Exploitation of water resources for irrigation, hydropower and flood moderation is a necessity for a developing country like India with a teeming population striving to survive on meagre resources and sub optimal services rendered by increasingly degraded environmental assets and resources both natural and physical. Yet, the evaluation of economic benefits of such projects in the form of increased food production and added inputs of energy for industrial growth cannot afford to ignore the ecological feasibility of such projects from the standpoint of both environmental and ecological sustainability.

Past experience of environmental appraisal of hydroelectric projects continue to reiterate the fact that unlike developments in other sectors, hydropower projects will always be location specific thereby leaving little scope for consideration of the scales of impacts in alternative scenarios of locations. The significance of ecological impacts of mega development projects are now very well documented both for projects sited in India and other regions of the world (Goldsmith & Hildyard, 1984; Panwar et. al, 1990). Above ground power projects involving acquisition of large proportions of land mostly forested, creation of large reservoirs and rehabilitation of people have significant potential to impact upon the ecological environment and threaten the conservation of biological resources.

Run of the river schemes place lesser demands on land requirements for project infrastructure and water storage and therefore have lower impact potential. This fact however does not give a clear ‘pass’ to the run of the river schemes for implementation without an assessment of its impacts. Run of the river schemes also adversely affect the ecological environment by inevitable negative changes brought about in ecological and biological parameters of the ecosystems.
Although development of the Teesta Stage - V Hydroelectric Project is necessary in today’s context of increasing demands of power for economic growth of the state of Sikkim, its environmental and ecological appraisal is also critical for long term sustainability and economic viability of such a project.

The preceding sections have highlighted the floral and faunal values of this biologically rich state, the need for their conservation and the challenges that this project would pose in the conservation of biodiversity in this biogeographic zone. Some of the predicted impacts are too significant to be ignored and must be addressed prior to the implementation of this project.

6.1 SUGGESTED APPROACH FOR IMPACT MITIGATION

Mitigation approaches that best ensure the protection of vulnerable species of plants and animals and their specialized habitats likely to be impacted by the project require the implementation of following choices exclusively or in combination.
· Restriction of construction activities to defined areas which are ecologically less sensitive.
· Scheduling of operations to take account of animal breeding seasons.
· Removal of rare/endangered plants from the site and transplant them temporarily or permanently.
· Removal of rare/endangered animals from site or promote the use of suitable alternate locations.
· Management of site activities (e.g., use of machinery, transport, waste/overburden removal) to maintain acceptable soil, water and vegetation quality.
· Restoration/duplication of vegetation and other habitat features.
· Maintenance of viable population of animal species.
· Creation/restoration of habitats to compensate for damage caused.

The following recommendations have taken due care to ensure mitigation of most project impacts on ecological/biological values by adopting a combination of choices discussed above.

6.2 CONSERVATION STRATEGIES FOR VEGETATION & WILDLIFE HABITATS

(i) Plant such as Cinnamomum sp, Litsea sp, Macaranga spp, Aristolochia tagala, Bombax ceiba, Albizzia spp., Maesa sp, Saccharum sp, Oryza sativa, Digitaria sp, Osbeckia sp, Sida rhombifolia, Synedrella sp, Aslepias curassavica and Ficus spp. are the preferred food plants of a number of butterflies recorded in the Project area. Protection of these plant species is critical for the conservation of the butterfly fauna and its habitats. A large number of Ficus species such as Ficus auriculata, Ficus semicordata, Ficus benjamina and Ficus elastica are the most preferred food plants and arboreal habitats for flying squirrel, hoary bellied squirrel and flying fox. The tall trees such as Schima wallichii, Duabanga grandiflora, Engelhardtia spicata, Castanopsis tribuloides, Ailanthus integrifolia and Alnus nepalensis contributing substantially to the canopy cover are the equally preferred arboreal habitats for avian species such as Great pied hornbill, a highly endangered species of hornbill listed in the Schedule-I of the Wildlife (Protection) Act (1972). It is recommended that the Project Authorities must avoid intentional and unintentional removal and destruction of these species while clearing the land for construction related activities or during the transportation of equipment and material for construction. The specific clause for ensuring environmental safeguards should be incorporated in the various contacts for undertaking construction work. These clauses should specially impose restrictions on establishment of labour camps and residential complexes/camps for project staff near forest areas to avoid human induced secondary impacts on the critical habitat resources of endangered floral and faunal species.

