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
Cycad grow in sand or even on rock, some in oxygen-poor, swampy, bog-like soils rich in organic material. Some are able to grow in full sun, some in full shade, and some in both. Some are salt tolerant (halophytes). Species diversity of the extant cycads peaks at 17˚ 15"N and 28˚ 12"S, with a minor peak at the equator. There is therefore not a latitudinal diversity gradient towards the equator but towards the Tropic of Cancer and the Tropic of Capricorn. However, the peak near the northern tropic is largely due to "Cycas" in Asia and "Zamia" in the New World,