Studies revealed not only the extent of damage to cropfields and woodlots but browsing by deer as the cause of the damage. A comparison of the current condition of the crop fields and woodlots with the quantified desired condition showed that browsing by deer exceeded the acceptable damage. The park completed an environmental impact statement to determine the best control of deer browsing in that park. Deer are not managed in all parks where their densities are high either because specific goals have not been identified and objectives of natural-resource management have not been quantified or because the parks lack scientific data on environmental conditions that suggest deer as the principal cause for not achieving those objectives. In Valley Forge National Historical Park deer are not managed because deer numbers and densities are not preventing the park from meeting the goals and objectives and purposes for which the park was established.
Some people believe heavy browsing causes irrevocable change to ecosystems.
They feel that parks should prevent deer browsing even when compliance with mandates of parks are not impeded. Indeed, prolonged, intensive browsing by deer can reduce the number of plant species and cause plant species that deer do not eat to become the dominant vegetative species. Other wildlife that use such vegetation can thereby be deprived or favored. Astute determination of compliance or failure of compliance with mandates is therefore crucial to management of natural and cultural resources in a park. Conflicts between deer and humans are of concern to state and other federal agencies and private communities.