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Anthropogenic Influences on the Global Carbon Cycle and its Implications for the Future

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Title: Anthropogenic Influences on the Global Carbon Cycle and its Implications for the Future


1
Anthropogenic Influences on the Global Carbon
Cycle and its Implications for the Future
Pushkaraj Sardesai and Sarah Eggleston Earth
System Science and Policy
Abstract Carbon makes up approximately 50 of the
dry weight of all living things it forms the
structure of all life on Earth. While not one of
the major atmospheric gasses, carbon compounds
such as carbon dioxide (CO2) and methane (CH4)
are major greenhouse gases, and as such are major
contributors to global warming. Currently
atmospheric CO2 concentrations are increasing at
a rate of about 3.2 Pg C per year. Based on ice
core data and ongoing atmospheric CO2 monitoring,
anthropogenic sources, specifically combustion of
fossil fuels and land use changes, have been
cited for causing this increase. Here we give a
brief overview of how the natural carbon cycle
works and look at how fossil fuel combustion and
land use changes affect this cycle over time. We
focus on the modifications that have been, and
could be made to land use, as well as the
potential for carbon sequestration as a
mitigation for atmospheric carbon build up.
Human Impacts On The Carbon Cycle
Carbon Storage Potential of Biomes
As can be seen in the graphs to the left, carbon
storage capacity varies by biome. Currently the
Boreal Forest biome stores the most carbon,
followed by Tropical Forests. In terms of total
carbon per unit area, Wetlands are by far the
most efficient at carbon storage with Boreal
Forests next in efficiency. For carbon
sequestration purposes, the amount of carbon that
can be stored by a biome is quite important. The
location of these biomes is also important, since
the majority of carbon is emitted in the Northern
Hemisphere. The location of biomes such as the
Boreal Forest with their ability to store large
amounts of carbon can make a great difference for
atmospheric carbon concentrations.
Fossil fuel combustion and land use changes, are
the main ways in which humans affect the natural
carbon cycle. The natural carbon system cannot
keep pace with these new anthropogenic emission
sources. The natural processes that permanently
remove this additional carbon (i.e. ocean uptake
and sedimentation) work extremely slowly so, the
concentration of CO2 in the atmosphere increases.
Fossil Fuel CO2 emission and carbon sequestration
CO2 emissions from combustion of fossil fuels is
of concern because combustion adds the long
dormant stock of C from Earths crust in to the
active carbon cycle. This increased CO2
concentration in atmosphere is a major factor in
global warming. The potential ways to reduce the
CO2 concentration in atmosphere are 1) Carbon
sequestration 2) Replace fossil fuels with
bio-fuels 3) Reduce the CO2 release from energy
use (by switching to alternative sources of
energy)
Effect of CO2 Greenhouse gases
Natural Carbon Cycle
The Earth maintains a natural carbon balance.
Carbon is continually exchanged within a closed
system consisting of the atmosphere, oceans,
biosphere, and landmasses. When, natural
perturbations in concentrations of carbon dioxide
(CO2) occur, the system gradually returns to its
natural state through the processes shown here.
These process can be either long term or short
term.
Biomes
OCEAN UPTAKE Dissolving of CO2 gas into the
oceans and inflow of carbon carried from land by
rivers. OCEAN RELEASE Return of carbon in the
oceans directly back to the atmosphere as CO2
gas. SEDIMENTATION Slow burial of plant and
animal matter on land and on the ocean floor,
which eventually becomes limestone, coal, gas,
and oil. RESPIRATION Slow combustion of carbon
compounds, producing energy within organisms and
releasing CO2. PHOTOSYNTHESIS Conversion of CO2
into energy-rich carbon compounds by plants.
www.clarkson.edu/.../ Fig8_small.jpe
Possible way to mitigate Point Source Carbon
dioxide Pollution
http//www.blueplanetbiomes.org/world_biomes.htm
With help of atmospheric modeling and satellite
images, determine the effective radius from a
point source within which the concentration of
CO2 are high. With help of satellite images
identify the type and concentration of biomass in
the area. Determine the uptake of carbon dioxide
by this biomass. (carbon sequestered). Determine
the potential for carbon sequestration with help
of local man managed ecosystems. e.g. Trees
planted in this radius will sequester carbon more
effectively and rapidly then elsewhere, and
reduce overall national emissions.
Humans change the way land is used in many ways.
The most significant of these ways is through
deforestation, desertification, conversion of
land to cropland, and wetland destruction. The
map above shows the basic location and extent of
major Earth biomes. What biomes are changed is of
significant importance to the carbon cycle, as
each biome has a different potential for carbon
storage.
www.koshland-science-museum.org/exhibitgcc/images/
carbon02.jsp.
References
1) Janzen, H.H. Carbon cycling in earth systems
a soil science perspective. Agriculture,
Ecosystems Environment 104 (2004) 399-417. 2)
Jorge L. Sarmiento Steven C. Wofsy Co-Chairs A
U.S Carbon Cycle Science Plan. A report of the
Carbon and Climate working Group. 1999 3)
http//www.cypenv.org/Files/sequest.htm 4)
http//cdiac.esd.ornl.gov/trends/emis/em_cont.htm
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