The human ecology of climate change - Climate Change: Biological and Human Aspects - page 404

and African slaves. Malaria was not controlled with pesticides in the USA until the
1940s, but eradication has proven difficult and there are still sporadic outbreaks.
Eradication programmes elsewhere have been more successful, such as in Brazil and
Egypt.
The disease used to be found in Europe, including in southern England. Historically,
in England malaria was known as ague and was frequently found around coastal salt
marshes. Indeed, 200 years ago it was thought to be a leading cause of death in
many marshland communities including the Fens (in Norfolk), the Thames estuary
and further along the Kent and Essex coasts, and the Somerset Levels. It declined
in the 1840s but there were still pockets of the disease in Kent and in other low-
lying areas through to the early 1900s. The last major UK outbreak took place in
Queenborough on the Isle of Sheppey (in Kent). Soldiers returning from World War
I carried the malaria parasite, and they were bitten by local mosquitoes that went on
to transmit the disease to 32 people over several years. However, indigenous malaria
remained and from 1917 to 1952, 566 people contracted the disease in Britain. The
indigenous disease died out in 1953 with two final cases in London: mosquitoes
(probably Anopheles plumbeus ) were found breeding in a tree hole near one of the
victims' houses.
Twentieth-century England typifies the problem of malaria in many temperate
zones in the 21st century. First, we currently have a far more internationally mobile
population than ever before. This increases the chance of re-introducing malaria.
Indeed, in 1971 Europe as a whole saw around 1400 cases of imported malaria. The
subsequent years saw Europeans travel further outside the continent so that by 1986
cases of imported malaria had increased to around 6800 (Martens, 1999). By the turn
of the millennium the number importing malaria into the UK alone approximated
2000. Fortunately, only 25% of these had P. vivax , which used to be common.
Second, the disease's range is complex and the areas in which it may exist are
determined by many factors. Just as climate change threatens many wildlife species
(and note that the malaria parasites and vectors are wildlife species) so climate change
may not necessarily serve to help promulgate the disease as might be thought. The
actual theoretical areas where malaria may exist are determined by a number of
factors, of which climate is one. Just as human land use restricts wildlife species
and impedes their migration/expansion (see Chapter 6), so it does with malaria.
In the UK the extent of many wetlands near to large centres of population have
declined. Climate itself is multifactorial and malaria, or rather the parasite in the
Anopheles vector, not only requires a specific temperature range but also humidity
and duration of these conditions, as well as the aforementioned land-use criteria.
In 2000 David Rogers and Sarah Randolph showed, using climate change models,
that during the rest of this century - even under the more extreme climate change
scenarios - P. falciparum malaria might move into new areas, but that more or
less equally it would move out of old ones. The overall potential health effects of
climate change appear to be marginal; it is just the distribution that will change.
This is further complicated by whether the new areas contain more humans to infect
compared to the areas vacated. The picture is complex and again is not untypical of
the way ecosystems might respond to climate change: species assemblages may not
always shift uniformly with climate change (see Figure 6.2b). The aforementioned