use and obesity. More traffic means more dangerous kinetic energy on our streets which keeps the podgy children indoors and the cyclist scared.

That was the vicious circle part now here is the crunch. Obesity increases food demand and prices because obese populations eat more food calories. Despite the claims by fatties to be small eaters, the physics of personal energy expenditure means that an obese person will consume substantially more food than a lean person. The human body is a vehicle designed for personal transportation and whether idling or moving a fat body is a gas (food) guzzler. The global demand for food is increasing because rich people are getting fatter and as well as eating more meat, which requires greater land use than is used in growing grains and vegetables, they are simply eating more. Because food production accounts for about 20% of greenhouse gas emissions, more than from transport or industry, the carbon footprint of an obese population is a chubby one. Greater food consumption means more organic waste which produces methane when it decomposes. As the obesity pandemic develops populations eat more and pollute more.

Only one of the twenty experts brought together in Gordon Brown’s food summit had a remit for transportation energy use and if more road building was their only contribution, then their claim to expertise must be challenged. It may be too late to escape the downward spiral of increasing body mass and vehicle use but we must act now and decisively. The current EU policy on biofuels was a sop to a car industry opposed to increasing vehicle energy efficiency but making cars more fuel efficient is not the whole answer. There is no place for private passenger cars in towns and cities. Walking, cycling and public transport is a lifeline to urban sustainability that will not empty the stomachs of the poor and will deliver huge health gains for rich and poor alike. With a quarter of UK adults now obese the prospects of a renaissance in active transport are not looking good. Brown acknowledged that while short term measures are needed to deal with immediate hardships, the structural causes of increasing food prices must be addressed. Transport policy is food policy and walking and cycling is the future for transport. The chances are slim for an obese planet.

Ian Roberts
Professor of Public Health

London School of Hygiene and Tropical Medicine