What is the impact of invasive species?

Encyclopedia of Opinion

Question: What is the impact of invasive species?
Position1 of 3›: Invasive species harm native animals
Argument1 of 3›: Invasive species eat native animals

Invasive species eat native animals. Without native species, the ecosystem they reside in will suffer.

The argument

Predation by introduced species is direct, and the Everglades in Florida shows it at scale. The system now holds anacondas, pythons, iguanas and wild boars, none of them native to it, and they eat the animals that are — crocodiles among them, along with smaller mammals throughout the food web. These are not marginal additions to an existing set of predators; they are additional mouths in a system that made no provision for them. The reason the damage is so one-sided is that the relationship is new. A native prey animal lives alongside native predators, and the two have developed together: the prey has the alarm responses, the hiding behaviour, the breeding rate and the physical defences that match the specific threats around it. None of that applies to a predator that was not present while those traits were forming. The prey does not recognise it, does not respond appropriately, and has no defence shaped against the way it hunts. Confronted with a predator that is not a natural one, native animals do not stand a chance of defending themselves. The consequence is a rate of loss that native predators never imposed. A natural predator-prey relationship settles into a balance, because a predator that takes too many prey animals undermines its own food supply and its numbers fall in turn. An introduced predator feeding on defenceless prey meets no such check early on, and the prey population can be driven down far faster than it can reproduce. This is why harm to native animals is counted among the central impacts of invasive species. The mechanism needs no indirect chain through habitat or competition: the introduced animals eat the native ones, the native ones cannot stop them, and populations that were stable before the introduction are consumed.

Premises

[P1]Invasive animals like the pythons and wild boars in the Florida Everglades eat native wildlife such as crocodiles and small mammals. [P2] Because they are not natural predators there, native animals cannot defend themselves against them. [C] Therefore, because invasive species eat native animals, invasive species harm native animals.

Counter-arguments

Invasive species can get rid of pests. The Harlequin Ladybird was introduced to Europe and North America to control aphids which killed crops. Invasive species benefit ecological systems, not harm them.

Rejecting the premises

[Rejecting P1] Not all invasive species eat native wildlife. [Rejecting P2] Native animal species can adapt to changes.