BIODIVERSITY |
The vegetation was studied using transect based quadrat sampling methodology in 140 localities of the Sharavathi upper catchment area and in 26 localities in the Sharavathi lower catchment area (field investigations are in progress in the downstream region of the river basin). The natural vegetation ranges from the climax tropical evergreen to semi-evergreen forests along the high rainfall areas of the main hill ranges of the Western Ghats to the moist deciduous forests in the undulating plains and low hills along the eastern drier tracts of the river basin. The landscape everywhere is in fact a mosaic of a variety of elements, which are caused by human impacts through historical times to current period.
The number of tree species per hectare in the evergreen to semi-evergreen forests is in the range of 35 – 60. The moist deciduous forests have 15 – 25 tree species per hectare. Basal area per hectare ranges from 35 - 60 sq. mt. in good forests. In the deciduous forests, the basal area ranges from 20 – 35 sq. mt. The evergreen forests are of high conservation value since they are great repositories of endemic species of the Western Ghats (50 – 80 % for trees). On the contrary, the deciduous forests, largely caused by human induced fires have endemism as low as 9 – 15 % for trees. We have observed that there exists a high correlation between vegetation endemism and endemic fauna. Endangered endemic animal species such as the Lion tailed macaque, Slender loris, Jungle striped squirrel, Malabar pied hornbill, Saw scaled viper and the butterflies like Southern birdwing, Budha peacock are associated with the last relics of the climax evergreen patches. Semecarpus kathalekanensis an altogether new species of tree has its precarious existence in the endangered Myristica swamps of Siddapur Taluk.
The evergreens to semi-evergreen forests are the major sources of perennial water sources throughout the catchment of Sharavathi. On the other hand in the deciduous tract, the streams mostly dry up in the summer months. Therefore conservation of evergreen forests and restoration of such forests in the eastern parts of the catchment are of paramount importance.
Bulk of the waters into the reservoirs comes from natural forests. Unfortunately in substantial part of the catchment area monoculture plantations have been raised causing the drying up of the streams and impoverishment of the ecosystems as a whole. Since the plantations do not yield any fodder or NTFP, the rural population is put to great hardships. Therefore such land uses are not desirable in the catchment area of this important river, which produces substantial part of hydropower for Karnataka state.
The river basin has a variety of habitats (21 listed in the report) that support rich flora of herbs, shrubs and climbers of which we have recorded about 215 species. Temporal seasonal surveys will reveal more number of herbs. Evergreen to semi-evergreen forests and grasslands of the Western Ghats have the largest congregations of endemic herbs. Some of the herbs are exclusive to specialized habitats like tree trunks and wet rocks. The increasing human impact and openings in forest canopy as well as over grazing by cattle are posing threats to many of the herbs.
The numerous streams and the banks of the river and its tributaries in the evergreen to semi-evergreen forest belt are lined with characteristic riparian vegetation of which the notable tree species are Calophyllum apetalum, Elaeocarpus tuberculatus, Mastixia arborea, Hydnocarpus wightiana, Madhuca neerifolia, etc. Towards the drier forests of the east the water bodies are lined with tree species such as Pongamia pinnata, Madhuca neerifolia, Hopea wightiana, Bambusa sp, etc. The riparian vegetation plays a crucial role in protecting the water bodies from siltation, creating shade conditions to maintain appropriate temperature regime for sustaining populations of endemic fishes, amphibians, phytoplankton, zooplankton and aquatic insects. Of late there has been numerous instances of misuse of the banks of streams and rivers in the catchment area causing severe upsets in the characteristic biota associated with them. Stream waters are often diverted to newly created horticultural farms thereby also affecting the water flow into the reservoir.
Sharavathi River Basin is rich in animal diversity. The basin also covers part of Sharavathi Wildlife Sanctuary. The region is also adjacent to Mookambika Wildlife Sanctuary of Udupi District and Shettihalli Wildlife Sanctuary of Shimoga District. Many animals from these sanctuaries pass through the catchment area. Due to rising human pressures including creation of numerous monoculture plantations many of the migratory paths of the animals are disrupted. We have therefore proposed the creation of wildlife corridors to facilitate animal movements. These corridors are depicted in the figures 5-10.
The study area harbours some of the endemic and endangered species of the Western Ghats. The major mammals found here are Gaur, Leopard, Sambar, Barking Deer, Spotted Deer, Mouse Deer, Common Langur, Wild Boar, etc. The Lion tailed macaque is an endangered endemic species found in dense evergreen forests. Tiger, Leopard, Wild Dog, Civet Cat, Sloth Bear, etc are rare animals in the study area. Some of the minor mammals are Indian Hare, Slender Loris, Flying Squirrel, Giant Squirrel, Common Indian Mongoose, Common Otter, Porcupine and Pangolin. Several species of bats, both frugivorous and insectivorous are also found.
