Remote Sensing Environmental Changes

Since 1972, remote sensing has provided scientists with an exceptional way to monitor Earth's environment and its natural resources.  Yet while there is a wealth of remotely sensed data that covers Africa, only a fraction of the existing data is utilized because it takes time to register the satellite images for analyzing change detection.  Multi-temporal data sets are needed to discriminate land cover changes between imaging dates.  "Remote Sensing is collecting and interpreting information about the environment and the surface of the earth from a distance, primarily by sensing radiation that is naturally emitted or reflected by the Earth's surface or from the atmosphere, or by sensing signals transmitted from a satellite and reflected back to it" (1).

"The environment is life, supporting people and other living things.  Environment is widely recognized as a 'pilar' of sustainable development.  It provides essential goods and services which contribute to meeting basic human needs, and is essential to human development and quality of life.  It provides services to ecosystems, including water catchments which protect freshwater resources, wetlands, riverbank environments, biodiversity habitats and ecologically functioning landscapes.  The environment is also a sink of the wastes generated from different human  and naturally occurring activities" (2).

Changes in climate lead to serious consequences for a number of ecosystems and the economies that rely on such ecosystems, in addition to the human impacts caused by the changes.  "Climate change is likely to bring increased frequency and severity of flooding and drought to those areas already experiencing variability in rainfall. Additional concerns are increased risk of desertification in Northern Africa and on the southern border of the Sahel, and reduced availability of freshwater in Southern Africa, resulting in lowered food security and the spread of infectious diseases (notably malaria) to new areas. The islands and low-lying coastal areas of Central and Western Africa are most vulnerable to the sea level rise resulting from climate change. Coral bleaching due to sea temperature rise is the biggest threat to the Western Indian Ocean Islands and to the coasts of the countries of Eastern Africa" (read more...).

DEFORESTATION

With population growth comes the need for population sustainability.  A growing population significantly increases the current demands on local ecosystems, and the consequence of the human activities accompanying such growth further exasperates the conditions that actually support the ecosystem.  Human activities such as logging, land clearing, fuel wood collection, cattle ranching, and cash crop plantations are all driven by the needs of populations both locally and globally and are all major contributors to deforestation.  In recent decades remotely sensed data has been used to assess, in a preventative approach, changes to the environment whether human induced or the result of natural processes and is now used more efficiently to enforce local policies relative to the assessment and protection of forest land areas.  "The Congo Basin, second in size only to the mighty Amazon, loses close to 1.5 million hectares of forest cover every year" (read more...).

"Africa has the fastest rate of deforestation in the world. Competing land uses (agriculture and human settlements mainly) are contributing to the decline of forest and woodland areas and the rising demand for fuel wood and charcoal is also a major cause of deforestation. In addition to ecological impacts, local communities are suffering from loss of livelihood and from loss of vital energy sources. Although policies and mechanisms for enhancing sustainable use of forests are in place in many countries and regional cooperative arrangements are well under way, implementation and enforcement of regulations are weak because economic forces are pressurizing governments and communities into unsustainable practices for short-term profits. Political commitment to protection of indigenous forests, sustainable harvesting practices and community ownership needs to be strengthened and development of alternative energy sources is a priority"  (read more...).

Fires

"A useful applications of ATSR data is the detection of forest fires and other hotspots on the Earth's surface" (ATSR).  "As Northern Hemisphere autumn progresses toward winter, fire activity in the Sahel and savannas just south of Africa’s Sahara Desert begins to increase. The practice of agricultural burning is widespread across central Africa during the month of December" (6).

For more information on deforestation in Africa please see:

Degradation and Deforestation in Southern Central Africa

Africa: Underlying Causes of Deforestation and Forest Degradation

Deforestation in Sub-Saharan Africa

See also: www.mts.net/~/gcg/resources/africa/index04.html 

DESERTIFICATION 

Landsat 1 image acquired on Dec. 8, 1972 showing Lake Chad about 1/10th its former size since the 1960's

Bands 7 , 5, and 2 (RGB) were used to create this image of Lake Chad acquired by  MERIS, on Sept. 12, 2003.  The image shows a higher water level then seen in the Landsat7 2002 image.