(ii) Wherever species of conservation significance exist in forested areas outside the limits of the Project area, the State Forest Department should protect these species by adopting specific protection measures such as the fencing of areas. The financial support for recruitment of staff to undertake protection work and acquire necessary infrastructure and equipment should be provided by the Project Authorities from the earmarked budget, based on the budgetary proposal that could be obtained from the State Forest Department to accomplish protection works.

(iii) The area identified for the proposed project and its surrounds is a habitat for several rare and threatened plants which are endemic to Sikkim Himalaya falling in the altitudinal range of about 800 m. These include Phoenix rupicola, Ophiorrhiza lurida, Lagerstroemia minuticarpa, Begonia rubella and Begonia satrapis. These species with restricted distribution at certain altitudes in Sikkim are likely to become extinct from the area in near future. The conservation of such species is therefore critical to arrest the process of rapid decline in biological diversity of the region. Ex situ conservation of these species should be undertaken on a priority in predetermined sites. Suggested sites can be developed in Sirwani and Dikchu. Funds for ex situ conservation will have to be provided by NHPC.

(iv) Good engineering practices for designing of roads in the Project area is a prerequisite for reversal of several impacts (slope instability, dust pollution, alteration in hydrological balance and soil erosion). Road rubble should not be allowed to be disposed off down slope. The road edges on each side should be planted with vegetation to control movement of loose soil down slope. Sufficient protective measures should be taken to ensure the stability of road edges by planting tufts of grasses.

(v) Removal of boulders from the riverbeds for use in construction should not be undertaken and should be prohibited by specific contractual clauses at the time of contracting a construction agency. The project authorities have provided a layout plan of rock quarry location and terrace deposits along the river in the stretch comprising of the project area (Annexure – IV). Considering the significant impacts from the use of the rock quarries for excavation of construction material on the riparian ecology it is recommended that only rock quarry locations TVR1, TVR2, TVR5, TVG5, TVG6, TVG7, TVG8, TVG9 would be allowed for excavating building material. Quarry sites TVR3, TVR4, TVG1, TVG2 and TVG3 should not be used for excavating the building material for the project.

(vi) The minimum discharge that is necessary in river to sustain aquatic life and retain the ecological characters of the riparian stretch must be maintained. The minimum discharge at any time specially during the lean season is therefore recommended to be at least one cumec even if this means limiting the number of turbines in operation at any given time.

(vii) Although there are not many resident endangered mammals in the Project area, species like Flying squirrel need special conservation efforts. Ficus species, which are not only important as food trees but also provide roosting sites for this species, need to be strictly protected. Felling of Ficus trees in the Project area should be avoided during the construction phase. Other arboreal species like Hoary bellied squirrel and Tree shrew also need to be afforded adequate protection as the status of both these species is not well understood. Protection of rubber plantation patch near Dikchu bridge should be ensured on priority. The area should be placed in the care of Forest Department and appropriate measures for its protection should be initiated in consultation with Forest Department.

(viii) Great pied hornbill is the only threatened species of bird occurring in the Project area. This bird being a highly specialized species is very sensitive to disturbance to its habitat. During the construction phase of the Project, special care should be taken to avoid disturbance of the climax forest patches. Protection of the trees like Ficus Elastica, Ficus auriculata and Ficus benjamina used by the bird for roosting and nesting is critical for conservation of hornbills in this area.

(ix) The impacts of the upcoming project are expected to severely affect the aquatic fauna. Appropriate mitigatory measures should be taken so as to ensure that the level of water in the river stretch between dam site and power house is not substantially lowered by the operation of the project. This may lead to destruction of habitats and populations of benthic fauna and other aquatic species.

(x) Riverbanks in the stretch between dam site and Power house should not be subjected to any major disturbance, as they are the crucial habitats for otters for breeding. Boulders from river banks should not used in construction activities as it would destroy the river banks that are ideal habitats/denning sites of otters.

(xi) Disposal of waste and debris generated during the construction of tunnels should not be done either in the river or on the river banks as it would increase silt load and sedimentation which would further degrade the riverine ecosystem. This needs to be ensured through contractual clauses and subsequent monitoring for compliance by NHPC.

