Geoscience Reference
In-Depth Information
old tires, gutters and drains, potted plants, rain
barrels, children's toys and wading pools, litter
(cans and bottles), wheel ruts, tree holes, tall
grass, stored boats, bird baths and pet bowls,
wheel barrows, ornamental ponds, septic i elds,
and any other small depression that holds water.
For natural ponds, in contrast, the mosquitos are
typically not nuisance biters or disease carriers
(Purdue 2008).
In the agricultural sector, any kind of irriga-
tion greatly increases the potential for mosquito
breeding in furrows, ditches, runoff basins, and
other water-storage structures. Rice agriculture,
which depends on l ooding i elds, is particularly
susceptible to mosquito breeding. In sub-Saharan
Africa, for example, the malaria epidemic is
attributable largely to human activities
-
irrigation,
deforestation, mining, hydroelectric power, and
human population growth, which have drasti-
cally altered the natural environment and brought
many more people into contact with mosquitos
(American Association for the Advancement of
Science 1991). Similarly, while the city of Mumbai,
India experienced contained malaria outbreaks
primarily during the monsoon season in the
past, the recent boom in residential construction
across the city has allowed for year-round mos-
quito breeding habitats at building sites close to
dense human settlements. Widespread malaria
outbreaks are now common throughout the year
across the city, and in recent years outbreaks of
dengue fever and chikungunya spread by the
Aedes aegypti
mosquito have also posed a trou-
blesome menace.
In the authors' experience, mosquitos are
generally more prevalent and problematic in
urban, suburban and irrigated agricultural set-
tings than in natural environments. Human activ-
ities and structures greatly increase the number
of potential breeding sites for mosquitos. For
control of mosquitos, four steps are recom-
mended (North Carolina State University 2004):
• Using appropriate personal protection,
such as clothing, bed netting, and chemical
controls.
In some parts of the world, DDT (dichlorodiphen-
yltrichloroethane) continues to be used for mos-
quito control long after it was banned in the
United States and most other countries (Curtis
2007). Although the environmental damage of
DDT is well documented, it is difi cult to control
the illegal trade and use of DDT in many poorly
developed countries. DDT has already been
replaced by organophosphate and carbamate
insecticides in many countries of South Asia and
Central America, but these chemicals are more
expensive and not as persistent. Pyrethroids
also are viable for households; treating of
bednets is among the most effective means to
protect people in poorly developed regions
(Curtis 2007).
From this discussion, it should be clear that
out of thousands of mosquito species only a few
genera are truly dangerous, most importantly
Anopheles
and
Aedes
; most mosquito species are
either relatively harmless or even benei cial. The
primary sources for mosquitos that affect human
populations are, in fact, mostly man-made struc-
tures that provide mosquito-breeding habitats.
The most effective controls are those that limit
such breeding and larval habitats in close prox-
imity to human populations, for example, screen-
ing water tanks and careful use of appropriate
insecticides (Curtis 2007). Most mosquito species
living in natural wetland environments are of
minimal consequence from a human health and
disease perspective.
7.2.3 Corals
Coral reefs are typically considered to be tropical
and subtropical features of the world's shallow
continental shelves (
100 m deep). However
cold-water coral reefs also exist at depths that
may exceed 1000 m (United Nations Environ-
mental Program 2004). The deep-water habitats
of cold-water coral reefs are beyond the scope
of this topic, so we focus herein on shallow
coral-reef wetlands, as dei ned by Ramsar (see
chapter 2). Such reefs are typically found at low
<
• Identii cation of species
-
many are non-
threatening and some are benei cial.
• Knowing about biology and behavior of
these species.
• Eliminating breeding sites, particularly arti-
i cial sites close to human habitations.
