18.104.22.168. Production Forestry
The production of wood and paper products is a major industry in the region.
In New Zealand, the industry is primarily based on plantations of fast-growing
exotic species, whereas in Australia there is still a considerable forest industry
based on native eucalypt forests in addition to expanding plantation forests.
A rising world population, combined with increased living standards, may (at
current prices) demand more wood than can be supplied from global resources
by the year 2050. Temperate forest products are expected to play an important
role in meeting demand (IPCC 1996, WG II, Sections 15.2.3, 15.4.3). There also
is an increasing trend to see plantation forests as a means of sequestering
carbon in the region (Maclaren, 1996).
CO2 fertilization is likely to increase growth, especially when trees are water
limited. However, growth enhancements due to increased temperature may occur
only in trees not subject to water limitations (Landsberg, 1996). As already
noted, however, the CO2 impact on tree growth decreases with time for many species
(Gunderson and Wullschleger, 1994). Any overall reductions in rainfall or changes
in seasonality that result in water limitations or prolongation of droughts
would negatively affect production and plantation seedling establishment. On
the positive side, in New Zealand forestry many of the worst exotic weeds are
C4 plants, so the competitive effects may be reduced if elevated CO2 concentration
favors growth of C3 over C4 plants in temperate zones. Again, however, this
gain might be negated by the relative advantage of C4 plants at higher temperatures.
Changes in tree and forest water use would alter the catchment hydrological
characteristics, particularly runoff and extreme events (IPCC 1996, WG II, Sections
The exposure of forests and forest operations to fire risk may increase, particularly
in Australia, and there is potential for changes in the frequency and intensity
of damaging events from wind and storm, particularly in New Zealand. More intense
rainfall events would exacerbate soil erosion and pollution of streams during
forestry operations and make these operations more difficult to carry out. Warmer
and wetter conditions could provide the opportunity for increased incidence
of arthropod pests and pine needle blight (Dothistroma pini). Pinus radiata
constitutes 91% of the exotic plantation forests in New Zealand and 68% in Australia,
so this blight is a major potential risk to production forestry.
An important distinguishing feature of forestry is the long time scale of the
tree lifecycle and the very large investment in the standing crop relative to
the annual yield. Whereas a wheat farmer stands to lose one year's production
in a climatic disaster, a forester may have at risk a full 30 years' growth.
Thus, more so than with agricultural crops, global change has the potential
to adversely affect the substantial accumulated capital of a standing forest.
Furthermore, the long time scale means there are less frequent opportunities
to apply adaptation options to any particular forest. The slower growing indigenous
forests will be even more affected than the fast-rotation exotic forest plantations.
Relatively little is known about how climate affects marine fishes-particularly
in the Southern Hemisphere, where data series tend to be short. Thus, it is
extremely difficult to predict how climate change may affect Australasia's fish
stocks and fishing industry, particularly in the context of the present stresses
on fish stocks. There is some evidence, however, that climate impacts can be
quite profound. The IPCC Second Assessment Report (SAR) concluded that although
global marine fisheries production may remain about the same-despite possible
changes in dominant species-there are likely to be collapses and expansions
of specific regional fisheries (IPCC 1996, WG II, Section 16.2.2). These conclusions
may likewise apply to large oceanic regions like Australasia, though current
knowledge is not adequate to predict the impacts-positive or negative-on total
productivity for the region.
In these circumstances, mobile high-seas fishing fleets are less likely to
be affected, provided that access regulation is not tied to geographical areas.
However, among the more localized small-scale fishers, who are dependent on
specific in-shore fisheries, there may be large gains and large losses if fish
populations shift their areas of abundance (IPCC 1996, WG II, Chapter 16). In
addition, in-shore fisheries and marine stocks that need to reproduce in freshwater,
estuaries, or mangroves may be negatively affected by changes in terrestrial
and coastal processes, such as increased pollution and sediment discharge or
loss of habitat. The economic impacts are unclear but could be significant for
some parts of the industry.
Climate conditions are a factor in the outbreaks of bloom-forming algae and
shellfish diseases that periodically occur in Australasian waters. These organisms
include naturally occurring species and exotic species introduced by discharge
of ships' ballast water. In the region's nontropical waters, some of the organisms
are likely to be at the margins of suitable temperature conditions, and warming
may give them increased opportunities to survive, spread, and form problem populations
(IPCC 1996, WG II, Section 16.2.4).
Aquaculture and freshwater fisheries at mid-latitudes may benefit from longer
growing seasons, lower natural winter mortality, and faster growth rates. Studies
for New Zealand suggest that rising sea level and temperatures may increase
oyster farm areas and productivity-but that sea temperatures may become excessive
for salmon farming. Any increases in rainfall intensity over land are likely
to increase coliform bacteria counts in runoff and result in more frequent closures
of shellfish beds (IPCC 1996, WG II, Section 16.2.3).