Ecological Assessment
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Collection of baseline information on floral and faunal components through some selected attributes is an essential step in the ecological assessment. The purpose of the baseline studies is to describe the ecological conditions of the area under investigation without the development having proceeded. Baseline studies provide a reference for the measure of the changes in environmental parameters that would be associated with the operation and post operational phases of the proposed development. This section of the report presents the ecological baseline of the Project area. 4.1 BIOGEOGRAPHIC CLASSIFICATION AND HABITAT ASSESSMENT The Sikkim state lies within the biogeographic province-2C, the Central Himalayas (Rodgers & Panwar, 1988). The Province stretches from the Gandak river in central Nepal to the Sankosh river in central Bhutan. Indian component of this zone comprise all of Sikkim and the northern part of west Bengal. The overall habitat in Project area is generally degraded. Large scale plantation of large cardamoms, interspersion of human habitations and encroachment of land for cultivation are the major factors (Table 4.1) responsible for overall decline of the wildlife habitat quality in the area. Good quality habitat is confined to few areas in Samdong, Amdara and Dikchu. Table 4.1 Habitat assessment survey in the Project area
4.1.1 Forest type and vegetation Though there is no distinct phytogeographic unit for the Sikkim state, the forest type of the Project area correspond to 3C/C3 b - "East Himalayan moist mixed deciduous forest" category of classification of Indian forests (Champion and Seth, 1968). Since the Project area falls in the altitudinal range of 500 - 650 m. The area falls in the high rainfall zone of eastern Himalayas that has well drained soils. It comprises of bhabar terraces and plateaux in the outer Himalayan ranges. Based on the classification of forest types (Singh and Singh, 1992) of certain eastern and central Himalaya in the altitudinal range between foothills to 3000 m, the forests of Teesta valley falls under Sub-montane seasonal broad leaf forests (elevation 1000 m). The tree layer and the shrub layers of these forests consist of a mixture of evergreen and deciduous species with fairly close canopy and high crown density. The middle tree layer is relatively less developed and bamboo is generally absent. According to Rau (1974), the Sikkim Himalaya in the altitudinal range, 600-1500 m, falls in the category of moist tropical and subtropical forests and comprise of the tree species such as Schima wallichiii, Eugenia sp., Duabanga grandiflora, Engelhardtia spicata and Castanopsis tribuloides. The other important associates recorded are climbers (Rapidophora sp., Piper longum, Dioscorea spp.) and epiphytes (Dendrobium nobile, Dendrobium aphyllum and Paphiopedilum sp.) 4.1.2 Results of the floristic survey During floristic survey in the Project area, efforts were limited to identification of the vascular plants. A total of 95 plant species were collected during the field survey from the Project area during the period from mid March’ to mid April' 99. These records of species additionally supplemented the checklist of plant species prepared by the State Forest Department from the Project area (Anon., 1998). A list of 190 plant species recorded from the Project area is placed as Appendix - II. Of these, 185 species represent the Angiosperms and the remaining five species represent the Pteridophytes. The Angiosperms belong to 85 families and 158 genera. Based on habit wise classification, there are 74 tree, 58 herb, 18 shrub, 16 climber and 18 grass species and 6 species of sedges. Phytosociological data revealed that Schima wallichii was the most common plant species in the forest of the Project area. Plant species such as Ostodes paniculata, Duabanga grandiflora, Engelhardtia spicata, Ficus auriculata and Ficus benjamina are other plant species which had high frequency and density (Table 4.2). Table 4.2 Frequency and density estimates of plant species in the Project area
This analyses also indicate that the overstorey is mainly dominated by tree species such as Schima wallichii, Ostodes paniculata, Duabanga grandiflora, Engelhardtia spicata, Ficus auriculata, Ficus benjamina and Ficus semicordata. Species such as Terminalia myriocarpa, Melia azedarach, Gynocardia odorata, Diploknema butyraceae, Betula cylindrostachys, Castanopnsis tribuloides, Bischofia javanica, , Alcimandra cathcartii , Albizzia marginata and Alangium chinense are also constituent species of the forest have relatively lower frequency and density. The shrubs and climbers were mainly represented by Cissus repanda, Cissampeos pareira, Piper longum, Dioscorea spp., Melastoma malabathricum, Boehmeria clidemoides and Colebrookea oppositifolia etc. The ground cover was dominated by Pteris biaurita, Onychium sp, Adiantum pedatus, Adiantum venustum, Arundo donax alongwith the other herbaceous weedy species like Eupatorium cannabinum , Urtica dioica and Artemisia vulgaris. Of these, Eupatorium cannabinum is an exotic species which has recently invaded Sikkim and other parts of north eastern Himalaya and have led to reduction in the biodiversity of the region by dominating the ground cover. The humid forests of the Project area of Teesta valley