Flora of Coastal Wetlands CHAPTER-1 AN INTRODUCTION TO WETLANDS Wetlands are defined as ‘lands transitional between terrestrial and aquatic eco-systems where the water table is usually at or near the surface or the land is covered by shallow water’ Wetlands provide many services and commodities to humanity. Each wetland is ecologically unique. They perform important functions in any landscape and are often described as “kidneys of the landscape” (Mitch and Gosselink, 1986). The wetlands of Karnataka are classified into inland and coastal categories, both natural and man-made. Natural inland wetlands include lakes, ox-bow lakes, and marshes/swamps. Man-made inland wetlands include reservoirs and tanks. Natural coastal wetlands include estuaries, creeks, mudflats, mangroves and marshes. Man-made coastal wetlands include salt pans Wetlands cover about 2.72 million ha, of which inland wetlands cover about 2.54 million ha and coastal wetlands cover 0.18 million ha. The area of 682 wetlands, scattered throughout the state of Karnataka, is about 2718 sq km. The fresh water ponds are very few along the coast, barring few medium to large ones in advanced stages of silting, and a number of small ones where water dries up in summer or only very little remains, many temple ponds being exceptions. Salinity tolerant species, mainly sedges (members of Cyperaceae), some grasses, Sphenoclea, Hygrophila, Alternanthera sessilis, Bacopa monnieri etc. persist in and around the brackish water wetlands. Of the notable salinity tolerant sedges are Cyperus corymbosus, C. malaccensis, Eleocharis dulcis, E. spiralis, Fimbristylis ferruginea, F. littoralis, Mariscus javanicus, Pycreus polystachyos etc. 1.1 Kinds of wetlands: Wetlands observed during the present survey consist the following: 1. Rice fields (both fresh water and brackish water or gazni fields) 2. Abandoned rice fields – due to brackish water ingression 3. Coastal marshes (seasonal and perennial) 4. Mangroves, estuaries, creeks, mudflats 5. Ponds/lakes 6. Reservoirs 7. Rock pools, ditches, quarries 8. Streams and rivers 9. Canals 1.2 Importance of wetlands: Wetlands play an essential part in the regulation of river flow, they filter pollutants, acts as buffer shorelines against erosion and fertilizers and they are spawning zones for some species of fish. Wetlands are vital to the balance of rivers and crucial for supporting high diversity of animal and vegetable species, can only be preserved through political resolve. They should not be merely abandoned but properly managed like other areas. 1.3 Area under wetlands: India According to the Directory of Indian Wetlands, India has 58.2 million ha of wetlands, including area under wet paddy cultivation. The majority of the inland wetlands are directly or indirectly dependent on the major rivers like Ganga, Brahmaputra, Narmada, Godavari, Environmental Management & Policy Research Institute 1 Flora of Coastal Wetlands Krishna, Kaveri and Tapti. Wetlands occur in all parts of India, including in Rajasthan and Andaman and Nicobar Islands (Prasad et al., 2003). Table 1. Area estimates of wetlands of India (in million ha) Sl. Activity Area (in No. million ha) 1 Area under paddy cultivation 40.9 2 Area suitable for fish culture 3.6 3 Area under capture fisheries (brackish and freshwater) 2.9 4 Mangroves 0.4 5 Estuaries 3.9 6 Backwater 3.5 7 Man-made impoundments 3.0 Total area of wetlands 58.2 (Source: Directory of Asian Wetlands, IUCN, 1989) Grouping of Indian wetlands I. Himalayan wetlands II. Indo-Gangetic wetlands III. Coastal wetlands IV. Deccan wetlands (Prasad et al., 2003) 1.4 Wetlands of Karnataka The wetlands of Karnataka are classified into inland and coastal categories, both natural and man-made. Natural inland wetlands include lakes, ox-bow lakes, and marshes/swamps. Man-made inland wetlands include reservoirs and tanks. Natural coastal wetlands include estuaries, creeks, mudflats, mangroves and marshes. Man-made coastal wetlands include salt pans Wetlands cover about 2.72 million ha, of which inland wetlands cover about 2.54 million ha and coastal wetlands cover 0.18 million ha. The area of 682 wetlands, scattered throughout the state of Karnataka, is about 2718 sq km (Ramachandra, 2005). As such there has been no comprehensive account of the wetlands of coastal Karnataka, except mangroves. The kinds of wetlands observed during the present survey are the following: 10. Rice fields (both fresh water and brackish water or gazni fields) 11. Abandoned rice fields – due to brackish water ingression 12. Coastal marshes (seasonal and perennial) 13. Mangroves, estuaries, creeks, mudflats 14. Ponds/lakes 15. Reservoirs 16. Rock pools, ditches, quarries 17. Streams and rivers 18. Canals 1.5 Value of wetlands Retain water