Where rich countries are buying farmland

Saudi Arabia has cut several deals, most recently in Tanzania

The sheer scale of some of the deals is enough to make even the most ardent colonialist gulp.

According to data compiled by the US-based International Food Policy Research Institute, Saudi Arabia has concluded a string of agreements in recent months, most recently approaching Tanzania in April to lease a 500,000-hectare (1.2 million acres) tract of farmland for rice and wheat production.

In the same month, South African farmers were offered 10 million hectares of farmland in the Republic of Congo.

Indian government-backed farming companies have pursued land in a half-dozen African countries. Chinese corporations have sought a succession of arrangements to make use of land in the Democratic Republic of Congo, Tanzania, and Zambia. Meanwhile, South Korea snapped up 690,000 hectares in Sudan. In fact, Sudan is a particular target country, with Egypt, Jordan, Kuwait, Saudi Arabia, and Qatar all pursuing deals there. A mooted Qatari deal in Kenya has prompted criticism from land rights activists there.

But it was Madagascar that provided the first clear warning that these deals may not be mutually beneficial. A bid by South Korea's Daewoo conglomerate to grow corn on 1.3 million hectares backfired spectacularly earlier this year, arousing such hostility that it contributed in part to a coup. The new president, Andry Rajoelina, promptly scrapped the deal.