Biodiversity: the whole of living beings, animals and plants, that inhabit our Planet in their wide variety, as a result of long and complex evolutionary processes. Biological diversity (biodiversity) can be assessed at different levels, from individual variability to that of the ecosystem, denoted by Greek letters.
sub-alpha (sub-α): diversity at the level of individuals (genetic diversity)
alpha (α): diversity at the species level
beta (β): diversity in the habitats
gamma (γ): diversity in the ecosystems
The reference is the Convention on Biological Diversity of Rio de Janeiro in 1992, signed by 168 countries, including Italy. The text claims the ecological, genetic, social, economic, scientific, educational, cultural, recreational and aesthetic value of biodiversity, understood as genetic diversity, population diversity, and species and ecosystem diversity.
Ecosystem: a portion of territory bounded naturally and made up of animal and plant organisms (biocoenoses) that interact with one another and with the surrounding environment (water, light, air, climate).
Habitat: it is the place where an organism lives and it is therefore the place where the organism can be found.
Species: it is the basic unit of the classification of living organisms. There are many definitions of "species"; the most commonly used one is derived from a biological definition: "the term means all living organisms with similar characteristics that are able to mate and produce fertile offspring".
Autochthonous (or indigenous) species: in a given region, it is a species that originated and evolved in the territory where it lives or that immigrated by itself, and established stable populations that are self-sustaining.
Allochthonous (or exotic) species: iy is a species that does not belong to the native wildlife of a specific area, but that arrived there by an (intentional or accidental) action of man.
It is important to keep in mind not only that the species have evolved over millions of years, but that they have co-evolved, i.e they have adapted to each other in order to co-exist in a dynamic equilibrium within certain areas characterized by specific interactions between species. Introducing new species means to alter this balance in unexpected ways.
Introduction: the release in nature, by man, of a species from other geographical contexts, that had not evolved in the geographic context in which they were entered (allochthonous). This action can be voluntary (for example the introduction of species for hunting or fishing) or unintentional (e.g. occasional transport of insects with timber), but in any case it is an alteration of ecosystems.
Reintroduction: the release of a species, subspecies or genetic variation in a part of its range of natural occurrence as documented in historic times, where it had become extinct because of natural disasters or human activity. Unlike the introductions, reintroductions want to remedy the extinction caused by man himself with an intervention that is of considerable conservation importance.