Use of chemical pesticides in plantations in the Western Ghats might have wiped out a few endemic odonate species including damselflies and dragonflies, fear experts.
While assessing the conservation status of odonates in the Ghats region by the International Union for Conservation of Nature (IUCN), data regarding 46 species have been found insufficient. Of the 46 species, 25 are endemic to the region. The deficiency of data may be attributed to the decline in the population of the species. The impact of pesticides such as organochlorines, organophosphates, and synthetic pyretheroides on odonates is yet to be assessed, according to the IUCN report.
The evaluation has been part of the IUCN-supported programme on the assessment of freshwater biodiversity of the Western Ghats.
The absence of some of the endemic odonate fauna in streams running through tea, coffee, cardamom, and rubber estates in the region, as indicated in recent field studies, may be due to the use of pesticides. Data are found insufficient mostly in the case of mountain species, says Francy Kakkassery, Associate Professor, Department of Zoology, St. Thomas' College, Thrissur, who has participated in the evaluation.
Of the 171 species assessed, four have been categorised as vulnerable, six as near-threatened, and 115 as least-concerned.
“Conversion of Myristica swamps into areca nut and other plantations is fast denuding important habitats for endemic odonates, especially monotypic species such as Phylloneura westermanni, Melanoneura bilneata, and Calocypha laidlawi . Riparian deforestation for agricultural development, along with diversion of streams and indiscriminate construction of dams, drastically alters the flow dynamics of the streams and fundamentally changes the larval habitats,” the report says.
Chlorogomphus xanthoptera , a vulnerable species, is currently known only from the upper reaches of the Cauvery river in Kushalnagara (Kodagu, Karnataka) and the Kuruva islands (Wayanad, Kerala). In these locations, the rivers and riparian forests are impacted by tourism-related activities. Disaparoneura apicalis , classified as vulnerable, is also found on the Kuruva islands. Protosticta sanguinostigma , another vulnerable species, reported from three to four localities in the southern Western Ghats, prefers unpolluted streams with good riparian forest cover. The expansion of agriculture in the catchment areas of these streams and the resultant pollution have affected the species, the report says.
A few odonate species play an important role in the control of mosquito population by feeding on them. The larvae of odonates also feed on mosquito larvae. The absence of breeding grounds following the shrinkage of freshwater bodies is a matter of concern for the odonates. There has been a general decline in the population of the species in urban and rural areas as well, mostly because of the absence of breeding grounds, says Dr. Kakkassery.