As you yourself said, cats have been living across most of Africa, Asia and Europe for over a thousand years. So unless you are talking about Australia, the Americas, or a few corners of the old world, cats are either native or naturalised enough that they are now a part of the ecosystem.
It depends on the ecosystem. Pollution famously caused certain moths to shift from being mostly light-coloured to mostly dark-coloured in a matter of years. The removal and reintroduction of wolves in Yellowstone caused observable changes in prey behaviour within a decade or so. Of course longer-lived species like trees take much longer to adapt, but we’re talking about birds, geckos and rodents here.
Edit: Also, most geckos, birds and rodents are r-strategists, meaning they are limited more by food than by predation.
As you yourself said, cats have been living across most of Africa, Asia and Europe for over a thousand years. So unless you are talking about Australia, the Americas, or a few corners of the old world, cats are either native or naturalised enough that they are now a part of the ecosystem.
deleted by creator
It depends on the ecosystem. Pollution famously caused certain moths to shift from being mostly light-coloured to mostly dark-coloured in a matter of years. The removal and reintroduction of wolves in Yellowstone caused observable changes in prey behaviour within a decade or so. Of course longer-lived species like trees take much longer to adapt, but we’re talking about birds, geckos and rodents here.
Edit: Also, most geckos, birds and rodents are r-strategists, meaning they are limited more by food than by predation.
deleted by creator
Introduction of a new predator will disturb the ecosystem. Removal of an existing predator will also disturb the ecosystem.
The absolute brain-dead mentality of the people who will just downvote anything that doesn’t fit their predetermined conclusion.