Wetlands for Wildlife and Education

Wetlands for Wildlife and Education in the Bangalore Area[*]

M. B. Krishna, October 2002.

 

The Background

“Water is essential to the survival of any plant or animal and natural wetlands are vital cogs in the ecological machine. Linking one habitat to another like a silver thread, the waterways and wetlands of the world are like the bloodstream of the body, vital and highly efficient distribution and cleansing systems.” [1]

Wetlands are defined as areas marginal between land and water, inundated or saturated frequently enough to support plant and animal communities adapted to a life dominated by water. It encompasses areas of marsh, swamp, standing or flowing water, which is fresh, brackish or salty. This definition thus includes man made systems, and the lakes in and around Bangalore fall into this category. Apart from the occasional seasonal stream, the Bangalore area has no natural wetlands. All the lakes (technically ‘tanks’, used interchangeably here), which occur in the area, are thus, man made. A wetland of our parts basically consists of an impoundment across a stream to form a lake, and irrigated fields down the embankment. As such these usually form a series, a number of them being found in a valley.

A vast majority of our wetland areas occur in the outskirts, on the urban-rural fringe. The uneven survival of Bangalore's lakes with reference to the city at present is obviously the result of the explosive increase in the extent of the city from around 67 km² in 1961 to presumably over nine times that area today. The growth of the city has not only engulfed the lakebeds but also disrupted the drainage pattern in these basins. In addition, the lakes which have survived in the City area have sewage flowing into them. A survey of tanks within a forty-kilometre radius of the GPO in 1995 revealed that, of the thirty tanks which had high water levels during the survey in the month of January, twenty-five had sewage waters flowing into them [4]. Today we treat wetlands as wastelands, dumping our refuse in them or filling them in order to provide farmland or building land [1].

Remote sensing studies have revealed that water bodies and wetlands account for just 4.8% of a sample area of 640 km² covering both urban and rural zones of Bangalore [2]. The number of man made lakes, in the existing BCC and BDA area, has fallen from 262 in 1960, to some 81 lakes at present [5]. Obviously most of these lakes were created to serve the needs of irrigated agriculture, but were destroyed once the pressure for land became high.

 

Wetland Birds and other Wildlife

“Freshwater habitats can be as productive as any on earth, and support natural communities of great beauty and diversity. Many wetland birds are large and spectacular creatures, nesting in huge colonies. Many are also long distance migrants, with long established flyways linking one wetland habitat to another.” [1]

From an ecological point of view, the lakes in the Bangalore area form a unique and irreplaceable local system. A man-made lake of our parts can be viewed as a basin with several zones of water of varying depths, abutting a deeper zone that lies towards the embankment. This zonation is dynamic and promotes the growth of a variety of emergent, floating, anchored floating and submerged vegetation, each of which shows a preference to a particular range of water depth. These fresh water plant communities accommodate a large number of small organisms like periphyton, insects, molluscs, etc. which form the staple diet of many species of invertebrates and vertebrates in the lakes' food chain [3].

Light, temperature and the availability of oxygen and nutrients govern the growth of plants, of which the smallest and simplest are phyto-plankton, which in turn are devoured by zooplankton, insect larvae and fish fry. There are even some adult plankton feeding fish and birds [3].

Even the lake sediments support a large variety of soil invertebrates, which thrive on organic matter from decaying plants and animals. These invertebrates are in turn eaten by a variety of other predatory animals such as fish and birds, sometimes along with the sediment itself. Food chains in these lakes can often be complex, lengthening and branching, and forming a food web. Often, at the end of this food web is man himself.

Wetlands account for a disproportionately large number of bird species compared to the physical extent of the habitat. Over three hundred and thirty species of birds have been recorded in Bangalore and its environs so far. Of these, around a hundred and forty bird species are found in or near lakes and wetlands [6], spread over some nineteen different bird families. Though the area accounted for by wetlands in the Bangalore area is just around five percent, the bird species accounted for is around forty percent of Bangalore’s total.

These birds make use of a variety of conditions from dry ground and meadows bordering lakes to the open water zone. There are also birds which just make use of the open air space above these wetlands. Depending upon their size, the availability of food and suitable conditions for foraging, different bird groups can be seen occupying different regions of the lake. A large number of species can be found in regions with shallow water. Often large congregations of migratory ducks can be found massed on the open waters of large lakes. Sheer distance from the shoreline affords protection to these birds, and they can even be seen sleeping over the water with their beaks tucked-in on their back!

