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Fragile Environments. What does it involve?. Management of soil erosion e.g. farming practices. Consequences. The fragile nature of environments/ concept of sustainability. Causes of soil erosion & desertification. Case study Sahel. Causes. Case study Amazon. Management. Deforestation.

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Fragile Environments

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what does it involve
What does it involve?

Management of soil erosion e.g. farming practices


The fragile nature of environments/ concept of sustainability

Causes of soil erosion & desertification

Case study Sahel


Case study Amazon





Case study: Bangladesh

Named egs of causes/


Greenhouse effect and global warming


Examples of solutions eg Kyoto


  • There is a natural but delicate balance between the non-living soils, rocks and climate and the living plants animals.
  • There are natural disasters such as volcanoes and cyclones but the world has always recovered from these in the past.
  • Until recently, man has trod lightly on earth, living in harmony with it. Some native tribes still do this, e.g. the Awa in the NE Amazon. But this is a rare example. 90% of the Earth has been disturbed by man.
  • We focus on 3 processes that have increased fragility – soil erosion, desertification, deforestation. These link to climate change as they are both a cause and a consequence of it.
  • These are not the only ones – river and coastal management, pollution in general, and exploitation of natural resources also figure in this as well.

in fragile environment studies
In fragile environment studies …

This is NOT the Carbon footprint – how is it different?

  • Ecological foot print
    • [The amount of land, resources etc we need to support our lifestyle. To find what we use, add the land to give us enough water, food, energy, raw materials and waste disposal. It has been worked out that 1.8 hectare per person is sustainable – the 4.9 hectares per person in the UK is not]
  • And
  • Sustainability
    • [Activities and forms of progress that meet the needs of the present without reducing the ability of future generations to meet their needs.]
  • keep coming up

Dark Green have an OK footprint– does not look good for the rest of us! Red is seriously bad, orange and yellow still above the world average; both greens are below average (2.7 hectares per person), but only dark green is less than the planet can stand (1.8 hectares)

  • The link between ecological foot print and sustainability is that the footprint informs as about just how sustainable (or not) we are being.
  • We know the footprint is influenced in turn by how fast the population grows (could mean we will all need to have a smaller footprint if it goes up too much?), what we consume and the type of technology we use.
what are fragile environments
What are fragile environments?

What is a biome?

  • Fragile environments are those biomes that under threat from change, damage or unsustainable use.
  • Although natural hazards, such as earthquakes, volcanoes, hurricanes can cause a lot of damage, it is mainly human intervention that causes the most – even seemingly natural events like floods and droughts are often made worse by man.

Why do I say that?

what are the issues
What are the issues?
  • Issues include
  • Undeveloped land is becoming scarcer: as there is less undeveloped land available, the pressure increases on that that remains.
  • Protecting biodiversity (plants and animals) is more difficult: we want to conserve that which we have but our desire to visit and see these areas is destroying them
  • Desert edges are becoming deserts through overgrazing and the removal of trees/shrubs which give rise to soil erosion, and the decreasing rainfall all combine to turn productive farmland into useless scrub.
what are the issues1
What are the issues?
  • At the other end of the scale, deforestation of rain forests flows as the natural resources are exploited.
  • Illegal logging - 20% of the timber supply comes from illegal sources.
  • "Europe remains one of the main markets for illegal timber despite a 2003 EU action plan to combat illegal logging and related trade. Strong legislation to halt illegal timber trade and to decrease Europe's devastating impact on the world's forests should be adopted as a bare minimum - there is no time to lose," said Friedrich Wulf from ProNatura / Friends of the Earth Switzerland.
what else are we doing wrong
What else are we doing wrong?
  • Human and industrial waste pollute rivers and seas.
  • At sea, oil spills and deliberate toxic dumping causes widespread pollution.
  • Many local problems cause more widespread difficulties.
  • Traffic in towns causes congestion and pollution.
  • Building new roads can solve these problems but causes others such as the destruction of rural environments.
  • This can also lead to more traffic and acid rain, production of greenhouse gases and global climate change.
what else are we doing wrong1
What else are we doing wrong?
  • If the diversity and the environment are to survive then careful management is necessary.
  • Local decisions have international effects.
  • International co-operation and legislation will be the only way to resolve the issues which will help us work together and sustain the world for future generations.
what else are we doing wrong2
What else are we doing wrong?
  • This diagram shows some of the ways the world is being used in an unsustainable way.
soil erosion

