1Energy and Wetlands Research Group, 2Centre for Ecological Sciences, 3Indian Institute of Science, Bangalore – 560012, India.
*Corresponding author: cestvr@ces.iisc.ernet.in Citation: Ramachandra T V, Alakananda B and Supriya G, 2015. Efficacy of current restoration approaches - Bangalore wetlands, ENVIS Technical Report 73, CES, Indian Institute of Science, Bangalore 560012
INTRODUCTION
Wetlands include marsh, fen, peat land/ open water, flowing water (rivers and streams) or static (lakes and ponds) aquatic habitats, which are fresh, brackish or salt water. They are ecologically vital systems with respect to stability and biodiversity of a region and also in terms of energy and material flow. Wetlands are often described as “Kidneys of the landscape” as they aid in the remediation with the uptake of nutrients, purification of water, recharge groundwater aquifers and protect shorelines. These fragile ecosystems act as giant sponges, soaking up runoff water originating with rainfall which helps in slowing floodwaters, lower flood heights, reduce shoreline and stream bank erosion. The non-stratified photic zone extends up to sediment layer enhancing the growth of photosynthetic benthic and planktonic algae. Wetlands with the higher photosynthetic activities sequester carbon (2.23-3.71 metric tons/acre/year) higher than terrestrial forests (0.05-3.9). The interactions among basic components (soil, water, animals and plants) of wetlands aid in sustaining diverse life. Wetlands are often branded as “ecological super complexes” as they aid in maintaining trophic levels and a repository of rich biodiversity (Ramachandra, 2001, Prasad et al., 2002, Ramachandra et al., 2002, Ramachandra 2005). Characteristics of wetlands depend on its physical (sediments deposition, water depth, etc.), chemical (organic matter, etc.) and biological components (macrophytes type). Wetlands are threatened due to the disturbance caused by flooding, sustained inflow of domestic sewage, industrial effluents (in urban environment), agricultural runoff containing inorganic fertilisers and pesticides (rural environment). Ancient human societies have traditionally recognised wetlands resources in practical as well as symbolic ways. Failure by modem societies to deal with water as a finite resource is leading to the destruction of rivers, lakes and marshes that provide us with water. This failure in turn is threatening all options for the survival and security of plants, animals, humans, etc. There is an urgent need [Ramachandra, 2005] for
Enhanced anthropogenic activities consequent to the burgeoning population and unplanned rapid urbanization have led to the reclamation of wetlands and freshwater resources. Several wetlands have been encroached resulting in either drastic shrinkage or deterioration of water quality; sedimentation and shrinkage; decrease in productivity along with flora and fauna; loss of aesthetic values and decrease in tourism potential. These acting stressors, along with climate variability, can synergistically contribute to the degradation of biological diversity at the species, genetic, and/or habitat– ecosystem levels and thus are a primary cause of the present extinction crisis (Collinge, 1996; Adriaensen et al., 2003). Subtle changes in water chemistry constitute ecological barrier for the interaction of species/ species assemblages with their immediate ecology. Thus, water quality is one among the numerous crucial factors and nutrients as resource for the primary producers for their distribution due to their high sensitivity and tolerance responses to sudden shifts in immediate environment. Long term monitoring, bio-monitoring of wetlands are required for the maintenance of wetland ecology, towards the sustainable management of wetlands (Alakananda et al., 2011). The biological structure of a wetland depends on its water retaining capacity, water flows, and seasonal alterations. Study of wetlands begins from its basic hydrological characteristics like depth, sediment texture, photic zone, temperature and subsequently towards the understanding of biological existence like bacteria, protozoa, planktonic, benthic/littoral representing the ecosystem diversity. The diverse groups of organisms contribute in wetland functioning by water purification (nutrients uptake, Friedrich et al., 2003; Ying et al., 2011); carbon dioxide sequestration (phytoplanktons, Kenning, 2009); balancing food chain (ESA, 2003); sediment erosion; habitat for flora and fauna diversity and balancing the ecosystem health (Townsend and Gell, 2005). Although, many wetland functioning processes benefited human civilization, knowledge about wetland dynamics is scanty compared to its exploitation. Initial wetland investigations have often been made in isolation, specific to a river-drainage system, region/ community, without adequately considering the synergistic relationships. Later, it was extended to every geographic region and information compiled on individual wetlands at the regional scale. In late 20th century extensive wetland studies unraveled of human intrusion, unanticipated anthropogenic activities and population stress lead to unplanned urban expansion (Ramachandra and Kumar, 2008). Anthropogenic activities like construction of