Land and Water Degradation Due to Agriculture

Land Degradation
Due to Agriculture:
Part 3 Impacts of Deforestation
and Soil Erosion
Fall 2012 , Lecture 7
Earth Observatory
• On March 19, 2012, MODIS, on
NASA’s Terra satellite, captured this
natural-color image of a storm sweeping
across Iran, Afghanistan, and Pakistan
• Some source points are visible in southern
Afghanistan, and the dust blew in
southeast-northeast arcs
• Most of the dust plumes in this storm were
thick enough to completely obscure the
land and water surfaces below
Soil Loss
• Deforestation often leads to soil erosion
• Agricultural use of land can also produce soil
 Modern methods used in advanced countries have
greatly cut these losses
 In developing countries, agricultural soil loss is
still a major problem
On-site Impacts of Soil Erosion
• Reduction in soil quality resulting from
 Loss of the nutrient-rich upper layers of the soil
 Reduced water-holding capacity of many eroded soils
• Increased use of artificial fertilizers can mitigate the
first problem in developed countries
• Not an option in most developing countries
Time-Scale of Problems
• On-site impacts of soil erosion are a presentday problem for many of the developing
• For developed nations, on-site impacts will be
a problem only in the long term future because
they are outside the relatively short time
horizon within which their policy makers work
Off-site Impacts of Soil Erosion
• Water erosion’s main
off-site effect is the
movement of sediment
and agricultural
pollutants into
• China's Yangtze River at
the Three Gorges, in Hubei
province. Note the
sediment-rich water
Watercourse Sedimentation
• Sediment in watercourses
can lead to the silting-up
of dams, disruption of the
ecosystems of lakes, and
contamination of drinking
• Satellite view of the delta of
the Yangtze River as it
discharges into the East
China Sea. The sediment
plume is clearly
visible. (Image: NOAA)
Down-stream Flooding
• Increased downstream flooding may also occur
due to the reduced capacity of eroded soil to
absorb water, and to the reduced capacity of
streams and lakes to hold water
Time-Scale of Off-Site Problems
• Short-term effects of erosion's off-site effects can be a
notable problem for developed nations
• Policy change in developed countries may be driven
by off-site impacts
• For less developed nations, there may be less
incentive for short-term policy change
Examples of Soil Erosion
• We will examine soil loss in several areas
 Indonesia
 Madagascar
 Haiti
Kalimantan, Borneo, Indonesia
• In less than 25 years, threequarters of Kalimantan, which
occupies a large part of the
Island of Borneo in Indonesia,
half of the thick forests have
been cut by loggers for
agricultural land, including oil
palm plantations
Agricultural Land Clearing
• Kalimantan locals have
long burned forestland
to create plots for
• Formerly small,
controlled fires were
“A” is Borneo, in relation to SE Asia
Drying the Land
• As deforestation has progressed, the island has
become drier
• The small fires have changed to
• The cause is burning peat
Loss of Swamp Land
• Peat has formed over thousands of years from decomposed
trees, grass and scrub
• It contains huge quantities of carbon dioxide
• Formerly, that was safely sequestered in the ground
• Deforestation has caused drying, and the peat is disintegrating
• Once-soggy swamps are shorn of trees and drained by canals
• When peat burns, carbon dioxide gushes into the atmosphere
Indonesian Photo Gallery
• Washington Post Photo Gallery – Indonesia
• The link is from a story “A climate threat,
rising from the soil”, by Andrew Higgins,
which appeared in the Washington Post on
November 19, 2009
CO2 from Peat Burning
• Wetlands International, a Dutch research and lobbying group, estimated
Indonesia's peatlands released roughly 1.9 billion metric tons of carbon
dioxide in 2006
• This was equal to the combined emissions that year of Germany, Britain and
Canada, and more than U.S. emissions from road and air travel.
