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Traces of Humankind – South Africa

30.2S 24.6E

July 3rd, 2013 Category: Earth Observation, Snapshots VIIRS/MODISSuomi-NPP/Aqua

South Africa – July 1st, 2013

VIIRS – Night Visible Image

MODIS – True-Color Image

Satellite images are an incredible tool to assess the health status of the Earth.

However, while macro-effects of human activities are clearly evident (i.e. deforestation, oil spill, etc.), the real impact of mankind on our Planet was not always easy to identify from Space.

Sometimes it is possible to understand how a region is changing just by combining data from different satellite instruments. Paradoxically, sometimes you just simply turn off the light to notice details not otherwise visible.

The main image represents the combination of the Night band of the VIIRS instrument (on-board the NASA’s Suomi-NPP satellite) with the True-Color band combination of the MODIS instrument (on-board the NASA’s Aqua satellite).

The extent of urban areas captured by the Night Image is clearly visible using the True-Color Image as a background. Small agricultural fires are visible as small groups of white dots close to the major villages (in the middle right part of the image).

The city of Cape Town is visible in the lower left part of the image, while the municipalities of Johannesburg, Pretoria, Vereeniging, Brits and Rustenburg (in the upper right part of the image) show that the extent of the towns has become a single (giant) urban area.

In the small boxes at the beginning, the two images used for the combination.

Environmental Issues Affecting Orange River, South Africa

28.6S 16.4E

February 16th, 2013 Category: Climate Change, Rivers

South Africa – January 27th, 2013

Draining an area of just under 1million km2 or 77% of the land area of South Africa, the Orange River has its source in the Drakensberg mountains, but starts as the Senqu River in Lesotho. From here it flows westwards to the Atlantic Ocean. Here, it can be seen flowing more or less horizontally across the upper left quadrant of the image.

The headwaters are located at an altitude of 3300 m and consequently parts freeze in the winter months. After the town of Kimberly the river is joined by the Vaal river, its main tributary and from here it enters the arid region of the southern Kalahari and Namib desert. Dams along the river provide water for irrigation and hydropower, however because of the unpredictable flow and sand bar at the river mouth navigation is limited.

Given the length of the Orange River, combined with its range of altitude and climacteric zones, the basin covers a wide range of ecological systems, and can be regarded as being a linear oasis. Its bio-geographical isolation means that potential for re-colonisation from adjacent rivers and wetlands is very low. The river biota is therefore unusually susceptible to the permanent loss of species.

Its biomes contain a vast array of faunal and floral species variety with several endemic species. However, they also comprise areas facing environmental threats, such as the extinction of species and changes brought about by desertification. The economic utilisation of the Orange River’s water as well as the land use patterns in the basin strongly influences the environmental state of the river basin.

In this context four issues are of particular significance, namely the problem of soil erosion and wetland losses in Lesotho (the most severe problem), the impact of industrial and municipal effluent in the Vaal River system, agricultural pollution in the Vaal and Orange River and the environmental threats to the Orange River Estuary Ramsar site at the mouth (click here for more information).

Fires in South Africa

26.6S 30.5E

February 1st, 2013 Category: Fires

South Africa – January 24th, 2013

Fires can be seen burning in South Africa, near the border with Swaziland (center) and Mozambique (upper right). The largest plume of smoke is located just west of the Swaziland border. Most fires appear to be burning in or near the numerous nature and game reserves in the region.


Mountains of Cape Fold Belt in South Africa’s Western Cape Region

33.9S 18.4E

May 16th, 2012 Category: Mountains, Rivers

South Africa - May 15th, 2012

Visible near the bottom of this image is the Western Cape region of South Africa, an area with great topographical diversity. Most of the province falls within the Cape Fold Belt, a range of sandstone folded mountains. The far interior forms part of the Karoo Basin and is generally arid and hilly with a sharp escarpment in the north. Coastal areas range from sandy between capes, to rocky to steep and mountainous in places. Located by the coast in the lower left quadrant are Cape Town and the Cape of Good Hope.

Moving northwards, visible crossing the upper part of the image is the Orange River, appearing as a thick green line, despite what its name might suggest. Some sediments can be seen entering the Atlantic Ocean by the river’s mouth. The river forms part of the international borders between South Africa and Namibia and between South Africa and Lesotho, as well as several provincial borders within South Africa. Visible near the coast in Namibia, north of the river, is the southern part of the Namib Desert.

Smoke Over Botswana and South Africa

20.6S 25.3E

April 20th, 2012 Category: Fires, Rivers, Salt Flats

Botswana and South Africa - April 15th, 2012

Smoke can be seen near the border between South Africa and Botswana in the lower right quadrant of this image of central southern Africa. The white area visible north of the cloud of smoke is the Makgadikgadi Pan, a large salt pan in northern Botswana, and the largest salt flat complex in the world. These salt pans cover approximately 16,000 km2 and form the bed of the ancient Lake Makgadikgadi that began evaporating millennia ago.

Also visible northwest of the pan is the Okavango Delta (or Okavango Swamp), in Botswana, is the world’s largest inland delta. It is formed where the Okavango River empties onto a swamp in an endorheic basin in the Kalahari Desert, where most of the water is lost to evaporation and transpiration instead of draining into the sea.