Counts of birds taken in the wetlands and water bodies in and around Bangalore in winter indicate that as high as eighty percent of the individuals that we see, could be migratory. We get many species which only breed around the Arctic Circle, and almost all migratory wetland birds that come to our tanks and man made lakes breed beyond the Himalayas. Unlike popular impression, many of these birds are small, and fly fast, enabling them to cover large distances in reasonable time.

Not all these birds are common, nor are they found in every wetland right through the year: for example, a large number of trans-continental migrants are present only between September and April. The occurrence and numbers of birds is a complex interplay of food and resource availability, population movements, seasonal fluctuation, water levels and wetland structure, compounded by disturbance and other factors introduced by man.

Therefore, a variety of habitats and microhabitats are required for the survival of a variety of species. In Bangalore, there would be a gradient in the kind of microhabitats which would be provided by the sequence of tanks from within the city to the outskirts and the adjoining rural areas. The city tanks like Ulsoor and Yediur are walled, and others newly engulfed by the city would have lost the associated meadows and sloping shoreline. The 1995 survey revealed that nearly a third of the tanks in the Bangalore area (within a 40 km radius from the GPO) had lost their sloping margins and were either walled or had an abruptly sloping margin [4]. As one moves outwards, the sloping shorelines are seen but meadows are absent, until one reaches the relatively remote rural areas where all zones could be present. The shoreline and the water spread would have a major influence on the kind of birdlife that would be present in urban tanks. Preliminary investigations in the Karnataka region reveal that the extent of the water body would have a bearing on the bird populations but not diversity, which would be determined by the quality of the wetland and the shoreline [7].

Life began in water, and even the larger forms of life like amphibians and fish, depend on it for survival. More than fifteen forms of amphibians and over twice that number of fish have been recorded in the Bangalore area so far [8], and one even new to science!

 

The Issues

“Nature conservationists are recognising that battles to save biodiversity can not be won if they are only fought in habitats such as rain forest. The urban population are the key group to be motivated. Attitude change has to come in the areas of greatest political importance and highest resource consumption, and it is well recognised that such changes need to begin close to hand.” [9]

It is always good to remind ourselves that the largest body of tomorrow’s technical manpower comes from today’s cities. Nowhere else would ecological education and awareness be more relevant than in the urban context. There is a great opportunity in making the most of what is available locally, and to get an idea and feel of the processes which go on in nature, in our own environs and habitations. If used well, it would be but a stepping stone for further understanding of the processes in wilderness areas and a strong foundation to manage our own urban system. However, the ability to appreciate the plants and animals around us, and the ability to comprehend their value to us, is of paramount importance. The necessity to educate the citizens of today, as well as the necessity to sustain this teaching process for the citizens of tomorrow, is an aspect which can hardly be over-emphasized. It is in this context that maintaining urban wildlife habitats and green spaces takes a very special meaning.

If one takes even a cursory look at the amount of research work that has gone on in our universities on lake and wetland ecology related issues, one would see a distinct bias towards local sites being used for study. This is hardly surprising given that logistics and accessibility to analytical resources often determines the choice. But if one looks at awareness and education at a lower level, there is a fair amount of ignorance about what local habitats have to offer. This is notwithstanding the richness and accessibility of local habitats for informal and extramural education and learning.

Much of the general biology portions in the school and college syllabi review organisms which are essentially aquatic, from algae and other aquatic plants, to fish and amphibians. Traditional syllabi have perhaps not given enough importance to field biology to the extent non-destructive studies could have given an opportunity for. In a changing world where technology is shrinking barriers, non-destructive observational learning and studies could very effectively find a place. This is where natural urban habitats could play a key role. And urban lakes and wetlands would be very accessible habitats which could be used to even illustrate ecological processes.

There has been a tendency to view and use every urban lake for recreation purposes. Most urban lakes are eutrophic, and letting people come into contact with contaminated water may not be a wise thing to do. This also includes proposals for aquatic sports, where people in their prime are involved. Again, boating dives birds away [e.g. 10] and could have serious consequences for other wetland wildlife too. Even rescue, under our local conditions, in the case of a mishap would become difficult in large lakes. It could perhaps be said that any medium or lager sized lake, say larger than say 7 hectares, would be problematic for rescue efforts in time, without some danger to the individuals involved.

Many of the eutrophic urban lakes are seeded with fish and the harvests sold subsequently. It is well known in biology that contaminants could get concentrated in successive stages of a food chain and reach damaging levels, by a process which is referred to as ‘biological amplification’. In spite of this, consumption of fish from such sites continues. The global experience as in the case of DDT and mercury contamination should serve to warn people.

