Geography of Brazil clearing. Public policies intended to promote sustainable management of timber extraction, as well as sustainable use of nontimber forest products (such as rubber, Brazil nuts, fruits, seeds, oils, and vines), were being discussed intensely in the mid-1990s. However, implementing the principles of sustainable development, without irreversible damage to the environment, proved to be more challenging than establishing international agreements about them. Although 90% of the country is within the tropical zone, the climate of Brazil varies considerably from the mostly tropical North (the equator traverses the mouth of the Amazon) to temperate zones below the Tropic of Capricorn (23°27' S
Tropic of Capricorn year (it was at exactly 23° 27′S in 1917 and will be at 23° 26'S in 2045). See under circles of latitude for information. There are approximately 13 hours, 35 minutes of daylight during the summer solstice. During the winter solstice, there are 10 hours, 41 minutes of daylight. In southern Africa, where rainfall is reliable, farming is possible, though yields are low even with fertilisers. In Australia, areas on the Tropic have some of the most variable rainfall in the world and thus even the wetter areas cannot be generally farmed, since irrigation sources invariably dry up in drought