Biodiversity threatened by alien species today

The problem of exotic or alien species is very broad and complex, touching strings that go beyond biology and ecology. But it is the laws of biology and ecology that must guide us in reading this phenomenon.

There are some major differences between the Gardens of Babylon and the invasion processes we have been witnessing in recent decades.

The introduction of species from one continent to another has always existed. Just think of our oldest Italian botanical gardens whose directors travelled the world in search of 'strange' species to cultivate and show; or the orchid or succulent plant collectors willing to pay astronomical amounts of money to own a certain species (often leading to their extinction in their country of origin!).

What has changed profoundly is the scale of the phenomenon, which has grown with the growth of trade between countries, leading to an exponential increase especially in involuntary, uncontrolled introductions. In its century-long history, the Botanical Garden of Padua has introduced perhaps twenty species from other continents. There are currently more than 3,000 alien species in Italy, an increase of 96% over the last 30 years.

The other aspect, profoundly and dramatically changed, is the state of our ecosystems, impoverished and damaged to the limit of survival, by unprecedented anthropic land use. Our natural and semi-natural habitats are often fragmented and reduced to small clusters in a modified landscape that puts great pressure on habitats and their native species.

Many of the species that are introduced do not survive, but others successfully establish themselves in the area where they are introduced, and spread too rapidly, causing serious damage to the original species and ecosystems. These species are referred to as invasive alien species. From an ecological point of view, the arrival of a new species, which has a different evolutionary history from the native species, is potentially a disruptive process for an ecosystem, which can upset all its internal balances. Especially if this occurs in already damaged ecosystems. It has often been shown that the arrival of an alien species leads to the disappearance (extinction) of native species, which in turn leads to a different (often worse) functioning of the ecosystem and the loss of services that a healthy, functioning ecosystem is able to provide.

The phenomenon of alien species introductions represents one of the greatest global threats to biodiversity, with an increasingly significant economic and social impact: in the European Union alone, it is estimated that the impacts caused by these species result in losses of over €12 billion.

It is therefore a phenomenon that must be seen in its entirety and complexity and certainly cannot be assimilated with other migratory processes that involve spheres that are not the domain of biology and ecology.