The human ecology of climate change - Climate Change: Biological and Human Aspects - page 379

using fossil carbon for fertilizers are limited, although biogas may provide part of the
solution.
Today's copious energy supply resulted, in the industrialised world, in our becoming
used to supermarket goods that are largely independent of the seasons and consisting
of produce from around the planet (i.e. with high 'food miles'). Furthermore, as the
global economy becomes wealthier, so the meat content of the average human diet
increases. The point here is that meat is an inefficient food source in terms of both
energy and land - feeding grain to animals that we in turn consume - compared to
humans consuming grain directly. World meat production per person increased more
or less linearly throughout the 20th century through to the present day, from 17.2 kg
per capita in 1950 to 39.0 kg in 2002 (FAO, 2002).
Consequently, the food dimension is not just a fundamental part of human ecology
and the way we as a species relate to others, it is also an important driver of human
activity - which depends on a societal food surplus above subsistence - as well as
being a sector that consumes energy.
This energy relationship is two-way. Not only does the agricultural production
of food - its processing, storage and delivery - consume energy, which in turn, if
fossil fuel energy, has a climate impact. These climate impacts also impact back
on agriculture. For example, the vagaries of the Holocene climate have affected
European agricultural activity (see Chapter 5), and so future climate change is also
likely to affect agriculture (see Chapter 6 and the case studies on the probable US
and Australasian impacts, sections 6.2 and 6.4).
If human food supply is fundamental to the nature of human activities, if it is
dependent on fossil energy and if food supply is shaped by climatic patterns, then
what about food security against a backdrop of an increasing and unsurpassed global
population? Will future climate change improve or weaken the global security of food
supply? This question will be addressed in section 7.4.
7.1.5 Impactonotherspecies
Because the Earth's population is now so large, and the commensurate need for food
is so great, food production dominates much of the most biologically productive
temperate land. Together with the land required to house, transport and provide a
location for economic activity, this has seen our species take much land away from
purely natural systems. Indeed the (perceived market) value of economic activity
can be such that it surpasses that of purely agricultural value, which in turn leads
to housing and urban settlements being constructed on fertile land. As mentioned in
Chapter 4, the extent of this domination over natural systems is such that it is estim-
ated that just under a third of global terrestrial net primary production (the biomass
arising from the energy trapped by photosynthesis) is appropriated for human use
(Imhoff et al., 2004). Another perspective on the degree of human management of
global ecosystems is provided by the amount of nitrogen fixed by humans (primarily
for fertilizers), which already exceeds that fixed globally by natural means. In addi-
tion, more than half of all accessible fresh water (i.e. excluding sources such as the
Antarctic ice cap) is put to use by humanity (Vitousek et al., 1997), and 10-55%
of terrestrial photosynthetic production is managed by humans (which includes not