There is growing evidence that greenhouse gas emissions from human activity contribute to climate change. Many people blame modern farming practices for accelerating this - agriculture produces between 16.8 and 32.2 percent of global greenhouse gas emissions. But could agriculture also hold some solutions to climate change?Research for Geenpeace
International by the University of Aberdeen, in the UK, analyses the
contribution of modern farming to human-induced climate change. The main
greenhouse gases (GHGs) associated with agriculture are nitrous oxide and methane. GHG emissions from farming
include direct sources, such as soil and livestock, and indirect emissions.
These include fossil fuel use, fertiliser production and changes in land use,
particularly the expansion of agriculture into uncultivated areas such as
tropical forests.
All farming systems emit GHGs, with intensive farming producing more emissions per
area, but not necessarily per unit of product. Globally, livestock are the main
source of methane, and intensive animal farming also increases the demand for
feed crops and synthetic fertilisers.
Economic growth in the developing
world is increasing the demand for meat, as more people can afford it. The
greatest increase in meat consumption has occurred in developing countries - 77
percent from 1960 to 1990. Even
without these dietary changes, the growing population in developing countries is
increasing the demand for food and more intensive farming.
From 1990 to 2005, developing
countries and countries in economic transition collectively showed a 32 percent
increase in GHG emissions.
By 2005, these countries were
responsible for about three quarters of global agricultural emissions.
Three sources together contribute 88
percent of this increase: methane from livestock, soil nitrous oxide emissions
and biomass burning.
Between
2001 and 2004, the rising demand for beef and high energy feed crops (especially soya)
led to the deforestation of 93,700 square kilometres of rainforest in Brazil.
Among
developing countries, China
and India
are the main drivers behind the increased use of fertilisers and manure to meet
demands for food, caused by rapid population growth.
Despite these problems, agriculture
has the potential to reduce the impact of almost all its direct emissions
(known as mitigation). The researchers suggest that 89 percent of agriculture’s
mitigation contribution will come from soil carbon sequestration (the removal
and long-term storage of carbon from the atmosphere using soil as a natural carbon
sink). In the short term, the most important measure is to avoid deforestation,
especially in tropical countries.
The researchers suggest other ways in which agriculture can mitigate its GHG emissions:
avoid bare soil and rotate crops
with legumes such as peas and beans - these fix nitrogen in the soil and reduce
reliance on fertilisers.
reduce tillage (preparing
soil by digging it up) to restore the carbon content of degraded soils and
reduce soil disturbance.
avoid burning
crop residues.
practise agro-forestry (growing trees on farming land for timber and other
forest products).
adopt a
vegetarian diet or at least reduce meat consumption.