Effects of Anthropogenic Activities on the Environment

7/29/2019 Effects of Anthropogenic Activities on the Environment

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CENG 4710 Environmental Control

Module 3 Effects of anthropogenic

activities on the environment



Module 3 Learning Outcomes

• Be able to show the effects of anthropogenic activities on the

atmospheric environment


aquatic environment


land environment



Topics

• Effects of Anthropogenic Activities on the Atmospheric

Environment – Acid Rain; Particulates

• Effects of Anthropogenic Activities on the Aquatic

Environment – Chemicals, Coral Reefs; Oil Spills;

Eutrophication; Algal Bloom

• Effects of Anthropogenic Activities on the Lithosphere -

Deforestation; Desertification; Sand Storms



Effects of Anthropogenic Activities on the

Atmospheric Environment



Acid Rain





Acid Rain

• The term acid rain or more accurately acid precipitation is commonly used

to mean the deposition of acidic components in rain, snow, dew, or dry

particles.

• Acid rain occurs when sulfur dioxide and nitrogen oxides are emitted into

the atmosphere, undergo chemical transformations, and are absorbed by

water droplets in clouds.

• The droplets then fall to earth as rain, snow, mist, dry dust, hail, or sleet.

• This increases the acidity of the

soil, and affects the chemical

balance of lakes and streams.

http://www.marietta.edu/~biol/102/arain.html



Acid Deposition

Wet deposition

Dry deposition



Causes of Acid Rain

1. Burning of fossil fuels

2. Burning of forests, volcanoes, etc.

http://en.wikipedia.org/wiki/Image:Gavin_Plant.JPG



Effects on Forest Ecosystems

• Acid rain can slow the growth of forests, cause leaves and needles to turn

brown and fall off and die.

• In extreme cases trees or whole areas of forest can die.

• Forest decline has been seen in many parts of the world. It is manifested by

increased mortality and reduced growth in the forest.

Effect of acid rain on a forest, Jizera Mountains, Czech Republic

http://en.wikipedia.org/wiki/Image:Acid_rain_woods1.JPG



Effect of Acidic Precipitation on

Soils and Plant Growth

• Some plants are tolerant of acidic conditions, while others are not.

• Acidic soils may affect microorganisms in the soil, which play important

roles in plant growth.

• Acidity affects the availability of nutrients that are essential for plant

growth and increases leaching of aluminum and mercury, which are toxic

to plants at high levels.

• Nitrogen is a nutrient and at certain levels, nitrogen deposition from air

emissions has increased growth of vegetation; however, at higher levels,

excess nutrients can reduce plant growth.



Other Effects

• Acidification of surface waters and soils.

• Widespread loss of fish populations.

• Damage to certain building materials and historical monuments.

• Weathering on ancient and valuable statues

• The sulfuric acid in the rain chemically reacts with the calcium compounds

in the stones (limestone, sandstone, marble and granite) to create gypsum,which then flakes off.

• The inscription on old gravestones becomes completely illegible.

• Increased rate of oxidation for iron.

• Visibility is reduced by sulphate and nitrate in the atmosphere.

http://en.wikipedia.org/wiki/Image:Pollution_-_Damaged_by_acid_rain.jpg



Particulates





Particulates

Particulates, alternatively referred to as particulate matter (PM), aerosols orfine particles, are tiny particles of solid or liquid suspended in a gas.

Size ranges from <10 nm to >100 µm in diameter.

The notation PM10 is used to describe particles of 10 µm or less

PM2.5 represents particles less than 2.5 µm in aerodynamic diameter - thisrange of sizes represent scales from a gathering of a few molecules to the size

where the particles no longer can be carried by the gas.

Sources of particulate matter can be anthropogenic or natural.

Natural - originating from volcanoes, dust storms, forest and grassland fires,

living vegetation, and sea spray.

Anthropogenic - human activities, such as the burning of fossil fuels; averaged

over the globe, currently account for about 10 % of the total amount of

aerosols in our atmosphere.



