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
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