NATURAL HAZARDS

"A Natural Hazard is an unexpected or uncontrollable natural event of unusual magnitude that threatens the activities of people or people themselves" (Natural Harazrds.org).

Dust & Smoke

"Human activities, such as the burning of fossil fuels, prescribed fires, and the alteration of natural surface cover, generate aerosols (tiny particles suspended in the air).  Research shows that aerosol pollution can modify cloud properties to reduce or prevent precipitation in the polluted region" (6).

Floods & Severe Storms

Floods have been an integral part of the human experience ever since the start of the agricultural revolution when people built the first permanent settlements on the great riverbanks of Asia and Africa. Seasonal floods deliver valuable topsoil and nutrients to farmland and bring life to otherwise infertile regions of the world such as the Nile River Valley. Flash floods and large 100-year floods, on the other hand, are responsible for more deaths than tornadoes or hurricanes. (6).

MISR images acquired August, 25, 2000 showing the effect of  seasonal floods along the Zambezi River

Severe flooding in

Volcanoes and other hazards

Volcanic eruptions can present a major hazard to those who live near them for a variety of reasons:

 (a) pyro-clastic eruptions can smother large areas of landscape with hot ash, dust, and smoke within a span of minutes to hours;

(b) red hot rocks spewed from the mouth of a volcano can ignite fires in nearby forests and towns, while rivers of molten lava can consume almost anything in their path as they reshape the landscape;

(c) heavy rains or a rapidly melting summit snow-pack can trigger lahars-sluices of mud that can flow for miles, overrunning roads and villages; and,

(d) large plumes of ash and gas ejected high into the atmosphere can influence climate, sometimes on a global scale. (6).

Stereo anaglyph derived from a SRTM image blended with a  Landsat image of Nyiragongo volcano in the Congo which erupted on January 17, 2002 The Landsat image used here was acquired on December 11, 2001, about a month before the eruption. 

URBANIZATION

Urbanization in Africa has been increasing over the last few decades and continues to alter the natural landscape in its path.  "The reasons for rapid growth of urban populations include overall high population growth rates, and ‘pull factors’ such as opportunities for employment, education, and improved access to health care which attract people from urban areas. African cities account for 60 per cent of the region’s GDP and are important centres for education, employment, and trade" (UNCHS 2001b).

"The colonial influence on development resulted in many of Africa’s urban centres and national capitals being located on the coast, maximizing access to trade, international travel, and development. However, there are also many social challenges associated with urbanization, such as the influx into urban areas of people forced out of rural areas by declining agricultural yields and who come to the urban areas in the hope of employment and greater income security. In many urban areas rates of economic growth and infrastructure development have lagged urbanization rates, resulting in high levels of unemployment, inadequate standards of housing and services, and impacts on human health and development. Environmental disasters and conflicts have also caused many people to flee rural areas and to seek refuge in urban centres. In Mozambique about 4.5 million rural people were displaced to urban areas because of civil strife in the 1980s (Chenje 2000) and the third largest settlement in Sierra Leone is a displaced persons camp" (7) read more....

Mosiac of two ASAR images acquired November 11, 2003, showing Benin, Togo and Nigeria.  The major Nigerian cities are visible as large bright areas.

MERIS image of South Africa acquired July 6, 2002.  Visible are the coastal cities of Port Elizabeth and Durban

MERIS image of Morocco acquired June 18, 2003. Visible are the Moroccan cities of Tangier, Tétouan and Casablanca

ATSR image acquired May 9, 1992 showing the Nile Delta in Egypt.  Towns are visible as  bright blue spots

ERS-2 image of Cape Town acquired Aug. 31, 2001, shows the urbanized areas of the Southwestern coast of South Africa.

Image of Southern Africa acquired March 1, 1999.

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