Soil erosion

One of the major problems in fragile environments

Where removal by removal of portions of the soil by various means so that fertility of the soil is reduced

what are the causes of soil erosion
What are the causes of soil erosion
  • There are 3 main physical causes of erosion
    • Sheet erosion
    • Gulley erosion
    • Wind erosion
  • And then accelerated or human induced erosion
sheet erosion
Where there is sufficient rainfall, exposed soil will be moved downhill as a mass movement – sheet erosion

Raindrop impact is the major cause of soil particle detachment which can result in the particles moving down slope as sheet erosion during a rainfall event.

Sheet erosion is the removal of fairly uniform layer of surface material from the land surface by continuous sheets of runoff water rather than concentrated into channels.

Sheet Erosion
sheet erosion1
Heavy rain that leads to a sheet of water removing a more or less uniform layer of fine particles from the entire surface of an area is sheet erosion. It often includes the best soil particles along with much of the organic matter.

While it causes severe erosion, it is very difficult to see, as the amount removed is often slight from any particular spot. Notice how these ploughed areas in Romania have been covered by the sheet erosion.

Sheet Erosion
gulley erosion
Gulley Erosion
  • More frequently, the water gathers together and quickly erodes a channel. This is called gulley erosion.
  • The example below can be seen in it all its glory in the blog ( ). It was named locally as the Durham Great Canyon and appeared literally over night in a cornfield.
gulley erosion1
Gulley Erosion
  • You may also see mention of rill erosion which is a diminutive example of something similar.
  • This is an example of a rill forming during one particularly heavy rainstorm in Autumn 2008 in the field behind our house – notice the murky colour of the water – that is soil erosion
wind erosion
Soil erosion by wind may occur wherever dry, sandy or dusty surfaces, inadequately protected by vegetation, are exposed to strong winds.

Erosion involves the picking up and blowing away of loose fine grained material within the soil.

Wind erosion
short term effects of wind erosion
Dust storms are very disagreeable and also the land is robbed of its long-term productivity (humus (vegetable matter) is lighter and likely to be removed first).

Crop damage, especially of young crops, can be serious.

Either the roots are exposed as the wind blows away the top soil or else wind blown soil from elsewhere cover the seeding up – either way the crop will be lost.

Short-term effects of wind erosion
long term effects of wind erosion
Long term damage is even greater.

Finer soil fractions (silt, clay, and organic matter) are removed and carried away by the wind, leaving the coarser fractions behind.

This sorting action not only removes the most important material from the standpoint of productivity and water retention, but leaves a more sandy, and thus an even more erodible, soil than the original.

