Cool Farming: Climate impacts of agriculture and mitigation potential

Executive Summary
Overall finding and conclusions:
Agriculture contributes significantly to greenhouse gas
emissions (GHG). Agricultural soil and livestock directly emit
large amounts of potent greenhouse gases. Agriculture’s
indirect emissions include fossil fuel use in farm operations,
the production of agrochemicals and the conversion of land
to agriculture. The total global contribution of agriculture,
considering all direct and indirect emissions, is between 8.5 –
16.5 Pg CO2-eq 1,2 , which represents between 17 and 32% of
all global human-induced GHG emissions, including land use
changes (Figure 1).
Some historic anomalies in the atmospheric GHG
concentrations can be attributed to early changes in farming
practices such as the development of wet rice cultivation
several thousands of years ago. In the last century, there have
been even more substantial changes in agriculture, with the
uptake of synthetic fertilisers, development of new crop
varieties (“Green Revolution”) and the adoption of large-scale
farming systems. The sustainability of modern “industrial”
agriculture has been questioned.
The solution to the environmental problems caused by today’s
agricultural methods lies in a shift to farming practices which
could provide large-scale carbon sinks, and offer options for
mitigation of climate change: improved cropland management
(such as avoiding bare fallow, and appropriate fertiliser use),
grazing-land management, and restoration of organic soils as
carbon sinks. Since meat production is inefficient in its
delivery of products to the human food chain, and also
produces large emissions of GHG, a reduction of meat
consumption could greatly reduce agricultural GHG
emissions. Taken together, these could change the position of
agriculture from one of the largest greenhouse gas emitters to
a much smaller GHG source or even a net carbon sink.
Footnote 1) 1 Pg (Peta gram) = 1 Gt (Giga tonne) = 1000 million tonnes. To
convert Pg CO2-eq to million tonnes multiply by 1000; e.g. 15.5 Pg CO2-eq
equals 15.5 Gt CO2-eq or 15500 million tonnes CO2-eq.
Footnote 2) Emissions of greenhouse gases nitrous oxide (N2O) and methane
(CH4) are often expressed as the equivalent units in CO2 in terms of their
global warming potential in 100 years: N2O has 296 times the warming
potential of CO2 and CH4 23 times.
Figure 1. Global contribution of agriculture
to greenhouse gas emissions.
18
16
14
12
10
8
6
4
2
0
10 - 12 %
Direct methane
and nitrous oxide emissions
Fertilisers production
and distribution
Farm operations
©Les Stone/Greenpeace
0.2 - 1.8 %
0.6 - 1.2 %
6 -17 %
Land conversion
to agriculture
17 - 32 %
Total global contribution of agriculture to greenhouse gas emissions, including
emissions derived from land use changes. The overall contribution includes
direct (methane and nitrous oxide gases from agriculture practices) and
indirect (carbon dioxide from fossil fuel use and land conversion to
agriculture). Percentages are relative to global greenhouse gas emissions.
Total
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