There is evidence that tree-thickening is a widespread
phenomenon on uncleared native pastures, not just restricted to the
region, but across Northern Australia. In contrast to clearing,
thickening occurs in remnant woodland vegetation, mainly through a
change in fire regimes (i.e. reduced frequency of fires, allowing
saplings to grow out of the fire sensitive phase). Thickening also
occurs where regrowth of pulled country is not managed, or when the
fire regime is inappropriate to retain the structure of open
woodlands (
McCullough 2004 ).
Effects on biodiversity in this case are more related to the
loss or change in ground layer species as a result of denser tree
canopies. The major effects of the impact of treethickening on
biodiversity include:
- changes in species and in biodiversity composition and
ecosystem function;
- loss of aesthetic and amenity values (
Roth et al. 2002 ).