They can devastate ecosystems, annihilate native species and cause substantial losses to the economy. Aníbal Pauchard, a scientist from Chile has recently said that «invasive species are increasing in the Americas and particularly in South America. In addition, human activity on the South American continent is increasing, with new roads, crop areas and cities which makes the continent more prone to these invasions», explained the expert, who is currently one of three co-directors of the global report on invasive species of IPBES, a UN-dependent agency. «Without a doubt, climate change will further weaken the ability of native species to be able to withstand the entry and impact of these invasive species», he added.
When is a species considered invasive?
«Invasive species are exotic species, that is to say from other regions or continents, that the human being has introduced into the environment, and that they reproduce in large numbers generating impact for biodiversity, ecosystems and human well-being», explained the Chilean expert. Pauchard selected some examples of invasive and harmful exotic species that are emblematic in Latin America.
Beaver (Castor Canadensis)
It was introduced in southern Argentina and Chile and occupies «Tierra del Fuego», generating dikes that destroy native forests. The first 20 beavers were introduced by the Argentine Navy with the idea that local people began a fur trade. But in the absence of natural predators – such as bears and coyotes – these semi-aquatic rodents have reproduced rapidly and it is estimated that their population exceeds 100,000 individuals. The beaver gnaws the trees until they are knocked down and logs them to build their burrow. While trees in North America can grow again after being affected by these rodents, those in South America die after being gnawed by these animals.
Invasive leguminous trees and shrubs
Pauchard cites as an example the «mimosa» (Acacia dealbata), the spiny broom (Ulex europaeus) and the «marabou» (Dichrostachys cinerea). «In South America there are many species of plants that were introduced as ornamental, forestry or to control erosion. Some of them grow out of control by competing with native species, causing economic damage and increasing the frequency of fires», said the expert.
Mimosa, for example, a plant native to Australia, was introduced as an ornamental plant for gardens for its yellow flowers. But the tree is a great survivor. It grows rapidly, adapts to any type of soil and secretes a substance that hinders the growth of other plants in its vicinity, so that native species fails to compete. The spiny broom, originally from Europe, also competes with native species for nutrients, in addition to forming dense thickets difficult to eradicate and spread fires because they are very flammable due to their resins.
In this group are the golden mussel (Limnoperna fortune), the African snail (Achatina fulica) and the sea venomous snail (Rapana venosa). «Land and marine mollusks have been introduced with multiple impacts, from the transmission of diseases due to the African snail, to the destruction of infrastructure such as the golden mussel. This occurs throughout South America», said Pauchard.
In the case of the golden mussel, it is believed that this species native to China arrived in South America through the ballast water of transoceanic vessels. Ballast water is the water loaded in the port of origin that a ship transports when it travels with empty holds so they don’t turn over at sea. When they arrive at their destination port, the ships discharge the water releasing the mussels. The giant African snail carries various parasites in its tissues and slime secretions. In contact with people, parasites can cause various conditions such as eosinophilic meningoencephalitis.
These mollusks occlude pipes and water intakes for human consumption, as well as irrigation canals and sockets in power plant generators.
With Information from: https://www.bbc.com