Since their introduction by Portuguese traders in the 16th century, maize and cassava have replaced traditional African crops as that continent's most important staple food crops.

This is because there are too few profitable perennials that can replace crops or that can be adopted at the scale required.

And the growing demand has led farmers to replace traditional crops like rice with betel palms, causing severe erosion on many hillsides in southern Taiwan.

Since being introduced by Portuguese in the 16th century, maize and manioc have replaced traditional African crops as the continent's most important staple food crops.

Bread made from American wheat replaced domestic crops as the cheapest staple food.

The governors want to replace illicit crops by prodding farmers to eradicate in exchange for subsidies and markets for their products.

MANY critics see biotechnology as the latest incarnation of corporate agriculture, which is heavily dependent on pesticides and which replaces diverse crops with single varieties.

When the Army obtained the site in 1950, for a radio transmitting station, fields of antennas replaced cows and crops.

Agricultural researchers are stepping up efforts to develop heat-resistant and drought-resistant crops that might gradually replace traditional crops if the climate changes.

Furthermore, cotton has replaced other intensive crops which generate more pollution and greater surpluses.