Following the destruction of the forest caused by colonial plantations, a determined rewilding initiative is now striving to guarantee the preservation of Rio de Janeiro's historic rainforest.

Suddenly, I find myself suffocating from the toxic gases in the vicinity of a cement bridge. Within a few minutes, my body is drenched in perspiration, covered in the moist exhalations of the surrounding forest. Now, that's not a sensation experienced in every metropolis, particularly one with a population over six million. Many are unaware that Rio de Janeiro is home to the Tijuca forest, which happens to be the biggest urban forest in the world, despite its reputation for beaches, football, and Carnival. Tijuca is an atypical woodland. Tijuca forest, which was originally protected in 1861, predates the establishment of the first national park in the United States by a decade. It spans an area of 40 square kilometers and is part of the Atlantic Forest, a once extensive ecosystem that encompassed 1,000,000 square kilometers of the Brazilian coastline. Currently, only around 15% of the Atlantic Forest exists, having been severely reduced by the establishment of sugarcane and coffee plantations, as well as the logging activities carried out by the European colonists who arrived in Brazil during the 16th Century.

The depletion of the Atlantic Forest in Rio de Janeiro over the course of the following two centuries posed a significant threat to the survival of the emerging metropolis. The rivers that provided water to the city have been depleted, and a drought is now inevitable. Emperor Peter II of the nineteenth century proposed a solution: reintroduce the forest. In the 1860s, those living on forested property, including both farmers and city people, were forcibly dispossessed, while enslaved Africans were compelled to cultivate over 100,000 trees. Nevertheless, they failed to reintroduce a significant number of the animal species that once flourished in the forest.

In 1967, the Tijuca forest was designated as a national park, consisting of three separate sections: Tijuca Forest to the west of the city center, Carioca where the iconic Cristo Redentor monument is situated, and Pedra Bonita and Gávea mountains which provide scenic views of the coastline. Tijuca National Park has since emerged as the most frequented destination in the country, attracting over 3.5 million tourists on an annual basis. «Imagine, if you will, Rio without its lush forest, only the rugged mountains and the vast seas. Rio would cease to be the magnificent city it is», expressed Fernando Fernandez, an esteemed professor of ecology at the Federal University of Rio de Janeiro and a co-founder of the conservation organization Project Refauna.

However, the Tijuca forest serves a vital role beyond its aesthetic appeal. It plays a crucial role in regulating temperatures and providing a supply of freshwater for Brazil's second-largest city. As to Fernandez's assessment, the forest is deemed to be in an unhealthy state. When traversing Tijuca National Park, the vegetation seems to be flourishing. The trails that lead to over 30 waterfalls and ascend prominent mountains such as Pedra da Gávea and Pedra Bonita showcase abundant vegetation with hanging vines, large jackfruit scattered on the ground, and adorable capuchin monkeys dissecting bananas.
The lack of seed-dispersing animals in Tijuca's forest is hindering the proliferation of its towering trees. «The presence of animals is essential for the existence of trees», - said Catharina Kreischer, a researcher affiliated with Project Refauna. Kreischer noted that trees produce vibrant and delectable fruit to entice hungry animals, who then consume the seeds and excrete them in other areas, so dispersing the plant species across the forest. However, several seed-dispersing animals vanished from this specific area of the forest after it was removed and have not reappeared since. Project Refauna aims to reintroduce fauna to Tijuca, recognizing that a forest encompasses not only trees but also animal life.

In 2009, Project Refauna successfully restored red-rumped agoutis, a feline-sized rodent species that had previously been driven to extinction in Tijuca Forest due to hunting activities. However, these agoutis were still found in other areas of the city. Upon my return fifteen years later, I saw the discernible influence of the project. Upon disembarking from the 301 bus at Praça Afonso Viseu, situated exactly at one of the primary gates to the park, Kreischer and I proceeded to enter the park (admission is free). We then stopped beside the main road to retrieve a brown, apple-sized arara nut under a colossal tree. «When I began working at Refauna, I noticed a significant increase in the number of seeds, particularly on the main road. However, the current situation is quite different», -said Kresicher, as she pulled up her pant leg to reveal an agouti tattoo on her ankle. «Currently, my observations in the forest reveal a significant decrease in the number of fruits and seeds undergoing decomposition on the ground» This is a positive indicator that the agoutis are successfully establishing their presence and carrying out their intended function.

We proceeded down dirt paths and passed the cascading Cascatinha Taunay waterfall until we arrived to Titan, an enormous yellow-footed tortoise that was brought to the park in 2020 as part of Project Refauna. As I neared his enclosure to get a photograph, Titan's eyes bore a fierce and menacing expression, causing my pulse to race with an intensity I hesitate to acknowledge for a seemingly lethargic danger. Due to Titan's aggressive disposition, he had to be isolated from other tortoises, resulting in the termination of his lineage. However, this was not the only unfortunate development.