Geography Reference
In-Depth Information
Tropical monsoon
Unlike the rainforest realm, tropical monsoon regions experience a distinct dry season. That is be-
cause tropical monsoon regions generally lie in the area located between Latitudes 5° and 10° North
and South, where the drying effect of the sub-tropical high-pressure belts are felt for part of the year.
Despite high annual rainfall, the periodic dryness is sufficient to prevent the presence of many plant
species that grow under tropical rainforest climatic conditions. Other than that, the characteristics and
problems facing the world's monsoon lands are rather similar to the rainforest realm. In fact, expect
for the monsoon's wet and dry seasons, the characteristics are so similar that many climate maps in-
clude tropical monsoon regions within the tropical rainforest category — as is done in Figure 10-2.
Malaria: A case study in climate and disease
Each year about 300 to 500 million cases of malaria occur globally and some 1.1 million
people — mainly residents of sub-Saharan Africa — die from the disease or related com-
plications. The disease is caused by a parasite that consumes red blood cells, caus-
ing high fever and other side effects. Species of mosquitoes that belong to the genus
Anopheles
are responsible for malaria in humans.
When a mosquito “bites,” it actually sticks a syringe-like appendage into its victim and
sucks up some blood. (Mosquitoes have no teeth, so they literally couldn't bite if their
lives depended on it.) This rather antisocial behavior is necessary for mosquito reproduc-
tion, blood being required to produce eggs. Accordingly, and with no disrespect intended,
it is only the females that bite. When a mosquito sucks up blood from a person or animal
that has malaria, it may also suck up the malarial parasite. Hundreds of species of mos-
quitoes exist; and fortunately for humans, in just about every case, sucked-up malarial
parasites die soon after entering the insect's body. For whatever reason, however, in the
body of an
Anopheles
mosquito, the parasite remains viable, and thus is capable of be-
ing spread to the next human or animal that the insect “bites.” The geography of malaria,
therefore, is largely determined by the geography of the
Anopheles
mosquito, which is in
turn is determined by the geography of the environmental conditions that the mosquito
requires in order to live and reproduce. The principal criteria are temperatures that stay
above about 75° F, and standing, shaded fresh water in which the insect can lay its eggs.
In other words, it requires conditions that exist in abundance in areas that experience hu-
mid tropical climates.
People used to think that tropical air was unhealthy (hence,
mal aria
— “bad air”), and
in many circles, belief persists that tropical climates are dangerous to humans. In truth,
nothing is innately harmful about a warm and humid atmosphere. But what does occa-
sionally happen is that climate gives rise to environmental conditions that are ideal for
