* Soil's carbon store being depleted, releasing CO2
* Draining peatlands produces 6 pct of manmade emissions
By Nina Chestney
LONDON, Feb 13 Global warming will get
worse as agricultural methods accelerate the rate of soil
erosion, which depletes the amount of carbon the soil is able to
store, a United Nations' Environment Programme report said on
Soil contains huge quantities of carbon in the form of
organic matter. which provides nutrients for plant growth and
improves soil fertility and water movement.
The top metre of soil alone stores around 2,200 billion
tonnes of carbon, which is three times the level currently held
in the atmosphere, said the UNEP Year Book 2012.
"Soil carbon is easily lost but difficult to rebuild," the
"Soil carbon stocks are highly vulnerable to human
activities. They decrease significantly (and often rapidly) in
response to changes in land cover and land use such as
deforestation, urban development and increased tillage, and as a
result of unsustainable agricultural and forestry practices."
Such activities can break down soil's organic matter. When
this happens, some carbon is converted to carbon dioxide, a
greenhouse gas that is one of the main contributors to global
warming, and it is lost from the soil.
Around 24 percent of global land has already suffered from
declines in health and productivity over the past quarter of a
century due to unsustainable land use, UNEP said.
Some 60 percent of carbon stored in soils and vegetation was
lost as a result of land use changes, such as clearing land for
agriculture and cities, since the 19th century.
As global demand for food, water and energy is forecast to
rise dramatically, soils will come under increasing pressure.
Without changing the way land is managed, over 20 percent of
forests, peatlands and grasslands in developing countries alone
could lose vital ecosystem services and biodiversity by 2030,
the report said.
The degradation of peatlands is a particular concern.
Peatlands contain over a third of the world's soil carbon,
making them the most effective carbon store on earth. But the
draining of peatlands currently produces over 2 billion tonnes
of CO2 emissions a year - equivalent to around 6 percent of
manmade greenhouse gas emissions, the report said.
To ensure soil carbon stocks are enhanced, not depleted,
UNEP suggested agricultural methods such as reduced tillage and
the careful use of animal manure or chemical fertilisers and
Financial incentives to improve land use such as payments
for carbon storage, flood control and water quality improvement,
and a global climate deal that includes the trade of carbon
credits for soils could help improve management of soil
resources, the report said.
Although rules governing the treatment of land use, land use
change and forestry are being debated as part of a new global
climate deal, UNEP said there was a "critical need" to develop
universal ways to measure, report and verify changes in soil
carbon over time.
(editing by Jane Baird)