The human ecology of climate change - Climate Change: Biological and Human Aspects - page 410

most frequent cause of natural disaster after windstorms but affect more regions and
more people than any other phenomenon (WHO, 2001b). Against this background
any factor, such as climate change, likely to increase the frequency of floods (not to
mention severe windstorms) needs to be examined so that the appropriate measures
required can be anticipated.
The WHO consider the most vulnerable victims of flooding globally to be the poor
and the marginalised, most of whom live in low-quality housing, in flood-or drought-
prone regions. Those fleeing floods often drink unclean water. If the drinking-water
supply and sanitation systems are already inadequate, flooding poses a major health
risk. Flooded areas that have industrial waste, such as used engine oil, and refuse
dumps add to health risks. The WHO says that, 'people who have lost everything
in the flood - their homes, their food, their livelihood - are all the more prone to
disease'. It also noted that floods are becoming more frequent: from 66 major floods
in 1990, the number rose to 110 in 1999. Further, the number of people who died
in floods in 1999 was more than double that in any other year of the 1990s (WHO,
2001b).
In tropical countries receding waters provide an ideal breeding ground for mos-
quitoes and other insects, so creating an increased risk of diseases such as malaria
and dengue (see the previous subsection) as well as Rift Valley fever viral infec-
tions that affect both humans and animals. Flood water combined with the effects of
open sewage and reduced opportunities for good personal hygiene lead to cholera,
diarrhoea and gastrointestinal viruses, and displaced rodent populations can them-
selves cause outbreaks of leptospirosis and hanta virus infection. Flooding may also
encourage Cryptosporidium infections. Cryptosporidium is a widespread protoctistan
found in both tropical and temperate climates, the infection of which causes crypto-
sporidiosis, a diarrhoeal disease. Cryptosporidium oocysts (the cysts formed around
two conjugating gametes) can survive for long periods and are capable of penetrating
groundwater sources. In addition Cryptosporidium spp. are readily spread from per-
son to person. Infections have also been linked to swimming pools. Campylobacter
is similarly associated with water.
As with disease impact and the resistance to anti-infectives (antibiotics and anti-
virals), the health impact from floods can be exacerbated by such non-climate-related
factors, and others. For example, regional development increased the impact in 2004
of heavy storms that hit the Philippines early in December of that year, which resulted
in exceptional floods along rivers. By 3 December more than 650 people were dead
and some 400 were missing. Thousands more were made homeless. Extensive log-
ging was blamed as a compounding factor. The next day the government announced
that all logging was to be banned, subject to a review.
Another example of a major flood imparting the aforementioned health impacts
is that of the Bangladesh flood in July and August 2004. Aside from this low-lying
area having a large population, it has also been identified by the IPCC (1990) as
likely to have a higher summer rainfall in a warmer world. In 2004 the region exper-
ienced heavy monsoon rains, the worst on record. It was an extreme weather event,
again of the kind that the IPCC anticipate. In this instance 1 million people were
displaced from their homes, out of the 10 million in the nation's capital, Dhaka, mos-
quitoes, escaped sewage, disrupted food supplies and disease (for example, more than