In the earlier classes we have studied about different types of pollution
as a result of human interventions in ecosystem. In this section we will try
to understand that when we cut forest to grow food crops, how this activity
brings harmful changes in ecosystem and affects organisms of each trophic
level.
Let us study a pond ecosystem to understand the components of
environment, their interactions and effects of human interventions in the
following story
Story of Kolleru Lake
Fresh water lakes provide the nutritional requirements of the world’s
poorest people. One such lake is Kolleru which is no ordinary wetland. It
is one of the largest fresh water lakes in India, existing between West
Godavari and Krishna districts of the state of Andhra Pradesh. The
catchment of the lake extends up to 6121 km2.
The lake Kolleru discharges
its excess water in to the Bay of Bengal through the twisty channel called
Upputeru, which is about 65 km long. Nevertheless, the Kolleru wetland
receives huge quantity of nutrient rich sediments from the flood plains of
these rivers.
November 1999, the Government of India had declared the lake as
Bird Sanctuary. This lake is hosting 193 species of birds and a variety of
flora and fauna, including medicinal plants. It attracts migratory birds from
northern Asia and Eastern Europe between the months of October and
March and it is estimated as 20,00,000 birds per year. The lake was also an
important habitat for an estimated
20 million residents. This largest
sweet water lake has not only
shrunk in size but faced great threat
due to pollution in the last three
decades as revealed by satellite
pictures. The decrease in water area
and muddy ground in the lake
resulted in flooding problems in the
lake area.
