The document discusses various human-induced modifications to ecosystems and their impacts. It describes how weather modification techniques like cloud seeding are used for rainmaking and prevention of hail or hurricanes. It also discusses other modifications like greenhouse effect, ozone layer depletion, acid rain, artificial rainmaking, desalination etc. and their consequences like global warming, sea level rise, extinction of species if corrective actions are not taken.

1. By,
DAMARIS BENNY DANIEL
II Msc. Zoology

2.  Ecosystems have always been subjected to change.
 Under the impact of anthropogenic influences, change may be
accelerating in many ecosystems.
 Some are deliberately created, others are a consequence of human
activities.
 Weather modifications
 Artificial rain making
 Desalination
 Green House Effect
 Destruction of ozone umbrella
 Acid rain

3.  It is the act of intentionally manipulating or altering the weather.
 The most common form of weather modification is cloud seeding
to increase rain or snow.
 Weather modification can also have the goal of preventing
damaging weather, such as hail or hurricanes, from occurring.
 It includes
 Cloud seeding and production of artificial rain
 Fog dissipation
 Frost prevention
 Lightning and hail suppression

4.  Is the act of attempting to artificially induce or increase precipitation.
 Process of normal rain fall…..
 Rainfall occurs when cloud droplets grow large enough to fall to earth.
 Growth of cloud droplets occurs around a cloud seed.
 Cloud seeds or cloud condensation nuclei (CCNs) are small particles
typically 0.2μm about which cloud droplets coalesce.
 No CCN – no rainfall
 Cloud seeding is a process which attempts to change the amount or type
of precipitation that falls from clouds, by dispersing substances into the
air that serve as CCN.

5.  Any technique of cloud seeding depends on the release of millions
of tiny particles of dry ice or silver iodide into a cloud.
 Methods
 Ignite solid silver iodide in burners on the ground. The smoke
thus formed consists of many tiny particles of the compound
which are then carried upward into a cloud.
 Dropping the seeding agent from an airplane onto the top of the
cloud (spraying)
 The particles are fired into clouds from aircraft-mounted flare
guns at a height of over 2,000m.
 Cloud seeding is the most common method of rain making.

7.  Dry ice grains with high-pressurized air at almost sonic speed
is blasted into the fog.
 The dry ice grains collide with the fog droplets, acts as a
seeding agent
 The fog droplets grows in size and precipitates out of air.
 Thus fog may disappear.
 It can be applied anywhere where fog hinders functioning like
airports, roads, harbours etc.

8.  Hail - devastating effects on crops
 Hail can be prevented if the atmosphere is flooded with nuclei on
which moisture can condense and freeze.
 The more nuclei present, the less likely large pieces of ice (hail)
are to form.
 Relatively little work is now being done in the field.

9.  Desalinisation is the process that remove salt and other minerals
from saline water to create fresh water.
 Imp in places where availability of freshwater is limited.
 One potential byproduct of desalination is salt.
 2 main methods
 Multistage flash distillation
 Reverse Osmosis (Membrane desalination process)

10.  Water is heated in a container called brine heater.
 The heated water then flows to a second container called stage,
where pressure is lower.
 Low pressure causes water to boil, some part forms steam
 The remaining water is moved into the next stage.
 The vapour produced is condensed in tubes of heat exchange.
 Same process repeated, so produces clean water & brine.

12.  It is done by reverse osmosis (RO)
 Reverse osmosis is a process where the solvent molecules move
across a semi permeable membrane from high solute
concentration to low solute concentration.
 It requires input of energy.
 A RO membrane is a semi permeable membrane that allows the
passage of water molecules but not majority of dissolved salts and
other larger molecules.
 Saltwater is forced through membrane sheets at high pressures
(600 to 1000 psi)
 Process produces clean water and brine

13.  A greenhouse is a glasshouse in
which plants are grown in colder
countries.
 Principle
 The sun's energy enters through the
greenhouse glass easily, plants absorb
it and utilize it.
 A part of the radiation is re -emitted
by the plants and soil
 It cannot get out as easily thus heat
gets trapped inside.
 Earth’s atmosphere acts as a green
house.

