Spread of invasive plants, habitat destruction destroying food for herbibores, which in turn is affecting carnivores
This is the second part of a series exploring the food crisis for wildlife. Read the first part here.
Chakkakompan has a soft spot for jackfruits. Every now and then, the bull elephant ventures out of the Idukki Wildlife Sanctuary in Kerala and raids farms and homesteads in the adjoining Santhanpara and Chinnakkanal panchayats for its choice of food. Troubled by its frequent incursions, most farmers in the region have now switched to other crops; those who still have the trees in their homesteads pluck the fruit while it is raw.
While Chakkakompan is easily chased back to the forest, Arikomban, another bull elephant from Idukki Wildlife Sanctuary, was not. For at least five years till 2022, Arikomban raided paddy fields, ration shops, home kitchens and grocery stores in the highlands of the district for grains.
After repeated failed attempts by the forest officials to prevent Arikomban from straying into human habitations, it was tranquillised, captured and translocated to Kalakkad Mundanthurai Tiger Reserve in Tamil Nadu in June last year.
While such incidences are easily passed off as human-wildlife conflicts, both the elephants started raiding the crops because of the shortage of food in Idukki forest.
This food shortage has been primarily brought on by habitat destruction, the spread of invasive species such as Lantana camara (lantana) and Senna spectabilis (weeping cassia) and a lacklustre attitude towards eco-restoration efforts. Monocultures of species like eucalypts and acacia have also harmed plant biodiversity and led to a lack of food.
Human-wildlife conflict has increased in Kerala over the last two decades, causing deaths and injuries among farmers living near forest areas, as well as crop damage. Since 2011, wild animal attacks have claimed the lives of 1,233 people in Kerala.
While Wayanad and Palakkad districts are particularly vulnerable to wild animal attacks, all districts in Kerala except Alappuzha have reported such attacks. Conservation programmes and tight enforcement of anti-poaching legislation have led to an uptick in the number of animals and conflict events, claimed forest officials.
Forest authorities are not doing enough to ensure enough food for Kerala’s wild elephants, claimed Thiruvananthapuram-based environmentalist Veena Maruthoor. Relocating one elephant may not be the best solution, she further pointed out.
“We know that the native plants across Kerala have been replaced by alien species that have now become the region’s common plants and trees,” said T V Sajeev, senior scientist at the Kerala Forest Research Institute in Thrissur district.
Invasive species like Lantana camara and Senna spectabilis unleash a form of chemical warfare as their shed leaves decompose and change the chemical composition of the soil, rendering it unsuitable for the growth of other plant species, said P A Vinayan, president of Ferns, a Wayanad-based nature conservation society.
Wayanad, along with Idukki and Palakkad districts, is undergoing rapid infestation by alien species, as per a study released by the Kerala forest department in May 2023. “This has a significant impact on forest productivity. Under the invading plants, the forest floor is nearly barren. Grasses and herbs are eradicated, depriving herbivores of food,” said Vinayan.
The invasive species arrived in Wayanad in the 1980s, when seedlings of the plant were first produced in the social forestry wing nurseries and planted as avenue trees. About 25 years after its introduction, the plant started spreading rapidly. It spread over time to the Karnataka tiger reserves of Bandipur and Nagarhole, as well as the Tamil Nadu tiger reserves of Mudumalai and Sathyamangalam. These areas have all reported an increase in wild animal conflict as well.
Arikomban was located earlier in a 365-hectare-wide land region filled with inedible eucalyptus trees. If it had been converted to grasslands, the jumbo would likely not have strayed into human habitation and discovered his fondness for rice.
Invasive or exotic species pose a huge challenge due to their rapid growth and tolerance for a wide range of environmental conditions. As a result, continual monitoring and clearance are required to remove the invasive species. Agricultural lands are thus much safer from harmful weeds because they are constantly maintained and cleaned.
A July 2023 report by the international non-profit World Wildlife Fund said the 2018 floods in Kerala aided in the spread of invasive plants such as those in the genus Senna, Mikania, Lantana and Eupatorium in the state’s elephant habitats.
Water hyacinths from South America are another invasive species that have taken over Kerala’s waterbodies, choking the waterways. Another similar species is the African payal, which is endemic to Australia but was identified as a pest in 1956.
The lack of food and water is driving away the herbivores and in turn, affecting the carnivores. “The survival of carnivores is directly dependent on high densities of herbivores and the food shortage is one of the primary reasons their population is shrinking in Kerala,” said Vinayan.
In Kerala, the elephant population has shrunk by over 40 per cent in the past six years (2017-23) to just 1,920 in 2023, shows data released by the state forest department. In Wayanad landscape of the state, tiger population has also shrunk by 30 per cent between 2018 and 2023.
Nearly 10 years ago, the Forest Departments of Karnataka and Kerala recognised that the tree was a threat to native biodiversity and began taking steps to limit its spread. Senna spectabilis infests around 23 per cent of the area of Wayanad Wildlife Sanctuary, according to a study by Ferns’ Vinayan.
The survey found 1,305 trees in one hectare of the sanctuary’s worst-impacted locations. The species is spreading at about the same rate in the neighbouring tiger reserves.
Officials of the Kerala forest department say they are working on a “big plan” to manage micro-habitats like marshy grasslands, which are critical in maintaining herbivore numbers by providing luxuriant fodder. In Wayanad, the forest department has recently initiated a scheme to remove the skin of invasive trees.
The department tried to remove invasive species trees by uprooting, girdling, cutting, and chopping the limbs, as well as testing the use of chemicals. However, all efforts were futile. Instead, coppice shoots began to sprout from each cut tree stump.
Senna eradication is a key component of the sanctuary’s forest management strategy, but it has yet to have noticeable results in the forest.
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