provide a very suitable habitat for the growth of both terrestrial and epiphytic orchids. Diplomeris pulcherra and Paphiopedium venustum are the two orchids found at the altitude ranging between 300-850m in the Sikkim Himalaya. These are vulnerable due to excessive collection and biotic interferences in their habitats (Nayar and Sastry, 1987). Indirect sources revealed that many of orchids are found in the Project area although only two species of Dendrobium (Dendrobium nobile and Dendrobium aphyllum) could be observed in flowering stage, during the survey. Tree species like Ailanthus integrifolia, Antidesma acidum, Oroxylum indicum, Cinnamomum sp, Duabanga grandiflora occur in the area and serve as hosts for epiphytic orchids found in the Project area. 4.1.3 Floristic significance Table 4.3 Food plants of butterflies recorded in the Project area
(Source: The Food plants of Indian Rhopalocera. Sevastopulo, 1973) 4.2 RESOURCE UTILIZATION BY THE LOCAL PEOPLE The state's economy is basically agrarian. The principal crops are maize, paddy, millet, wheat and orange. Barley and cardamom are the main cash crops. Sikkim has highest production of large cardamoms in India. Other important crops are potatoes, apples and buckwheat. Villagers mostly depend on surrounding scrub jungle for fodder, fuel wood and timber. Excessive removal of grasses, sedges and Ficus species is common in the area. About 22 fodder species were recorded during the survey. Of these, Ficus species (Ficus benjamina, F. auriculata, F.elastica, F. semicordata) are highly preferred. Rapidophora sp., Thysanolaena maxima, Artocarpus lakoocha, Macaranga denticulata are other fodder species found in the area. Castanopsis tribuloides, Albizzia marginata, Albizzia procera, Schima wallichii, Alnus nepalensis, Engelhardtia spicata, Erythrina arborescence and Betula cylindrostachys are used for fuelwood and as timber. The other timber species like Alnus nepalensis, Juglans regia, Schima wallichii, Terminalia myriocarpa, Michelia cathcartii are highly preferred. Bambusa nutans, Ostodes paniculata and Alstonia scholaris are other substitutes for timber that are used by people belonging to low income category. As far as the medicinal plant collection and their use is concerned the locals are familiar with the traditional and medicinal values of plants found in the region. The species such as Urtica doica, Artemisia vulgaris, Eupatorium cannabinum, Drymaria cordata, Ficus cunia, Centella asiatica, Litsaea citrata, Oroxylum indicum, Piper longum, Pteris biaurita, Rhus semialata and Holarrhena antidysenterica all found in the Project area are used for treatment of ailments and clinical disorders like dysentery, and other stomach disorders, blood pressure, soar throat, asthma, gall bladder malfunctioning, wounds and skin disorders like boils. 4.3 RARITY AND ENDEMISM The Project area is generally degraded due to high human pressure, large scale lopping and removal of fodder and timber species, clearing of ground cover for the cultivation of large cardamom, construction of roads, culverts. Despite this, some of the forest areas harbour rare and endemic species of plants that are important from conservation standpoint. Nayar and Sastry (1987) have discussed the rare and the endemic plant species from Sikkim Himalaya. Begonia rubella, Begonia satrapis, Ophioorrhiza lurida , Calamus inermis , Livinstonia jenkinsiana and Phoenix rupicola are some of the rare and endemic species reported by them from the Sikkim hills at 700 m elevation. This altitudinal range also includes the Project area(Table 4.4). Table 4.4 Rare and endangered plants in the Project area
Source: Red data book of Indian Plants (1987), (eds) M.P. Nayar and A.R.K. Sastry. Published by Director, Botanical Survey of India, Calcutta. Vol I, II & III. Since the Project area falls within this altitudinal range (around 700 m) there is a possibility that some of these plants occur in the Project area though they were not encountered during the brief survey conducted during the summer season. 4.4 FAUNA The Project area falls in the biotic province of eastern Himalaya the biogeographic zone - Himalaya and covers low elevation habitats. The records of faunal species collected during the survey (Fig 3) were based on both direct and indirect evidences. Except for a few surveys conducted for butterflies in this stretch of Teesta river, no surveys or systematic studies have been conducted in the past in the Project area. The faunal groups recorded from the Project area and the number of species represented from the Project area are presented in Table 4.5 below. Table 4.5 Number of faunal groups recorded in the Project area
4.4.1 Mammals Rhesus macaque (Macaca mullatta), Assameese macaque (Macaca asemenses), otter (Lutra spp.), Himalayan yellow throated marten (Martes flavigula), Tree shrew (Tupaia belangeri) and Jungle cat (Felis chaus) were the only mammals sighted during the surveys (Table 4.6). However the presence of eight more mammalian species viz., Barking deer (Muntjacus muntjac), Goral (Nemorhaedus goral), Flying squirrel (Petaurista petaurista), Asiatic black bear (Selenarctos thibetanus), Common leopard (Panthera pardus), Jackal (Canis aureus), Himalayan Indian civet (Paguma larvata) and Porcupine (Hystrix indica) was confirmed from the Project area based on indirect information and secondary sources (Fig. 3).
