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This is the Agriculture Report. |
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Irrigation systems can make a big difference |
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in agricultural production. |
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Irrigation can also improve the lives of farm families. |
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However, the addition of water to the land or soil |
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may cause problems in some areas. |
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A new study describes how irrigation water |
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can lead to an increase in malaria cases |
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that could last for ten years or more. |
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Malaria is spread by mosquitoes, |
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the insects like to reproduce in standing water. |
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So when a dry area is irrigated, |
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the disease can appear and spread. |
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Mercedes Pascual is a scientist at the University of Michigan. |
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She and her team studied areas in northern India |
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where irrigation systems were built over a number of years. |
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They compared how malaria progressed with the spread of irrigation. |
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"What happens is that when you irrigate, there is more, |
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in a sense, more breeding habitats for the mosquito." |
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She and the other scientist found |
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that after farmers began irrigating their crops, |
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the risk of malaria rose sharply. |
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At first, her team thought maybe the number of cases rose |
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because there was little effort to control the mosquitoes |
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that spread the disease. But they were wrong. |
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"In fact, we saw the opposite. |
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This transition stage was characterized not just |
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by heightened malaria risk, |
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but also by more intervention to control the mosquito vector." |
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Even after the mosquito control efforts were in place, |
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the researchers found high rates of malaria |
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continued for ten years or longer. |
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Mercedes Pascual suggests that the irrigation project supervisors |
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need to work more on reducing places |
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where mosquitoes might reproduce. |
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She also says health officials may need to try other methods of |
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malaria prevention that would work for long periods of time. |
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"And what we are saying is that those measures have to be sustained, |
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and sustained and also planned for, for the long term." |
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In the words of the researchers, |
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irrigation offers considerable rewards in areas with low rainfall. |
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But as Mrs Pscual and her team discovered irrigation |
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also can bring years of high rates of malaria. |
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The only way to avoid the problem |
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is through better planning and control measures. |
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A report on the study was published |
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in the Proceedings of the National Academy of Sciences |
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of the United States of America. |
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And that's the Agriculture Report from VOA Learning English. |
