that person or the Minister, as the case may be, having regard to the desirability of preserving natural beauty, of conserving flora, fauna and geological or physiographic features of special interest, and of protecting buildings and other objects of architectural or historic interest, shall take into account any effect which the proposals would have on the natural beauty of the countryside or on any such flora, fauna, features, buildings or objects, and in so doing shall have particular regard to the desirability of ensuring that things constructed in the course of the execution of the proposed works are kept below ground so far as that is practicable.