Rhesus macaques and Assameese macaques were often seen together in troops. The troops were sighted all along the Project area. This mammalian species seems to be fairly common in the Project area. One otter (Species not identified) was sighted moving on rocky outcrops on the bank of river Teesta 1.5-km upstream of proposed Power house (Plate 5). The status of otters is still unknown from the area. As per the informal discussions with the local people, otters are not very frequently seen in the Project area. Very few fishermen are reported to have seen otters in this area. Jackal was reported to be found in the entire Project area as per the information gathered from local people. Goral pellets were encountered on steep slopes in Adit I and Adit II. From other places goral presence was confirmed from secondary information collected from locals. Porcupine quills were collected from Adit V and Adit I. Porcupine was reported from all the villages. The presence of Asiatic black bear was confirmed based on secondary sources from villagers in the Project area. In submergence area, one Black bear was seen in March 1998 and was subsequently shot and eaten by local people. Jungle cat was seen only once at Adit III moving in a scrub patch. Tree shrews were relatively quite common and were seen at all survey sites especially in areas with good tree cover. Flying squirrels were confirmed based on interviews with local people. The presence of flying squirrel was confirmed only from Submergence zone. People confirmed the presence of this species from areas having good number of Rubber trees (Ficus elastica). Presence of common leopard locally known as chitwa was also confirmed based on secondary information given by local people from Adit III, Adit IV and Adit V. Though not frequent, some cases of goat lifting are reported from the area. Common palm civet’s droppings were seen at Adit I, Adit V and submergence zone. People often reported their poultry being raided by civets. One small colony of Indian flying fox was seen on a Ficus elastica tree in Adit II zone of Project area. Table 4.6 List of Mammals Recorded in the Teesta Stage - V Project Area
ES = Entire stretch, SZ = Submergence Zone, A I = Adit I, A II = Adit II, A III = Adit III, A IV = Adit IV, A V = Adit V
4.4.1.1 Status of Mammalian Habitats The Project area has low vegetation cover and high levels of human activity in terms of hunting, fishing and tree felling. A series of small local saw mills could be seen all along the banks of Teesta river in the Project area. The habitats in Project area can only support generalist species like macaques, porcupine, jackal and common leopard. Flying squirrels were reported only from submergence zone from areas having high density of rubber trees. Black bear in the Project area is a seasonal visitor to the crop field. Barking deer was also reported from areas having good forest cover on slopes. Open steep grassy slopes seemed suitable for goral. 4.4.1.2 Status of Mammals The status of mammalian species occurring in the Project area was evaluated based on their listing in the Schedules I to VI of the Indian Wildlife Protection Act (IWPA), 1972. The status of various mammals in Project area is given in Table 4.7. Table 4.7 Conservation status of mammals recorded in the Project area.