The composition of aerosol particles depends on their source.

• Wind-blown mineral dust tends to be made of mineral oxides and other

material blown from the Earth’s crust; this aerosol is light-absorbing.

• Sea salt is considered the second largest contributor in the global aerosol

budget, and consists mainly of sodium chloride originated from sea spray

• Other constituents of atmospheric sea salt reflect the composition of sea

water, and thus include magnesium, sulphate, calcium, potassium, etc.

•

Sea spray aerosols may also contain organic compounds, which influencetheir chemistry.

• Sea salt does not absorb light.

Aerosol pollution over Northern India and Bangladesh –

Photo: NASA

http://en.wikipedia.org/wiki/Image:Aerosol-India.jpg



• Secondary particles derive from the oxidation of primary gases such

as sulfur and nitrogen oxides into sulfuric acid (liquid) and nitric acid

(gaseous).• The precursors for these aerosols may have an anthropogenic origin

or a natural biogenic origin.

• In the presence of ammonia, secondary aerosols often take the

form of ammonium salts, i.e., ammonium sulphate and ammonium

nitrate (both can be dry or in aqueous solution).

• In the absence of ammonia, secondary compounds take an acidic

form as sulfuric acid (liquid aerosol droplets) and nitric acid

(atmospheric gas).

• Secondary sulphate and nitrate aerosols are strong light-scatterers.- the presence of sulphate and nitrate causes the aerosols to

increase to a size that scatters light effectively.



• Organic matter (OM) can be either primary or secondary, the latter

part deriving from the oxidation of VOCs; organic material in the

atmosphere may either be biogenic or anthropogenic.

• Organic matter influences the atmospheric radiation field by both

scattering and absorption.

• Another important aerosol type is elemental carbon (EC, alsoknown as black carbon, BC): this aerosol type includes strongly

light-absorbing material and is thought to yield large positive

radiative forcing.

• Organic matter and elemental carbon together constitute the

carbonaceous fraction of aerosols.



•Sulphate aerosol has two main effects, direct and indirect.

• The direct effect, via albedo, is to cool the planet.

• The effect varies strongly geographically, with most cooling believed to

be at and downwind of major industrial centers.

•

The indirect effect (via the aerosol acting as cloud condensation nuclei ,CCN, and thereby modifying the cloud properties) is more uncertain

but is believed to be a cooling one.



• The chemical composition of the aerosol directly affects how it

interacts with solar radiation. The chemical constituents within the

aerosol change the overall refractive index. The refractive index will

determine how much light is scattered and absorbed.

• Aerosols, natural and anthropogenic, can affect the climate by

changing the way radiation is transmitted through the atmosphere.

• Direct observations of the effects of aerosols are quite limited so any

attempt to estimate their global effect necessarily involves the use of computer models.

Solar radiation reduction due to volcanic eruptions

http://en.wikipedia.org/wiki/Image:Mauna_Loa_atmospheric_transmission.png

http://en.wikipedia.org/wiki/Image:Mauna_Loa_atmospheric_transmission.png



All aerosols both absorb and scatter solar and terrestrial

radiation.

Absorbing - a significant amount of radiation is

absorbed by the substance; but part of the radiation is

scattered.

Scattering –radiation is reflected by a substance ;

quantified in the Single Scattering Albedo (SSA), the

ratio of scattering alone to scattering plus absorption

(extinction) of radiation by a particle.

The SSA tends to unity if scattering dominates, with

relatively little absorption, and decreases as absorption

increases, becoming zero for infinite absorption. The albedo of an object is the extent to which it reflects

light, defined as the ratio of reflected to incident

electromagnetic radiation. It is a unitless measure

indicative of a surface's or body's diffuse reflectivity.

Percentage of reflected sun light

in relation to various surface

conditions of the earth

http://upload.wikimedia.org/wikipedia/commons/1/18/Albedo-e_hg.svg



Health Effects of Particulates

• The effects of inhaling particulate matter include asthma, lungcancer, cardiovascular issues, and premature death.

