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"from dirt flowers are born,
from diamonds nothing comes"
"Via del Campo" by Fabrizio de André (Italian poet-musician)
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December 5th was proposed in 2002 by the International Union of Soil Sciences (IUSS) as "World Soil Day", to remember the important role that "dirt" plays for life on earth and human civilisations.
In Geology soils are defined as the uppermost layer or substratum of earth. More specific definitions consider soils as the results of the complex interactions between the lithosphere (which provides the rocks as parent material), the atmosphere and hydrosphere (which cause physical and chemical weathering), the biosphere (which provides organic components) and time (soil needs long periods to form) - oversimplifying we can say that soils are the remains of the weathering of rocks enriched by organic debris.
A soil is a unique feature of earth - it supports most of the plant life and is therefore also essential for all heterotrophic life-forms and terrestrial civilisations. Soil degradation and erosion was and still is one of the major threats to soil quality and function in the world. Erosion is a natural process; however human influence and mismanagement can significantly increase the velocity and extent of this process. Unprotected soil can be rapidly eroded by wind or washed away by running water - logging, overexploitation and monocultures can damage, even destroy the plant cover protecting the soil. Irrigation and heavy equipment can condense the soil or modify its chemistry. The collapse of many civilisations in the past was triggered by the erosion and degradation of soil, followed by decrease in the agricultural production and widespread famine and death. Even in the 20th century humans - mainly politicians - made errors when initiating, as claimed by some environmentalists, a war against soils, ending in terrible consequences for the entire population.
The areas of China covered with the aeolian sediment Loess are characterized by very fertile soils and for thousands of years these regions were cultivated by farmers. However this yellowish, fine-grained, carbonate rich sediment is very vulnerable to erosion, wind and water can easily erode and transport the silt and sand fraction of this sediment.
Fig.1. Near the small village of Westeregeln (Thuringia, Germany) past quarrying activity has exposed a gypsum and limestone formation, covered by Pleistocene sediments. The uppermost part of the stratigraphy is represented by a postglacial soil developed on Loess - an aeolian sediment deposited during the last glacial period. Note the secondary infillings of the burrows of animals and the different colours of the single horizons that compose a soil.
The rise to power by the communist party under the leadership of Mao Zedong in the years after 1949 had a profound impact on the Chinese society and the environment. Inspired by the apparent success of the U.d.S.S.R. under Stalin the party planned to transform the rural agriculture economy into a socialistic power - this project was named "The Great Leap Forward" - following a strange mix of science, personal opinions and pseudoscientific claims, like these formulated by Trofim Denissowitsch Lyssenko, one of the leading agriculture scientists of Stalin's regime.
A preliminary 5-year plan was adopted in the years 1953 to 1957; consisting of a complex pattern of land clearing and reforestation - in only few months estimated 10% of China's forests were transformed into farmland. To increase the industrial production of iron primitive furnaces were constructed in the backyards of farmhouses, the increased demand for fire-wood led to an even faster deforestation and subsequent soil erosion. Heavy equipment, as used on the cultivated fields in the Russian plains, lead to slope erosion in the soft soils of the Loess plains.
In the years 1957/1958 a second, even more ambitious plan for the next 12-years was proposed - with even more catastrophic effects.
Farmers should plant 12-15 million seedlings per hectare instead of the previous 1,5 million, as Mao thought that plants would grow better in a large collective. In the fierce competition for light and nourishment from the soil most seedlings soon starve to death.
Plant species ill-suited to the local soils and climate were planted on large areas - especially maize (Zea mays mays). The dense root system of this grass species tends to seal off the soil, water can no longer infiltrate and the upper part of the soils get cloaked by mud particles, limiting the diffusion of oxygen into the soil. The roots of plants however need oxygen to grow and the suffocating roots affected the growth of the entire plants.
The construction of dams and canals modified the catchments of rivers and the hydrology of entire regions; this lead to widespread erosion of the fertile soil and reservoirs became clogged with sediments and could no longer be used.
The resulting decrease in agricultural production lead to a terrible period of starvation in the years 1958 to 1961, estimated 40 to 30 million people died in this artificial famine. Mao Zedong and many of the leaders of the communist party ignored however the environmental problems and affirmed instead that the famine was the result of saboteurs or opposing political forces - a fiercely which-hunt to find a scapegoat was initiated. Only in 1962 the agricultural dispositions were modified and the situation improved.
Despite the disastrous results other countries - like Cambodia, Ethiopia and North Korea - adopted questionable agricultural methods during the 20th century and with similar results.
Soil degradation and erosion are still problems in modern China, 19% of the area of the country is at erosion risk, but also in many other industrialized countries of the world soil has become a valuable resource on the global market. China and India are for example buying or renting large areas in underdeveloped countries. This fast "solution" is however problematic considering that the food production in many of the involved countries is not capable to sustain even their own population.
China's today politics is an example of a conflict of interests similar to all developed countries - it invests large efforts in reforestation, conservation areas and the environment protection - realizing that we need the "services" provided by intact soils - however the development of industry and the increasing welfare of the population demands for further land use.
How this conflict will end is still unclear at the moment…
Bibliography:
BORK, H.-R. (2006): Landschaften der Erde unter dem Einfluss des Menschen. Wissenschaftliche Buchgesellschaft, Darmstadt: 207