.The
impact of global warming on agriculture
By Saleem Abid and M Asif Masood Ghumman
The issue of global warming is
now becoming more critical as humans are more actively engaged in burning of
coal and other fossil fuels for heat along with removing of forest for urban
developments. These activities lead to higher concentrations of greenhouse gases
like carbon dioxide and methane in the atmosphere and as a result advance the
greenhouse effect exponentially contributing to global warming.
Moreover, industrial revolution
and increase in human population have also resulted in tremendous increase in
greenhouse gas emissions and both have significant bearing on the global
climate. According to a report by the IPCC (Intergovernmental Panel on Climate
Change, 1995) the average temperature on the earth has increased by about 0.3 to
0.6 centigrade over the past 100 years and global warming will further advance
if appropriate measures are not taken in this regard.
Furthermore, the IPCC (2001)
has also projected rise in average global temperature by 1.4 to 5.8 centigrade
during the 21st century. This would have enormous biological, agricultural and
socio-economic implications.
Global warming will also
largely damage world’s agriculture threatening food security for the world’s
most vulnerable people. It will cause heat stress resulting in decrease in the
soil moisture and will give rise to sea level imposing high costs of protection
of coastal areas and cities along with the loss of land areas. The climate has
direct affect on food supply. Temperature, radiation and water all these
determine the carrying capacity of the biosphere to produce enough food for
human population and domestic animals. Therefore, any change or fluctuation in
climate can have dramatic effects on the agricultural productivity.
Demographic studies indicate
that world population will reach 3 billion by the year 2050. Unless the
population size is stabilized, agriculture will have to face an increasing
challenge to feed the growing population of the world.
Weather is a key factor in
agricultural productivity despite technological advances such as improved
varieties, genetically modified organisms or irrigation systems. The effect of
climate on agriculture is related to variability in climate rather than in
global climate pattern. Agronomists consider that it has to be monitored for
each local area. High summer temperature together with low summer rainfall will
likely have adverse impact on global agriculture despite the efficient use of
water. The intensification of the hydrological cycle will have more frequent
droughts in northern sub-tropical areas.
Global warming will also cause
soil degradation and soil fertility would probably be modified. A doubling of
carbon is likely to imply a higher storage of nitrogen in soils, thus providing
higher fertilizing elements for plants, and better yields thereafter. The
average need for nitrogen could decrease and provide an opportunity for
improving the fertilization strategies.
Some scientists think
agriculture could be affected by any decrease in stratospheric ozone, which
could increase biologically dangerous ultraviolet radiation. Excess ultraviolet
radiation could directly impact plant physiology and indirectly change
pollination behaviour, though such changes are difficult to exactly quantify.
In the long run, the climatic
change(s) could affect agriculture in several ways: productivity, in terms of
quantity and quality; agricultural practices through changes of water use
(irrigation), agricultural inputs (herbicides, insecticides, fertilizers);
environmental level, in particular in relation to frequency and intensity of
soil drainage, soil erosion, reduction of crop diversity; rural space, through
the loss of previously cultivated lands, land speculation and renunciation etc.
There are large uncertainties to uncover, particularly the lack of information
on the local scale, the uncertainties on magnitude of climatic change, the
effects of technological changes on productivity, global food demands, and the
numerous possibilities of adaptation.
Experts believe that developed
nations have friendly atmospheric conditions whereas developing nations are
strictly suffering from social or technical constraints that could prevent them
from achieving sustainable production levels. Therefore, in view of the above
facts, the need is to adopt efficient new techniques meaning better varieties,
planting date, and irrigation practices.