• The size of the particle is a main determinant of where in the

respiratory tract the particle will come to rest when inhaled.

•Larger particles are generally filtered in the nose and throat and donot cause problems, but particulate matter smaller than about 10

µm, referred to as PM10, can settle in the bronchi and lungs and

cause health problems.



•

Similarly, particles smaller than 2.5 µm, PM2.5, tend to penetrate intothe gas-exchange regions of the lung, and very small particles (< 100

nm) may pass through the lungs to affect other organs.

• PM2.5 leads to high plaque deposits in arteries, causing vascular

inflammation and atherosclerosis — a hardening of the arteries that

reduces elasticity, which can lead to heart attacks and othercardiovascular problems.



• There is also evidence that particles smaller than 100 nm can

pass through cell membranes.

• Particles may migrate into the brain. It has been suggested

that particulate matter can cause similar brain damage as that

found in Alzheimer patients.

• Particles emitted from modern diesel engines (commonly

referred to as Diesel Particulate Matter, or DPM) are typically

in the size range of 100 nm (0.1 µm).

• In addition, these soot particles also carry carcinogenic

components (e.g., benzopyrenes) adsorbed on their surface.



Phase 1

from 1 January

2005

Phase 2

from 1 January

2010

Yearly average 40 µg/m³ 20 µg/m³

Daily average (24-hour)

allowed number of exceedences per

year.

50 µg/m³

35

50 µg/m³

7

In directives 1999/30/EC and 96/62/EC, the European Commission

has set limits for PM10 in the air:



Most Polluted World Cities by

PM Particulate matter,

μg/m3 (2004) City 169 Cairo, Egypt 150 Delhi, India 128 Kolkata, India (Calcutta) 125 Taiyuan, China 123 Chongqing, China 109 Kanpur, India 109 Lucknow, India 104 Jakarta, Indonesia 101 Shenyang, China

Affected areas



Effect of inhaled tobacco smoke on the

respiratory structure of the lung



Effects of Anthropogenic Activities

on the Hydrosphere



Pollution of the Aquatic Environment



Pollution of the Aquatic Environment



Toxic chemicals: the legacy of a chemical

society

• We are a "chemical " society, using hundreds of chemicals in our normal

daily activities: washing, eating, house-cleaning, tending the lawn and

garden, and driving. Of the almost 10 million chemicals known today,

approximately 100 000 chemicals are used commercially.

• Most toxic chemicals are discharged directly into our waterways as waste,

discharges from homes, agriculture and industry.

• Seepage

• Runoff



• The chemicals can cause problems with the taste, odor and color in water.

• Fish and wildlife can experience reduced fertility, generic deformities

immune system damage, increased incidence of tumors, and death.

• Many chemicals are, even in minute amounts, toxic to human, plant and

animal life. Pesticides, PCBs, and PCPs (polychlorinated phenols).

• The very qualities which make them desirable for use – toxicity and

persistence – make them harmful to the environment.



Non-persistent (degradable)

• Domestic sewage

• Fertilizers

• Some industrial wastes

• These compounds can be broken down by chemical reactions or by natural

bacteria into simple, non-polluting substances such as carbon dioxide andnitrogen.

• The process can lead to low oxygen levels and eutrophication if the

pollution load is high. But this damage is reversible.



Persistent (degrade slowly)

• Some pesticides (e.g. DDT, dieldrin)

• Some leachate components from landfill sites (municipal, industrial)

• Petroleum and petroleum products

• PCBs, dioxins, polyaromatic hydrocarbons (PAHs)

• Radioactive materials such as strontium-90, cesium-137, radium-226, anduranium (Fukushima!)

• Metals such as lead, mercury, cadmium

• This is the most rapidly growing type of pollution and includes substances

that degrade very slowly or cannot be broken down at all; they may

remain in the aquatic environment for years or longer periods of time. Thedamage they cause is either irreversible or reparable only over decades or

centuries.



