Absence of native species
Native species are any species that occur naturally in a local ecosystem. They have been present within the local ecosystem for many years and originally arrived by normal processes of dispersal and colonization.
Since everything in an ecosystem has evolved to be dependent on everything else in it, loss of any native species results in an overall weakening of the ecosystem, making it less resilient to change .
The American Beech is a tree that is native to Cape Breton. Currently, beech trees in northern Cape Breton are being affected by a disease which eventually will kill many of them. Beech trees are an extremely important source of food for many kinds of animals which feed on the beech nuts. If most of our beech trees die because of beech bark disease, then there will be fewer beech nuts for animals to eat, and thus fewer of those animals.