Can the Great Wall of China be seen from space? It’s a common belief, yet the answer is no. While the wall stretches over 21,000 kilometers counting its tributaries, it is too narrow to stand out against the rugged terrain. Anything created by humans is not easily discernible from space, especially when viewed with the naked eye.
The most visible artificial structure from Earth orbit is found in Spain. This is Almería’s sea of greenhouses, around the town of El Ejido. It is the region with the highest density of plastic-covered crops in the country and can be spotted from the International Space Station with its bright, reflective surface.
Located in the Campo de Dalías region, where El Ejido sits, more than 20,000 hectares are dedicated to greenhouses. The 2020 Agricultural Census notes that the Almería province covers roughly 30,000 hectares, nearly half of Spain’s agricultural plastic area, which totals around 65,000 hectares according to the National Institute of Statistics. Recent data from the Junta de Andalucía in 2021 suggests the plastic-covered agricultural area in the region reached 32,000 hectares.
Approved by Pedro Duque
Almería hosts one of the planet’s largest greenhouse concentrations, making the landscape easily identifiable from space. This was underscored by Pedro Duque, a Spaniard who recently visited the area. Duque, a former Minister of Science and Innovation and an astronaut, spoke about the visible greenhouses when asked on a television program, noting that a large, white, reflective patch marks the area rather than a high wall or a single structure. Even the first Chinese astronaut to photograph the Wall confirmed it cannot be seen with the naked eye from above.
The key visibility from orbit is not the wall of a distant country but the Iberian Peninsula’s own distinctive feature: a vast field of greenhouses around southern Almería, which becomes highly noticeable due to its sheer scale and intense reflectivity. This phenomenon is amplified by the way the white roofs bounce sunlight, making the area stand out against the landscape.
A NASA publication from recent years notes that the white-roofed greenhouses cover such a large area that their light reflection could even influence local temperatures, a cooling effect tied to the surface albedo. The region’s reflective surface contributes to regional energy balance, setting it apart from surrounding lands.
High reflectivity of greenhouses
Observations from NASA’s MODIS sensors on the Aqua and Terra satellites have shown that Almería’s surface albedo rose by almost 10 percent between 1983 and 2006 due to greenhouse reflectivity. Researchers concluded this shift probably contributed to a cooling effect of about 0.3 degrees Celsius per decade in Almería. This trend is slightly lower than the regional average increase in temperature, which stands around 0.5 degrees per decade.
Estimates indicate that Almería’s greenhouses now produce between 2.5 and 3.5 million tons of fruits and vegetables annually. This output provides a steady supply of out-of-season tomatoes, peppers, cucumbers, and melons for residents across Europe.
The spread of these facilities also raises discussions about the environmental impact of plastic waste from greenhouses and the potential reach of residue into land or sea ecosystems.
The sea of greenhouses around El Ejido is not the only human feature visible from space. Southeast of Salt Lake City, the Bingham Canyon Mine stands out as one of the world’s largest excavations. Astronauts have noted that other landmarks such as China’s Three Gorges Dam on the Yangtze River or Dubai’s Palm Jumeirah are visible as well. There is ongoing debate, however, about whether the great pyramids of Egypt can be seen from space with the naked eye.
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