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Global warming may affect pesticide effectiveness

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New Delhi: The effectiveness of an important mosquito-fighting insecticide may be impaired by global warming, according to a recent study.

Two researchers from Montana State University, graduate student Shavonn Whiten and Robert Peterson, have shown that permethrin becomes less effective at killing the yellow fever mosquito (Aedes aegypti) as temperatures increase.

These mosquitoes, which are found in the tropics and the subtropics, can transmit viruses that lead to dengue, chikungunya, yellow fever, and other diseases.

“Many of the areas where these insecticides are employed have varying drastic temperature changes,” Shavonn Whiten said.

The researchers exposed adult mosquitoes to varying concentrations of permethrin at a range of temperatures.

They found an inverse relationship between death and temperature from 16 AoC to 30 AoC, which showed the highest negative correlation.

From 30 to 32, there was, however, a positive correlation between mortality and temperature. And from 32 to 34, the negative correlation resumed.

“It probably has something to do with variability and heat stress,” said Peterson.

“Once you get to those higher temperatures, there are other things going on regarding stress on the mosquito that cancel out the effect of the pyrethroids (a class of pesticides to which permethrin belongs) working better at lower temperatures and worse at higher temperatures,” he explained.

People involved in mosquito-control efforts should take temperature into account when choosing a pest control product, researchers said.

The study was published in the Journal of Medical Entomology.

(IANS)

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A rise in 2 degrees Celsius in global warming could cause droughts

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A rise in 2 degrees Celsius in global warming could cause droughts
A rise in 2 degrees Celsius in global warming could cause droughts. wikimedia commons

New York, Jan 2, 2018: A rise of just 2 degrees Celsius in global warming could make over a quarter of the world’s land to become drier and more desert like, increasing the threat of widespread drought and wildfires, new research led by one of Indian origin has found.

The study showed that reducing greenhouse gas emissions into the atmosphere to limit global warming under 1.5 or 2 degrees Celsius would dramatically reduce the likelihood of significant aridification emerging in many parts of the world, the researchers said.

Aridity is a measure of the dryness of the land surface, obtained from combining precipitation and evaporation.

“Our research predicts that aridification would emerge over about 20-30 per cent of the world’s land surface by the time the global mean temperature change reaches 2 degrees Celsius,” said Manoj Joshi from the the University of East Anglia’s School of Environmental Sciences.

“But two thirds of the affected regions could avoid significant aridification if warming is limited to 1.5 degrees Celsius,” Joshi added.

For the findings, published in the journal Nature Climate Change, the team examined projections from 27 global climate models to identify the areas of the world where aridity will substantially change when compared to the year-to-year variations they experience now, as global warming reaches 1.5 and 2 degrees Celsius above pre-industrial levels.

The world has already warmed by one degree Celsius. As a result, drought severity has been increasing across the Mediterranean, southern Africa, and the eastern coast of Australia over the course of the 20th Century, while semi-arid areas of Mexico, Brazil, southern Africa and Australia have encountered desertification for some time as the world has warmed.

“Aridification is a serious threat because it can critically impact areas such as agriculture, water quality, and biodiversity. It can also lead to more droughts and wildfires – similar to those seen raging across California,” explained Chang-Eui Park from the Southern University of Science and Technology (SUSTech) in China. (IANS)

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