Climate change includes both rising average ambient temperatures and increased frequency and ferocity of weather extremes. Both have direct and indirect effects on health. They also have important effects, mostly adverse, on food crops and on animals, including marine animals that are staple parts of human diets. In short, climate change seriously threatens food security.
Weather extremes -- droughts, floods, violent storms -- have obvious effects on human health. Hurricane Katrina which struck New Orleans and the Mississippi delta in 2005 caused about 2,000 deaths and displaced several hundred thousand people. But it was only a Category 3 hurricane by the time it made landfall. Several more severe storms have hit the southern USA and Mexico since 2005, but most have struck unpopulated regions. Hurricane Sandy (2012) caused tremendous property damage along the New Jersey and adjacent New York coasts but relatively little loss of life. Similar severe storms in other parts of the world with less efficient disaster preparedness, e.g. south China, can lead to far greater numbers of deaths, injuries and infrastructure damage. Droughts and floods disrupt food crops and are a serious threat to food security. The effects of extreme weather are most pronounced in regions where the people are poverty-stricken, can't afford air conditioning, have flimsy huts rather than solidly built homes, or are crowded in shanty towns on flood plains.
Many insect species flourish in warmer weather. These include insect vectors of diseases that have great public health importance, particularly the varieties of mosquitoes that carry malaria and dengue. Epidemiologic surveillance and monitoring habitat of insect vectors have revealed that the range of vectors has extended further into previous temperate zones and higher altitudes that in the past have been free of malaria and dengue (and other vector-borne diseases). Nairobi, Harare, Kampala, and other large cities in the East African highlands are outside the range of vectors for malaria and dengue, but as the climate gets warmer these dense human settlements will become vulnerable. Some ecological relationships between vectors, pathogens and people are complex. For instance, Lyme disease is spread by ticks that feed on deer which normally are not in contact with humans; but as affluent suburbia extends further into rural regions, humans and wild deer become more likely to be in closer contact. Hence the risk of Lyme disease is increased. Other ecosystem disruptions also occur. For instance, marine species such as salmon and mackerel reproduce successfully within a narrow temperature range. As sea surface temperature rises there are many disruptive consequences, among which collapse of marine species such as mackerel may be relatively minor in the grand scheme of things. But it is a calamity for predators (seabirds, dolphins, etc) that feed on mackerel, as well as a serious loss of seafood for humans.
Rising temperature in inland freshwater lakes and rivers accelerate reproductive cycles of micro organisms, including pathogens. The ecological consequences are complex, and include an increase in waterborne diseases -- cholera, diarrhea, parasitic infections. The South American cholera epidemic that began in the early 1990s and lasted over 10 years was started when the cholera organism was introduced by ships trading from the Bay of Bengal. It was facilitated by a symbiotic relationship between the cholera vibrio and other freshwater organisms, notably zooplankton. This epidemic caused over half a million cases and almost 100,000 deaths. Persistence of the epidemic was fostered by interaction of the cholera vibrio, marine zooplankton, and the warmer water temperature of river estuaries along the Pacific coast of South America. A southward fluctuation of the El Nino tropical Pacific Ocean current made those coastal waters unusually warm, thus enhancing survival of the cholera vibrio and increasing the risk of infection. Warmer weather also leads to proliferation of allergenic grasses and weeds, and is responsible for rising prevalence of asthma and hay fever.
There are many other health-related consequences of rising environmental temperature. For instance, riots and civil disturbances occur more often in hot weather than cold, which tends to encourage people to stay indoors to keep warm, rather than congregate in unruly crowds. on city streets These social disturbances tend to cause deaths and injury of those who take part. The moral of this story: avoid crowds and eschew demonstrations in hot weather.
There is much more I could say, but this is probably more than enough for casual readers. There's plenty more available for anyone interested. See, for example,
No comments:
Post a Comment