|Diversity, Globalization, and the Ways of Nature (IDRC, 1995, 234 p.)|
The temperate grasslands were planted with crops such as wheat and barley very early in history. Farming was widespread on all primary prairies of the Eurasian continent, especially in the Ukraine and southern Russia. Similar activities took place later in other regions of the world: the South American pampas, the North American prairies, the South African rangelands, and southeastern Australia. The remaining grasslands are often secondary (regrowth after cessation of agriculture); they are associated with intensive cattle-farming activities (such as dairy farming); or their soils are inappropriate for farming (too stony, rocky, or sandy, or grassy wetland).
In some countries, grasslands with agricultural potential can remain relatively unaffected for various reasons, such as inadequate access to markets or cultural history. This situation exists in South America and, to a lesser degree, in Australia, Texas, and the Transvaal of South Africa.
A typical surviving prairie ecosystem is found in the South American pampas. The pampas are net or undulating landscapes extending for about a million square kilometres between 28° and 40°S latitude and east of the 500-millimette isohyet. This isohyet (a line on a map joining points of similar precipitation) is the approximate boundary between the semi-arid and subhumid areas of temperate South America.
The Buenos Aires pampas are flat and largely used for farming, particularly in the more humid zones (with more than 750 millimetres of rainfall per year). East of the Parana River, the flatlands gradually become more undulating and, in Uruguay and Rio Grande do Sul, Brazil, undulating and flat areas are interspersed with hilly landscapes. It is in these areas that grasslands have remained less disturbed by farming.
It is important to note that the South American pampas are grasslands not because trees cannot grow, but because they cannot compete with the grasses. Human intervention can radically change this situation through the deliberate planting of trees, which are typically exotic but occasionally indigenous. However, artificial forests in the pampas remained a limited phenomenon until very recently.