• In 1997, particularly bad fires raged across Kalimantan and, according to a
study led by a British scientist, the amount was up to four times as high -more than the total emissions by the United States in that period
Economics versus the Environment
• Logging and palm oil companies deploy
formidable resources across Kalimantan
• These are both economic, and physical forces,
used against environmental activists trying to
protect the fragile peat
Palm Oil Operations
• At the PT Globalindo Agung Lestari, an oil
palm estate, a wooden barrier separated a
dozen or so out-of-town environmental
activists with a bullhorn
• On the other side, company security guards,
local police officers and Indonesian soldiers,
armed with automatic weapons, stood ready
Supporting the Company
• Villagers were angry at the plantation, but had to stay
• They couldn’t afford to lose their jobs tending oil palm
• The pay is about $3 a day and the work is backbreaking
• Budi, a 21 year old worker, said "when you don't have
anything, you have to support the company"
Ethics vs. Economics
This video, from Time movies, shows the ethical problems faced by indigenous
peoples, when choosing to exploit the environment or be unemployed
Erosion in Action
• Video clip shows
erosive rainfall in a
region of steep
topography in Indonesia
• The effect of vegetation
removal is evident
Kuala Cenaku,
Riau Province,
• Riau is a province of Indonesia, located in the center and eastern
coast of Sumatra along the Strait of Malacca
• Extensive logging has led to a massive decline in forest cover
from 78% in 1982 to only 33% in 2005
WWF Information
• Riau Province is the home of two of the world’s largest pulp mills,
produces more than two thirds of Indonesia’s pulp, and is covered
with more timber plantations and more oil palm concessions than
any other province in Indonesia
• Between 1988 and 2005, half of Riau’s forests disappeared at an
average rate of 170,000 hectares per year or 460 hectares per day
• The loss of some of the most diverse forests on earth is accelerating
rapidly - the annual rate of forest cover loss was 2.2% in 2002, 4.2%
in 2004 and 6.8% in 2005
Peat Depth
• According to Indonesian law, it is illegal to
clear forest where peat exceeds 3 meters in
• The law is largely ignored, with disastrous
Palms: The
Impact of
Palm Oil
• Video from
the Paradigm
Shift Project
Air Pollution
• A final problem caused by fires in the thick peat
deposits is severe air pollution
• The haze can travel hundreds of miles in SE Asia
• The following video shows the effects in Malaysia
• The video also some of the products palm oil is used
Malaysian Haze Video
• Fourth largest island in the world
• Madagascar split from India around 88 million
years ago, allowing plants and animals on the
island to evolve in relative isolation
• Isolated areas often see less evolution than
other regions
Restricted Evolution
• In Madagascar, there are no woodpeckers or
ungulates (hooved animals) present
• Instead, animals like lemurs dominate rare
ecosystems, present no where else on earth
• More than 200,000 known species are found
on Madagascar, and about 150,000 exist
nowhere else
Madagascar History
• Beginning in the early 19th century, most of the island was
united and ruled as the Kingdom of Madagascar by a series of
Merina nobles (Merina is the largest cultural sub-group)
• Collapse of the monarchy occurred in 1896 when the island
was conquered and absorbed into the French colonial empire,
from which the island gained independence in 1960
• The autonomous state of Madagascar has since undergone four
major constitutional periods, termed Republics
Coup d'état
• Since 1992 the nation has officially been governed as a
constitutional democracy from its capital at Antananarivo
• However, in a popular uprising in 2009 the last elected
president Marc Ravalomanana was made to resign and
presidential power was transferred in March 2009 to Andry
Rajoelina in a move widely viewed by the international
community as a coup d'état
Patricia Wright
• Before Rajoelina came to power, the state of
Madagascar's ecological health was actually
improving, according to Patricia Wright, professor of
anthropology at the State University of New York at
Stony Brook, executive director for the Institute for
the Conservation of Tropical Environments, and a
recipient of a MacArthur Foundation "genius award"
Wright’s Opinion
• “It's one of the success stories in all of the
conservation world. Because of big inputs from
conservation agencies — U.S. AID [Agency for
International Development], the European Union —
the infrastructure of the country improved. The
protected areas were being protected. Everything
looked really optimistic for keeping the island's
forests in place.”
Effects of the Coup d'état
• The problem with the coup d'état, according to Wright,
“Everyone assumes they can literally take anything they want.
So we have major rosewood being extracted from the beautiful
forests in the north. We have a certain amount of lawlessness
that's going on, also in the north. Inside protected areas, the
National Park Service [rangers] abandoned their posts because
they were afraid. They've since returned, but it's been a very
difficult year for protecting wildlife.