Long term effects of wind erosion
the impacts of humans on soil erosion
The Impacts of humans on soil erosion
  • The most common human impact is due to population growth.
  • This leads to increased pressure on the land and its resources.
  • Overgrazing is a major problem.
  • This causes vegetation loss and makes the soil much more vulnerable to erosion without the protective net of roots to withstand the pressures of water and wind.
  • Intensive cultivation can cause loss of nutrients and soil exhaustion.
  • Another major cause is deforestation which is the cutting down of trees for fuel wood or clearing it for agriculture.
  • In practice the causes of soil erosion are usually a combination of physical and human causes, as you see below.
what is desertification
What is desertification?
  • Desertification, as defined in Chapter 12 of "Agenda 21" and in the International Convention on Desertification, is the degradation of the land in arid, semi-arid and sub-humid dry areas caused by climatic changes and human activities.
  • When there was widespread famine in Africa in the 1980s, the major cause was laid at the door of human activity, but as we shall see when we look at the Sahel, this is not the whole story
the lighter orange and yellow are all in danger
The lighter orange and yellow are all in danger
  • Note that while many areas are adjacent to current deserts, this is not always the case
as with soil erosion there are both physical and human causes
As with soil erosion, there are both physical and human causes:
  • Physical causes
  • Soil erosion – exposed soil is easily removed by wind or water
  • Changing rainfall patterns rainfall has become less predictable and prolonged droughts more common (although whether this is a human and physical cause is a moot point)
  • Intense rainfall when it does happen – hard to store and causes more soil erosion
as with soil erosion there are both physical and human causes1
As with soil erosion, there are both physical and human causes:
  • Main human causes
  • Population growth – more people need more food which puts pressure on the and
  • Overgrazing – too many goats, sheep, cattle can destroy the vegetation
  • Over cultivation- grow too much without replenishing the soil and it becomes exhausted
  • Deforestation – tress are cut down for fuel and building. The loss of roots to hold the soil down gives rise to erosion
  • War – many sub-Saharan countries have suffered for years from civil war, where crops and animals have been destroyed leading to famine
Desertification is a world-wide phenomenon which causes the earth's ecosystems to deteriorate.
  • It affects about two-thirds of the countries of the world, and one-third of the earth's surface, on which one billion people live, namely, one-fifth of the world population.
what are the consequences of desertification
What are the consequences of desertification?
  • Desertification reduces the land’s resilience to natural climate variability.
  • Soil, vegetation, freshwater supplies, and other dryland resources tend to be resilient. They can eventually recover from climatic disturbances, such as drought, and even from human-induced impacts, such as overgrazing. When land is degraded, however, this resilience is greatly weakened. This has both physical and socio-economic consequences.
  • Soil becomes less productive.
  • Exposed and eroded topsoil can be blown away by the wind or washed away by rainstorms. The soil’s physical structure and composition can change for the worse. Gullies and cracks may appear and vital nutrients can be removed by wind or water. If the water table rises due to inadequate drainage and poor irrigation practices, the soil can become waterlogged, and salts may build up. When soil is trampled and compacted by cattle, it can lose its ability to support plant growth and to hold moisture, resulting in increased evaporation and surface run-off.
what are the consequences of desertification1
What are the consequences of desertification?
  • Vegetation becomes damaged.
  • The loss of vegetation cover is both a consequence and a cause of land degradation. Loose soil can sandblast plants, bury them, or leave their roots dangerously exposed. When pastures are overgrazed by too many animals, or by inappropriate types, edible plant species may be lost, allowing inedible species to invade.
  • Some of the consequences are borne by people living outside the immediately affected area.
  • Degraded land may cause downstream flooding, reduced water quality, sedimentation in rivers and lakes, and siltation of reservoirs and navigation channels. It can also cause dust storms and air pollution, resulting in damaged machinery, reduced visibility, unwanted sediment deposits, and mental stress. Wind-blown dust can also worsen health problems, including eye infections, respiratory illnesses, and allergies. Dramatic increases in the frequency of dust storms were recorded during the Dust Bowl years in the US, in the Virgin Lands scheme area in the former USSR in the 1950s, and in the African Sahel during the 1970s and 1980s.
what are the consequences of desertification2
What are the consequences of desertification?
  • Food production is undermined.
  • Desertification is considered a major global environmental issue largely because of the link between dryland degradation and food production. A nutritionally adequate diet for the world’s growing population implies tripling food production over the next 50 years. This will be difficult to achieve even under favourable circumstances. If desertification is not stopped and reversed, food yields in many affected areas will decline. Malnutrition, starvation, and ultimately famine may result. The relationship between soil degradation and crop yields, however, is seldom straightforward. Productivity is affected by many different factors, such as the weather, disease and pests, farming methods, and external markets and other economic forces.
  • Desertification contributes to famine.
  • Famine typically occurs in areas that also suffer from poverty, civil unrest, or war. Drought and land degradation often help to trigger a crisis, which is then made worse by poor food distribution and the inability to buy what is available.
what are the consequences of desertification3
What are the consequences of desertification?
  • Desertification has enormous social costs.
  • There is now increased awareness of the relationship between desertification, movements of people, and conflicts. In Africa, many people have become internally displaced or forced to migrate to other countries due to war, drought, and dryland degradation. The environmental resources in and around the cities and camps where these people settle come under severe pressure. Difficult living conditions and the loss of cultural identity further undermine social stability.
  • Desertification is a huge drain on economic resources.
  • There is little detailed data on the economic losses resulting from desertification, although an unpublished World Bank study suggested that the depletion of natural resources in one Sahelian country was equivalent to 20% of its annual Gross Domestic Product (GDP). At the global level, it is estimated that the annual income foregone in the areas immediately affected by desertification amounts to approximately US$ 42 billion each year. The indirect economic and social costs suffered outside the affected areas, including the influx of “environmental refugees” and losses to national food production, may be much greater.
the sahel

