The above shows the fraction of land area devoted to agriculture for a selection of developed countries according to the UN's Food and Agriculture Organization. The data run 1961-2009 (all available data). The country sample is hand-picked - most of the current European crisis countries plus some of the more important economies in the OECD.
I assume the sharp drop in Ireland in 1990 is some change in the definitions in the statistics rather than a massive step-function in the country's agriculture. Also, in the 2000s Greek values started fluctuating wildly and I have removed the values that don't seem plausibly related to the prior trend.
My overall impressions are as follows:
- Land devoted to agriculture tends to decline over time in developed countries.
- This trend doesn't seem to be very sensitive to agricultural prices - for example the huge run-up in commodity prices in the 1970s didn't result in an increase in agricultural land usage, and the similar run-up in recent years hasn't either.
- There's also no sign of a response to macroeconomic events - Sweden and Japan had financial crises in the early 1990s, and Spain and Greece have been in very severe crisis in recent years. So far, these events have left little discernible trace in the data.
- The 2002-2007 four percent increase in farm count in the US is associated with a small decline in the total area in agriculture, so presumably it must represent a splitting of existing farms, rather than colonization of unused land.