• “Tavy” is a Malagasy word for the slash and burn agriculture
practiced in Madagascar
• An acre or two of forest is cut, burned, and then planted with rice
• After a year or two of production the field is left fallow for 4-6
years, then the process is repeated
• After 2-3 such cycles the soil is exhausted of nutrients and the
land is likely colonized by scrub vegetation or alien grasses
• On slopes, the new vegetation is often insufficient to anchor soils,
making erosion and landslides a problem
Economic Necessity
• Madagascar is among the world's poorest countries
• As such, people's day to day survival is dependent upon
natural resource use
• Where day-to-day subsistence is a question, people show little
concern for the long-term consequences of their actions
• As long as there is more forest land freely available for
clearing, you might as well use the land before a neighbor
Erosion in Madagascar
the air
Erosion in
• Betsiboka River, Madagascar, running like liquid chocolate,
January 2012
• Astronauts have remarked that it looks as if Madagascar is
bleeding to death, with its rivers running blood red and staining
the surrounding Indian Ocean
Image from
• Nearly a century of extensive
logging of Madagascar’s
rainforests and coastal mangroves
has resulted in nearly complete
clearing of the land and fantastic
rates of erosion
• After every heavy rain, the bright
red soils are washed from the
This image of the Betsiboka Estuary on
hillsides into the streams and
the northwest coast of Madagascar
rivers to the coast
reveals the mouth of the country’s
largest river and one of the world’s fast39
changing coastlines
NASA Description
• Astronauts describe their view of Madagascar as 'bleeding into
the ocean'
• One impact of the extensive 20th century erosion is the filling
and clogging of coastal waterways with sediment - a process
that is well illustrated in the Betsiboka estuary
• In fact, ocean-going ships were once able to travel up the
Betsiboka estuary, but must now berth at the coast
Malagasy Agriculture
• Agriculture is the mainstay of the Malagasy economy, using
80% of the labor force
• Deforestation, unsustainable farming methods, low
productivity and insecure land tenure are all fuelling
diminishing soil yields and threatening the island's food
security, putting the agriculture section at risk
Agroecological Techniques
• The Agence française de développement (AFD) is developing,
the use of agroecological techniques with Malagasy farmers
• This approach involves protecting the soil with a green cover
crop, as a way of avoiding plowing, and restricting the use of
• Soil fertility is restored, watershed erosion is reduced and as
are CO2 emissions
• The video on the next slide explains the use of agroecology
Agroecology in Madagascar
• Haiti occupies the western
third of the island of
Hispaniola, which is
situated in the Caribbean
between Cuba and Puerto
• The Dominican Republic
occupies the remainder of
the island
• The Atlantic Ocean borders
Haiti’s northern shores, while
the Caribbean Sea is to the
west and south
Haitian Topography
Haiti occupies the mountainous
portion of the island of Hispaniola
Five mountain ranges dominate
Haiti’s landscape and divide the
country into three regions⎯northern,
central, and southern
Slopes of more than a 20 percent
grade cover nearly two-thirds of the
Plains constitute only about 20
percent of Haiti’s land, making
cultivation difficult
Haitian Deforestation
• Haiti faces a severe deforestation problem
• In 1923, forests covered nearly 60 percent of the
country; today they cover less than 2 percent
• Wood and charcoal are the primary fuel source
Beginnings of Deforestation
• At the onset of colonialism, Haiti began to suffer deforestation
• Around 1730, coffee was introduced, producing a monoculture
• Within 50 years upland forest clearing resulted in 25% of the
land being under coffee
• Other crops included indigo, tobacco, and sugarcane
• Clean cultivation between row crops exhausted nutrients and
lead to erosion
Nineteenth Century
• Throughout much of the 19th century, the
government was forced to export timber to
repay a large debt to France
• Peasants were restricted to hillside farms,
where often steep slopes lead to severe erosion
