Like all science, invasion biology depends on clear and strict definitions. The concept of a native invasive species therefore sounds implausible, but is exactly what I have found on Fernando de Noronha. Without consistent definitions, scientists can talk at odds over one another, not realising they are talking about different things. Examples of important distinctions include the difference between introduced and invasive species, or between denial and disagreement over invasive species.
Ideas about native invasive species has been discussed differently elsewhere, but on Fernando de Noronha the existence of such native invasives comes about because nativeness is a geopolitical definition (e.g. a species found in Brazil is native to Brazil), but invasiveness comes from a damage threshold (i.e. an introduced species with overwhelming negative impacts). A number of species found on Fernando de Noronha are native to Brazil (i.e. found on continental Brazil) but have been introduced to Fernando de Noronha, and gone on to have overwhelming negative impacts. However, as Fernando de Noronha is politically Brazil, these species are still “native”.
The cats and rats abundant on Fernando de Noronha and causing damage are definitely non-native, introduced and invasive. However, other Brazilian species such as the teju and mocó, imported from continental Brazil, are potentially native invasives. As it turns out, the teju, also even CITES listed, is causing definitive widespread negative impacts across the ecosystem as an apex predator. However, due to the historical presence of a large native rodent the Vespucci’s rat, the ecosystem appears resilient to the impact of mocó. In this regard the mocó is perhaps better considered an ecological surrogate, albeit not the most appropriate one, and in no way a retrospective justification for its introduction.
Most recently we have also diagnosed the taxonomy of the cafifa ant introduced to Fernando de Noronha a generation ago. This ant rapidly spread through the national park and is now well known by the locals for its stinging behaviour. Benoit Guénard from The University of Hong Kong identified the culprit as the little fire ant (Wasmannia auropunctata), one of the worst invasive ants in the world. Ironically, the ant is also a native invasiveness, being found throughout South America. On Fernando de Noronha the status of these native invasives thus adds another dimension to their management.