Invasive species

There are at least 358 species known to be invasive or alien species in South America. Brought by natural causes, accidents or human influence, they present a great threat for the South American native species and the ecosystems. It is therefore extremely hard to indicate some invasive species as being the most harmful ones. Based on five qualitative determinants, these may be considered the WORST INVASIVE SPECIES: 

Qualities:

• Ability to adapt easily
• High rate of reproduction
• Significant disruption of an ecosystem
• Capable of reducing the number of another species or replacing it
• Distribution and demographics in South America 

1. Aedes albopictus (Asian tiger mosquito), known best in Brazil as "mosquito da dengue": original to Northern Africa, transmits deadly diseases such a malaria and dengue.
2. Carcinus maenas (European green Crab): has significant impacts on epibenthic and infaunal species, such as bivalves, other mollusks, and crustaceans, through predation, competition, and burrowing activities
3. Cervus elaphus (European red deer): competes with the endangered species of deer for food, prevents regeneration of favored plant species 
4. Anoplolepis gracilipes (yellow crazy ant): devastates species, causing a rapid alteration of the ecosystem.
5. Acacia longifolia (tree): some impacts include reduction in native biodiversity, ecosystem change, changes in habitat and in hydrology and fire regimes