The medicinal plant wealth of both Maradavally State forest and Devrayanadurga forests is declining constantly over the years. Of the 147 species of medicinal plants reported from Maradavally range forest, fourteen species are listed as endangered of whichCatuneregam spinnosais at the verge of extinction. The other endangered species are:Garcinia cambogea, Acacia pinnata, Ficus benghalensis, Zanthoxzyllum rhesta, Hemidesmus indicus, Terminalia chebula, Wrightia zeylanica, Cinnamomum verum, Bombax ceiba, Sapindus laurifolius, Alangium salvifoliumandCalophyllum inophyllum.
In Devarayanadurga forest, out of 307 species reported,Abrus precatorius, Adenanthera paronina, Aegle marmelos, Caesalpinia bonducella, Cardiospermum halicacabum, Corallocarpus epigaeus, Gloriosa superba, Andrographis paniculatahave become uncommon andJatropha curcasis endangered.
The major factors threatening the species and genetic diversity of medicinal plants in Maradavally and Devarayanadurga are similar to those operating elsewhere in India. Many factors both natural and man made have been responsible for limiting the distribution of medicinal plant species and are causing them to become rare or even extinct.
Rainfall:
In the forest areas the annual rainfall has decreased to the extent of 40% in Maradavally forest and 50% in Devarayanadurga forest resulting in the death of many herbaceous species during summer months.
Deforestation:
Deforestation to an extent of 10% in Maradavally and 25-30% in Devarayanadurga forests has been reported over the last two decades. The spread of agriculture, logging, fire wood collection, heavy grazing etc, are the main reasons for reduction in area under valuable forest.
Siltation of water bodies:
In Maradavally forests, 4 tanks have silted up to 30% of their capacity and in Devarayanadurga forest, siltation is up to 40%. Siltation of water bodies in both the forests has resulted in the reduction of water holding capacity leading to depletion of underground water.
Lack of pollinators:
Honey bee colonies have declined in numbers to the extent of 60% in Maradavally and 90% in Devarayanadurga forests. Loss of pollinators has resulted in reduced seed set and dispersal of seeds.
The Maradavally forest is the catchment of Linganamakki Dam, the main reservoir of Karnataka for irrigation and power generation. Submersion of nearly 10 sq. km of forest area during monsoons has resulted in loss of valuable medicinal plant species.
Infrastructure:
Expansion of roads of about 14 kms in Devarayanadurga, and installation of power lines in Maradavally forests have caused extensive damage to forests and medicinal plants.
Monoculture:
There has been a progressive increase in monoculture plantations of economically important indigenous as well as exotic species in both Maradavally and Devarayanadurga forests. Nearly 5-10% in Maradavally and 10-15% in Devarayanadurga forests have been planted with Eucalyptus and Acacia species. Monoculture plantation totally affects the organic productivity and reduces the natural stability and complexity resulting in loss of medicinal plants.
Encroachments:
Encroachments over forest lands in Devarayanadurga forests have assumed alarming levels. Apart from felling of trees and clearing vegetation, the cultivation practices followed on high slopy lands have caused soil erosion, and decline of medicinal plant wealth. Encroachment is minimal in Maradavally forest.
Over exploitation:
Gathering of medicinal plants from both the forests of Maradavally and Devarayanadurga are rampant. About 20-25 collectors engaged by a licensed contractor, gather nearly 40 types of medicinal plant products from the forests of Maradavally between November to April, where as the forest record shows only 5 types. The approximate quantity of material collected every year would be approximately 20-25 tonnes. In Devarayanadurga forests, collection of medicinal plants by outsiders was severe a few years back. Every year about 5-10 tonnes of material were gathered by the outsiders. The collection was by unorganized forest collectors, who in turn sold the product to a contractor at the price fixed by the latter. But now, due to the awareness created by the members of the 'Local Traditional Medicinal Practitioners' Association', illegal gathering has been controlled to a certain extent.