The hemlock wooly adelgid is an invasive insect species that is destroying native hemlock trees in New York State. These insects can upset natural ecosystems because the

disrupt habitats that native species depend  upon

Explanation:

(1) provide food for native bird species

  (2) can carry diseases that can be spread to pets

  (3) increase biodiversity in New York State forests

  (4) disrupt habitats that native species depend

      upon

The insects have the potential to cause an upset in the natural ecosystem because their destruction of native hemlock trees leads to the automatic destruction of the habitats of several native species.

Trees generally function to provide habitats for many plant and animal species. Their destructions mean that these habitats would be destroyed and the species they harbor would become displaced. Displacement of species from their natural habitat can cause an upset to the ecosystem.