Others

• Warm water from cooling towers (thermal pollution)

• Floating debris

• Garbage

• Foam

• These are examples not of chemical pollution, but of physicalpollution which interferes mainly with the usability and/or aesthetic

appeal of the water. In certain cases, thermal pollution can kill fish.



Plastic beads spill in Hong Kong water



Threats to the Coral Reefs

• Water pollution – petroleum products and chemicals are

lethal to coral reefs.

• Raw sewage dumped into the sea brings an overload of

nutrients.

• Algae take over the reefs, blotting out the sunlight corals need

to live on.

• Fishing with explosives or cyanide in depleted fisheries to

catch the fish that remain.

• The explosions send dead fish to the surface and destroy

living reefs.



http://oceanworld.tamu.edu/students/coral/coral5.htm



Coral Bleaching

•Coral bleaching is the whitening of coral colonies due to the loss of symbioticzooxanthellae from the tissues of polyps.

• This loss exposes the white calcium carbonate skeletons of the coral colony.

• Corals naturally lose less than 0.1% of their zooxanthellae during processes of

regulation and replacement.

• Bleaching in itself kills coral; but if they cannot recruit further zooxanthellae, theywill be unable to get sufficient food to survive.

• However, adverse changes in a coral's environment can cause an increase in the

number of zooxanthellae lost.

http://www.ringo.com/photos/

http://photo.ringo.com/227/227583126O271580764.jpg



Coral Bleaching

• Stresses or environmental changes that may cause bleaching - disease,

excess shade, increased levels of ultraviolet radiation, sedimentation,

pollution, salinity changes, and increased temperatures.

• Corals tolerate a narrow temperature range between 25o Celsius and 29o

Celsius depending on location.

• Corals bleach in response to prolonged temperature change and not due

to rapidly fluctuating temperatures.

Photo credit:Ove Hoegh-Guldberg ©

Centre for Marine Studies

University of Queensland

4072 QLD Australia



Pressure on Shore Ecosystems

• A large and increasing percentage of the human population lives near the

coast - pressure on the shore ecosystems.

• Mangrove swamps were destroyed in Louisiana (for oil and gas

exploration) and in Indonesia (for shrimp farms and other aquaculture).

• The human shoreline inhabitants thus bore the brunt of Hurricane Katrina

and the Indonesian tsunami.

• Boats leak (Exxon Valdez!).

• Oil rig leaks (Gulf of Mexico, Bohai!)

• Fishing gear gets lost.

• Construction, agriculture and forest clearing bring

pollution and sediment to the coasts throughrivers.

http://wzeu.ask.com/r?t=p&d=eu&s=uk&c=a&l=dir&o=322&sv=0a652826&ip=56968088&id=D8D45EB477FC75A4EC22D5604E1ABFD0&q=Exxon+Valdez+Oil+Spill&p=1&qs=2089&ac=5&g=567771LzEsQB3l&en=vs&io=0&ep=&eo=&b=rr1&bc=&br=&tp=d&ec=2&pt=&ex=&url=http://www.blinkx.com/burl?v=FL6hWXzrvw5jT4sZWs96KEo-5C3pTYS4&u=http://www.blinkx.com/burl?v=FL6hWXzrvw5jT4sZWs96KEo-5C3pTYS4

http://wzeu.ask.com/r?t=p&d=eu&s=uk&c=a&l=dir&o=322&sv=0a652826&ip=56968088&id=D8D45EB477FC75A4EC22D5604E1ABFD0&q=Exxon+Valdez+Oil+Spill&p=1&qs=2089&ac=5&g=567771LzEsQB3l&en=vs&io=0&ep=&eo=&b=rr1&bc=&br=&tp=d&ec=2&pt=&ex=&url=http://www.blinkx.com/burl?v=FL6hWXzrvw5jT4sZWs96KEo-5C3pTYS4&u=http://www.blinkx.com/burl?v=FL6hWXzrvw5jT4sZWs96KEo-5C3pTYS4



Oil & the Environment



Oil and the Environment

• Exploration and drilling for oil - may disturb land and ocean

habitats.