roads, agriculture, removal of vegetation cover in the catchment, and others imbalances the nutrient input rate and organic content of wetlands often increasing the overall productivity of wetland (Ramachandra et al., 2011). At present, many wetlands, ponds and wetlands are in the verge of extinction resulting in either drastic shrinkage of water bodies or major impacts being deterioration of wetland water quality; sedimentation and shrinkage; decrease in productivity along with flora and fauna; loss of aesthetic values and decrease in tourism potential. These acting as stressors, along with the climate variability, leading to the degradation of biological diversity at the species, genetic, and/or habitat– ecosystem levels (Collinge, 1996; Adriaensen et al., 2003). Water quality is one among the numerous crucial factors and nutrients as resource for the primary producers for their distribution due to their high sensitivity and tolerance responses to sudden shifts in immediate environment. Subtle changes in water chemistry constitute an ecological barrier for the interaction of species/ species assemblages with their immediate ecology (Alakananda et al., 2011). For the monitoring and management of water bodies and its ecosystems, Ramsar convention defined water bodies (with depth less than 6 m) like marsh, fen, peat land or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, including fresh, brackish or salt, as Wetlands. For the purpose of restoration of degraded wetlands, Ramsar convention (since 1981 in India) includes 25 wetlands among several polluted wetlands of India for monitoring restoration and sustainable water use by humans. However, yet hundreds of wetlands decline every year without appropriate management. 3.1 Significance of Restoration Wise-use of wetlands entails the maintenance of ecological character. This requires the implementation of ecosystem approaches, within the context of sustainable development. Restoration is a significant step in ecosystem management for recapturing the ecosystem assets to a close approximation of its condition prior to disturbance. This ensures that the ecosystem structure with functional abilities are recreated or restored, and that natural dynamic ecosystem processes operate effectively again. The main component of the wetland restoration involves either diverting contaminations like sewage flows (as distinct from rainwater), road runoff, away from the wetlands or construction of waste water treatment plant for sewage and industrial waste surrounding the wetland. Current approaches of wetland restoration involve engineering techniques such as plugging agricultural ditches, sediment disturbance, nutrient mixing, constructing percolation tanks etc., in order to restore the hydrology of that area. Many wetlands fails in regaining the desired water quality as ecological components (ex., biological such as disruptions in the food chain - birds, amphibians, planktons, etc. and microhabitat) are affected (Zheng and Stevenson, 2006). Ecological restoration techniques include regular biomonitoring, developing biotic indices, accessibility of substrata for growth of primary producers, maintaining riparian vegetation, ensuring appropriate slope, etc. This will be the definitive way to preserve freshwater environment alive and with them the algae, fish, birds, and other creatures which balance ecology. The precautions to be taken in retaining the natural ecosystem during restoration program includes,
Even though chemical assessment of water was initiated 200 years ago, it doesn't capture complete condition of an ecosystem enabling both preventive as well as restorative measures. The better realization of interactions between environmental quality and ecosystem integrity has increased the interest in finding biological indicators that provide a more accurate guide to changes in ecological conditions and biodiversity (Lavoie et al., 2003). A survey was carried out (1984-1987), with the objectives to document and analyze the flora, fauna and habitats of only the protected areas such as wild life and statuaries of India. In 1995, the entire extend of Krishna river system was assessed for the content and quality of the bioresources (Jayaram, 1995). Pollution loads from the urban sources at several sampling sites signaled to minimize the contamination load through waste water treatment though; the maintenance of river system was not referred to. Xianguo and Rongfen, (1996) studied biodiversity of wetlands accounting for the floral and faunal diversity and thus suggested the investigation of environmental function of wetland, the influence of human impacts on wetland resources and polices for species protection ‘prior to restoration measures’. Investigation of flora and fauna of Gujarat appended 732 species and subspecies of fauna and 180 species of flora to be known (Subba Rao and Sastry, 2005). Determining the variation in environmental conditions and subsequent impairment in biotia during restoration has been studied extensively through algal species composition. Janousek et al., 2007 assessed the variation in microalgal and phototrophic bacterial at a restoration site by sampling for a period of 3 yr. 3.2 Bangalore wetlands Even though, threats to the environment and