• Lack of economic capital make farming difficult
• Average per capita income is less than one-seventh of
the average for Latin America and the Caribbean
• With inheritance, land is subdivided, and plots grow
increasing smaller
• One estimate claims the average peasant has less the
one-quarter of a hectare
Leased Land
• Many families lease or sharecrop additional
• Farmers on leased or share-cropped land have
little incentive to take care of the land
• In addition, most agricultural work is by hand,
with no mechanical equipment
Lack of Government Aid
• The government has been controlled by a
string of dictators for many years
• They are much more intent on enriching
themselves, not using the few resources they
have to improve conditions
Effects of Deforestation
• Deforestation has a number of effects
 Soil erosion
• Soil erosion has decreased agricultural yields
• Soil erosion into the ocean also blankets coral reefs with sediment, killing
the reefs
 Floods due to disruption of the natural hydrologic cycle
 Landslides
• When vegetative cover is removed from the
land, the rate of infiltration decreases
• Since water has to go somewhere, if it can’t
infiltrate, it runs off
• Rapid runoff leads to flooding
Haiti’s Unnatural Floods
• Landslides have also been a frequent cause of
death in Haiti
• For example, there was a landslide in late
March of 2012 in which six people in Port-auPrince were killed by a landslide
Tropical Storm Hanna, 2008
• As Hurricane Hanna approached Haiti in September
2008, Dave Petley (Wilson Professor of Hazard and
Risk in the Department of Geography at Durham
University in the United Kingdom) blogged on an
American Geophysical Union site that 136 people
have been killed in flash floods and landslides as a
result of Hanna, but time might reveal more casualties
Haiti-Dominican Republic Border
• The river in the photo is the
border between Haiti (left)
and the Dominican Republic
• The lack of vegetation in
Haiti has made landsliding a
tremendous problem
Aftereffects of Gustav/Hanna
• On August 26, 2008 Hurricane Gustav brought strong
winds and heavy flooding to Haiti
• On 1 September 2008, only days after Gustav hit
Haiti, Tropical Storm Hanna surprised the country,
worsening the effects of Gustav and leaving more
people affected, especially in the city of Gonaives
Post Storm Damage Estimates
• According to Haitian government statistics:
A total of 793 people lost their lives
310 were declared missing
548 were injured
Damage to homes and infrastructure affected 165,337
• It is estimated that 22,702 families’ homes were completely
• Another 84,625 families’ homes were damaged
Aftereffects of Haitian Storms, 2008
• This is a series of
still photos showing
the aftereffects of
the 2008 Haitian
• Note especially the
extent of the
Video Interview
• The following video interview by Amy
Goodman, the host of Democracy Now!, an
independent global news program broadcast
daily on radio, television and the Internet, with
Dr. Paul Farmer
Paul Farmer, M.D.
• Paul Farmer is an American anthropologist and physician
• Named chairman of Harvard Medical School's Department of
Global Health and Social Medicine in May 2009
• In December, 2010, Harvard University's President, Drew
Gilpin Faust, and the President and Fellows of Harvard
College, named him a Kolokotrones University Professor of
Harvard University, the highest honor that the University can
bestow on one of its faculty members
Partners in Health
• This video conveys the magnitude of the problems that Haiti
faces, much of which has been caused by deforestation
• Dr. Farmer co-founded Partners In Health, which began in
Cange in the Central Plateau of Haiti and has developed into a
worldwide health organization
• His extensive experience in Haiti and other third world
countries give him a perspective most commentators do not
Haitian Earthquake
• On January 12, 2010 Haiti suffered a magnitude 7.0
earthquake, which caused the death of more than 200,000
people, the injury of about 300,000 people, and left about two
million people homeless
• A year and a half prior to the earthquake, Haiti was subjected
to another severe disaster, flooding induced by two hurricanes
and two tropical storms (Fay, Gustav, Hanna and Ike)
Hurricane-Earthquake Connection?
