An old problem – that of invasive exotic animal and plant species – is beginning to be fought. On November, after almost two years of debate between specialists from government bodies, research institutions, non-governmental organizations and companies, the State Environment Council (Consema) of the State of São Paulo published a list containing 14 animal species that have invasive potential, like the wild boar, the European hare and the giant African land snail. On the same day the council authorized the formation of a working group, with representatives from government and civil society, to define ways of controlling the population of these animal species and to propose a list of invasive exotic plant species (by definition an invasive exotic species is found outside its area of natural distribution, has no predators and proliferates relatively easily to the point of compromising the survival of native species). It will probably not be easy to eliminate undesirable animals, nor approve a viable list of undesired plants.
One of the barriers to eliminating animals from the list is that the São Paulo Constitution prohibits hunting. This fact presents lawyers and public prosecutors with a challenge when it comes to complying with the law, without contravening other laws. Two javaporcos (the result of crossing wild pigs with domestic pigs), seized by court order, are being reared in a wild animal recovery center in the University of the Vale do Paraíba (Univap), in São José dos Campos. The plan of José Evaristo Merigo, administrator of the breeding center, was to have the animals slaughtered in an authorized municipal slaughterhouse and distribute the meat to needy communities, in accordance with the guidelines of Ibama, but the state prosecution office did not authorize it, since the animals are sub judice. “I can’t let the animals escape,” moans Merigo.
In a study from 2007 in the journal, Natureza & Conservação, André Deberdt and Scherezino Scherer, both from Ibama, recorded animals that had been released into the wild in nine states (Rio Grande do Sul, Santa Catarina, Paraná, São Paulo, Minas Gerais, Mato Grosso do Sul State, Mato Grosso, Goiás and Bahia) and that were destroying plantations and water sources and interbreeding with the domestic pig. The researchers observed that the animals fed on pine cones (Araucaria angustifolia), and even on buried seeds in Rio Grande do Sul, thus harming the regeneration of Parana pines. Hunting, which is permitted in some states, was not sufficient to eliminate the large pigs.
The working group is also likely to look for and propose adequate ways of controlling invasive species that are sometimes not very visible, like the invertebrates that continue gaining ground. Such is the case with two species of coral, now seen as invasive, which 30 years ago were limited to stretches of the coast of Rio de Janeiro. According to a study from January 2011 in Coral Reefs, they formed colonies along 130 kilometers of the coast in the direction of São Paulo.
Plants are another problem, because some that are called invasive are economically important, such as signal grass (Urochloa decumbens), which is widely used as pasture for cattle in Brazil. “No one would be incoherent enough to the point of proposing the elimination of signal grass,” says Cristina Azevedo, director of the department of biodiversity protection at the Department of the Environment (SMA) of the State of São Paulo.
Another mission of the working group will be to present native species that can substitute invasive exotic plants, like the white ginger lily, a plant that is native to Asia, which forms clumps in streams and damp areas and has a team of defenders because, by virtue of its intense scent, it is widely used at wakes. Cristina found out about this after a conversation she had with representatives of funeral homes, who sought her out to ask that this plant be removed from the list that the SMA was preparing.
“It’s up to us researchers to present alternatives; we have a lot of native species,” says Dalva Matos, a researcher at the Federal University of São Carlos (UFSCar). She has been following the construction and deconstruction of lists since the first debate, which was held in São Paulo on May 22, 2009, right after the United Nations Organization recognized invasive exotic species as a worldwide problem. It is calculated that 480,000 exotic species that have spread worldwide can cause annual losses of US$ 1.4 trillion, the equivalent of 5% of the global economy.
Cancer of the land
Carried in the intestines of birds and mammals and in the baggage of colonizers, invasive species are now a cause for concern. Avid for light, water and nutrients, they are uncontrolled in their occupation of free spaces or those taken by communities of native species. Like a cancer of the land, out of control, if there was ever a day they could have been controlled. Can they be now? Specialists believe they can, but richer and better organized countries, like the United States and England still struggle hard to rid themselves of these pests. Sometimes, the only solution for eradicating species that are harmful to the environment, and one that is entertained in the US, is to kill all the organisms in a lake or river that has been taken over by invasive species of fish and then restock the place with native species only.
