12.1.3. Socioeconomic Trends
The region's population is growing at a rate of about 1.2% yr-1,
approximately equally from natural increase and immigration. The population
is progressively aging, in line with other OECD countries. Health status is
improving, but indigenous peoples lag significantly. The main population centers
are growing faster than rural areas. Australian lower latitude coastal zones
are developing two to three times faster than the Australian average (see Section
12.6.4), for urban/suburban uses and for recreation and tourism. In New
Zealand, there is a steady internal migration northward to Auckland.
Agricultural commodity prices have tended to fall, but yields per hectare have
risen, and farm sizes and total volume of production have increased (ABARE,
1997; Wilson and Johnson, 1997). Average return on agricultural assets is low.
Service industries are an increasing fraction of all industry, and there is
a trend toward more intensive agriculture and forestry and to diversification
of rural land use, including specialty crops and tourism. There is increasing
competition for water in areas of low rainfall where irrigation is essential
to intensive cropping; urban demands are rising quickly, and water is needed
to maintain natural ecosystems (Hassall and Associates, et al., 1998).
Tourism is a major growth industry that is increasing the pressure on areas
of attractions such as coastal zones and reefs.
Environmental concerns include air and water pollution from urban industries,
land transport, and intensive farming and related processing and soil erosion,
rising water tables, and salinization. Environmental management increasingly
is based on the principle of sustainable management, as enshrined in New Zealand's
Resource Management Act, and an integrated approach to environmental impacts
in both countries. A major trend to a "user pays" principle and, especially
in Australia, to market-driven water rights, with caps on irrigation supplies,
is causing significant changes in rural industry. However, there still are many
instances, particularly in coastal management, where these principles are not
12.1.4. Climate Trends
Trends identified in the region continue to be generally consistent with those
elsewhere in the world. Research on regional trends has been summarized in Salinger
et al. (1996) and in specific studies by Plummer (1996), Torok and Nicholls
(1996), Holbrook and Bindoff (1997, 2000), Lavery et al. (1997), Plummer
et al. (1997), Zheng et al. (1997), McKeon et al. (1998), Collins and Della-Marta
(1999), Hennessy et al. (1999), and Plummer et al. (1999).
Mean temperatures have risen by 0.05-0.1ºC per decade over the past
century, with a commensurate increase in the frequency of very warm days and
a decrease in the frequency of frosts and very cold days (Plummer et al., 1999;
Collins et al., 2000). Nighttime temperatures have risen faster than daytime
temperatures; hence, the diurnal temperature range has decreased noticeably
in most places. The past decade has seen the highest recorded mean annual temperatures.
Trends in rainfall are less clear. Australian annual mean rainfall has increased
by a marginally significant amount over the past century (Collins and Della-Marta,
1999; Hennessy et al., 1999). However, increases in the frequency of heavy rainfalls
and average rainfall are significant in many parts of Australia. Average rainfall
has increased most in the northwest and southeast quadrants (Collins and Della-Marta,
1999). The largest and most statistically significant change has been a decline
in rainfall in the winter-rainfall-dominated region of the far southwest of
western Australia, where in the period 1910-1995, winter (June-July-August,
JJA) rainfall declined by 25%, mainly during the 1960s and 1970s. Previous studies
(Wright, 1974; Allan and Haylock, 1993; Yu and Neil, 1993), as well as a more
recent one (Smith et al., 2000), have noted this decrease and attribute it to
atmospheric circulation changes, predominantly resulting from natural variability.
There are marked interdecadal variations over northern and eastern Australia
in summer half-year rainfall, which are dominated by ENSO-induced variations
(Power et al., 1999a). There also are clear interannual and decadal variations
in central and eastern Australian rainfall associated with Indian and Pacific
Ocean sea surface temperatures (SSTs) (Power et al., 1999b). Some of the regional
linear trends observed during the past century merely may reflect a particular
pattern of decadal variation. Thus, the high degree of decadal variability may
enhance or obscure a signal that is related to climatic change for several decades.
A growing body of evidence is being obtained about past climate variability
from coral cores (e.g., Lough and Barnes, 1997; Isdale et al., 1998; Quinn et al., 1998).
The strength of the relationship between eastern Australian climate and ENSO
has been observed to vary over the past century. This seems to be linked to
longer term climate oscillations such as the North Pacific Decadal Oscillation
(NPDO) (e.g., Power et al., 1999a). Salinger and Mullan (1999) examined the
20-year periods before and after 1977 and showed increases after 1977 (some
statistically significant) in mean rainfall for New Zealand's west coast,
associated with strengthening westerly winds. These fluctuations in rainfall
are partially explained by the increase in El Niño conditions over recent
decades. There is some evidence of long-term variations in the Australasian
region in storm frequency and tropical cyclones (Nicholls et al., 1996a; Radford
et al., 1996; Hopkins and Holland, 1997; Leighton et al., 1997).
Nicholls et al. (1998) show that although there has been a decrease in tropical cyclone
numbers from 1969 to 1996 in the Australian region (105°E to 160°E),
there has been an increase in the frequency of intense tropical cyclones with
central pressures of less than 970 hPa.
The average rise in sea level in the Australia/New Zealand region over the
past 50 years is about 20 mm per decade (Rintoul et al., 1996; Salinger et al.,
1996), which is within the range of the current estimate of global sea-level
rise (IPCC, 1996, WGI Section 7.2.1). However, the greater frequency and duration
of El Niño episodes since the mid-1970s has reduced local New Zealand
sea-level trends: The average sea-level change since 1975 at Auckland is close
to zero (Bell et al., 1999). There has been a weak warming trend in ocean temperatures
to 100-m depth in the southwest Pacific (39°S to 49°S, 141°E to
179°E) of about 0.13°C during the 34-year period 1955-1988 (Holbrook
and Bindoff, 1997), and there have been shorter period SST fluctuations associated