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PUBLIC HEALTH
2 November 2014 18:01

Rising temperatures will delay disease reduction in China, study shows

Robert McSweeney

Robert McSweeney

11.02.14
Dong village, China.
Robert McSweeney

Robert McSweeney

02.11.2014 | 6:01pm
Public healthRising temperatures will delay disease reduction in China, study shows

Efforts to reduce water-related diseases in China will be hampered by climate change, a new study finds.

Despite continued improvement in access to clean water and sanitation across China, rising temperatures could set back progress in reducing infectious diseases by as much as seven years by 2030.

Warmer temperatures

According to the UN, China has made significant progress on reducing water-related diseases in recent years. It has already met its Millennium Development Goal to halve the number of people without access to safe drinking water.

Recent decades have seen a huge drop in cases of water-related diseases in the country. Between 1990 and 2010 deaths from diarrheal diseases fell by  94 per cent. Malaria and Japanese encephalitis, both spread by mosquitoes that breed in water, fell by over 60 per cent and over 80 per cent, respectively.

However, a study published in Nature Climate Change suggests further progress on water-related diseases will be stunted by climate change.

Delay

The research estimates how much progress China will have made on reducing diseases by 2020 and 2030, and compares that with scenarios where temperatures have risen because of climate change.

The results show that efforts to reduce the spread of infectious diseases will be delayed by as much as seven years by 2030 if greenhouse gas emissions continue to rise at current rates.

Under a moderate climate change scenario, where the rise in global greenhouse gas emissions is curbed, the average setback across China is still as much as three years.

The researchers also mapped how the delays would vary depending on how much progress China makes on providing clean water and sanitation. Despite recent improvements, as of 2011, 471 million people in China still lack access to proper sanitation and 401 million lack piped water in their homes. Success in combating disease will also depend on how quickly these needs are met.

The maps below shows three different levels of progress and the how much of a delay rising temperatures will cause.

China Disease Reduction Delay Maps

Maps of delay on disease reduction because of rising temperatures, using a moderate scenario of climate change. The different development paths refer to projections of progress on water supply and sanitation improvement, from limited (top) to rapid progress (bottom). Hodges et al. (2014).

You can see by the dark reds that the longer delays are projected when less progress is made on clean water and sanitation. The maps also reveal regional differences, with longer delays expected for the rural areas of the northeast and south (which includes Tibet), and shorter delays for the more urbanised areas towards the centre.

Complicated relationship

The relationship between climate and water-related diseases is a complicated one, which the study’s authors acknowledge is difficult to put into numbers. There are many factors that affect the spread of disease, many of which are related to poverty, such as access to clean water.

For climate change, the obvious link to disease is through changes in extreme rainfall. Heavy rain and flooding can increase the risk of clean water mixing with sewage, while drought can reduce access to water altogether. However, few studies have been able to quantify the link, which is why the authors chose to concentrate on temperature changes only.

Water-related diseases may spread more easily in warmer temperatures because the disease organisms can grow more quickly. A study in Lima, Peru, for example, found that for every degree the air temperature increased during an  El Niño event there was an eight per cent increase in hospital admissions for diarrhea.

For diseases spread by mosquitoes, such as malaria, dengue fever and Japanese encephalitis, warmer temperatures mean they can  expand into areas that had previously been too cold.

So, even without taking into account changes in rainfall, climate change is likely to make it more difficult to for China to reduce the burden of disease. It remains to be seen how the progress China makes on access to clean water and sanitation will interact with the impact of rising temperatures.

Main image: Zhaoxing – gorgeous Dong village is packed whit traditional wooden structures, several wind-and-rain bridges and remarkable drum towers, China. Guizhou province.

Hodges, M. et al. (2014) Delays in reducing waterborne and water-related infectious diseases in China under climate change, Nature Climate Change,  doi:10.1038/nclimate2428.

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