Explore Rio de Janeiro Rio de Janeiro state Share When the Portuguese arrived, the area that is now the city of Rio was covered by dense green tropical forest. As the city grew, the trees were felled and the timber used in construction or for charcoal. However, if you look up from the streets of Zona Sul today, the mountains running southwest from the Corcovado are still covered with exuberant forest, the periphery of the Parque Nacional da Tijuca, which covers an area of approximately 120 square kilometres. In the seventeenth century, the forests of Tijuca were cut down for their valuable hardwood and the trees replaced by sugar cane and, later, coffee plantations and small-scale agriculture. In the early nineteenth century, the city authorities became alarmed by a shortage of pure water and by landslides from the Tijuca slopes, and in 1857, a reafforestation project was initiated: by 1870, over 100,000 trees had been planted and the forest was reborn. Most of the seeds and cuttings that were planted were native to the region, and today the park serves as a remarkable example of the potential for the regeneration of the Mata Atlântica. Following on from the success of the forest, fauna have gradually been reintroduced to the extent that it is once again the home of insects and reptiles, ocelots, howler monkeys, agoutis, three-toed sloths and other animals. Most successful of all has been the return of birdlife, making Tijuca a paradise for birdwatchers. At the same time, however, overstretched park rangers have been struggling to keep residents of the eight neighbouring favelas from hunting wildlife for food or for trade.