• New technologies – satellites, global positioning systems, remote

sensing devices, and 3-D and 4-D seismic technologies, make it

possible to discover oil reserves while drilling fewer wells.

• The use of horizontal and directional drilling make it possible for a

single well to produce oil from much bigger areas.

• Today's production footprints are only about one-fourth the size of those 30 years ago, due to the development of movable drilling rigs

and smaller "slimhole" drilling rigs.

http://www.youtube.com/watch?v=jgAkye6svgQ





• When the oil in a well is gone, the well must be plugged

below ground.• “Rig-to-reefs" program - old offshore rigs toppled and left on

the sea floor to become artificial reefs that attract fish and

other marine life. Within six months to a year after a rig is

toppled, it becomes covered with barnacles, coral, sponges,

clams, and other sea creatures.



Oil Spills

•

Oil spilled into rivers or oceans can harm wildlife.• When we talk about "oil spills" people usually

think about oil that leaks from ships when they

crash. Although this type of spill can cause the

biggest shock to wildlife because so much oil is

released at one time, only 2 percent of all oil inthe sea comes from ship or barge spills.

• While oil spills from ships are the most well-

known problem with oil, more oil actually gets

into water from natural oil seeps coming from

the ocean floor. Or, from leaks that happen when

we use petroleum products on land.



http://www.youtube.com/watch?v=Q4itfAVq19U







Gulf of Mexico

• The well leaked about 42,000 gallons of oil a day into the

ocean.



Bohai (勃海）Oil Spill



Other Sources of Pollution from Petroleum

•

Gasoline is used in cars, diesel fuel is used in trucks, and heating oil isused for heating in homes.

• When petroleum products are burned as fuel, carbon compounds

(CO2 …) are released into the atmosphere.

•

The use of petroleum products also gives off pollutants - carbonmonoxide, nitrogen oxides, particulate matter, and unburned

hydrocarbons - that help form air pollution.

• Many environmental laws aim at changing the make-up of gasoline and

diesel fuel so that they produce fewer emissions.

• These "reformulated fuels" are much cleaner-burning than gasoline and

diesel fuel were in 1990.

• Sulfur contained in gasoline and diesel fuel is also reduced dramatically

so that they can be used with new, less-polluting engine technology.



Eutrophication

• Eutrophication means an increase in chemical nutrients -- typicallycompounds containing nitrogen or phosphorus -- in an ecosystem.

• It may occur on land or in water.

• Often used to mean the resultant increase in the ecosystem's

primary productivity -- in other words excessive plant growth anddecay -- and even further impacts, including lack of oxygen and

severe reductions in water quality and in fish and other animal

populations.

The bright green water

in the Potomac River estuary

is the result of a dense bloom

of cyanobacteria.

http://upload.wikimedia.org/wikipedia/commons/7/78/Potomac_river_eutro.jpg



• Eutrophication is frequently a result of nutrient pollution such as the

release of sewage effluent and run-off from lawn fertilizers into

natural waters (rivers or coasts) although it may also occur naturally in

situations where nutrients accumulate (e.g. depositional

environments) or where they flow into systems on an ephemeral basis

(e.g. intermittent upwelling in coastal systems).

• Eutrophication generally promotes excessive plant growth and decay,

favors certain weedy species over others, and is likely to cause severe

reductions in water quality .



• In aquatic environments, enhanced growth of choking aquatic

vegetation or phytoplankton (that is, an algal bloom) disrupts

normal functioning of the ecosystem, causing a variety of problems

such as a lack of oxygen in the water, needed for fish and shellfish

to survive.

• The water then becomes cloudy, colored a shade of green, yellow,

brown, or red.

