Photosynthetic Capacity Reverses
Christine Jones, PhD
2 July 2007
The process of
well documented that loss of perennial groundcover is causing
increased desertification across the African, Indian, Asian, North
American, South American and Australian continents.
energy from the sun is converted to heat energy when it makes
contact with bare ground.
the rapidly expanding areas of unprotected topsoil on most major
land masses, excessive heat energy is radiated back into the
ground and low levels of groundcover also result in declining soil
structure and reduced soil water holding capacity. Lower soil moisture
retention results in elevated levels of atmospheric water vapour.
atmospheric water vapour serves as a trap for the heat radiated
from bare ground.
the beginning of the 'industrialised agriculture' era, in which
billions of hectares of land around the world have been laid bare for
long periods of time, water vapour has been the 'man-made greenhouse
gas' that has increased to the greatest extent. This water vapour does
not necessarily form clouds.
better than we found it.
and the step-wise CO2 curve
energy intercepted by green leaves
(crops, grasses, trees) is
converted to biochemical energy through photosynthesis. This is a cooling
process. Photosynthesis is a two-step endothermic reaction that
removes CO2 from the atmosphere and releases oxygen.
are significant, and consistent, annual fluctuations in global
the Northern Hemisphere is in the dormant winter phase, and the
Southern Hemisphere in the hot summer phase, levels of green
groundcover are low in Eastern and Western Europe, Northern Asia,
Canada, North and South America, non-monsoonal Africa and the southern
half of Australia.
capacity is reduced and global CO2 levels rapidly rise.
the Northern Hemisphere is in the summer phase with green crops,
green pastures and green deciduous trees - and the winter-rainfall
areas of the Southern Hemisphere are also green due to winter crops and
winter-active annual pastures, photosynthetic capacity is high and
global CO2 levels rapidly fall.
pattern is repeated every year.
carbon fixed as glucose in green leaves is transformed to a
wide variety of carbon compounds, some of which are used for metabolism
and the formation of plant structural materials - with the remainder
translocated to the roots and exuded into soil to form a microbial
bridge to enhance the bio-availability of nutrients. Under appropriate
conditions, a portion of the carbon exuded from the rhizosphere
undergoes polymerisation to form high molecular weight humic compounds
which are relatively resistant to decomposition.
significant proportion of the world's land mass was 'Yearlong
Green' due to changed farming practices, CO2 levels would fall as
atmospheric CO2 became safely sequestered in plant material and highly
complex soil carbon pools. Plants and soils would retain higher levels
of moisture. These factors would enhance biological activity in the
terrestrial biosphere and improve the productivity of agricultural
land. Furthermore, actively growing green groundcover increases the
incidence of rainfall.
groundcover and increased photosynthetic capacity across the
globe would reduce the 'Global Warming Effect' and reverse Climate
Change. The slope of the 'atmospheric CO2 curve' would be step-wise
downwards rather than step-wise upwards.
Agriculture vs the Industrial Revolution
soil carbon levels have been recorded worldwide under most
current broadacre cropping and grazing regimes. This soil carbon has
been emitted to the atmosphere.
sobering to compare the CO2 emissions from soil with those from
the burning of fossil fuels. Dr Rattan Lal, Professor of Soil Science
at Ohio State University and Director, Carbon Management and
Sequestration Center, USA, has calculated that 476 Gt of carbon has
been emitted from farmland soils due to inappropriate farming and
grazing practices, compared with 270 Gt emitted from over 150 years of
burning of fossil fuels.
trends can be reversed by increasing the photosynthetic capacity
of the landscape through the adoption of Yearlong Green Farming (YGF)
any process, technique or practice that turns bare soil into
soil covered with green plants for most of the year. Yearlong Green
Farming increases the quality, quantity and perenniality of green
groundcover in broadacre cropping, horticultural, silva-pastoral and
grazing enterprises. YGF practices include (but are not limited to)
pasture cropping, over-cropping, cover-cropping, use of microbial
stimulants and compost teas, green manuring, alley farming and planned
grazing. Livestock are an important component of YGF. Grasslands and
grazers have co-evolved for over 20 million years and are mutually
beneficial if managed appropriately.
significantly reduces the amount of incoming light energy
converted to heat energy
significantly reduces the amount of heat radiated from the
earth's surface and trapped in the atmosphere
significantly reduces evaporation (which commonly accounts for
around 80% of the water-balance equation), retaining soil moisture that
would otherwise form atmospheric water vapour
converts incoming light energy to biochemical energy through
uses CO2 from the atmosphere to fuel biological processes and
build organic carbon in soils
Points to note
grasslands and grassy woodlands were the major vegetation type
over much of the African, North American and Australian continents
prior to European colonisation
every 2.7 tonnes of carbon sequestered in soil as a result of
the photosynthetic process removes 10 tonnes of CO2 from the atmosphere
(conversely every 2.7 tonnes of carbon lost from soil adds 10 tonnes of
carbon dioxide to the atmosphere)
more soil carbon is sequestered in grassland ecosystems than in
any other type of vegetative cover
increased soil carbon levels enhance nutrient density in
plants, improving the immune response and reversing symptoms of trace
element deficiencies (such as cancer) in livestock and people
in countries where agricultural production is falling or
erratic, YGF techniques enhance the quality, quantity and reliability
of supply of basic food requirements
techniques are available worldwide but are not widely adopted due
to lack of appropriate information. Incentive payments based on
percentage green cover, calculated on an annual basis, would provide a
catalyst for change. Levels of green cover could be remotely sensed and
recorded at regular intervals (eg monthly) using satellite imagery. An
overlay of spot testing of soil carbon and soil moisture levels would
indicate the quantity of atmospheric CO2 sequestered and atmospheric
water vapour retained in soil. A simple incentive scheme of this nature
may prove easier to manage and have broader application than intensive
testing for soil carbon, particularly in countries where the
infrastructure and resources for scientific research and development
'greening of a brown land' would increase soil carbon
sequestration, increase soil moisture retention, reduce heat radiation
and reduce the concentration of both CO2 and water vapour in the
atmosphere. These factors would reverse the 'Global Warming Effect'. As
a bonus, the adoption of Yearlong Green Farming techniques would
markedly improve the productivity agricultural land.