One way of protecting the past without interfering with its use in the present is through recording. Text, illustration by hand and photography can be used together to create a near-complete record of a site or building which can then be preserved.
Recording is very important because in archaeology, and especially in archaeology in advance of development, there will not be a chance to go back to the site or building and look at it again. We cannot reproduce everything, but we have a duty to record as much as we can so that others can examine the evidence for themselves.
Recording is an essential part of excavation, but it can also be an end in itself. Excavation destroys sites as surely as development, and is invariably expensive and time consuming, so in some cases recording alone may be preferable.