Neither the Great Wall of China nor the pyramids of Egypt: the most visible man-made construction seen from space is in the south of Spain

US space agency Nasa has debunked the myth and said on a number of occasions that neither The Great Wall of China nor the pyramids in Egypt are the most-visible human constructions that can be seen from space. What can be seen most clearly are the greenhouses of Almeria province in the south of Spain, specifically those located in the Campo de Dalías, whose central nucleus is in El Ejido.

Nasa has been periodically releasing images that confirm this and the latest images were released in 2022, but they were also released in 2011 and 2004. "The clear skies and plastic have made it possible for the arid province of Almeria in southeastern Spain to become a major exporter of tomatoes and other produce," the agency said.

The last image of the greenhouses from space was captured by the Landsat 9 satellite on 24 May 2022 for the Earth Observatory. Nasa has even dedicated an article to the sea of greenhouses in Almeria. "According to some estimates, greenhouses in Almeria now cover more than 40,000 hectares which is almost the entire Campo de Dalías. They have also spread to neighbouring areas. The greenhouses cover such a large area that they have probably even caused a localised cooling effect because the white roofs reflect a substantial amount of sunlight," the space agency's article pointed out.

The images were captured thanks to the vast expanse of the greenhouses and the reflection of sunlight off the plastic. This new concept of 'solar greenhouse' has been welcomed by the various growers' associations. In this way, they justify that "by creating a microclimate, we achieve a greater production of our fruit and vegetable crops at any time of the year, without resorting to the use of fossil fuels or renouncing their quality and flavour".

"In this way we generate greater productivity, at a very competitive cost, favouring a circular economy through optimal management of scarce resources such as water and the reuse and recycling of as many of the elements involved in the production process as possible," they explain.

The Nasa article refers to research done by the University of Almeria that calculated that surface albedo (the amount of sunlight that is diffusely reflected by a body) had increased by almost 10% due to the high reflectivity of plastic sheeting. In conclusion, the researchers determined that the greenhouses would have contributed to a cooling effect of 0.3C per decade compared to an increase of 0.5 degrees in the rest of the region.