Page 359 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

11.3
CARBON EMISSIONS FROM DEFORESTATION
Earth’s forests are a major carbon sink, storing large amounts of carbon in their wood and leaves. Today, forests worldwide are threatened as they are cut for wood products and as forest lands are converted to other types of land use. Deforestation releases about one Gt of carbon into the atmosphere each year, amplifying climate change.
[Based on Climate Change and Environmental Risk Atlas, 2012, Maplecroft.]
geosystems in action 11 The GLObAL CARbOn budGeT
Ice wedges
Carbon released by decomposing microbes
15+ yrs later
35+ yrs later
0°
NIGERIA
0°
20°N
ATLANTIC OCEAN
PACIFIC OCEAN
INDONESIA
20°N
1 20°SNigeria
2 Indonesia
3 North Korea
4 Bo4l0iv°iSa
5 P.N.G.
6 DR Congo
extreme extreme extreme extreme extreme extreme
BOLIVIA
AUSTRALIA
40°N
40°N
NORTH KOREA
PACIFIC OCEAN
NICARAGUA
RANK COUNTRY CATEGORY
7 Nicaragua extreme
ROBINSON PROJECTION
Low risk
8 Brazil extreme
9 Cambodia extreme
10 Australia
11.4
Carbon
In Plants
high
photo- synthesizing
60°S
60°S
160°W
0°
160°E 80°N
Neutral carbon balance
11.4a Permafrost Intact Arctic vegetation absorbs carbon
through photosynthesis during the warm summer months. At the same time, vegetation and microbial activity release carbon to the atmosphere by respiration.
GEOquiz
1. Infer: Refer to GIA 11.1. Some of the 9 Gt of carbon from human emissions is taken up by plants and some is dissolved in the oceans. How much is left to increase CO2 levels in the atmosphere?
More carbon out than in
11.4c More thawed
As warming continues, thawing of
permafrost and soil allows microbes to flourish and decompose even more organic material, thus releasing larger amounts of carbon.
Extreme risk
DEFORESTATION INDEX 2012
High risk Medium risk
No data
BRAZIL
DEMOCRATIC REPUBLIC OF THE CONGO
PAPUA NEW GUINEA (P.N.G.)
20°S
40°S
Forests are under intense pressure across the tropical regions of Central and South America, Africa, and Southeast Asia.
Explain: On which continent do forests seem most threatened? Least threatened? What factors do you think might account for the difference?
CARBON EMISSIONS FROM ARCTIC PERMAFROST THAW
40°E
80°E
120°E
CAMBODIA
INDIAN OCEAN
2000 KILOMETRES
When permafrost remains intact, the carbon budget remains in balance. Because soil organic matter decays slowly (if at all) in cold temperatures, Arctic soils absorb and release only a small amount of carbon (GIA 11.4a). Warming temperatures cause vegetation and soils to take up more carbon
(GIA 11.4b), and as permafrost thaws, more carbon from tundra soils is released than is absorbed (GIA 11.4c). [Data from Zina Deretsky, NSF, based on research by Ted Schuur, University of Florida.]
Carbon Out
Plants respiring
Carbon
Carbon Out
More old carbon respired
Carbon
Carbon Out
Even more old carbon released
11.4b
In
Ice wedges melting
Plants growing faster
In
Plants still growing faster
More carbon in than out
Starting to thaw
As temperatures warm, the Arctic growing season lengthens, and carbon uptake by vegetation and soils increases. Higher concentra- tions of atmospheric CO2 can accelerate plant growth, causing plants to take up even more carbon. Soil microbes that decompose organic material become more abundant and release more stored carbon.
0
1000
2. Analyze: What are the inputs, actions, and outputs in the Arctic permafrost system shown in GIA 11.4? Explain.
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