The Sahel

Why is it like that?

What are the impacts of desertification on the people?

How can it be managed for the future?

the sahel1
The Sahel
  • Where is it?
  • What is it like?
  • How has it changed?
  • What are the main causes?
  • What are the consequences?
  • What are they doing about it?
the sahel where is it
The Sahel – where is it?
  • The Sahel is a semi-arid tropical savannah and steppe ecoregion in Africa, which forms the transition between the Sahara to the north and wetter grasslands in the south. It extends from the Atlantic on the west to the Indian Ocean in the east.
the sahel what is it like
The Sahel – what is it like?
  • The picture on the left was taken in the wet season while that on the right was taken in the dry season.
  • Some places have a few more trees and some have less, but this should give you a flavour
the sahel what is it like1
The Sahel – what is it like?
  • What do you notice about the temperatures in all these places?
  • The rainfall?
  • When does it occur?
the sahel how has it changed
The Sahel – how has it changed?
  • In recent years, the rainfall has become irregular - from the graph what do you notice?
    • Anomalies are differences from what is expected
the sahel how has it changed1
The Sahel – how has it changed?
  • When was there the longest period of heavier than expected rain?
  • In 1951 there was about 3cm per month more than expected – how many millimetres was that in a year?
  • When did the rain change to being in general to less than was expected? How many mm a year was that at worst?
when there was a severe famine in the eastern sahel in the early 1980s
When there was a severe famine in the Eastern Sahel in the early 1980s …
  • It was put down almost entirely to human landuse issues, and all the projects were geared to tackling this problem. However as you can see, in this particular case, rainfall had a greater influence.
  • Having said that, if the precipitation does reduce, then man needs to take more care than before of the scarce resources and of water and good soil.
  • Looking back over thousands of years of history, these episodes of low rainfall are a feature and have had consequences for man in the past.
let s look at the last episode of wet weather in this area
Let’s look at the last episode of wet weather in this area
  • It was wetter than average between 1915 and about 1964. What do you think was the affect of this unusually damp period?
  • What effect would you expect that to have on the population?
  • What do you think would happen to the number of animals and the amount ground under production?
  • The extra people would need housing and to cook their food? What effect would you expect that to have on the Savannah-like existence of the Sahel?
then came the 1960s
Then came the 1960s
  • What would the people try to do?
  • This lead to over cultivation, over grazing and bare soil.
  • With fewer trees to add humus to the soil, what would the soil be like?
  • Not only would the nutrients not be replaced, but soil without humus cannot hold water so well and it dried out.
  • This kind of soil is eroded easily by flash floods, which still occurred occasionally and wind erosion the dry season.. As a result there have been widespread crop failure and millions of animals have died.
  • Many people have had to leave the area but even then more than 100,000 have died across the Sahal from Ethiopia in the east right across to Burkino Faso and Mali in the West.