• Human society is impacted as well: eutrophication decreases the

resource value of rivers, lakes, and estuaries such that recreation,

fishing, hunting, and aesthetic enjoyment are hindered.

• Health-related problems can occur where eutrophic conditions

interfere with drinking water treatment.



Ecological Effects

Many ecological effects can arise from stimulating primary production, but thereare three particularly troubling ecological impacts:

• decreased biodiversity

• changes in species composition and dominance

• toxicity effects

Eutrophication is apparent as increased turbidity in the

northern part of the Caspian Sea, imaged from orbit.

http://en.wikipedia.org/wiki/Image:Caspian_Sea_from_orbit.jpg

http://en.wikipedia.org/wiki/Image:Caspian_Sea_from_orbit.jpg



• Human activities can accelerate the rate at which nutrients enter ecosystems.

• Runoff from agriculture and development, pollution from septic systems and

sewers, and other human-related activities increase the flux of both inorganicnutrients and organic substances into terrestrial, aquatic, and coastal marine

ecosystems (including coral reefs).

• Elevated atmospheric compounds of nitrogen can increase soil nitrogen

availability.

• Phosphorus is often regarded as the main culprit in cases of eutrophication in

lakes subjected to point source pollution from sewage.

• The concentration of algae and the trophic state of lakes correspond well to

phosphorus levels in water.



There are two common sources of nutrients and organic matter: point and

nonpoint sources.

• Point sources

• Nonpoint sources





Effects of Anthropogenic Activities

on the Lithosphere



Deforestation



The Driving Forces of Destruction

• Logging for Tropical Hardwoods

• Fuel Wood and the Paper Industry

• Grazing Land

• Subsistence Farming

• Infrastructure building



Deforestation

Oil company illegally clearing rainforest

in Ecuador, South America

Between May 2000 and August 2006, Brazil lost

nearly 150,000 square kilometers of forest—

an area larger than Greece—and since 1970, over 600,000 square kilometers

(232,000 square miles) of Amazon rainforest have been destroyed.



Deforestation





Burning of Forests



Deforestation

Plane view of deforestation

in the Amazon

Rainforest cleared for maize

Poor farmers use fire for clearing land andevery year satellite images pick up tens of

thousands of fire burning across the Amazon.

Typically understory shrubbery is cleared and

then forest trees are cut.

The area is left to dry for a few months and

then burned.

The land is planted with crops like bananas,

palms, manioc, maize, or rice.

After a year or two, the productivity of the soil

declines, and the transient farmers press a

little deeper and clear new forest for moreshort-term agricultural land.

The old, now infertile fields are used for

small-scale cattle grazing or left for waste.

http://travel.mongabay.com/pix/peru/aerial-rainforest-Aerial_1026_3227.html



Threats to the World's Rainforests

• Rainforests are among the most important and yet

threatened ecosystems on the planet.

• Today, more than half of Earth's original rainforests have all

been destroyed, victims of unsustainable agriculture,

ranching, logging, mining and other destructive practices.

These stresses have increased enormously in the last 50 years

alone.



Threats to Rainforests

• Less than seven percent remains of Brazil's Atlantic Forest

which once covered 330 million acres - expanding urban

areas, increased agricultural and industrial development.

•

Chile's Valdivian Coastal Range - highway construction,overharvesting native trees for firewood and unsustainable

logging - the loss of former home of the indigenous Mapuche

people.

Threats to Rainforests Indigenous People



Threats to Rainforests, Indigenous People

and Species

• New technologies have been developed to assess the chemical

makeup of plants - using medicinal plants identified by Indians

makes research more efficient and less expensive.

•

Drug development has returned to its roots: traditional medicine.• Tribal peoples of the rainforest - the key to finding new and useful

tropical forest plants.

• A single Amazonian tribe of Indians may use >200 species of

plants for medicinal purposes alone.



The Medicine Man?

