Pest exclusion fences are not new. In Australia there are fences to exclude rabbits and dingoes. Both animals, one a recent arrival from European the other came over with Aborigines 4,000 years ago, threatened agricultural activities on the continent. Fences were constructed to protect the industry and meet mostly with success. The fences allowed cultural reformation of the landscape. The reserve is true in New Zealand were fences were put up to prevent European animals and people from changing the landscape.
The term “pest” is explicitly relative. Some invasive species like wild horses in America are allowed to roam freely and efforts exist to protect their access to water and fields against the wishes of ranches. All that matters in the issue of “preservation” is keeping the environment that way humans want it; not the “original” condition.