Prior to human colonisation, it is thought that the New Zealand landmass was almost entirely covered in forest, apart from alpine areas. Between the beginning of Polynesian settlement in New Zealand around the fourteenth century and the beginning of organised European colonisation in the nineteenth century, it is estimated that forest cover was reduced by about half, largely through fire. When the European settlement of New Zealand began in earnest in the 1840s, it is estimated that forest, or ‘bush’ in the vernacular, covered about two thirds of the North Island and about 25 to 30 per cent of the South Island. In the decades that followed, bush was destroyed through milling and fire to make way for settlements and farms. By 1900, forest cover had been reduced by half again, to about 25 per cent.
Figure (below): Forest cover AD 1000, 1840, 2001 (Source: Kiwi Conservation Club)
envirohistory NZ 
While the above illustrations may display the loss of our original forest cover,what they do not show, is the regrowth of tree plantings in what once was bare pastureland.Or in pastureland now converted to urban use.And while initially, that urban sprawl may be bare of trees, there are millions of trees that have been planted in our urban environment, and lifestyle blocks.There is a continuing cycle of man deforesting large areas,cropping or grazing ,and then urbanisation.But then within those uses, there is massive new plantings of trees.Are we taking these into notice?Consider the mature areas of Waikanae?They are covered with trees.
Perhaps we could be viewing human intervention in NZ, as similar to elephants in Africa.Altering the environment,and creating a different balance between tree cover,grasslands and human use?