during dry periods, thus keeping the water table high and relatively stable. Environmental Management & Policy Research Institute 2 Flora of Coastal Wetlands Mitigate floods and trap suspended solids and attached nutrients. Thus streams flowing into lakes by way of wetland areas will transport fewer suspended solids than if they flow directly into lakes. Recycling of nutrients Purification of water Maintenance of stream flow Recharge of groundwater Important feeding and breeding areas for wildlife and fish and provide a stopping place and refuge for waterfowls. Wetlands support high diversity of species Buffer shorelines against erosion Offer recreation to society (Prasad et al., 2003) 1.6 Threats to wetlands Wetlands are one of the most threatened habitats of the world. Wetlands in India, as elsewhere are increasingly facing several anthropogenic pressures. Prasad et al. (2003), quoting different sources, find various reasons for Acute and Chronic wetland losses. The following are the various reasons for wetland losses: Agricultural conversion Deforestation in wetlands Hydrological alteration Alteration of upper watersheds Degradation of water quality Ground water depletion Species introductions 1.6.1 Acute wetland losses 1. Agricultural conversion: Rice farming is a wetland dependent activity and is developed in riparian zones, river deltas and savannah areas. Due to captured precipitation for fishpond aquaculture in the catchment areas and rice-farms occupying areas that are not wetlands, the downstream natural wetlands are deprived of water. About 1.6 million ha of freshwater are covered by fresh water fishponds in India. Rice fields and fishponds come under wetlands, but they rarely function like natural wetlands. Of the estimated 58.2 million ha of wetlands in India, 40.9 million ha are under rice cultivation 2. Deforestation in wetlands: Farming in mangrove areas and fisheries production, particularly shrimp farming, have destroyed considerable area under mangroves. The shrimp farms also cause excessive withdrawal of freshwater and increased pollution load on water. 3. Hydrological alteration: The changes in hydrology include either the removal of water from wetlands or raising the land-surface elevation, such that it no longer floods. Substantial increase in irrigated farming in recent times, after an initial increase in crop productivity, has given way to reduced to fertility and salt accumulation in soil due to irrigated farming in arid soils. 4. Inundation by dammed reservoirs: More than 1550 large reservoirs covering more than 1.45 million ha and over 100,000 small and medium reservoirs covering 1.1 million ha in India significantly affect hydrology and wetland ecosystems. Environmental Management & Policy Research Institute 3 Flora of Coastal Wetlands 1.6.2 Chronic wetland losses 1. Alteration of upper watersheds: When agriculture, deforestation or overgrazing removes soil water-holding capacity, erosion becomes more pronounced, affecting the hydrology with adverse consequences on downstream wetlands. 2. Degradation of water quality: Water quality is directly proportional to the human population and its various activities. More than 50,000 small and large lakes are polluted to the point of being considered ‘dead’. Sewage, industrial pollution, and chemicals from agricultural runoff are major polluting factors. 3. Ground water depletion: Draining wetlands has depleted ground water recharge in numerous localities of India. 4. Species introductions: Wetlands in India support around 2400 species and subspecies of birds. But losses in habitats due to exotic weeds such as water hyacinth (Eichhornia crassipes) and Salvinia have threatened the wetlands, competing with native vegetation. 1.7 Conservation of wetlands Wetland conservation in India is indirectly influenced by various legislative measures, the important ones are noted below: The Indian Fisheries Act, 1857 The Indian Forest Act, 1927 Wildlife (Protection) Act, 1972 Water (Prevention and Control of Pollution) Act, 1974 & 1977 Territorial Water, Continental Shelf, Exclusive Economic Zone and other Marine Zones Act, 1976 Forest (Conservation) Act, 1986 Coastal Zone Regulation Notification, 1991 Wildlife (protection) Amendment Act, 1991 National Policy and Macro Level Action Strategy on Biodiversity, 1990. India is also a signatory to the Ramsar Convention on Wetlands and the Convention on Biological Diversity. Lacuna: None of the coastal wetlands of Karnataka has so far met the criteria for consideration under The Ramsar Convention on Wetlands. Of the many wetlands in India, only 68 are protected. But there are thousands of other wetlands that are biologically and economically important but have no legal status. Estuaries of the Karnataka