• Both natural disasters results in death and
destruction, but because their origins are very
different, they are generally considered to be
unrelated phenomena
• A pr by Shimon Wdowinski et al. suggested
there may be a connection
Earthquake Location
• The earthquake was thought
to have occurred along the
Enriquillo-Plantain Garden
Fault, part of the fault
system that separates the
North American plate to the
north from the Caribbean
Previous Tectonics
• In 1770, there had been a large earthquake to
the west of Port-au-Prince
• GPS measurements suggest that the underlying
tectonics are a left lateral shear at 8 mm per
year and shortening (convergence) at about 5
mm per year
Strike and
The strike-dip symbol, used on geologic
maps, is shown - the long direction points in
the horizontal direction, and the shorter side
shows dip direction
Strike-slip Direction
• Strike-slip faults are further
described as "right-lateral" or
"left-lateral" depending if the
block opposite the viewer
moved to the right or left,
Left-Lateral Strike Slip
• Block is displaced to the
left, looking across the
Strike Slip Faults - Left Lateral
Near Lillooet, British Columbia
Westward Movement
• So the previous work indicated that the area
north of the fault was moving west relative to
the area south of the fault
• The earthquake showed westward movement
on the Enriquillo fault, but there was no
evidence of surface rupture on that fault
Discovery of a New Fault
• Post earthquake investigations suggest shortening as well as
strike slip movement
• The data suggest a different fault, not the Enriquillo fault, was
responsible for the earthquake
• This new fault, which is orientated sub-parallel to the
Enriquillo Fault, is now known as the Leogane Fault, with a
combination of strike slip and dip slip movement
Dip-slip Faults
• Dip direction is always
perpendicular to the strike
• Combination of dip and
strike slip produces obliqueslip
Fault Models
• From remote sensing data it was evident there was no surface
• There was evidence of coastal uplift
• Measurement of the uplift suggested movement of about 64
cm over a distance of 50 km of coast
• Two fault models have been proposed to explain this, one with
movement along two faults, the other with movement along
three faults
Movement on a Blind Fault
• Both models suggest that most slip was on
south dipping blind fault.
• A blind fault is one which does not reach the
• The presence of blind faults is often unknown
until an earthquake reveals their presence
Haitian Scientific Effort
• Jean Altidor, from the Haiti Bureau of Mines and
Energy, working with the USGS and the Canadian
natural resource bureau, deployed seismometers in
March 2010 to measure aftershocks
• Worked with various other groups to undertake
geological and geodetic measurements
Earthquake Amplification
• Found that downtown Port-au-Prince is
underlain by soft sediments
• Soft sediment behaves like a bowl of jello
during an earthquake and will amplify shaking,
causing much greater destruction
Sediment Unloading
• Wdowinski et al. suggest that the hurricanes trigger surface
unloading due to rapid erosion, which then triggers the
• Unloading may decrease pressure perpendicular to the
ground’s surface
• In the case of the earthquake, movement on the fault was
atypical (dip slip)
River and
• “Google Earth image of Haiti
taken November 8, 2010,
showing the capital of Port-AuPrince and the mountainous
region to its west where the
epicenter of the 2010 earthquake
was. Note the brown color of the
mountains, where all the
vegetation has been stripped off,
leaving bare slopes subject to
extreme erosion. Heavy rains in
recent years have washed huge
amounts of sediment into the
Leogane Delta to the north.”
Google Earth
(From figure caption on Dr. Jeff Masters blog)
• Zoom-in view of the Leogane
Delta region of previous figure,
showing the large expansion in
the Delta's area between 2002
and 2010. High amounts of
sediments have been eroded from
Haiti's deforested mountains and
deposited in the Delta. Recent
expansion of the river channel
due to runoff from Hurricane
Tomas' rains is apparent in the
2010 image. Image
credit: Google Earth, Digital
Globe, GeoEye.
Leogane Delta
(From figure caption on Dr. Jeff Masters blog)
Rapid Erosion as Earthquake Trigger
• Hurricane induced rapid erosion in the mountains
would release downward pressure, allowing vertical
• Previous movements were estimated at 5 mm per year
of convergence, which would produce vertical uplift
• Reducing load might act as a trigger, allowing
movement to initiate
Sediment Deposition in Delta
• The calculated sediment deposition in the
delta of the river draining the mountains gives
an erosion rate of 6 mm per year
• This is much higher than expected, and is due
to deforestation
Digitial Elevation Model
• A (DEM) was used to calculate stress change at the earthquake
focus due to sediment unloading
• Wdowinski et al. modeled resultant stress change on the fault
• The model shows that unloading promotes fault movement on
a south dipping fault and that the magnitude of change is at
least hypothetically able to trigger the earthquake
Delay Between Hurricane and Earthquake
• Why was there a delay between the hurricane and the
• Possibly the increased soil moisture help to keep
normal stress high, due to the increased mass of the
water in the soil
• Once the soil dries out, mass is reduced, causing a
reduction in normal stress
• Fault movement may have resulted
Hypothesis, not Theory
• This is a very interesting speculation
• However, it is a hypothesis
• The paper was presented at a meeting of the
American Geophysical Union in the Fall of
2010, but has yet to appear in the scientific
literature, possibly due to peer review