A drought is a nasty thing to happen. A drought is an extended period of months or years when a region has a deficiency in its water supply.

Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region. Although droughts can persist for several years, even a short, intense drought can cause significant damage and harm the local economy. Without rain, a rain forest does not last too long.

For the second time this decade, drought grips the Amazon Basin. The lack of rain is drying up rivers like the Rio Negro, a main tributary of the mighty Amazon. The drought is primarily drying out the northwest region of Brazil, near the borders with Colombia and Peru. The same region suffered drought in 2005.

Periods of drought can have significant environmental, agricultural, economic and social consequences. The effect varies according to vulnerability.

For example, subsistence farmers are more likely to migrate during drought because they do not have alternative food sources. Areas with populations that depend on subsistence farming as a major food source are more vulnerable to drought triggered famine.

Recurring droughts leading to desertification in the Horn of Africa have created grave ecological catastrophes and food shortages. To the north-west of the Horn, the Darfur conflict in neighboring Sudan was fueled by decades of drought, desertification and overpopulation.

The Amazon Rain Forest is a moist broadleaf forest that covers most of the Amazon Basin of South America. This basin encompasses 1.7 billion acres, of which 1.4 billion acres are covered by the rain forest. This region includes territory belonging to nine nations. The majority of the forest is contained within Brazil, with 60% of the rain forest, followed by Peru with 13%; also with some are Colombia, Venezuela, Ecuador, Bolivia, Guyana, Suriname and French Guiana.

Last year the Rio Negro (a major Amazon tributary) hit a record high of 98 feet. Now it is at the lowest level since records began in 1902. The river dropped to a low of 45 feet on October 24, 2010.

Shrinking waterways are affecting everyone who depend on the Amazon River and its tributaries, from soy farmers on the Rio Madeira to indigenous fisherman. Many people have been stranded without river transport, since only the smallest boats can navigate the shriveled waterways.

In Brazil's Amazonas state, 62,000 people are affected by drought. Many are running out of food. Fish and other wildlife are dying as habitats disappear and the water warms up.

What might happen if the Amazon Rain Forest "failed" due to drought? The area might become a vast savanna or grass land or a desert. In either case millions will suffer not to mention the effect on the environment and biodiversity.