The drought of 2012 has reminded us that water is a scarce resource, even though we pay fractions of a penny per gallon for it and expect that it’ll be there every time we turn on the tap. We depend on it not only for our drinking and washing and especially for the food we eat, but also for generating the electric power on which our economy depends.
There’s no doubt that we can use water more efficiently and that this would be socially and ecologically desirable. But this week, as I’ve being participating in the Annual Meeting of the Ecological Society of America (ESA) in Portland, I’ve started to doubt whether efficiency will really solve our drought and water problems. The reason is that for another vital resource — the land — efficiency doesn’t seem to be enough.
The hypothesis that using land to produce food more efficiently — that is, increasing agricultural yields — will “save” more land for nature, is called “land sparing” and is often associated with the famous crop breeder Norman Borlaug. It was the subject of a session of scientific presentations here at the ESA yesterday, including one by me. Although I’m by no means unbiased on this subject, I’d say that the messages of the presenters about the validity of the land sparing hypothesis mostly ranged from “It’s wrong” to “it depends.” (I gave both answers, but with more emphasis on the first one.)
An example of the first was the talk by Jahi Chappell of the University of Washington-Vancouver, who showed that increasing agricultural yield seems to do much less to reduce hunger in developing countries than social changes such as improving the status of women. The second kind of answer came in the presentation of Frank Egan of Penn State, who argued that land sparing works to preserve plant biodiversity in simple environments, but that in more complex landscapes a different strategy, “land sharing,” is preferable.
Laurie Drinkwater of Cornell University made the connection between agriculture and water quality, showing how U.S. agricultural and biofuels policies that promote massive corn production in the Midwest lead to excessive applications of nitrogen fertilizer, much of which runs off and contaminates streams, rivers, and ground water.
If there’s any place that land sparing ought to work, it’s in the Corn Belt, where high-input farms produce record crop yields (except in drought years like this one, likely to be increasingly common in the future). Yet the result, contrary to the land sparing hypothesis, has been a landscape with practically none of its original nature (the tallgrass prairie) remaining, and water pollution that creates an enormous “dead zone” in the Gulf of Mexico, a thousand miles away.
If high productivity doesn’t spare land, how about water? As I said in my presentation, the error of the land sparing hypothesis was first pointed out 150 years ago by the British economist William Jevons. That error is to ignore the economics, which often leads to more use of a resource whose yield increases, not less. Jevons was talking about coal, but the same point applies to land. And if it’s true for water as well, then more efficiency won’t save us from this drought – or the next.