In 1981, the government of the UK, an archipelago the size of the State of São Paulo, started a national campaign to eliminate the nutria, a rodent that is native to South America and now on the São Paulo list. The elimination of the animals (it is believed that the last one was killed in 1989) and recovery of the environment cost £ 3 billion (R$ 8 billion), but recently the English saw that snails, another exotic species, are out of control and destroying their precious gardens.
In Brazil, this problem began to be outlined just a few years ago. In 2006, a group from the Ministry of the Environment (MMA) recognized the existence of 543 invasive exotic organisms with the potential to alter the land or marine environment, agriculture and livestock farming, or human health in the country. Various counts have been undertaken. In a study from July 2011 in the Revista Brasileira de Botânica, Rafael Zenni and Sílvia Ziller, from the Hórus Institute, present 117 species, just of plants that are recognized as invasive and that are already established or with the potential of invasion in the country.
Various states, like Paraná, Santa Catarina, Espírito Santo, Minas Gerais and Pernambuco, have already approved their lists of unwelcome species and are putting pilot eradication projects into the field. The problem is that the seeds of grasses, like the South African lovegrass (Eragrostis plana), which covers 2 million hectares of degraded pastureland in Rio Grande do Sul, may remain in the soil for 24 years.
“We have to monitor the seed bank in the soil, not just the vegetation,” warns Dalva. She and her team from São Carlos found that in the cerrado a native fern, Pteridium arachnoideum, releases long roots, rhizomes, which liberate compounds capable of inhibiting the growth of other plants. One solution would be to turn over the soil and remove the maximum number of rhizomes, since the application of lime to the soil may not be fully efficient.
The São Paulo list of undesired beings was huge, but was reduced as the debates between representatives of government, companies and NGOs that go to make up Consema progressed. Of 42 species of animals, including the iguana, the sparrow, the domestic goat and the gecko, there were only 14 about which there was no doubt that they were exotic, invasive and recognizably harmful to the survival of other species or to agriculture.
The initial list, which is likely to be reassessed by the working group, contained 22 species of plants considered to be invasive. It included the assai, avocado, mango, guava, castor oil, eucalyptus, pine, jackfruit and chayote. None, furthermore, was voted for by the representatives of government bodies and civil society that go to make up Consema.
Just as the owners of flower shops had done with the white ginger lily, the agronomists came out in defense of the assai palm, brought to the Southeast region to produce palm hearts as an alternative to a native palm, juçara, which was threatened with extinction. The assai palm is native to the Amazon region and classified as an invasive exotic species in the Atlantic rainforest because it grows more quickly, produces more fruit and attracts more pollinators than the juçara.
There is no room for inflexible concepts. As a result of the next debates, perhaps species will be considered as having invasion potential depending on the environment in which they are found: the jackfruit, for example, may be harmful to other species when it spreads through the Atlantic rainforest, but is rarely harmful in other natural environments. Or they may be only unpopular when they spread to places where they are not welcome. Such is the case with the slash pines (Pinus elliottii) that occupied areas of the cerrado in up-state São Paulo, transforming them into dense areas of pines, with a visible loss of biodiversity.
Another problem that has begun to be debated is that of native species that are not invasive, but that should be controlled, in the assessment of the group from São Carlos. This is the case of the taquaruçu or giant bamboo (Guadua tagoara), a native of the Atlantic rainforest, but with invasive potential. This bamboo grows on trees and dies after flowering, breaking branches. According to Dalva, the seeds that germinate in areas close by may attract rats, which eat the bamboo seedlings and then spread them through plantations or nearby houses.
DEBERDT, A.J. and SCHERER, S.B. O javali asselvajado: ocorrência e manejo da espécie no Brasil. Natureza & Conservação. v. 5, n. 2, p. 31-44. Oct. 2007.
ZENNI, R.D. and ZILLER, S.R. An overview of invasive plants in Brazil. Revista Brasileira de Botânica. v. 34, n. 3, p. 431-46. Jul-Sep. 2011.