Australia Yearbook - 2001

602 Year Book Australia 2001
The Australian landscape has undergone
significant change since European settlement. For
example, in 1788 forests covered around 252
million hectares, but by 1997 this had diminished
to around 156 million hectares, a 38% reduction
in 209 years. The growth of agriculture, which has
been a feature of the growth and prosperity of
the Australian nation, has been a key reason for
tree clearing. By 1980 Victoria, New South Wales
and South Australia had cleared half of their
native forests (table 14.33). Clearing has occurred
in all State and Territories since 1980, with
Queensland clearing the greatest area between
1980 and 1997 (Glanzig 1995; Barson 1999).
However, the percentage of forests cleared in
Queensland (39%) is lower than in all other States
and Territories except the Northern Territory
(effectively zero) and Western Australia (25%).
The clearing of native vegetation, whether for
agriculture or forestry, has been a significant
environmental issue for more than a decade,
because the loss of trees can lead to declines in
the abundance of wildlife and increased levels of
land degradation.
14.33 ESTIMATED CHANGE IN FOREST
COVER(a)—1788 to 1980
1788 1980 1997
Difference
1788–1997
State/
Territory mill. ha. mill. ha. mill. ha.
%
ACT 236 124 120 –0.49
NSW 54 710 22 910 20 787 –0.62
NT 27 565 27 474 35 385 +0.28
Qld 80 609 55 963 49 056 –0.39
SA 18 417 9 058 5 499 –0.70
Tas. 5 604 3 871 2 904 0.48
Vic. 18 513 7 538 7 285 –0.61
WA 46 346 32 934 34 800 –0.25
Aust. 252 000 159 872 155 835 –0.38
(a) The total area of native forest differs from other
estimates given in Year Book Australia 2001 due to
differences in the definition of forest and improved data
sources.
Source: Australia’s State of the Forest Report, 1998.
Land degradation
Salinity
Land degradation is a significant concern of
Australian farmers, governments and the general
public. In 1999 around 20% of farms experienced
some form of land degradation, 16% reported
productivity declines and 10% removed land from
agricultural production (Kemp and Alexander
2000). Estimates of the cost of land degradation
vary. One estimate put the cost at 6% of the value
of agricultural production or $1.5b per annum
(Gretton and Salma 1996). Another study
estimated the cost of three types of land
degradation—salinity, acidity and sodicity—to be
$2.4b per annum (CRCSLM 1999). The variation
in the estimates reflects the difficulties and
different approaches used in valuing the damage,
which includes the cost of lost production as well
as the damage to public and private
infrastructure. For example, saline (salty) water
can cause damage to water pipes, hot water
systems, rainwater tanks, roads, municipal water
treatment plants, dams, and sewers (Wilson
2000). Estimates of the cost of salinity to Australia
are in the range $250–330m per annum (MDMC
1999; CRCSLM 1999).
Salinity is related to the loss of trees as well as the
increasing use of irrigation for crops and
pastures. This gives rise to two types of salinity:
irrigation salinity and dryland salinity. Both types
occur when water tables rise, bringing salts
normally stored well below ground to near the
soil surface. In the case of irrigation salinity, water
is applied in greater amounts than is used by
crops. The excess water feeds into the water table
and may cause it to rise. Dryland salinity occurs
outside of irrigated areas. It can occur naturally,
but is also caused when trees and other deep
rooted native vegetation are removed and
replaced with annual shallow rooted agricultural
crops. The shallow rooted crops do not use as
much rainwater as native vegetation and hence
more water reaches the water table, causing it to
creep nearer to the soil surface.
Around 2.5 million hectares of land are currently
affected by salinity, which could in time rise to
over 15 million hectares (PMSEIC 1999). At
present around three-quarters of the salt affected
land is in Western Australia, but the State with the
greatest potential problem is New South Wales
with 7.5 million hectares at risk (table 14.34). The
National Land and Water Resources Audit has
produced a map of ground water flows which can
be used to assess the risk of areas becoming
saline (see http://www.nlwr.gov.au).
Salinity can be prevented and reversed in many
cases. Appropriate measures depend on local
circumstances, but could include reducing the
amount of water used in irrigation, growing
alternative, more deeply rooted crops, planting
salt tolerant trees (Bell 1999), pumping water and
building drains or other engineered works.