Using beach she-oak (Casuarina equisitifolia) as an example (Fig. 2), it
was found that one obtains a sense of natural progress as one moves from
Level A to Level D. Modern scientific thinking has taken no notice of this.
It is often the practice, for example, when a lesser-known species has been
chosen for development to move immediately to Level D for environmental studies and to have little or nothing to do with the coarser levels available.
Whilst there are almost always good grounds for doing some work at Level
D, recognising Levels B and C as being useful complementary levels would
be likely to save much time and money.