(xii) Abstraction of water from streams joining Teesta should not be permitted during construction. All care should be taken to ensure that water table is not adversely altered during the construction phase. All naturally occurring water channels draining the forests in the Project area should be left untapped for maintaining sufficient water level in lean season.

6.3 CONSERVATION OF BUTTERFLY FAUNA

Butterflies are one of the important food chain components of the birds, reptiles and spiders. Butterflies are also extremely good indicators of environmental changes and respond immediately to the disturbance caused due to alteration of their habitat. Butterflies are of primary importance in recycling of nutrients and play a significant role in the maintenance of soil structure and fertility. Butterflies would be the most severely affected group of fauna by the implementation of the proposed Project.

Special conservation measures are needed for protecting the butterfly fauna of the Project area. A range of mitigatory approaches will have to be adopted to prevent the project-induced impacts on the butterfly fauna. These are discussed below.

6.3.1 In situ Approach

Survival of butterflies depends mainly on the availability of the larval food plants which are generally secondary growths consisting of shrubs, creepers and saplings. During the construction phase, all such areas with good ground cover should not be disturbed because some of the rare species of the butterfly already discussed in section on baseline status (Chapter 4) have very subtle habitat requirements. Such species may become locally extinct as a result of minor habitat changes in habitat characteristics. It is therefore recommended that all potential butterfly habitats be protected in the Project area.

6.3.2 Ex situ approach

6.3.2.1 Butterfly rearing park

· The various species of butterflies which are endangered and rare can be reared artificially. The basic requirement for this would be establishment of large, well lit enclosures with adequate air circulation with various larval food plants, adult attractants like nectar, salt patches and rotting fruits.
· It is therefore proposed to create three such butterfly-rearing parks in Sirwani, Amdara and old Dikchu area respectively. A total of six enclosures should be constructed, two at each site mentioned above.
· Collection of butterfly eggs and young stages from Project area and rearing them in these butterfly parks is also recommended. The Sikkim Forest Department should be involved and entrusted with the task of creation and subsequent maintenance of butterfly rearing parks. The Forest Department should work out the financial requirements for these and the funds should be made available by NHPC. The project authorities are also expected to get timely reports from Forest Department on progress with respect to activities accomplished and targets set for butterfly protection. These reports should be made available to monitoring committee of MOE & F at the time of compliance of the project.

6.3.2.2 Creation of garden habitats

Though community gardens that would be developed as part of the Project complex are not, and never will be substitutes for wild butterfly habitats yet gardens managed exclusively for butterfly protection can become good butterfly habitats. Gardens should be broken up by internal borders or hedges so that it attracts more butterflies as they prefer to fly along the sides of hedges or over areas of mixed vegetation. The efforts should be made to preserve the larval food plants belonging to Lauraceae, Aristolochiaceae and Rutaceae family. The nectar yielding plants are of paramount importance and should be raised in abundance in these gardens, along the fringes of the approach road and in other areas of project complex. Plant species that can ensure a succession of blooms from spring to late autumn should be planted after careful study of phenological calendar of select species. Ornamental species like Rosa chinensis, Euphorbia pulcherrima, Bottlebrush (Callistemon citrinus) and horticultural species such as Citrus spp. are recommended. These will enhance both the ornamental values of gardens and the suitability of these gardens for butterfly species. Sikkim Forest Department should be retained as the nodal agency for the professional advice for developing such gardens and for the preparation of feasibility report for landscape planning and for providing professional inputs subsequently in the development and maintenance of these garden habitats. NHPC should invite Sikkim Forest Department to prepare the feasibility report prior to initiating the project. The cost towards the feasibility report should be borne by NHPC.

6.4 DEVELOPMENT OF A CONSERVATION PLAN

Based on the suggested approaches for impact mitigation, strategies for conservation of vegetation and wildlife habitats, the conservation plan earlier prepared by State Forest Department on the request of NHPC should be made more comprehensive. Apart from specific actions required for ex situ conservation of butterflies and their habitats and the maintenance of garden habitats, the Plan should incorporate specific measures and actions to protect the food plants of butterflies in their natural habitats within the project area, conservation of locally rare and endangered species both floral and faunal and protection of hornbill habitats more specifically the tree species used as roosting and nesting sites.