Stone quarrying has affected population in some areas of East Khasi Hills district.
An army of blue earthworms, some measuring up to 1.6 feet, migrate about 300 metres up and down the steep slopes in Meghalaya’s East Khasi Hills every year.
Scientists of the Zoological Survey of India (ZSI) have for the first time prepared a report on the two-way mass migration in the district’s Mawlyngot area.
But the locals apparently beat them to observing these earthworms, scientifically called Perionyx macintoshi, and the role they play in enhancing the fertility of soil on their land to shift to ecologically sustainable organic farming.
On the flip side, the scientist duo of Ilona Jacinta Kharkongor and Bhaskar Saikia found areas where “unsustainable land-use practices” have drastically reduced the population of earthworms to a few “lethargic wrigglers”. Much of the damage has been done by stone quarry and heavy earth-cutting for road connectivity and village expansion.
“The blue earthworms migrate twice annually — uphill in spring and downhill in autumn on inclines of up to 80-85 degrees to evade environmental factors that affect them. The research was done from 2011 to 2015 around the Mawlyngot plateau and the rivers Um Stew and Um Ñiuh around it,” Bhaskar Saikia of ZSI’s Shillong-based North East Regional Centre told The Hindu on Saturday.
The study he co-authored with Ms. Kharkongor was published in the latest issue of the journal, Records of the Zoological Survey of India.
The uphill migration starts in April-May coinciding with the onset of the monsoon when they emerge from the rivers and streams where they ‘overwinter’ under the rocks. Increased flow of water in such rivers and streams, signalling arrival of the rains, is said to trigger their emergence for the migration.
The downhill migration happens during September-October when the vegetation begins to dry off and the temperature and humidity drop.
Ms. Kharkongor said the timing is crucial during downhill as the worms fail to reach their favoured destination if there is any deviation in the ecological factors. For instance, they had in October 2013 observed hundreds of earthworms having died of desiccation before they could reach the water body from 800 metres above sea level to a gorge 300 metres downhill.
“The rain had stopped abruptly in September-end that year after a short burst of showers,” she said.
Mr. Saikia said the worms help enrich the soil. The local farmers had the wisdom to observe them and adopted organic practices, shifting from broomstick cultivation to grow organic tea that has gained in brand value abroad.
But the scientists observed the population dwindling in areas where human interference in the form of stone quarrying and earth-cutting has increased. “As in the case of other animals, factors like developmental activities, predation, erratic weather patterns and climate change pose risks to successful migrations of earthworms,” he said.