The interaction of native and adventive plant species in New Zealand

[First paragraphs...]
The probable and actual results of the interaction of native and adventive plant species in New Zealand have been and still are topics of considerable interest and discussion, and over the last one hundred and twenty years such eminent authorities as J. D. Hooker, W. T. L. Travers, Chas. Darwin, A. W. Wallace, T. Kirk, T. F. Cheeseman, G. M. Thomson, L. Cockayne, H. H. Allan and C. M. Smith have all contributed papers on different aspects of the subject.
In brief review, it can be stated that neither Hooker's original thesis that many small local genera would ultimately disappear owing to the usurping tendencies of the Northern Hemisphere adventives, nor the later prophecies which forecast large-scale displacement of the native vegetation by "all-conquering" adventives, was fulfilled; the true position has been clearly described by the last four authorities cited above. The marked diminution in total area of native vegetation and abundance of some native species was due, not to inherent superiority of the adventive species, but to actual physical destruction of, or modification of, the primitive vegetation by man and his associated agents—fire, cultivation, oversowing and grazing animals.
Allan (1931) pointed out that we have in New Zealand two floras and two vegetations, while C. M. Smith (1957) very pertinently stated that". . . the local botanist is now witnessing the phase of modification of the initial pioneer communities of adventive plants, and the initiation of the much more advanced phase of communities composed of an amalgam of indigenous and adventiveelements"; both writers made a plea for intensive study of the second vegetation as well as the second flora.