A total of 140 species of birds has been sighted in the study area. Of the birds the order the most abundant are Passeriformes, which include the Flycatchers, songbirds, Warblers, etc. Notable endemic bird species include, Blue Winged Parakeet, Crimson Throated Barbet, Grey Headed Bulbul, Heart Spotted Woodpecker, Malabar Grey Hornbill, Malabar Pied Hornbill and Small Sunbird. The endangered Great Indian Hornbill was sighted near the Malemane village of Siddapur taluk.
The wetland habitats include the reservoirs and their environs, the Sharavathi estuary and several tanks in the study area. The wetlands are dominated by both Passeriformes and the Ciconiiformes, the latter includes the Egrets, Herons, Ducks, Kites, Kingfishers, Coots, etc. While the lands are dominated by resident birds the aquatic habitats have by both resident and migratory birds.
A spate of construction activities in the lower catchment of Sharavathi river and ongoing and threatened fragmentation from the burgeoning human population are perilous to the habitats of several forest birds. There has also been considerable decline in the mangrove vegetation threatening the estuarine birds as well.
The notable reptiles are crocodiles (in the reservoir), turtles, King Cobra, Python, Saw Scaled Viper, Russel’s Viper, Malabar Pit Viper, Striped Keel-back, Johnson/s Boa and the Flying Snake.
The notable amphibians and Caecilians observed in the river basin are, Rana tigrina, Rana limnocharis, Rana curtipes, Philautus sps, Ansonia sps, Ichthyophis sps, etc.
A total of 134 species of Butterflies were reported from the study area. Some are endangered and some are endemic species. Notable among the butterflies are, Fluffy Tit, Monkey Puzzle, Southern Birdwing (the largest south Indian butterfly), Malabar Raven, , Paris Peacock, Malabar Banded Peacock, etc. The diversity of butterflies is correlated to the diversity of host plants. The varied kind of human impacts are posing threats to several rare plants thereby also affecting their dependent butterflies. Examples are Crimson Rose, Malabar Rose, Southern Birdwing, (dependent on members of Aristolochia family), Blue Nawab (host plants unknown), Malabar Banded Swallow Tail (dependent on Acronychia and Euodia). Therefore while redesigning vegetation in the human impacted landscape of the catchment attention should be paid to the rehabilitation of these rare and endangered butterflies by planting their host plants.
Except for stray references no systematic study has ever been undertaken of the beetles, of which there is an amazing diversity in the Sharavathi catchment area. We could record during a short period about 122 species belonging to 26 families. Many of these beetles are very specific to their microhabitats. The beetles have important role in the ecosystem, as they are pollinators of several plant species including the endangered Myristica of the swamps.
The diversity of common beetles such as the root grubs is high in the monoculture plantations. These root grubs, of late, have become a major threat to the horticultural plantations, which contribute substantially to the economy of Uttara Kannada and Shimoga.
In the absence of any previous studies on the ants of the Sharavathi catchment area, ours is a benchmark study. A total of 84 species of ants representing 31 genera under 5 subfamilies have been recorded from this study. Of the various habitats studied for ants maximum number of 64 species was found associated with deciduous forests. Some of the ants such as members of Myrmicinae are associated with all vegetation types.
Ants like Polyrhachis mayri are exclusively found inside undisturbed evergreen forest patches. Some species of ants are indicators of disturbances. The islands of Sharavathi frequented by tourists are being inhabited by hot climate specialist ants suggesting disturbances (open canopy, hard soil and absence of litter cover). Such findings highlight the importance of keeping the pristineness of the fragile ecosystems of the Western Ghats from the forays of unplanned tourism.
Lichens are indicators of pristineness as well as disturbances of terrestrial ecosystems. They are pioneers of vegetation and many of them can endure hostile environmental conditions. Some of the lichens have economic importance too. The catchment area is very rich in lichens. Of the 175 species reported from the Karnataka Western Ghats, the study area has 143 species.
The disturbing trend is that the crustose lichens, with 108 species are found dominating the human impacted areas, especially exposed and fire affected places. On the contrary, the semi-evergreen to evergreen forests are poor in lichens because of denser shade and humid conditions. Therefore a constant monitoring of such indicator species is essential for the upkeep of the ecology of the catchment.
