As relief work is underway and the residents of Kerala return to their homes to begin rebuilding their lives and the state, scientists, researchers and farmers have begun noticing some intriguing, possibly worrying, changes in Kerala’s ecosystem.

WhatsApp forwards have indicated that a variety of foreign species are now being found in Kerala, with fisherfolk and others finding rare, exotic fishes that have never been found in the state before. One photo, which went viral, seems to indicate that an arapaima, a human-sized fish native to the Amazon river, was found by locals in Chalakudy river, Thrissur.

Scientists and researchers, who have been studying Vembanad Lake for over a decade now, have also found marked changes in the fauna in the lake after the floods. “We have been doing a fish count every year in the third week of May, and have these records as the baseline data available about the diversity of Vembanad Lake,” says Priyadarsanan Dharma Rajan of ATREE, Bangalore. “This year, soon after the floods, we repeated the survey again, and noticed that the catches of fish had increased several-fold.”

Anu Radhakrishnan, also of ATREE, says that local fisherfolk, who returned to Vembanad’s waters on August 18 after the incessant rain of August 15, 16 and 17, began noticing remarkable sightings of rare exotic fish almost immediately. “In the first week after the flood, we saw yields of up to 300 to 400 kg of exotic fish that had never been seen in the lake before, including fishes like the South American red-bellied pacu and the Assam wala. There were yields of up to 700 kg of red-bellied pacu in the first week, which soon dropped to about 100 kg in a few days.”

He also mentions other exotic species that have been found in Vembanad Lake after the floods, such as the African catfish, a large and voracious predator that has proven to be a huge menace to indigenous fish populations, and other unusual fishes found elsewhere in Kerala, like the alligator gar, a large sluggish carnivore.

But how did these fish enter Kerala’s ecosystem in the first place? Priyadarsanan says that while the raising of such exotic fishes is actually banned in Kerala, many aquaculture farms breed them illegally. He also mentioned that many dam reservoirs introduce fishes into the dams, ostensibly to provide local tribal populations a source of income and livelihood, but ended up as a source of additional revenue for the concerned government department.

Anu says, “These fishes had to come from somewhere, right? These exotic fishes come from other countries, and the government surely knows if new species are coming into India, because they have to be quarantined first, so this needs to be checked out. There needs to be stricter regulation and implementation of the existing policies.”

Introducing these fishes, many of which are sturdy hybrids that can withstand adverse weather conditions and have no natural predators in Kerala, into the ecosystem could have disastrous consequences for indigenous fish populations, and poses a severe threat to these native fish varieties. Priyadarsanan says, “Our scientists are also not developing enough breeding methods for locally available fish. Research in fishery universities needs to focus on breeding practices, creating high-yielding varieties of local fish and stock improvement, which is currently not being done.”

Across in Wayanad

While Vembanad Lake and the marine ecosystem of Kerala seem to be facing rising populations of exotic fish, over in Wayanad, farmers and researchers have noticed an alarming development about a fortnight after flood waters receded: mass deaths of earthworm populations, numbering in the thousands.

PU Das, soil quality officer in Wayanad, says that the flood waters have “flushed out organic matter and humus in the soil, which has caused a reduction in the soil’s water holding capacity.” This has resulted in an increase in soil temperature, causing delicate earthworms, which have a tolerance of between 15-28 degrees Celsius, to perish en masse. This extreme and unusual reduction in the earthworm population could have huge implications for soil fertility, which will impact agricultural production.

Great African Snail population on the rise

Meanwhile, the incessant rains and flooding in Kerala have also upped the chances of the notorious Giant African Snail spreading. “Given that there have been good rains, lots of moisture in the soil and air, and the removal of many geographical barriers due to the floods, there’s a high likelihood of these snails being easily carried or dispersed from the few districts their populations were restricted to in Kerala before the floods to other districts,” says NA Aravind, a Fellow at ATREE who specialises in research on molluscs.

Natives of Eloor and neighbouring regions have noticed alarming invasions of African Giant Snails in their homes post the recent floods. These snails, listed as one of the top 100 most damaging invasive species in the world, like to nibble on lime and cement walls, and weaken these structures with their activities.

Aravind says they pose a variety of threats to humans. “They can cause eosinophilic meningitis, which can spread to humans from their slime, either from eating them directly, which is rare in India, or from eating crops that have come in contact with their slime. They are also notorious for causing massive damage to agricultural and horticultural crops, as they feed voraciously on more than 500 different kinds of plants. Given that they are hermaphrodites that lay between 300-500 eggs at a time, the chances of invasion are high.”

The snails can be killed with salt trails, and should not be handled by direct contact.

New dragonfly species found

A recent study by the Periyar Tiger Conservation Foundation and the India Dragonfly Society conducted on 7 and 8 September also found 80 varieties of dragonfly species in the Periyar Tiger Reserve, including 8 new species, 3 of which are possibly entirely new to science itself. Periyar Tiger Conservation Foundation biologist Patrick David told The Hindu that the recent incessant rains might have affected the hatching of dragonfly eggs.

As life in Kerala slowly returns to normalcy, it's clear that researchers will need to keep an eye on all the different ways in which the floods have affected flora and fauna in the state, and the implications that these changes will continue to have on Kerala's ecosystem.