- Anchieta Island, just off the coast of Brazil near São Paulo, has seen the worst side of humans. Now, scientists and local authorities are laboring to restore its biodiversity.
- The island is located 800 meters (about 874 yards) from the municipality of Ubatuba, in one of the few regions of Brazil where the Atlantic Forest still thrives.
- Most of the island’s original forest was devastated over a long period of human habitation, and more recent attempts to introduce foreign mammal species have also had a significant ecological impact.
- Scientists are now studying the complex interactions at play during environmental restoration, including removing some invasive species, as they embark on an intensive reforestation program.
ANCHIETA ISLAND, Brazil – From a distance, Anchieta Island is a mosaic of different shades of green. The lighter ones correspond to areas where ferns and a handful of broad-range species reign. In the darker patches, shrubs and trees have taken the place of the ferns. This verdant patchwork is a picture of some of the different stages a degraded area goes through as it spontaneously restores its biodiversity. Biologists call this process “ecological succession,” and Anchieta has been experiencing it for several decades, since the island became a protected area and its devastated forests were left unbothered.
But lack of biodiversity is not the same as lack of life. Anchieta Island has the highest density of mammals in all the Atlantic Forest, the highly threatened biome that covers much of the Brazilian coast. The reason for this unusual concentration of large animals is that 35 years ago, 95 mammals from 14 different species were released onto the island to try to repopulate it.
“The animals that were introduced in the island all have high reproductive rates. There were too many of them in the zoo of São Paulo, which seems to be one of the reasons why they were released here,” says Mauro Galetti, an ecologist from São Paulo State University, who’s been studying the biodiversity of the island for more than 20 years.
The introduction of the animals was made without any scientific overview whatsoever. And while some of the species failed to adapt to their new habitat, others thrived. In the absence of predators and with food readily available, they increased in number exponentially. According to a census performed by Galetti and his team, in 2005 there were 486.77 mammal specimens per square kilometer. That’s about 16 times higher than on Bela Island, located 28 kilometers (17miles) from Anchieta.
Go on a short stroll in Anchieta and you’re likely to spot some relatively large animals, particularly blacked-tufted marmosets (Callithrix penicillata) and agoutis (genus Dasyprocta), which are the most abundant. Other introduced species, such as the nine-banded armadillo (Dasypus novemcinctus), the capybara (Hydrochaeris hydrochaeris) and the coati (Nasua nasua), are also present in high numbers. This draws tourists to the island, but it also represents an important setback to the regeneration process of the local ecosystem, as the foreign animals disturb local species, causing an ecological imbalance.
“We are using Anchieta Island as a living laboratory. We are learning how difficult it is to restore a degraded land,” Galetti says. “You can’t just plant the trees, put the animals and leave, you have to monitor them. And in many cases we don’t have enough biological information about who will eat who.”
When the boat docks at the small pier on Anchieta, the first thing visitors find is a white, rectangular building that used to be a high-security prison. Built in 1908, the prison was operational until 1955, when a bloody riot forced the authorities to shut it down. During those 47 years when hundreds of people lived on the island, the local biodiversity suffered immensely. A large part of the original forest was destroyed, which in turn caused a great decline in the number and diversity of animal species. The introduction of the non-native wildlife poses the latest disruption to the local ecosystem.
Take birds, for example. Although birds of different shapes and colors abound on the island, there are substantially fewer species than on the mainland. In particular, there is a shortage of birds that nest in tree holes and on the forest floor. Using artificial nests with quail eggs and camera traps, Galetti and his team have determined that these nests suffer a predation rate three times higher on the island than on the mainland, and that coatis, agoutis and opossums are to blame.
“Many of these birds spread seeds, so we have a domino effect where a few species affect the regeneration of the whole forest,” Galetti says.
However, the impact of the introduced species isn’t wholly negative. Some may even help in the regeneration process, provided their population levels are kept low.
“Agoutis, for example, are important seed spreaders. About 70 percent of all palm-tree species of the Atlantic Forest depend on them,” Galetti says. “They also help to keep under control foreign species such as the jackfruit [Artocarpus heterophyllus]. If you go to nearby places such as Ilha Grande, Ilha Bela or Tijuca, you will see that the jackfruits are taking over the forest, and this is not happening in Anchieta.”
This means that removing the agoutis from the island could help increase the diversity of birds, which in turn would help some tree species to multiply and spread. But at the same time, in the absence of agoutis, the jackfruits could invade new areas, hindering the spread of other plant species.
Restoring the forest
Since 1977, the whole of Anchieta Island has been protected in the form of a state park. There are no hotels or houses in the island, so the human impact has decreased significantly since the prison days. Accordingly, the vegetation is re-emerging.
“If you compare [aerial] images from today and 15 years ago, you will see that there has been an important regeneration,” says Priscila Saviolo, the park manager. “And in a short period I think we are going to advance even more in the restoration of these areas.”
The reason for her optimism is a reforestation program funded by Petrobras, the Brazilian state oil company, that will be rolled out in the next few months. The program is part of an environmental compensation scheme, a legal instrument that obliges companies that exert a significant impact on the environment to earmark part of the value of each undertaking for protected areas.
“The program will last four to five years. During that time we will have periods of planting, but we will also monitor everything to see how the plants respond and to replace some of them if necessary,” Saviolo says.
Monitoring will be critical, especially to see if the introduced animals are feeding on the seedlings. If so, it is also likely that some actions regarding the foreign species will be taken in the coming years. For now, Galetti’s team is finishing a new mammal census. Their preliminary data suggest that some of the species may have reached a population plateau.
“With those figures in hand we will start discussing what to do. Regarding the capybaras, that discussion is a bit more advanced and we are considering [sterilizing them],” Saviolo says. “In the long term they will stop existing in the island.”
One of the reasons for eradicating the capybaras is that they tend to carry ticks, which can potentially transmit Rocky Mountain spotted fever. According to Saviolo, the capybaras on Anchieta are tick-free.
Galetti shares the view that the island would be better off without these large rodents, which he says do more harm than good. He also says the marmosets should be removed, as there are too many of them and they have a high rate of nest predation.
Although restoring the original biodiversity of the island will take time, and the project will likely face difficulties, these steps seem to point in the right direction. There’s a deeper lesson, though, as Galetti puts it: “Destroying a piece of land is easy, but rebuilding nature is very complicated.”
Banner image: Flowers in Anchieta in Brazil. Photo by Ignacio Amigo/Mongabay.
Ignacio Amigo is a freelance journalist based in São Paulo, Brazil. You can find him on Twitter at @IgnacioAmigoH.
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