Monoculture and the Risks of Crop Failure

See: Martin L. Weitzman, “Economic Profitability Versus Ecological Entropy,” Quarterly Journal of Economics, February 2000.

“The Risk of Catastrophic Crop Failure,” Economic Intuition, Summer 2001.

By cultivating a small number of crops over large areas, farmers can dramatically increase profitability. This is why monoculture, cultivation of a single crop over a large area, is increasingly common in agriculture. But despite its short-run advantages, monoculture may also impose a long-term risk of crop failure. Economist Martin Weitzman of Harvard University says the vulnerability of a crop to a pathogen is highest when the amount of the plant in cultivation is small – or when it is very large. The vulnerability of a small crop is obvious, but that of a widespread crop is less so. Weitzman explains why it may in effect be too much of a good thing:

1. Large, homogeneous crops enable parasites (bacteria, viruses, fungi and insects) to specialize on one specific host, increasing the chance they will mutate into a more pathogenic form.

2. Farmers tend to choose the same crop cultivated by neighboring farms because of efficiency gains (e.g. in spraying and seed storage); but this makes it easier for a disease to spread – for example, foot and mouth disease spreads more easily where neighboring farms raise the same species.

3. Weitzmam’s statistical modelling shows that once the size of a crop passes a certain threshold, crop extinction can be very abrupt.

Diversity makes sense, even if this entails lower yields, as matter of food security.

[Clipped from: Monoculture and the Risks of Crop Failure ]