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• The freshwater ecosystem covers only 0.8% of Earth’s surface and contains 0.009% of the total water.
The ecosystems are habitats to reptiles, amphibians and fi shes. Three basic kinds of freshwater
ecosystems are:
• Wetlands: Places in which the soil is inundated or saturated for a lengthy period of time.
• Lotic: Fast-moving water such as streams and rivers.

• Lentic: Slow-moving or still water such as pools, lakes or ponds.

Ecological Imbalance
Anything that attempts to alter the balance of the ecosystem can threaten the existence of that ecosystem. Some
of the threats can be resolved if the natural conditions are restored. However, others can harm its life forms and
destroy ecosystems. Various factors cause ecological imbalance.
Let us read about some of the important factors.

 Overpopulation: Human overpopulation is among the most demanding environmental issues. It is the
root cause of various other ill effects like global warming, environmental pollution, habitat loss, intensive
farming practices and consumption of fi nite natural resources such as freshwater, arable land and fossil
fuels faster than their rate of regeneration.
 Landfi lls: Landfi lls are the places where we put our garbage and other waste materials. This waste rots
and decomposes and produces harmful gases that contribute to global warming. Landfi lls also pollute the
local environment including the ground water and the soil. Majority of landfi lls are located in metro cities
and towns.
 Agricultural Practices: In modern agricultural practices, fertilizers and pesticides are used to produce
more crops. The biggest issue facing the use of chemical fertilizers is groundwater contamination. For
example, nitrogen fertilizers break down into nitrates and travel easily through the soil. Being water-
soluble they can remain in groundwater for decades. The pesticides that are used don’t just fall on the
crops and stay there but are transported via wind and water and affect the surrounding ecosystems.
 Industrial Wastes: For a developing country like India, industrialization has been the result of rapid
development in technology and the increasing demands in our daily lives. But the main concern is that
most of our factories are not eco-friendly. These factories produce a lot of waste every day. They dump
their wastes indiscriminately, thus polluting the air, rivers and land. This causes soil pollution and climate
change, which is dangerous for the earth’s biodiversity.

 Plastics and E-waste: Polythene and plastics are not biodegradable. Once discarded, they end up piling
up on lands, river beds and sea beds. Plastic cannot break down into simpler, harmless substances. Plastic
stays for hundreds of years and can be a hazard to wildlife as it produces toxins into the environment. With
the excess use of polythene, the pollution level caused by it also increases, affecting almost every kind of
environment including terrestrial as well as aquatic ecosystem. This leads to groundwater pollution, land
pollution, air pollution, and poisons our food chain.
 Deforestation: Deforestation is the permanent destruction of forests in order to make the land available
for other uses. Deforestation affects environment badly with loss of habitat, increased greenhouse gases
(carbon dioxide, methane, water vapor and nitrous oxide), water in the atmosphere, soil erosion, fl ooding,
etc.

Natural Resource Conservation
Resources that we obtain from nature and use them without much modifi cation are called natural resources. Air,
water, soil and minerals are all natural resources. Many of these resources are used directly, but in some cases,
technology may be needed to use a natural resource in the best possible way. Natural resources are broadly
categorised into renewable and non-renewable resources.

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