Indicators of ancient woodland – the use of vascular plants in evaluating ancient woods for nature conservation
It is a useful rule of thumb that the older the habitat, the more species it will support. And the more species it supports, the greater, in general terms, will be the site's importance for nature conservation. Hence, in theory, it should be possible to use the number of species present as an indication of habitat quality. In practice, however, there are drawbacks. It is exceedingly difficult to find out how many species of, say, insects or fungi are present, and even small sites would require many years to survey adequately.