Today, it was yet another delightful class with PFC for the 6th graders. It was about wetlands. Earlier, they learnt about the terrestrial and aquatic land forms. Now, what are wetlands? Is it just a land that is wet or is there more to it? Wetland is a place where the land is covered with water either permanently or seasonally due to the monsoon. The two main classifications are inland - where land is covered with freshwater, or coastal - where it's covered with sea water or a mix of fresh and seawater what we know as brackish water.
The principal feature of a wetland is the flooding or saturation of soil. This flooding or saturation leads to low oxygen environment in the soil or what is called an anaerobic soil which is less fertile and acidic. Due to the anaerobic soil, the layer of dead plant litter on it does not decompose quickly. This partly decomposed plant matter formed on the acidic soil forms peat which is also a cheap form of fuel.
Wetlands have a unique and diverse flora and fauna which adapts to the flowing or stagnant water, acidic, and anaerobic soil. The different types of wetlands are swamp, marsh, bogs, and fen and the vegetation, soil, and water movement for each classification varies; examples being the Pallikaranai marsh, the closest to us, the fens of Estonia, the biggest bog being the West Siberian lowlands covering 2.745 million square kilometres.
We learnt that trees abound in swamps and grasses and sedges are more in marshes. Bogs predominantly contain a layer of sphagnum moss while fens support all types of flora from grasses to sedges, herbs, shrubs and trees which in turn supports a variety of animal species that thrive in such productive habitats.
Krishnaveni along with Mahesh described in detail the different fauna of the wet lands. The life cycle of a dragon fly tells us that they lay eggs in the water. The egg hatches to a larval stage called nymph and there is no pupa stage. Once the nymph comes out of the water, it molts out into an adult dragonfly - it is most vulnerable to predators at this stage. Another stunning creature was the water strider which creates ripples on the surface of the stagnant water in the wetland so all the dry leaves move away from the surface of water to the sides.
It was an astounding experience to know about the ecosystem engineers - the hippopotamus, how they eat on land and poop in water bringing nutrients to the water enriching the plant and animal life there. We got to know how they create spaces in and around wetlands leading to the formation of new habitats.
We watched a video clip on a beaver dam. It was breathtakingly impressive to see how a beaver builds a dam across a river to create deep calm waters to build its home. The dam slows the flow of water spreading it across and down the river bringing in more silt thereby creating an ideal habitat for wetland species.
We now saw how frogs are different from toads. The frog is an excellent jumper with long legs and a soft, moist skin. Also, they lay eggs in clusters. Toads have warty and rough skin with short legs ,and they lay eggs in straight lines.
We now know how the birds found in wetlands like pelican, spoonbill, stork, and avocet have long, slender beaks with thin, long legs adapted to the habitat and food they eat like fishes, crustaceans, shrimps and other micro plankton. The avocet sticks its head underwater to catch the crustaceans and bugs with its long, sharp upturned bill. The best part was about the beautiful flamingos and how they are called the filter feeders which means they take in food and water. The water is then expelled out. They eat crustaceans, snails, algae and even diatoms. We also watched a video clip on the mudskipper fish which lives in the wetlands and the cat fish and climbing perch fish. It is astonishing to know how these fishes adapt to the harsh environment of the wetlands.
The children got an extensive details on the plants that live in fresh water wetlands known as hydrophytes or water loving plants and their different adaptations. They have big leaves that float on the water and have a waxy coating on them to keep them as dry as possible. Another interesting feature was the presence of aerenchyma which are air filled cells in the leaves, stems and roots of such plants for adaptation in waterlogged environments to provide them buoyancy. Krishnaveni presented a cross section of the lotus stem where the kids could visualize the aerenchyma. Algae are also abundant in wetlands.
Next, we got to learn the layers of the coastal wetlands - the closest plants to the harsh conditions of shoreline water being Rhizophora or the red mangroves which have stilt roots for stability and to get oxygen, the next layer formed by the Avicennia or the black mangrove which have breathing or pencil roots also know as pneumatophores, then comes Laguncularia or the white mangroves occupying higher land than the black mangroves with smaller stilt roots, the last being the buttonwood or mangrove associates, an example being Portia tree known as "Poovarasu" in Tamil, very commonly found locally. The mangrove leaves are adapted to excrete salt from its under surface.
After gaining this stupendous knowledge, it was time for a snack break as the kids became restless sitting for an hour and half soaking all the information. After the break, it was time for the most exciting part - the walk - to take a look at the mangroves in the brackish water and the flora of the freshwater wetland, both of which are available at the Adyar Eco park. It was explained to us by Krishnaveni and Maya that this restored wetland was not a naturally formed wetland but a restored urban wetland. Yet, we were able to see the long grasses growing close to the water along with the sedges and then the other trees. We also observed the agile water strider moving swiftly across the water surface. We were able to look at the Avicennia's roots with its pneumatophores and the mangrove associate Portia tree.
We assembled again for a short session on a platform in the serene atmosphere of the Poonga. This session was a real eye opener for all of us. The children were given two maps of the Chennai city one from 1815 and another from the 1980s. They were asked to trace the Adyar river on both the maps. We could see on the old map Quibble Island, a river island formed by the encircling Adyar river abutting the beach. But the recent map did not have the island and what remained is only the Adyar creek. The next thing to be traced was the Nungambakkam Tank and Spur Tank. All that remains of the Nungambakkam tank is Tank Bund Road while the spur tank lake now exists as Chetpet lake which is dry most of the time. The biggest of all water bodies was the Long Tank, which does not even exist anymore on the map, all due to the post independence development of the City.
Krishnaveni then gave data on how the city has grown and how the water bodies have shrunk. Maybe because the growing city needs more land for housing. The Pallikaranai marsh shrunk from 235 sq km to 50 sq km in the 1980s and it is only 5.5 sq. km today. About 90% of the marsh has shrunk at an alarming rate due to the creation of residential areas around it. Chennai had over 300 water bodies but it's saddening to see the sorry state of the city today.
It was now time for the kids to leave back to school and the insight gained was how the city has expanded but at the expense of its water bodies. The question now is not who is to blame for this but how shall we contribute to the protection of the environment and the ecosystems of the city along with its progress and expansion. It was heartening to see the children interact with the PFC team confidently and how they could recall some of the information they learnt earlier and how the PFC members encouraged the kids to analytically think before answering the questions put forth to them. We need to sensitize the children to value the education they are getting, how they are fortunate enough to learn this hands-on while there are few who don’t get such opportunities, and some who don’t even know that this is real education. We need to engage and involve the children in environmental issues and to encourage them to find sustainable solutions to the modern age problems.
By Naqeeb Sultana