associated biodiversity have been identified, the already fragmented/degraded wetlands such as Bangalore ecosystem, are still experiencing degradation due to unplanned urbanization. Bangalore, once was known as city of wetlands comprising more than 400+ wetlands in 19th century has dwindled from 250 to 81 (1985) and 33 in 2006 (Ramachandra and Uttam kumar, 2008). A large number of water bodies (locally called wetlands or tanks) in the City had ameliorated the local climate, and maintained a good water balance in the neighborhood. Wetlands in Bangalore has been grouped into 3 valleys viz., Hebbal valley; Vrishabhavathi Valley and the Koramangala and Challaghatta Valleys. These form important drainage courses for the interconnected wetlands, which carry storm water beyond the city limits. Government committee was constituted in 1986 to record the water quality of several wetlands which was followed by a series of studies (Ramachandra et al., 1998- 2008) explaining the physical and chemical variables of wetlands. These studies recommend the need for conserving biological diversity and the ecological integrity of wetlands. The sustained inflow of untreated sewage, industrial effluents, etc. has deteriorated water quality, evident from the results of regular water quality monitoring (Rajinikanth and Ramachandra, 2000; Ramachandra and Malvika solanki, 2007 & Ramachandra, 2008). Comparative analysis of water quality estimation resulted with the impact of pollution on the quality as well as the decrease in wetland catchment. Degradation of wetlands environs resulted in flooding (Krishna et al., 1996) mass fish kill (Benjamin et al., 1996) reduction of migratory bird population (Kiran and Ramachandra, 1999) and ground water contamination (Shankar et al., 2008). These studies lack the comprehensive account of the ecosystem biodiversity with the implementation of restorative measures. Therefore the investigation was carried out on water analysis accounting flora and fauna of wetlands, chosen for restoration by Bangalore development authority – BDA. 11 wetlands considered for restoration with detailed pollution problems in watershed are listed in table 1 and sampling codes are listed in Table 2. Wetlands were considered for restoration following the engineering techniques. Steps involved in current process of restoration in Bangalore are,
NOTE: Documentation of flora and fauna of post restoration was not fulfilled because of (1) decreased floral and faunal diversity or unavailability of aquatic birds, aquatic insects and mollusks, and (2) incomplete restoration (as per the date announced). Post restoration wetland quality was investigated using diatoms as bioindicators of ecosystem integrity as they form the basis of the food chain. 3.3 Diatoms for post restoration studies Diatoms, the unicellular group of algae have so far been widely recognized as an easy and simple proxy for environmental changes (Zalack et al., 2010). Few species of diatom community grows and reproduce quickly to the changes in nutrients, salinity, pH or a number of other factors. Hence the community composition as a whole changes in response to changes in environmental conditions. Diatoms are the most diverse and dominant group of algae in rivers, streams, wetlands and wetlands forming an important component of the aquatic ecosystem (Stoermer and Smol, 1999). Shift in diatom community structure is used to detect changes in the environmental condition such as pH, conductivity and organic nutrients (Bennion et al. 2000, Potapova and Charles, 2003), eutrophication (Kitner and Poulícková, 2003) and global warming problems (Leelahakriengkrai and Peerapornpisal, 2010). Diatoms have been used successfully in water assessments across different habitats such as streams, (Simkhada et al. 2006); ponds, (Poulíčková et al. 2008); wetlands, (Blanco et al. 2004). In this context, diatom distribution before and after restoration provides insights to the efficacy of wetlands restoration. Ecological monitoring programs that include diatoms are exceptional and in many cases uncertain especially in India. Though diatom study was initiated with expedition of different ecosystems, ecological values of diatoms and its diversity in India is yet to be explored. In this scenario, there is a need for taxonomical, systemic, ecology and biomonitoring studies in diatom field to evolve appropriate management and restoration strategies of urban wetlands, which in turn aid in protecting flora, fauna and habitats Table 1 Details of wetlands selected for the study. (*compiled by BDA.** data compiled by BBMP)
Table 2 List of Bangalore wetland sampling sites with codes
Figure 1: Bangalore map showing sampling sites and Bangalore boundary (Courtesy: BBMP).  Figure 2 Detailed view of sampling sites with codes (Codes- Refer Table 2) 3.4 ObjectivesTo evaluate wetland restoration in maintaining characteristic ecosystem functions, objectives covered (1) documentation of flora and fauna of 11 wetlands prior to restoration, (2) water quality before and after restoration; (3) diatom assemblages before and after restoration and (4) conservation priority of wetlands. This helps in understanding about the effectiveness of restoration.
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