Agriculture Reference
In-Depth Information
1
I NTRODUCTION
INTRODUCTION
The tropics, with its warm climate and little temperature variation, occupies
approximately 40% of the earth's land surface. The region also has half the
world's population. The majority of the world's biodiversity is also found in
the tropics, biodiversity being the total of all living organisms on earth. These
endemic animals and plants are adapted to the diverse tropical environments,
which range from wet tropical rainforests to deserts and snow-covered, high
mountains.
The tropics can be divided into three major zones. The zone most
recognized is that with year-round rainfall and lies on the equator (Amazon,
Central America, Central Africa, Indonesia, New Guinea) and is ~8% of
the world's land surface. As one moves away from the equator, the rainfall
becomes more seasonal, and this zone occupies 16% of the land area (Central
America, north and south Amazon, West Africa, India, South-east Asia,
northern Australia). The last is the dry tropics, which makes up 16% of the
land area and ranges from deserts to large areas with long dry seasons of 9
months or more. Examples would be the Sahara, Bolivian El Chaco lowlands,
central India and northern central Australia.
About half of the plant families are tropical, and the tropical region
contains 15 of the 25 world biodiversity 'hot spots' (Crane and Lidgard, 1989;
Meyer et al. , 2000). The 'hot spots' are regarded as centres for agricultural
origins, and it is thought that crop domestication took place in or near these
'hot spots'. This domestication refl ects the role of hunter-gatherers and early
farmers, and their dependence on these crops for their daily subsistence. The
abundance of species with dif erent life cycles, adaptations and useful products
in these 'hot spots' would facilitate their selection by hunter-gatherers and
early farmers. Examples of these centres include half of the southern part
of Mexico and the northern half of Central America, Ecuador, western and
central Brazil, the Indo-Burma region, South-east Asia, the Indonesian and
Philippine archipelagos, the East Melanesian Islands and Pacifi c Micronesia.
 
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