4.4.2 Avifauna A total of 47 species of birds were recorded during avifaunal survey in the study area. Of these Cormorant, Himalayan greyheaded fishing eagle, Marsh harrier, Redwattled lapwing, Himalayan pied kingfisher, White capped red start, Little forktail, Spotted forktail, Blue whistling thrush and Large pied wagtail were seen close to the Teesta river and other streams in the Project area. Red jungle fowl an indicator of good forest, inhabited dense areas with good forest cover. Kalij pheasant was heard calling in the morning hours from a well-wooded hill slope near Adit II on the right flank of river Teesta. Indian pied hornbill (Anthracoceros malabaricus) falls in schedule I category of Indian Wildlife (Protection) Act (1972). A detailed inventory of bird species encountered during the survey is given in Table 4.8. Table 4.8 List of birds recorded in Teesta stage - V Project area
4.4.3 Fish Fauna Six species of fishes were encountered from the river stretch passing through the Project area (Table 4.9). These six species are the most commonly occurring species in Teesta river system and are caught by fishermen for sale in the local market. Mahseer (Tor putifora) locally known as Sahar is also reported from Teesta though we could not get any evidence of this fish from the Project area. As per the information provided by Sikkim Fisheries Department, Mahseer do migrate to the lower reaches of Teesta. About, 37 species of fishes are reported from the Teesta river system in Sikkim (Tamang, 1993). Table 4.9 List of fishes found in the Project area
4.4.4 Reptiles Among reptiles, there was no direct sighting of any snake species. The moult of a Cobra (Naja naja) found in the Submergence zone was the only indirect evidence of a reptilian species. House gecko (Hemidactylus flaviridis) was commonly seen in entire Project area. Common skink (Mabuya carinata) and Calotes (Calotes versicolor) were also commonly seen in Project area. 4.4.5 Butterflies Sikkim’s landscape features and floral wealth has been a haven for butterfly species. First ever report on butterflies of Sikkim was published by H. J. Elwis (1880). During the same period L. De. Niceville also made several trips to Sikkim. In 1980 De. Niceville and G. A. Gammie recorded a list of 631 butterfly species from Sikkim (Haribal 1992). Although, Sikkim is one of the smallest Himalayan states, with an area of 7,096 km2. its floral and faunal diversity has given it a unique status. Of a total of about 1,400 butterflies recorded from Indian subcontinent, almost 50% of butterflies are recorded from Sikkim (Haribal, 1992). The lower valleys still have great number of species. Lower altitudes of Teesta valley have been recognized as hotspots for butterfly diversity and richness (Haribal, 1992). 4.4.5.1 Results of Butterfly Survey A total of 183 species of butterflies belonging to five families, 20 sub-families and 106 genus were recorded from different sites within the Project area during the survey. A total of 13 rare species were recorded from the Project area. Out of the total species encountered 45 species were seen at all the sampling points. Butterfly diversity of Sikkim was compared with that of the Project area and it was found that Project area harbors approximately 26.5% of the total lepidopteran fauna of the state (Table 4.10). Family Nymphalidae was represented by 77 species followed by Lycanidae, and Paplionidae represented by 38 and 31 species respectively. Family Pieridae and Hespiridae were represented by 18 and 8 species respectively. the detailed checklist of butterfly species recorded during the survey from Project area is given in Appendix - III. Submergence zone A total of 114 butterfly species were recorded from submergence zone. This represents the highest numbers of butterfly species recorded from a region within the Project area. A total of five rare species were encountered during the intensive survey carried out in this zone (Table 4.11). Common pierrot (Castalius rosimon) a species of more open habitat and thinly wooded country and also recorded as rare (Haribal 1992) was seen twice in submergence area. This butterfly was seen basking on a grassy patch on a rocky outcrop during early morning hours. Common jezebel (Delias eucharis) was recorded once, flying over cardamom plantation. One battered specimen of common wanderer was seen resting over a bottle brush plant close to Dikchu bridge. Three specimen of Blue imperial were seen close to the zero point of submergence zone. Crusier (Vindula erota) was sighted fluttering over Euphorbia plant only once on a gentle slope. Adit I. Adit II Adit III Adit IV Adit V 4.4.6 Conservation Status of Butterfly Fauna of the Project Area A total of 13 species recorded from the Project area are rare (Haribal, 1992). Ten species of butterfly recorded from the Project area are covered under Schedule I and 13 species under schedule II of Indian Wildlife Protection Act, 1972 (Table 4.11). Species like Yellow kaiser (Penthema lisrada), Blue duchess (Euthalia duda), Cruiser (Vindula erota), Long branded crow (Euploea algea), Narrow spark (Sinthusa nasaka), Common albatross (Appias albina) and Red caliph (Enispe euthymius) were sighted only once in the Project area and are reported to be rare. Table 4.10 Comparative list of butterfly diversity of Sikkim State and Teesta stage V Project area
Table 4.11 List of rare species of butterflies recorded in project area during the survey
Table 4.12 Conservation status of butterflies in the Project area
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Last Updated: October 5, 2015
