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The earth gets only 2 billionths of
the sun's energy, but that is still a lot. However, you can see on
the chart that life (through photosynthesis) uses only .023%
of the energy that reaches the surface of the earth.
34% of the sun's energy is reflected
back into space by snow and clouds. This reflective quality of a
planet is called its
albedo.
42% of the energy goes to warm the land and water. The warmth
of the earth is constantly being radiated into space, and the
sun's energy replenishes this warmth.
The water cycle -- evaporation and precipitation -- uses 23%
of the solar energy.
Winds and ocean currents use 1%.
A
Math Page:
To
get the details on how to calculate energy available for plants,
click here.
The table below tells how many
KiloCalories (food calories) are available for animals to eat in
different biomes.
Primary Productivity
Table
|
Ecosystem Type |
Net Primary
Productivity
(Kilocalories per square meter per year) |
Approximate
Kilocalories per square meter per day |
Rainfall
per year in inches |
Growing Season |
Percentage
of earth's surface covered by this biome |
| Tropical
Rain Forest |
9000 |
25 |
More
than 60 |
365 days |
11% |
| Estuary
(the place where a river meets the sea
-may have many channels and be a delta.) |
9000 |
25 |
water environment |
|
3% |
| Swamps
and Marshes |
9000 |
25 |
water environment |
|
| Deciduous
Temperate Forest |
6000 |
16 |
30-60 |
More than 120 days |
22% |
| Boreal
Forest (Evergreen Coniferous Forest) |
3500 |
10 |
12-33 |
Less than 120 days |
Savanna
(grass, scattered trees,
little or no winter snow) |
3000 |
8 |
. |
|
21% |
| Temperate
Grassland (cold winters) |
2000 |
6 |
10-30 |
|
| Polar
Tundra |
600 |
2 |
Less
than 10 |
|
33%
includes sand and ice |
| Desert |
< 200 |
Less
than 1 |
--- |
|
| Open
Ocean |
300 |
Less than 1 |
Less
than 10 |
|
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Cultivated land covers about 9% of
earth's land surface, and has replaced tracts of forest and some of
the more generously watered grasslands. Humans require land with a
minimum of 20 inches of rain per year in order to grow their crops
and to survive. In some places, the natural rainfall is suppliment
with irrigation.
This table is from http://www.geog.ouc.bc.ca/physgeog/contents/9l.html
an online Geology course created by Dr,
Michael Pidwirny at Okanagan College, British
Columbia, Canada. I have added additional material from http://www.millersv.edu/~geograph/steve/101/exercise7.htm.
The numbers are not in perfect agreement, but they are close. (Dr
Viau's additons are in red)
The Caloric Content of
Foods
Some Animal Weights and
Caloric Requirements on Earth
Return to
© Elizabeth Anne Viau,
1999. This material may be used freely for instructional purposes
but not sold for a price beyond the cost of reproduction. Please
inform the author if you use it at eviau@earthlink.net
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