Past Climatic Fluctuations and Their Influence Upon Australian Vegetation

Abstract

The developmental history of the flora of Australia is very poorly understood. The marked botanical discountinuity with neighbouring regions like New Zealand and New Guinea gives the Australian flora a certain uniqueness. This uniqueness, however, is at the same time contradicted by the close affinities of certain elements with the floras of both nearby and distant land masses. As a result the history of the Australian flora and its relationship to that of other regions has long been a subject of much interest and speculation. In addition to plant geographical relationships, there is the equally fascinating topic of the mechanism and causes of the changes which have taken place in the evolution of the Australian flora and vegetation. Since the early Tertiary there has been a remarkable change in the distribution of plants in Australia. The direction of this change, in the broad sense, must have been largely due to climatic causes because there has been only minor orogeny since the beginning of the Tertiary and this has been almost confined to simple vertical uplifts. These changes in climate and their influence upon the vegetation have not been sufficiently elucidated yet to make anything but an interim appraisal of the present state of knowledge and ideas possible here.