Land value in many urban areas is high, and there is a lot of pressure on tank bed land from encroachers [11]. The most easily maintained deterrent to encroachments therefore, is standing water itself.

The past attitude of viewing lakes and wetlands as wastewater lagoons should change. Lakes and wetlands could effectively be very useful in an urban setting, in more ways than one. Lakes and wetlands could effectively double up with urban green spaces and also be used for increasing urban tree cover. Trees in lakes and tanks could provide an aesthetic screen and pleasant greenery, especially in sites which are too small to have a scenic value, and also be useful for treating the water [12].

Bangalore is on a plateau, and all the water which flows, flows out. Tanks are thought to be good sources of groundwater recharge, though how some five percent of the surface area could effectively recharge the rest of the ninety-five percent is to be elucidated. Whatever the reason, it makes sense to retain these tanks in good condition with fairly good water, and wildlife!

 

References

1. Diamond, AW; Schreiber, RL; Attenborough, D; Prestt, I; 1987. Save the Birds. Pro Natur GmbH & Cambridge University Press.
2. Behera, G; Nageswara Rao, PP; Dutt, CBS; Manikiam, B; Balakrishnan, P; Krishnamurthy, J; Jagadeesh, KM; Ganesha Raj, K; Diwakar, PG; Padmavathy, AS; Parvathy, R; 1985. Growth of Bangalore City since 1900 based on maps and  Satellite imagery. ISRO technical report number: isro-eos-tr-55-85.
3. Chakrapani, BK; Desai, M; George, Joseph; Karthikeyan, S; Krishna, MB; HarishKumar, U; Naveein, OC; Sridhar, S; Srinivasa, TS; Srinivasan, N; Subramanya, S; 1990. Survey of Irrigation Tanks as Wetland Bird Habitats in the Bangalore Area, India, January 1989. Birdwatchers' Field Club of Bangalore. Sponsored by the Karnataka State Forest Department.
4. Krishna MB; Chakrapani BK; Srinivasa TS; 1996. Waterbirds and Wetlands of Bangalore: a report on the status, water quality, plankton and bird populations of the lakes in and around Bangalore and Maddur, Karnataka, India. Birdwatchers’ Field Club of Bangalore and Bangalore Urban Division, Karnataka State Forest Department.
5. Lakshman Rau, N; Issar, TP; Parthasarathy, MA; Patil, SM; Vijaya Devi; Giri Gowda, P; Shenoy, PD; 1986, 1993. Report of the High Power Committee set up by the Government of Karnataka on 'Beautification of Bangalore'. Published by Shivashankar Engineering Co. Pvt. Ltd, Bangalore for the Government of Karnataka.
6. Krishna, MB; 1996. The Birds of Bangalore's Wetlands. Proceedings of the Seminar on Environment related Issues of Bangalore, pp.106-114. Environment Association of Bangalore & Civil Engineering Division, Department of Space, Bangalore.
7. Hussain, SA; Subramanya, S; Naveein, OC; Krishna, MB; 2002. Inland Wetlands of India Project: Preliminary Field Report for Karnataka Wetlands. Unpublished.
8. Karthikeyan, S; 1999. The Vertebrates and Butterflies of Bangalore: A Checklist. WWF-India, Karnataka State Office, Bangalore.
9. Rhode, CLE; Kendle, AD; 1997. Nature for People. In Kendle, T; Forbes, S; Urban Nature Conservation. E & FN Spon. London.
10. Krishna, MB; Gadgil, M; 1993. The Impact of Boating on the Birds of Lalbagh tank. Enquiry report submitted to the Department of Ecology and Environment, Government of Karnataka, Bangalore. CES, IISc, Bangalore. Unpublished.
11. Jayaram, C; 1996. Management of lake systems and surface water bodies in Bangalore. Proceedings of the Seminar on Environment related Issues of Bangalore, pp.94-104. Environment Association of Bangalore & Civil Engineering Division, Department of Space, Bangalore.
12. Krishna, MB; 2000. Using Mangrove Trees in Eutrophic Inland Waters. Proceedings of the Lake 2000 Seminar, CES, IISc, Bangalore. http://ces.iisc.ernet.in/…

 

 

---

 

[*] Presented at the Public Affairs Centre - Max Mueller Bhavan  collaborative workshop on “Water”, October 2002.