Figure 8-2: This figure shows
linkages between climate change and other environmental factors in food supply
and demand. Increasing food demand by a growing world population calls for
larger food production. This, in turn, brings a series of implications in the
use of land, such as converting wildlands to croplands (extensification), and
using chemical fertilizers and/or using irrigation to increase yield (intensification)
or enabling cultivation in otherwise non-usable land. Expanding the land under
cultivation results in loss of biodiversity, as ecosystems are converted to fields
growing only a few species (usually exotics). Change of forests to agriculture
brings a net loss of carbon to the atmosphere, as forests are replaced by grassland
or cropland. This clearing also increases flooding probability, as the agricultural
systems retain less precipitation than forests. Intensification of crop production
can involve a variety of chemical treatments, most of them being nitrogen fertilizers
bringing the side effect of release of nitrogen gas compounds (some of which are
strong greenhouse gases) to the atmosphere and nitrogen runoff into watersheds,
with many environmental and health implications. The expansion of irrigation affects
the supply of freshwater for other uses, leading to shortages and conflicts over
water-use rights. Meeting the needs for increased agricultural production has
the potential to increase global rates of biodiversity loss, climate change, and
desertification. There are interrelations, particularly to water, that underly
all these issues, but for simplicity are not shown in the figure.