What is all this about?

Michael Buerk: A famine of biblical proportions in the 20th century …

as you see
As you see …
  • .. While the precipitation shortage was the major cause of the problem, the situation that developed over previous decades, that led to more people moving there than the ecosystem could reasonable be expected to support in the long term, contributed in no small way to the disaster that followed.
  • During this period of drought, the problems of soil erosion were exacerbated both by natural and human causes.
human influences on the sahel
Human influences on the Sahel
  • The drying of the Sahel in the late 20th century caused widespread famine that attracted world-wide attention, including the United Nations Conference on Desertification (UNCOD) in Nairobi, Kenya in 1977, the 1993 Convention to Combat Desertification, the 2006 International Year of the Desert and Desertification, and the Millennium Ecosystem Assessment.
The studies show that climate change strongly influences the Sahel in recent decades, but it is only part of the story:
  • Rainfall variability is a major driver of vulnerability in the Sahel.
  • However, blaming the ‘environmental crisis’ on low and irregular annual rainfall alone would amount to a sheer oversimplification and misunderstanding of the Sahelian dynamics.
  • Climate is nothing but one element in a complex combination of processes that has made agriculture and livestock farming highly unproductive.
  • Over the last half century, the combined effects of population growth, land degradation (deforestation, continuous cropping and overgrazing), reduced and erratic rainfall, lack of coherent environmental policies and misplaced development priorities, have contributed to transform a large proportion of the Sahel into barren land, resulting in the deterioration of the soil andwater resources.From UN Environmental Programme, World Agroforestry Centre
the human influences include
The human influences include:
  • Population increase. Population is doubling every 20 years. The growth rate of population (3% per year) exceeds the growth rate of food production (2% per year). The total population is around 260,000,000 people.
  • Poverty. Per capita income varies from $500/year in Burkina Faso to $1,000/yera in Mali to $2,000/year in Nigeria. In contrast, the per capita income in Western Europe is about $35,000/year. All are estimates for 2007. The area includes three of the four poorest countries on earth.
  • Over grazing, poor farming methods, and use of trees and vegetation for firewood. Overgrazing and poor agricultural practices lead to soil erosion, further degrading the land.
the human influences include1
The human influences include:
  • The traditional Parkland system (integrated crop-tree-livestock systems), which is the predominant land use system and the main provider of food, nutrition, income, and environmental services, is rapidly degrading—woody biodiversity and cover is being lost, and soil fertility is declining from already low levels through exhaustive cropping practices and soil erosion
  • Colonial Influence. The Sahel was divided into countries by European nations. The boarders were set by political processes that mostly ignored the local people and their use of the land. The new countries began to enforce boundaries limiting the ability of nomads to move their herds in response to changing rain, from dry to wet areas. As a result, nomads were forced into villages, and in dry years their herds overgrazed the area around villages and cities.
  • Major historical migration routes used by nomadic herders in the past. Now the borders with Chad and the Central African Republic are closed, and even borders between provinces in the Sudan are closed, and herders must stay within their own province. The closing of the borders causes environmental and political problems. Click on the map for a zoom.
  • Migration due to political instability and war. Conflicts in Niger, Nigeria, Mali, Darfur, and Eritrea have caused mas migration of people from rural areas to refugee camps to nearby countries.
Complete a case study of the Sahel, using what we talked about today – and anything else you think may be relevant.
  • You need to fill in a table like this:
  • You have seen that soil erosion and desertification are closely linked – so to reduce or turn around desertification, practices that reduce soil erosion need to be implemented.
  • There are many examples of how soil erosion is being controlled – many are taking place in Africa, although not exclusively there. We need to build up a body of examples of how it is being tackled, by whom and where
  • Your task is to find one or 2 examples of how this is being achieved – good google searches would be soil erosion and either solutions or prevention or mitigation or management or conservation or control