Brazil holds about one-third of the world's remaining rainforests, including a majority of the Amazon rainforest. It is also overwhelmingly the most biodiverse country on Earth, with more than 56,000 described species of plants, 1,700 species of birds, 695 amphibians, 578 mammals, and 651 reptiles. Due to the vastness of the Amazon rainforest, Brazil's average loss of 3.46 million hectares of primary forest per year between 2000 and 2005 represents only about 0.8 percent of its forest cover. Nevertheless, deforestation in Brazil is one of the most important global environmental issues today. The bulk of Brazil's forest cover is found in the Amazon Basin, a mosaic of ecosystems and vegetation types including rainforests (the vast majority), seasonal forests, deciduous forests, flooded forests, and savannas. This region has experienced an exceptional extent of forest loss over the past two generations—an area almost certainly exceeding 6o million hectares, or about 15 percent of its total surface area of 400 million hectares has been cleared in the Amazon since 1970, when only 2.4 percent of the Amazon's forests had been lost. The increase in Amazon deforestation in the early 1970s coincided with the construction of the Trans-Amazonian Highway, which opened large forest areas to development by settlers and commercial interests. In more recent years, growing populations in the Amazon region, combined with increased viability of agricultural operations, have caused a further rise in deforestation rates. Since the close of the 1990s, deforestation rates of primary forest cover in Brazil have climbed by 35 percent.