14. Incoming solar radiations passes
through the atmosphere and
reaches earth’s surface.
The earth’s surface absorbs the solar
energy and releases it back to the
atmosphere as IR radiations some of which
goes back into the space.
Some of the IR radiations emitted by
the earth is absorbed by green house
gases in the atmosphere & they
re-emit the energy as heat towards
the earth’s surface.
This increases earth’s surface
temperature and this process
is known as ‘Green House Effect’.

15. GREEN HOUSE GASES
Water vapour:
 It is responsible for about two-thirds of the natural
greenhouse effect.
 A part of water cycle.
Carbon dioxide:
 Main contributor to the enhanced (manmade) GHE
 Globally, it accounts for over 60% of Enhanced GHE.
 The major source - from the burning of fossil fuels
Methane:
 Mining and burning of fossil fuels, livestock husbandry ,
rice cultivation – major contribution.
 Methane can trap heat 23 times more effectively than CO2.

16. Nitrous oxide (N2O)
 Is released naturally from oceans and rainforests and by bacteria
in soils.
 Human-influenced sources include nitrogen-based fertilisers,
fossil fuel combustion and industrial chemical production.
Fluorinated greenhouse gases:
 These are the only greenhouse gases that do not occur naturally,
but have been developed by man for industrial purposes.
 Share - around 1.5%. But they are extremely powerful
 can trap heat up to 22,000 times more effectively than CO2
 can stay in the atmosphere for thousands of years.
 The best known of these gases are chlorofluorocarbons (CFCs),
which are not only fluorinated greenhouse gases, but also deplete
the ozone layer.
 They are being phased out under the 1987 Montreal Protocol on
Ozone Depleting Substances.

17. CAUSES
Evaporation
EnhancedGreenhouseeffect
ANTHROPOGENIC
NATURAL
Volcanic
eruptions
Methane gas from
cattle dung.
Burning of fossil
fuels
Deforestation
Use of fertilizers
CFC’s from AC ,
fridges etc

18.  Enhanced GHE would lead to global warming and other climate
changes.
 Due to rise in global temp oceans will become warmer – affect living
organisms.
 Melting of glaciers and polar ice caps will lead to rise in sea level and
flooding of many low lying areas – islands at the risk of submergence.
 Several plant and animal species will become extinct due to their
inability to adjust quickly to new conditions.
 Coral reefs would be severly threatened.
 Water scarcity & drought.
 Spread of several diseases.
 Extreme weather events – rising intensity of floods, droughts, storms
etc.

19. We are running out of time
act now before
its too late.
Reduce fossil fuel
consumption.
Use of cleaner energy
sources.
Energy efficient
practices.
Preservation and maintenance
of existing forests
Plant more trees.
Better agriculture
practices.
SOLUTIONS

20.  Humans have been interacting with ecosystems and modifying
them for as long as human life has existed on Earth.
 The scale, speed and degree of change that is occurring threatens
the survival and integrity of many ecosystems and also human
life.
 The number of human-induced modifications to ecosystems
has increased as population and technology has increased.
 Its high time we address the consequences and take
appropriate steps to reduce the impacts.

21.  Using supercomputers, MIT (Massachusetts Institute of
Technology ) researchers have come up with a new
approach for desalinating water–using sheets of graphene, a
one-atom-thick form of the element carbon
 Graphene sheets with precisely controlled pores have
potential to purify water more efficiently and less
expensively than existing methods.

22.  Aloka Debi, Environmental Science and Engineering (2008), University
Press, Hyderabad
 Chaudary D.S and Sundaravadivel M, Environmental management
(2004), Scitech Publications, Chennai.
 Madhab Chandra Dash and Satya Prakash Dash, Fundamentals of
Ecology, 3rd edition, McGraw Hill Companies, New Delhi.
 Santra S.C , Environmental science (2004),New central book agency(p)
Ltd, New Delhi.
 http://www.epa.gov/climate/climatechange/kids/basics/today/greenhouse-
effect.html
 http://science.howstuffworks.com/reverse-osmosis.htm