Page 115 - Environment: The Science Behind the Stories

(a) Temperate rainforest 300 (a) Tropical rainforest 500

Mean monthly temperature (ºC) 40 80 Mean monthly precipitation (mm) Mean monthly temperature (ºC) 50 100 Mean monthly precipitation (mm)
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Time of year (Northern Hemisphere) 0 0 Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 0
Time of year (Southern Hemisphere)
(b) Nagasaki, Japan (b) Bogor, Java, Indonesia
Figure 4.21 Temperate rainforests receive a great deal of Figure 4.22 Tropical rainforests, famed for their biodiversity,
precipitation and have moist, mossy interiors. Climatograph grow under constant, warm temperatures and a great deal
adapted from Breckle, S.W., 2002. of rain. Climatograph adapted from Breckle, S.W., 2002.
Today people have converted most of the world’s grass- timber extraction, but they also suffer the consequences of
lands for agriculture, and almost no undisturbed native grass- overharvesting.
lands exist in North America. Vertebrate animals of the native
North American grasslands include American bison, prairie Tropical rainforest In tropical regions we see the same
dogs, pronghorn antelope, and ground-nesting birds such as pattern found in temperate regions: Areas of high rainfall
meadowlarks and prairie chickens. Because we have con- grow rainforests, areas of intermediate rainfall host dry or
verted so many grasslands for farming and ranching, most of deciduous forests, and areas of lower rainfall are dominated
these animals exist today at only a small fraction of their his- by grasses. However, tropical biomes differ from their temper-
toric population sizes. ate counterparts in other ways because they are closer to the
equator and therefore warmer on average year-round. For one
Temperate rainforest Further west in North America, thing, they hold far greater biodiversity.
the topography becomes varied, and biome types intermix. tropical rainforest (Figure 4.22)—found in Central
The coastal Pacific Northwest region, with its heavy rainfall, America, South America, Southeast Asia, west Africa, and
features temperate rainforest (Figure 4.21). Coniferous trees, other tropical regions—is characterized by year-round rain
such as cedars, spruces, hemlocks, and Douglas fir, grow very and uniformly warm temperatures. Tropical rainforests have
tall in the temperate rainforest, and the forest interior is shaded dark, damp interiors, lush vegetation, and highly diverse biotic
and damp. Moisture-loving animals, such as the bright yellow communities, with more species of insects, birds, amphibians,
banana slug, are common. The soils of temperate rainforests and other animals than any other biome.
are usually quite fertile but are susceptible to landslides and These forests are not dominated by single species of
erosion if forests are cleared. trees, as are forests closer to the poles, but instead consist of
We extract large amounts of lumber and other commer- very high numbers of tree species intermixed, each at a low
cially valuable forest products from temperate rainforests. density. Any given tree may be draped with vines, enveloped
Logging has eliminated most old-growth trees in these for- by strangler figs, and loaded with epiphytes (orchids and other
ests, driving species such as the spotted owl and marbled plants that grow in trees), such that trees occasionally collapse
114 murrelet toward extinction. Local people generally support under the weight of all the life they support.

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