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Seriously affected by floods of 2018
Farmer Sanmathy Raj was walking to his field last week when he stopped short. Dead earthworms covered the ground. “I couldn’t walk without stepping on them,” he said. It’s normal for earthworms to creep out of the soil after rains, but Kolavayal, Raj’s village in Kerala’s Wayanad district, has been dry since flood waters receded.
Baffling as the scene was, mass earthworm deaths have also been reported from other parts of Wayanad and Idukki districts. Scientists and the state government are worried, as earthworms maintain soil fertility, and their decimation so soon after the floods could mean another crisis.
The last time earthworms died in such large numbers in Wayanad was in the summer of 2016, and experts say high soil temperatures could be the cause. After the rains abated in the region, daytime temperatures have risen from 22 degrees Celsius on August 21, to 29.4 degrees on Thursday.
“Indian earthworms generally have a tolerance of 15-28 degrees,” said N Anil Kumar, senior director at the M S Swaminathan Research Foundation. He said earthworm deaths could hurt agriculture.
Changes in soil conditions after flooding could also be responsible. A tonne of soil contains about 5 kg of organic matter and retains 50 litres of water, Wayanad soil conservation officer P U Das said. “But floods flushed out organic matter from the soil, reducing its water holding capacity.” Drier soil heats up more, forcing earthworms out.
The types of earthworms found in Wayanad and Idukki and the reasons for their deaths are different, said S Prasanth Narayanan at the Mahatma Gandhi University.
He said preliminary reports indicate the earthworms in Wayanad are an exotic species that could have perished because of the sudden change in night temperature and severe soil dryness. In Idukki, deaths appear to have been caused by the prelandslide vibrations.