Geography Reference
In-Depth Information
modification by applying the changes that humans are seeking into
their DNA by inserting or deleting genes. This provides a precise
result rather than the less precise cross-breeding approach. Geneti-
cally modified food seems to be of concern to members of the
public in some countries although the reasons for this are not
entirely clear given the long history of domestication and selective
breeding.
There are relatively few species of domesticated livestock and
these tend to be herd animals which can survive on low nutrient
vegetation and therefore use land that may be less suitable for
crops. It seems that pigs and cattle have been living in proximity to
humans since about 10,000 years ago and by 2,000 years ago pigs,
cattle, sheep, goats and buffalo had all been domesticated and had
evolved into breeding groups distinct from their wild ancestors.
Selective breeding has brought about changes in the physical and
physiological features of these creatures but more recently geneti-
cally modified pigs have been developed. Selective breeding really
can result in fast changes to an animal species. For instance, the
variety of domestic dogs we are familiar with such as poodles, Lab-
radors, terriers, huskies, bulldogs, Alsatians and so on all originate
from one single species - the wolf - by humans selectively breed-
ing the animals only over the last 12,000 years.
Food consumption tends to be more protein rich in developed
countries with a high proportion of meat and dairy products.
Trends show that as developing countries progress, these demands
also increase. This is problematic because it takes more energy, land
and water to produce these foods. In fact, half of the agricultural
land of the USA and Canada is currently used to provide plants for
animal consumption. Therefore not only will population increase
drive changes in arable production, but the wealth of nations will
change the types of production as food preferences change too.
Many areas are already stretched for water resources but an
increased demand for meat and dairy products will increase water
use dramatically with impacts on other parts of the natural system.
Urban ecosystems
Half of the world's population lives in urban locations. These
urban locations, with specific domestic animals, pests and careful or
