Timber cruising involves selecting a representative sample from a stand of forest and noting the predominant species, their height and diameter, and average quality. While cruising, a forester will also think about issues which may come up during timber harvesting, like threats to the various animal species which might be nesting in the trees, the ease of access to the site, and the potential for erosion as trees are removed from the site. Once all of these factors have been accounted for, an accurate estimate of the total value of the timber can be made.