AERIAL ASSESSMENT OF DIEBACK OF
NORFOLK ISLAND PINE (ARAUCARIA
HETEROPHYLEA) IN ITS NATURAL
ENVIRONMENT
M.L. Benson and B.J. Myers
Division of Forest Research, CSIRO
Canberra, A.C.T. Australia
SUMMARY
Norfolk Island pine, Araucaria heterophylla, is a species of con-
siderable interest in horticultural and wood production plantings through-
out the world and has been grown successfully on a wide range of soil
types in a variety of temperate and sub-tropical maritime climates. The
species is extremely tolerant to salt and wind but has been reported to
suffer badly in a polluted atmosphere where its salt tolerance mechanism
has been adversely affected by detergents in the aerosol.
Concern has been expressed in recent years over the number of Norfolk
Island pines showing crown deterioration and ultimate death in its natural
environment - an isolated small island in the South Pacific Ocean of great
conservation and tourist value. An investigation of the problem was aided
by large-scale colour aerial photography taken for a detailed vegetation
survey and by supplementary oblique colour photography taken some 6 years
later. The occurrence of the damage was mapped and more than 25% of the
island showed at least some signs of deterioration with half of this area
being severely affected.
Through correlation with the history of land use and development
activities, coupled with site investigation and soil sampling, the problem
was identified as the result of severe ecological disturbance. Causes
advanced were overgrazing, nutrient depletion on colonised farmland, and
severe competition from imported grasses and shrubs.
The worst affected areas were those having the longest association
with human habitation.
Keywords : Colour aerial photography, ecological damage, dieback