A study tried to determine the effect that losing apex bird species in a large-scale environment would have, and to do so turned its eyes on Guam.
There, brown snakes were introduced by trade years ago. On the small island, insectivorous birds were the apex predators until the snakes were introduced, and have been almost entirely wiped them out.
The study found that during the wet season, Guam’s spider web density was almost 40 times as high as nearby islands with healthy bird populations. During the dry season, that number dropped to 2.3 times as high.
Another example of how dangerous a relatively benign non-native species may be to an environment, and the top-down effects they can have on the food chain.