Current warming and likely future impacts - Climate Change: Biological and Human Aspects - page 303

Adaptations needed, and again echoed in the 2009 report, are likely to include the
following:
changing sowing dates and other seasonal activities in response to phenological
changes;
introducing new cultivars (crop varieties), including those created through biotech-
nological methods as opposed to by conventional breeding;
improved water-supply management and water use;
changes in tillage practice to retain organic matter in soils;
increase use of short-term (6-month) forecasts relating to key climatic cycles, such
as El Ni no events;
tweaking of management systems from plough to gate, and even plough to market.
The USGCRP's reports also have a sector report on the related topic of forestry. Many
of the concerns focus on the Pacific north west, which is likely to suffer from changes
in water availability throughout the year. The Cascades coniferous forest, in the west
of the Pacific north west, covers about 80% of the land and, more importantly, this
accounts for about half the planet's temperate rainforest. Because of the length of the
forest crop cycle (decades rather than within a year for most agriculture) the need
is to plant species adapted to the forecasted climate rather than the climate as it is
now. Careful management is also required to reduce water stress and the risk of forest
fires. The net economic effect of the forecast climate change is thought to be marginal
but minor economic improvement is anticipated, with most of the gains relating to
hardwood as opposed to softwood. However, this does necessitate the adaptations
being undertaken in a timely manner and so climate-driven agricultural change is
unavoidable.
The other important sector the USGCRP's reports covered was water. As seen
from the above summary of the report's key points, water in the USA was considered
a key dimension to the biological impacts of climate change on both natural and
managed systems. The report notes that population in the USA increased by nearly
two-thirds (well above 60%) in the latter half of the 20th century. However, whereas
water consumption did increase between 1950 and 1979 by around 60%, it stabilised
thereafter to the century's end, at around 1.5 billion m 3 day − 1 . Farming today, at
85%, dominates water use, with 82% being used for crops and 3% for livestock (see
Figure 6.5). This highlights the importance of water management in food production.
However, water management throughout the year will become harder with warming
in those areas relying on seasonal mountains snow melt. With the amount of snow
due to decline as snow lines rise, and there being warmer years, snow melts will occur
earlier in the year and summer melt-fed streams will be drier. Models suggest that
the Southern Rocky Mountain, Sierra Nevada and central Rocky Mountain snowpack
volumes are likely to decline by between 50 and 90% by the end of the 21st century.
Given this, and that a number of groundwater aquifers (such as the Great Plains
Ogallala) are already diminishing due to extraction rates exceeding replenishment
rates, water storage combined with increased efficiency of use will be the important
management measures required by the main users of water in the USA, the farmers.
The 2009 report concludes that the past century is no longer a reasonable guide to the