A single centimetre of soil requires hundreds of thousands of years to form, while humans only need a few days, or just an instant, to degrade it. Any soil that contains more than 20% material handled by us has its own name: a technosol. Most of them have acquired harmful properties, but in some cases they serve more positive purposes, such as increasing productivity or recovering damaged areas.
A success storie is the fertile Terra Pretas found in the Amazon basin, the result of indigenous activity. And more recent are the à la carte technosols, which emerged at the beginning of the 1990s with the aim of recovering severely contaminated areas. This scientific development consists of designing and manufacturing soils that can change an entire ecosystem in record time. A procedure that could be the way to cultivated deserts or modify the soils of other planets to terraform them.
1. A way to accelerate the rhythm of nature
The advance of edaphology, a science that studies the composition and behaviour of the soil, has permitted the development of customised technosols, based on the very processes that take place in natural ecosystems. In the biosphere, soils constitute an important control system, reducing the mobility and availability of compounds that reach the water and living beings. Felipe Macías, Professor of Edaphology at the University of Santiago de Compostela, Spain, and director of its Environmental Technology Laboratory, the only one in the world that designs these types of soil, explains to OpenMind that “since we copy from nature, there are many models for generating technosols. But we can accelerate or magnify natural processes.”
Macías’ team studied for years how ancient cultures prepared their soils, from the floating islands of Lake Titicaca to the plaggen of Holland or the Guarani sambaquis of Brazil. These improved soils became a way of guaranteeing the harvests of those villages. The à la carte technosols reproduce them to a large extent, but to solve more concrete problems. “For example, we have a surface with an excess of toxic heavy metals such as zinc, cadmium, mercury or arsenic, so we generate a sambaqui soil that immobilises them based on the conditions we want to obtain,” explains Macías.
2. Alternative environmental treatment
To generate this type of soil, all possible resources that are in situ or in nearby areas are used. “You can add ground rock, sediments, other soils, raw materials (for example, kaolinite or gypsum) and also waste,” says Macías. To know the exact treatment that a surface needs, it is first studied in the laboratory, and later pilot technosols are created and tested on a small scale. After verifying their effectiveness, they are produced on an industrial scale and applied.
Making a technosol can take months, and after it has been applied it must be monitored to ensure it is working correctly by periodically checking the pH of the surrounding water and testing for the presence of polluting substances. Customised soils are now an environmental alternative to the use of encalantes, such as limestone, which are often used to neutralise hazardous materials that appear in the large excavations needed to build infrastructure. Macías points out that “the regulations indicate that a technosol must always have fewer pollutants than the soil where it is to be applied, and it must also be designed to converge with it, that is, over the years the technosol must blend in with the soil of the surrounding environment.”
3. Increasing the productivity of a surface
Although so far most of the technosols have been used for environmental improvement purposes —33% of the world’s soil is degraded— it is also possible to apply them to increase the productive capacity of a given area. “For example, we can design technosols that retain more water available for plants, so that they can better match their growing season and improve production,” says Macías.
Any of the characteristics that a technosol magnifies can be found in natural soil, such as the ability to produce vegetation, filter water or retain elements. But much can be achieved with this system in a very short time. Macías says that “we had a harvest of spring or summer canola without any problem, three months after having applied a technosol in a place where it didn’t grow before.” In this regard, the improvement achieved with this procedure in soils is comparable to the hybridization and selection of plants that agriculture did for centuries, to achieve better crops.
4. Solutions for extreme cases
The idea of using of technosols to make a desert bloom still seems far off in the future, but some tests have already been done in extreme places. “We have successfully designed technosols for the desert of La Guajira in Colombia and the Calanda desert in Spain. It is always possible to improve the conditions of existing soils, especially those degraded by erosion, both in desert areas and in places that have been burned”, says Macías. Therefore, deploying a technosol means a much faster recovery than the soil would need without any type of intervention.
An abandoned copper mine in Touro, Spain is the site where Macías’ team have carried out the greatest number of tests. There they have developed the most amazing technosols. Macías says that “one of them is capable of absorbing water with a very acidic pH of 2.6 and loaded with sulphates and aluminium, and return water to a pH of 6.5 without sulphates or aluminium. In that same soil, in a place where nothing once grew, vegetation is now established and even wood is produced. The trophic chain has also evolved, with the appearance of insects, worms, birds… and an increasingly complex ecosystem is being generated.”
5. Terraforming other planets
The idea of a place that recovers its ecosystem from almost nothing is reminiscent of the science fiction trilogy Red Mars, Green Mars and Blue Mars. In his novels, writer Kim Stanley Robinson explores the advantages and disadvantages of terraforming the red planet.
Macías explains that “if we were to succeed in establishing a colony on Mars, we could imagine how to make soil using the planet’s own materials by adding other soils that contribute organic matter, in order to generate the structure and water retention of a soil. But, today this is science fiction.” In any case, imagining it is the first step.
Bibiana García Visos