Geoscience Reference
In-Depth Information
In general, European settlement in Queensland was associated with increased
soil erosion as cycles of pastoral and agricultural expansion were followed by
drought, leading to the degradation of large land areas (Powell, 1988). Land
degradation was exacerbated by forest clearance and by the construction of
large-scale irrigation schemes. It was also due to the fact that, once the most
suitable sugar cane lands had been cultivated, farmers increasingly resorted to
the use of sloping land. Overall, the years 1880-1935 were characterised by high
rates of soil erosion in the GBRCA. By 1939, soil erosion was acknowledged
to be severe in almost every cane-producing district of Queensland, not least
because of the cultivation of sloping land, but soil erosion was also exacerbated
by the destruction of riparian vegetation in sugar cane districts. The problem
of soil erosion from sugar cane lands remained severe before 1945, prior to the
introduction of conservation tillage and contour farming practices. Consequently,
substantial terrestrial runoff of sediment and nutrients to the nearshore waters of
the Great Barrier Reef occurred (Courtenay, 1978; Crossland et al., 1997; Griggs,
2005, 2006, 2007, 2011).
By 1939, other extensive alterations of the Queensland coastal environment
had occurred: examples include the depletion resulting from the European marine
fisheries of that period, including the commercial bĂȘche-de-mer , pearl-shell,
dugong and turtle fisheries; the transformation of some islands as a result of guano
and rock phosphate mining; the establishment of coconut palm plantations; and
the construction of tourist resorts. Some of those activities, such as the operation
of the turtle soup factories at North West and Heron Islands during the 1930s,
occurred intensively until localised depletion of the marine resources caused
production to cease, as described in the narrative that follows (Chapter 6). On
the adjacent coastal land, insecticides and pesticides (including DDT, atrazine
and diuron) were increasingly used, which in turn degraded water quality in the
Great Barrier Reef (Crossland et al., 1997; Keating et al., 1997). In addition, the
introduction of irrigation in the Queensland sugar cane industry, combined with
inadequate drainage of farmland, contributed to waterlogging, a decline in soil
fertility and enhanced nutrient and sediment runoff (Meyer, 1997). Therefore,
while the modern form of the Queensland economy was established during the
period 1860-1900, the subsequent period until 1940 involved more intensive
exploitation of both terrestrial and marine resources and, by that year, the impacts
of terrestrial activities on the Great Barrier Reef had become substantial.
After 1945, the Queensland coastal environment continued to experience
modifications as a result of many human activities. More extensive environmental
degradation occurred in coastal Queensland for several reasons: extensive
drainage of swamps to create land for sugar cane cultivation; the destruction of
wetland habitats; a substantial increase in soil erosion; and the continued growth
of coastal settlements (Griggs, 2007, 2011). The impacts of human activities on
the Great Barrier Reef have also been described by Lawrence et al. (2002); those
activities include the expansion of the tourist facilities on Green, Hayman and
Heron Islands, mangrove clearance to create urban and industrial land in the
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