Transcript Document

THE CARBON CYCLE
What Is Carbon?
• Carbon is a key •
element for life,
composing
almost half of the •
dry mass of the
earth’s plants
(that is, the mass
when all water is
removed).
The basis of life of
earth
Found in rocks,
oceans,
atmosphere
Carbon Cycle
• The same carbon atoms are used
repeatedly on earth. They cycle
between the earth and the
atmosphere
Plants Use Carbon Dioxide
• Plants pull carbon dioxide from the
atmosphere and use it to make food
–— photosynthesis.
• The carbon becomes part of the plant
(stored food).
Animals Eat Plants
• When organisms eat plants, they take
in the carbon and some of it becomes
part of their own bodies.
Plants and Animal Die
• When plants and animals die, most of their
bodies are decomposed and carbon atoms are
returned to the atmosphere.
• Some are not decomposed fully and end up in
deposits underground (oil, coal, etc.).
Carbon Slowly Returns to Atmosphere
• Carbon in rocks and underground deposits is
released very slowly into the atmosphere.
• This process takes many years.
• The carbon cycle is the exchange of carbon
among three reservoirs or storage places:
the land, the oceans, and the atmosphere.
The global carbon cycle is usually thought to
have four major carbon sinks interconnected
by pathways of exchange. These sinks are;
• the atmosphere,
• the terrestrial biosphere (which usually
includes freshwater systems and non-living
organic material, such as soil carbon),
• the oceans (which includes dissolved
inorganic carbon and living and non-living
marine biota),
• and the sediments (which includes fossil
fuels ).
Figure 1. Magnitudes of the reservoirs (sinks) of
actively cycling CO2 in gigatons of carbon. Of the ocean
pool, roughly 1,000 Gt are in contact with the
atmosphere in any given decade. The terrestrial
biosphere consists of soil (ca. 1,600 Gt) and vegetation
(ca. 600 Gt). Data from Schimel et al. (1995).(after
Christensen, 1991).
•
The mechanism of the
Anthropogenic activities
which upset the
problem
carbon cycle include burning of fossil fuels and
deforestation.
• Fossil fuels, such as oil, coal and natural gas,
are the fossilized remains of prehistoric plants
and animals and represent stored carbon.
Cycle –
Repeats Over
and Over and
Over and
Over …
Carbon Cycle Diagram
Carbon in Atmosphere
Decomposers
break down dead
things, releasing
carbon to
atmosphere and
soil
Fossil fuels are
burned; carbon
is returned to
atmosphere
Carbon slowly
released from
these substances
returns to
atmosphere
Plants use
carbon to make
food
Plants and
animals die
Bodies not
decomposed —
after many
years, become
part of oil or coal
deposits
Animals eat
plants and
take in carbon
The Carbon Cycle
Environmental Impact
• Deforestation has two impacts: the
breakdown of carbon in the biproducts of the wood and the loss of
trees to draw carbon dioxide out of
the atmosphere.
• Global Warming
• Air Pollution
• Climate Change
Human Impact
• Fossil fuels release carbon stores very
slowly
• Burning anything releases more
carbon into atmosphere — especially
fossil fuels
• Increased
carbon
dioxide
in
atmosphere
increases
global
warming
• Fewer plants mean less CO2 removed
Mitigation
• A process called carbon sequestering involves
planting new forests to reduce atmospheric
carbon dioxide concentrations.
• The greatest opportunity for this is in tropical
areas where growth rates are the fastest.
What We Need to Do?
Recommendation:
•
•
Taking Action
We already possess the scientific, technical, and industrial know
how to solve the carbon and climate problem for the next halfcentury. A concept known as “carbon wedges” proposes to limit
the human contribution to the global carbon cycle, in an effort to
reduce global warming. Adoption of the wedge concept is essential
if we are going to curb our extraordinary abuse of fossil based
fuels.
•
Burn less, especially fossil fuels
•
Promote plant life, especially trees