The world is changing. It has gone beyond the perceptions of the skeptics who say it’s “a cycle” and demonstrated beyond any reasonable doubt that humans are having a dramatic and negative impact on the world.
Here are the images that portray the greatest human impact on the environment:
Almeria, Spain
“Agriculture Development”
This pair of satellite images shows the impact of massive and rapid agricultural development in Almeria Province along Spain’s southern coast.
In the earlier image, the landscape reflects rather typical rural agricultural land use. In the 2000 image, much of the same region-an area covering roughly 20 000 hectares (49 421 acres) - has been converted to intensive greenhouse agriculture for the mass production of market produce.
Greenhouse-dominated land appears as whitish gray patches.
In order to address increasingly complex water needs throughout Spain, the government adopted the Spanish National Hydrological Plan (SNHP) in 2001.
Initially, this water redistribution plan involved the construction of 118 dams and 22 water transfer projects that would move water from parts of the country where it was relatively abundant to more arid regions.
In 2004, the Spanish government announced it would begin exploring more environmentally friendly water-saving technologies, such as wastewater recycling and seawater desalinization.
Beira Fire Scars, Mozambique
“Arson”
During Mozambique’s dry season—May to October—fires leave burn scars on the landscape. Over a third of the country is affected by fire each year. NASA’s Earth Observatory recorded an especially large number of fires in August 2006.
The widespread nature of the fires suggests that they may have been intentionally set. Population growth in Mozambique has drastically intensified the need for agricultural land as well as for forestry and wildlife products, thus putting increased pressure on limited resources. Fires have become a primary means of clearing land for cultivation.
The 21 May 2006 satellite image was acquired at the beginning of the 2006 dry season, before many fires had left their mark.
The 9 August 2006 image shows the same area roughly 2.5 months later. Pink, dark red, and black fire scars cover much of the landscape.
Many plants in Mozambique are adapted to periodic fire. However, the increasing frequency of fires affects the natural regeneration of vegetation and is believed to be reducing species diversity in Mozambique’s forests.
Frequent fires can also increase soil erosion and negatively impact hydrology.
Aral Sea, Kazakhstan, Uzbekistan
“Diverting Rivers for Cotton Production”
The name “Aral Sea” comes from the word “aral” meaning island. The sea’s name reflects the fact that it is a vast basin that lies as an island among waterless deserts.
The Aral Sea was once the world’s fourth largest inland sea. Its problems began in the 1960s and 1970s with the diversion of the main rivers that feed it to provide for cotton cultivation in arid Soviet Central Asia.
The surface of the Aral Sea once measured 66 100 km² (25 521 square miles).
By 1987, about 60 per cent of the Aral Sea’s volume had been lost, its depth had declined by 14 m (45 feet), and its salt concentration had doubled, killing the commercial fishing trade.
Wind storms became toxic, carrying fine grains of clay and salts deposited on exposed sea floor.
“Re-engineering will leave the South Aral Sea completely dry, perhaps within 15 years.”
Life expectancies in the districts near the sea are significantly lower than in the surrounding areas.
The sea is now a quarter of the size it was 50 years ago and has broken into two parts, the North Aral Sea and the South Aral Sea.
Re-engineering along the Syr Darya River delta in the north will retain water in the North Aral Sea, thereby drying the South Aral Sea completely, perhaps within 15 years.
Santa Cruz, Bolivia
“Where People Go, Nature Dies”
Santa Cruz is situated in Bolivia’s rich, fertile lowlands, a region highly suitable for agriculture.
In the 1975 satellite image, the region’s forested landscape appears as a dense, essentially unbroken expanse of deep green that extends to the Rio Grande (Guapay) River. It was beautiful from the sky and on the ground.
By 1986 roads had been built that linked the region to other population centers.
As a result, large numbers of people migrated to the area.
A large agricultural development effort (the Tierras Baja project) led to widespread deforestation as forests were clear-cut and converted to pastures and cropland.
By 2003, almost the entire region had been converted to agricultural lands, including the area east of La Esperanza across the river.
In the area north and west of Los Cafes (upper left), notice the grid of squares on the landscape, each with an internal star-shaped pattern.
At the center of each square is a small community.
Nangbeto Reservoir, Togo
“First Law: Do No Harm”
A feasibility study in the 1960s identified the Nangbéto region as the best location for hydroelectric power development in Togo.
The site - 160 km upstream from the coast – is the only place where a dam of sufficient volume to regulate the flow of the Mono River was possible.
As demand for electricity grew, the decision was made in the 1980s to proceed with the Nangbéto Hydroelectric Dam.
Satellite images from 1986 and 2001 show the region before and after the dam’s construction.
The completed dam created a reservoir with a surface area of approximately 180 km2 and a volume of 1,465 million m3.
In addition to generating electricity for domestic and commercial use, the dam also provides water for agricultural irrigation and is a source of commercial fishing and tourism. However, these benefits have been offset by environmental costs.
Construction of the dam, creation of the reservoir, and installation of transmission lines resulted in the loss of nearly 150 km2 of savannahs and gallery forests that provided habitat for rare local fauna.
The reservoir submerged 1,285 households and 5,500 hectares of agricultural land. Loss of the natural vegetation in the region has altered the climate enough to have had a negative impact on nearly 350 hectares of banana plantations. The creation of the reservoir has also increased the population of two species of aquatic snails that serve as intermediate hosts of the parasite that causes the disease bilharzia.