• Dr. Robert Mendelsohn, an economist at Yale University, andDr. Michael J. Balick, director of the Institute of Economic

Botany at the New York Botanical Gardens, estimate the

minimum number of pharmaceutical drugs potentially

remaining to be extracted from the rainforests.• They estimate that there are at least 328 new drugs that still

await discovery in the rainforest, with a potential value of $3

billion to $4 billion to a private pharmaceutical company and

as much as $147 billion to society as a whole.



Desertification





Desertification

• Desertification is the persistent degradation of drylandecosystems (arid, semi-arid and dry sub-humid areas) by

variations in climate and human activities.

• Home to a third of the human population in 2000, drylands

occupy nearly half of Earth’s land area.

• Across the world, desertification affects the livelihoods of

millions of people who rely on the benefits that dryland

ecosystems can provide.

• Current desertification is taking place much faster worldwidethan historically and usually arises from the demands of

increased populations that settle on the land in order to grow

crops and graze animals.

http://www.greenfacts.org/en/desertification/



Linear dunes of the Sahara Desert encroach on Nouakchott,

the capital of Mauritania.

The dunes border a mosque at left

(photograph by Georg Gerster).



Impact of Desertification

• A major impact of desertification is biodiversity loss and loss

of productive capacity.

• Desertification has environmental impacts that go beyond the

areas directly affected.

• The social and political impacts of desertification also reach

non-dryland areas.



Causes of Desertification

• Deserts may be separated from surrounding, less arid areas by mountainsand other contrasting landforms that reflect basic structural differences in

the terrain.

• In other areas, desert fringes form a gradual transition from a dry to a

more humid environment, making it more difficult to determine the

desert border.• These transition zones have very fragile, delicately balanced ecosystems.

• In these marginal areas human activity may stress the ecosystem beyond

its tolerance limit, resulting in degradation of the land.

• By pounding the soil with their hooves, livestock compact the substrate,

increase the proportion of fine material, and reduce the percolation rate

of the soil, thus encouraging erosion by wind and water.

• Grazing and collection of firewood reduce or eliminate plants that help to

bind the soil.



Sand Storms





Sand Storms

• In large desert areas, sand dunes can encroach on human habitats.

• Sand dunes can move through saltation - sand particles skip along the

ground like a rock thrown across a pond might skip across the water's

surface.

•

When these skipping particles land, they may knock into otherparticles and cause them to skip as well.

• With slightly stronger winds, particles collide in mid-air, causing sheet

flows. In a major dust storm, dunes may move tens of meters through

such sheet flows.

• Like snow, sand avalanches, falling down the steep slopes of the

dunes that face away from the winds, also moving the dunes forward.



Prevention and Reversal of Desertification

• Major policy interventions and changes in management approaches,

both at local and global levels, are needed in order to prevent, stop

or reverse desertification. Prevention is a lot more cost-effective than

rehabilitation, and this should be taken into account in policy

decisions.

• The creation of a “culture of prevention” that promotes alternative

livelihoods and conservation strategies can go a long way toward

protecting drylands both when desertification is just beginning and

when it is ongoing.



• It requires a change in governments’ and peoples’ attitudes.

Building on long-term experience and active innovation, dryland

populations can prevent desertification by improving agricultural

and grazing practices in a sustainable way.

• Even once land has been degraded, rehabilitation and restoration

measures can help restore lost ecosystem services.

• The success of rehabilitation practices depends on the availability of

human resources, funds, and infrastructures. It requires a

combination of policies and technologies and the close involvement

of local communities.



Straw grids and vegetation irrigated by waterfrom the Yellow River stabilize dunes in this

part of China's Tengger Desert (shown at right)

and protect a nearby railroad from windblown sand

From wasteland to vineyard.Ground water and underground

channels help this vineyard flourish

on land reclaimed from desert

pavement in China's Turpan Depressio



Module 3 Learning Outcomes

• Be able to show the effects of anthropogenic activities on theatmospheric environment


aquatic environment

• Be able to show the effects of anthropogenic activities on theland environment

Documents

Effects of Anthropogenic Activities on the Environment