Ans: Ecosystem Balance and Human Impact
The interactions among organisms and between organisms and the abiotic components of their environment produce steady and balanced ecosystems. Biogeochemical cycles also maintain the balance in ecosystems by recycling natural resources, so that they do not deplete. Humans try to modify environment (e.g. cutting of trees) to fulfill their needs. This has upset the delicate balance in ecosystems and nature as well.
Some of the human impacts on the balance of ecosystems and nature are as follows:
1. Global Warming
The addition of greenhouse gases (e.g. carbon dioxide, methane, ozone) in atmosphere increases -the temperature of the Earth. These gases remain in the lowest part of Earth's atmosphere and do not allow solar radiations to reflect back into space, As a result, heat remains within the Earth's atmosphere and increases its temperature. This is called global warming.
Effects of Global Warming
Due to global warming, polar ice-caps and glaciers' are melting faster than the time taken for new ice layers to form. Sea water is also expanding causing sea levels to rise. Due to melting glaciers, rivers overflow and cause floods.
2. Acid Rain
When rain falls through air, it comes across chemicals such as oxides of sulphur and nitrogen. These chemicals interact with water vapours in the presence of sunlight to form sulphuric acid and nitric acid. These acids remain as vapours at high temperatures.
As temperature falls, the acids begin to condense into liquid form and mix with rain or snow, on the way down to the Earth. This makes rain acidic with pH range of 3 to 6.
Effects of Acid Rain
Some of the significant ill effects of acid rain are:
• Acid rain destroys the necessary nutrients present in the waters of rivers and lakes etc. It also lowers the pH of water. Most of the aquatic animals cannot survive at this pH.
• Acid rain washes nutrients out of soil, damages the bark and leaves of trees and harms root hairs. Leaf pigments (chlorophyll) are also destroyed.
• Metallic surfaces exposed to acid rain are easily corroded. Panics, paper and leather products lose their material strength or disintegrate easily.
• Building materials such as limestone, marble, dolomite, mortar and slate are weakened with acid rains because of the formation of soluble compounds. Thus, acid rain is dangerous for historical monuments. The building of famous Taj Mahal has been corroded at many places, due to acid rains.
3. Deforestation
Deforestation means clearing of forests by natural causes or humans. Large areas of forests have been cleaned for agriculture, factories, roads, rail tracks and mining. Humans cut trees for getting wood (lumber), which is then used for making structures and for heat production. Human preys upon forest animals, which are the predators of many insect pests. In this way, insect pests destroy forests by eating the shoots and spreading diseases.
Effects of Deforestation
The effects of deforestation include floods, droughts, landslides and soil erosions, global warming and loss of habitat of many species.
4. Overpopulation
When the industrial revolution started some 250 years ago, the world population was at 600 million-that seems like a lot of people but now the world population is almost ten times at 6 billion and will grow to 8 billion by 2025. Better health facilities and lowered mortality rates have contributed in population growth.
Year
Population
Year
Population
1981
85,096,000
1999
134,790,000
1984
92,284,301
2002
144,902,409
1987
99,953,232
2005
155,772,000
1990-
107,975,060
2008
166,111,487
1993
116,444,165
2009
169,708,303
1996
125,409,851
2010
173,510,000
3.66%
2.69%
The population of Pakistan
Pakistan population growth rate
5. Urbanization
Urbanization means growing of cities. People move from rural areas to cities in search of better jobs, education opportunities and higher standards of living.
Effects of Urbanization:
22.5
25
28.3
17.8
If there is rapid urban growth, 32-5
the governments find it difficult
to provide even the basic
facilities like health, education,
shelter, water, electricity etc.
Most of the migrants in cities
do not find good jobs and
become the part of urban poor.
There' is overcrowding in
schools, hospitals etc. The
slum areas increased number Pakistan urban population (%age)
and people living there are at greater risk of diseases. Urbanization is a global problem and cannot be stopped but it can be managed. The current level of urbanization in Pakistan is about 32% which is not high by global standards.
Solution
A planned urbanization can solve many problems. The cities should have thick green belts in their surroundings to control pollution. The open spaces in cities should be reserved through zoning and land plans. The urban spread-out should also be controlled. Utilizaiton of public transport instead of individual transports also proves effective way to manage urbanization.