Shume Magamba, United Republic of Tanzania
“TIMBER!”
Shume Magamba forest reserve is located in the West Usambara Mountains. It is one of the thirteen blocks forming the Eastern Arc Mountains of Tanzania and Kenya, along the Albertine Rift.
It is comprised of 12 000 ha of moist montane forest, which is a gazetted forest reserve, with 2 500 ha under exotic plantation.
The Eastern Arc is one of the most biologically rich regions in the world, with a large number of endemic animal and plant species. It is regarded as one of the world’s top 25 global biodiversity hotspots and is increasingly being managed for biodiversity conservation.
The forest is threatened by timber harvesting (pit sawing) and agricultural encroachment.
Part of the Shume-Magamba Forest on the West Usambara Mountains was degazetted from a Forest Reserve soon after independence in 1961 and was then converted to agriculture by land-hungry residents.
Other major threats to the forests in the West Usambaras include fire spreading from surrounding farmlands and gold mining. In the former case, the enhanced burning regime is believed to have been the main cause of the replacement of Afromontane forests with grassland and scrub-grassland across large areas.
The sharp boundaries at the edges of the forest indicate areas where forest has been converted to farmland. The 2005 image shows these boundaries pushing further into the forest in several places. The high resolution image (see photos panel below) shows detail of the area highlighted by the yellow box in the above images. In addition to crops, areas of forest plantation are displacing natural forest. Areas of trees with parallel lines cut through them are generally tree farms.
Tanzania had the sixth largest annual net loss in forest area between 2000 and 2005 in the world of about 412 000 ha/yr; second largest in Africa after Zambia. In total, between 1990 and 2005, United Republic of Tanzania lost 14.9 per cent of its forest cover. Currently, 39.9 per cent of the country is forested. Apparently, a number of mountains have lost at least 80 per cent of their original forest cover, including Taita, Ukaguru, Mahenge, and West Usambara.
The energy economy in Tanzania is largely focused on collecting, distributing, and consuming wood fuels (wood and charcoal) to satisfy household demands for cooking. As much as 90 per cent of all primary energy consumed in Tanzania is biomass based.
Lake Hamoun, Afghanistan and Iran
“Competing for Water”
Iran’s Lake Hamoun is fed primarily by water catchments in neighboring Afghanistan.
In 1976, when rivers in Afghanistan were flowing regularly, the lake’s water level was relatively high.
Between 1999 and 2001, however, the lake all but dried up and disappeared, as can be seen in the 2001 satellite image above.
The “dry phase” of Lake Hamoun is a striking example of how competition for scarce water resources can transform a landscape.
When droughts occur in Afghanistan, or when water in watersheds that support Lake Hamoun are drawn down for other natural or human-induced reasons, the end result is a dry lakebed in Iran.
In addition, when the lake is dry, seasonal winds blow fine sands off the exposed lakebed.
The sand is swirled into huge dunes that may cover a hundred or more fishing villages along the former lakeshore.
Wildlife around the lake is negatively impacted and fisheries are brought to a halt. Changes in water policies and substantial rains in the region saw a return of much of the water in Lake Hamoun by 2003 .
Huang He Delta, China
“Sediment Building Up”
Sometimes, it isn’t what humans do, but rather what we don’t do that have a dramatic effect on the environment. As you can see by the images, there is a large protrusion of land that is sticking out that wasn’t there before.
The Huang He (Yellow River) is the muddiest river on Earth and is China’s second longest river, running 5 475 km (3 395 miles) from eastern Tibet to the Bohai Sea.
The Huang He’s yellow color is caused by its tremendous load of sediment, composed primarily of mica, quartz, and feldspar particles.
The sediment enters the water as the river carves its way through the highly erodable loess plateau in north-central China (Loessial soil is called huang tu, or “yellow earth,” in Chinese).
Centuries of sediment deposition and dike building along the river’s course has caused it to flow above the surrounding farmland in some places, making flooding a critically dangerous problem.
Where the Huang He flows into the ocean, sediments are continuously deposited in the river delta, where they gradually build up over time.
Between 1979 and 2000 - as these satellite images show - the delta of the Huang He river expanded dramatically. Several hundred square kilometres of newly formed land were added to China’s coast during this period.
Sakhalin, Russian Federation
“People Increase Risk of Fire”
Mixed deciduous and evergreen needle-leaf trees dominate the boreal forests of Sakhalin Island, just off the eastern coast of Russia.
The tremendous natural reserves of the boreal forests serve as “carbon sinks” that help to regulate global climate. They are among the most important natural “CO2 blockers” in the world today. Boreal forests are also home to a unique collection of plants and animals, including rare and endangered species such as the Amur Tiger.
“Roughly 300 intensely hot fires burned an area nearly the size of Luxembourg.”
Fire is a natural and often vital component in maintaining the health of boreal forests. But since the 1950s, the frequency of fires has increased on Sakhalin Island as its forests have been subjected to rapid exploitation and disturbance in the acquisition of lumber, oil, coal, and peat.
As people moved into the region in greater numbers, the risk of fires started by trains, cars, trash fires, and wood stoves increased greatly. These satellite images show the impact of forest fires on Sakhalin Island.
In 1998, roughly 300 intensely hot fires burned an area nearly the size of Luxembourg. Three people died and nearly 600 were made homeless by a very rapidly moving crown fire that consumed the town of Gorki within a few hours. The 1999 image very clearly shows the extent of the fire damage to the island’s forests near the end of that year.
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