Interesting argument at the Boton Globe from this Harvard Professor of Economics and lover of big dense cities.
while neighborhoods benefit from the occasional communal garden, it is a mistake to think that metropolitan areas could or should try to significantly satisfy their own food needs. Good environmentalism is smart environmentalism that thinks through the total systemic impacts of any change. Farm land within a metropolitan area decreases density levels and pushes us apart, and carbon emissions rise dramatically as density falls.
In 2008, two Carnegie Mellon researchers …found that American food consumption produces greenhouse gas equivalent to 8.9 tons of carbon dioxide per household per year. Food delivery represents .4 tons of that total; all agricultural transportation up and down the food chain creates one ton of carbon dioxide per household annually.
We must weigh the environmental benefits from shipping less food against the environmental costs of producing and storing local food in a state that doesn’t exactly have ideal conditions for every kind of produce. One recent UK report found that the greenhouse gas emissions involved in eating English tomatoes were about three times as high as eating Spanish tomatoes…
But the most important environmental cost of metropolitan agriculture is that lower density levels mean more driving. Today, about 250 million Americans live on the 60 million acres of this country that are urban — which is about four people per acre. By contrast, America uses 442 million acres for cropland and 587 million acres for pastureland, which is about 1.4 and 1.9 acres per person respectively. If we allocated just 7.2 percent of this agricultural land into metropolitan area, we would halve metropolitan area densities.
The National Highway Travel Survey teaches us that when densities drops in half, holding fixed location within the metropolitan area, households buy about 107 gallons more gas per year. If halving densities also doubled distance to the metropolitan area center, this would add an extra 44 gallons of gas annually. Together, the increased gas consumption from moving less than a tenth of agricultural farmland into metropolitan areas would generate an extra 1.77 tons of carbon dioxide per year, which is 1.77 times the greenhouse gases produced by all food transportation and almost four and a half times the carbon emissions associated with food delivery….
Shipping food is just far less energy intensive than moving people. If the First Lady wants to help the environment, she should campaign for high rise apartments, rather than plant vegetables.
Glaeser is correct to question the unthinking approach to food miles. In the Middle East for example it makes no sense to burn oil and use precious water to grow food that can be imported by sea from East Africa. But his argument is incomplete.
The intensity of cultivation will always significantly increase in cities, and some forms of urban agriculture dont use up land to lower density at all, such as growing on roofs and on balconies, and every available space, often using new innovative techniques such as those pioneered by Dr Vishwanath.
Urban agriculture is typically opportunistic. Its practitioners have evolved and adapted diverse knowledge and know-how to select and locate, farm, process, and market all manner of plants, trees, and livestock. What they have achieved in the very heart of major cities, and dare to pursue despite minimal support, and often in the face of official opposition, is a tribute to human ingenuity. One survey by the United Nations Development Programme (UNDP 1996) identified over 40 farming systems, ranging from horticulture to aquaculture, kitchen gardens to market gardens, and including livestock as varied as cattle, chickens, snails, and silkworms!…The UNDP estimates perhaps as many as 800 million urban farmers produce about 15% of the world’s food. (Mougeot 2006)
It doesn’t make sense to grow food locally that is not climate appropriate, but there is nothing wrong with growing tomatoes in England (or Netherlands where so many are grown) providing they are not from fossil fuel fuelled greenhouses.
Cities largely grow as sectors along transport routes, in between these sectors increased density often makes little sense as it is away from public transport and it would only lead to greater car use. So why not leave areas open and have some as urban gardens? What is more urban greenery of all kinds has a huge benefit on improving amenity and increasing attractiveness of cities. Density without greenery is a nightmare.
If a garden is to remain a garden why not grow food on it? There is no opportunity cost and no moving of people. It is curious that an economist should neglect such a basic law of economics. Urban Farming is often an unexploited free good that can raise effective incomes of the poorest.
Similarly on an ‘urban prairie’ with no alternative use why not grow food, it is effectively free agricultural land which makes perfect sense to farm as it is making productive use of unproductive land? Praise the first lady on this professor as money not spent on food imports helps the balance of trade.
Another law he ignores is that of rent – or worse confuses the margin of cultivation/extensive rent with intensive rent. Transport costs add to rent and energy costs is the main input into transport costs. Doing some old fashioned Von Thunen rings will show that as energy costs rise intensive agriculture near and within cities will become more and more economic. In the future, as in J H Kunstlers Book ‘The World Made by Hand‘, we may all have to follow the first lady.
(Note halving densities doesn’t double distance (d) to the city core, it increases it by d2)
Decisions, Decisions, Decisions 