What should the ecosystem actually be like?
It is hard to say exactly what the ecosystem should be like, but to maintain ecological integrity, the ecosystem should be characteristic of its natural region and it also should be likely to persist - that is, all the non-living components, the native plants and animals should still be in the ecosystem, and the rates of change and natural processes which are an important force in the ecosystem should continue to occur with little or no intervention by humans.
One of the benefits of having protected areas is that they can give us a reference point for determining what the whole ecosystem should be like. Cape Breton Highlands National Park has been protected for nearly 70 years and the land within it is slowly approaching what the whole ecosystem probably looked like before we changed it. So, we can use the park as a model when trying to decide what sorts of activities we can carry out without severely harming the ecosystem.
How do we know how much we've changed the ecosystem?
By comparing the land inside a protected area with the land outside of one, we can see how much our actions have changed an ecosystem. Because natural processes are allowed to go on with little interference by humans within it, Cape Breton Highlands National Park can also serve as a reference point for how much we have changed our ecosystem.
Can the ecosystem heal itself after we are finished in an area in which we have made changes?
Before Cape Breton Highlands National Park was protected, people did live in a number of the valleys inside the park. The farms that once existed in the park have mostly been reclaimed by the forest. The ecosystem does seem to be healing itself in these areas, but it takes a long time.
Sometimes, however, it is just not possible to reverse some of the changes we have made to the ecosystem. Caribou, which once lived here, don't anymore. When a reintroduction was carried out in the 1960s, all the animals died out within a few years. It seems likely that caribou are gone for good from our ecosystem. This is why it is so important for us to consider what sorts of effects might occur as a result of any changes we make to the ecosystem.