Soil and Climate - Soil: Reflections on the Basis of our Existence - page 122

by the Finnish novelist V￤inö Linna, a tale about a farmhand's struggles to drain
a bog and build a farm. Forest grows on many of these bogs today, and though
drainage accelerates peat decomposition, the presence of trees creates a balance
between carbon inflow and outflow. The carbohydrates that the Finnish trees trans-
port to their roots to facilitate nutrient uptake correspond to the carbon lost when
the peat decomposes. The contrast compared to Indonesia is stark: peat degrades
much faster in the Tropics and the more nutrient-rich soil results in less carbohy-
drate being transported below ground.
Scientists Track Carbon from Peat to Air
Most soil carbon is found in northerly latitudes, where the slower pace of decom-
position allows more dead plant material to accumulate in the ground. Scientists
have been studying the carbon flow between earth and air at Stordalen, a large bog
near Abisko in Sweden's far north, for more than 50 years. When I visited the area
in 2008 it was clear that major changes were taking place. Located in a hilly area,
the bog consists of meres interspersed with palsas, which are peaty mounds with
permanently frozen ice layers. If the climate warms, the permafrost melts and the
mounds collapse, opening blackish cracks. When palsas collapse they are sub-
sumed into the surrounding water, accelerating the emission of methane gas from
the bog. Twenty times more potent as a greenhouse gas than carbon dioxide, meth-
ane is formed by bacteria-like Archaea in the anaerobic bog environment. As the
gas percolates to the top of a palsa, it encounters aerobic bacteria that oxidise it
into carbon dioxide. But if the methane instead bubbles up directly from wet areas,
it goes straight into the atmosphere. Hence, any expansion of wet areas results in
higher methane emissions and accelerates the pace of global warming.
Carbon Flow from Soil: The Scientists' Conundrum
Vast quantities of carbon are stored in the soil. The soil holds twice as much car-
bon as the global above-ground biomass. Scientists are unsure what will happen
to this carbon when global temperatures rise and rainfall patterns change. Higher
temperatures are likely to accelerate the decomposition of organic matter because
microbiological processes work faster in warmer conditions. This would increase
the amount of carbon entering the atmosphere, further raising temperatures and
creating a vicious circle of climate change. Conversely, higher temperatures may
lead to higher rates of forest growth and an increase in leaf and root litter, which
would raise soil carbon content and bind more atmospheric carbon, mitigating
global warming.
It is a complex subject. Soil consists of many different substances with myriad
properties. Higher temperatures hasten the decomposition of some materials but