Soil, a finite resource

Soil is a non-renewable natural resource essential for life on Earth. Its formation can be fast (tens or hundreds of years) or slow (thousands of years), depending on factors such as climate, topography, microorganisms and the minerals that make it up, but always on a geological scale. It is estimated that an average centimeter of soil takes 1,000 years to form (FAO, 2015), so it is considered as a non-renewable resource, since their renewal cycles are much longer than human life. On average, soil is composed of organic matter (5%), air (25%), water (25%) and minerals (45%) (FAO, 2015). Although organic matter forms only a small part of the soil, it houses around a quarter of the planet's biodiversity (FAO, 2015c). Currently, more than 100 types of soil are identified, since their composition plus the action of factors such as weather, water, wind and the organic matter that lives and dies in it, generate different types of structures and properties (FAO, 2021).

The value of soils has been recognized internationally for decades and is due to the fact that they play a crucial role in different natural and social aspects. Soil is an enabling resource, in other words, it creates a multitude of goods and services necessary for the environment and the human being. For example, a large part of the world's organic carbon, captured in the form of biomass and sediment, is stored in soils (45%). This characteristic of soil also makes it an important element for regulating the Earth's climate, since it stores large quantities of greenhouse gases, thus preventing them from reaching the atmosphere and contributing to global warming.

The soil is also a habitat for an immense number of microorganisms: it is estimated that millions of microorganisms can be found in just 1 g of soil, which are part of the soil nutrient cycle where other forms of life use them for food. These characteristics also make soil a source of priceless pharmaceuticals and genetic resources. On the other hand, it is extremely important for flood regulation, as it helps to store and filter water to the subsoil, which at the same time helps to purify the water by retaining contaminants in it. In addition, it supplies a wide variety of construction materials and is used as the basis for human infrastructures, so it also has a high cultural value as it contains vestiges of past civilizations. Finally, soil provides fuels and fibers necessary for humans, and approximately 95% of our food is directly or indirectly produced in the soil (FAO, 2015b).

Despite the fact that soil is created through complex actions and interactions of biological, geological and chemical processes as diverse as the services it offers, proper management of this resource can ensure that your current capabilities are maintained without affecting your functions (FAO, 2015a).

Unfortunately, the soil and its capacity to provide these services are threatened by the intensity of human activity and the management given to this resource. These processes are known as soil degradation or erosion.

Erosion is defined as the accelerated wear of the surface layer of the soil by water, wind or human activities (FAO, 2015c). It is a natural process that occurs under any climatic condition and in any part of the Earth, however, the intensity of human activities such as tillage, grazing and deforestation have increased the rate of soil erosion. This is why soil erosion is closely related to climate change and desertification. FAO estimates that if there are no immediate actions to protect this resource, by 2050 90% of the Earth's soils would have been degraded (FAO, 2019).

Thanks to the statistics generated by Oldeman in 1994 in the Global Assessment of Land Degradation (GLASOD) project, we know that water erosion—erosion generated by water—is the one that affects the most surface and the one that is most induced by human activities. However, despite extensive efforts to determine global erosion rates, the data are still highly uncertain. This is no exception in Mexico, since 2002 SEMARNAT estimated that 37% of the soil in Mexico was degraded by water erosion. Later, in 2014, the INEGI estimated that this percentage was actually 52.8%, and then corrected it in 2015 to a percentage of 66. In addition to this, in a study published in 2016 by the Mexican Carbon Program in conjunction with INEGI, it was determined that 76% of the national surface has some degree of damage due to water erosion, corresponding to 6.79% with an extreme degree of erosion, 5.79% strong, 26.37% moderate and 37.06% mild (Bolaños et al., 2016).

The difficulty in estimating the damage caused by erosion stems from the great variability of the factors that influence it, some of these are: the type of soil, the use given to the land, the topography and the type of climate, among others. However, the impacts it brings are evident and have great repercussions for the development of life. In order to illustrate the importance of conserving this finite resource, FAO lists 5 ways in which soil erosion threatens human development (FAO, 2019), these are: it restricts human capacity to produce food, leads to ecosystem degradation, affects water supply, damages human infrastructure, contributes to poverty and can aggravate migration.

Despite the fact that it has been known for decades that the loss and degradation of soils due to erosion is a problem that needs to be addressed urgently, in much of the world the adoption of measures for their protection and conservation is slow. That is why soil protection and restoration is part of the activities determined by the sustainable development goals adopted by the UN and its member states. In Mexico, national and international commitments have been made to combat desertification both with the Program of Action to Combat Desertification in Mexico, the National System for Combating Desertification and the Degradation of Natural Resources (SINADES) and with the United Nations Convention to Combat Desertification (UNCCD). These programs seek to generate action for sustainable land management and to prevent desertification through:

1. Promote informed and co-responsible awareness of Sustainable Land Management throughout society;

2. Promote Integrated Land Use Planning;

3. Strengthen Institutional Coordination and Policy Harmonization;

4. Promote the generation and dissemination of information for Sustainable Land Management;

5. Co-responsible participation, with inclusion and equity of gender and ethnicity;

6. Strengthening Research and Transferring Good Management Practices;

7. Promotion of International Cooperation;

8. Integrated Financial Strategy Design; and

9. Direct Actions for Sustainable Land Management (SEMARNAT, 2008).

Although there are strategies that seek to reduce and reverse the problems associated with soil degradation and erosion, it is important that we become aware of the problem as individuals. In this way, we can analyze our own consumption patterns and through them make informed decisions that help reverse the problem, in addition to using our voice to demand that our governments and private sector take action on the matter.

References

Bolaños, M.A., Paz, F., Cruz, C.O., Argumedo, J.A., Romero, V.M., Cruz, J.C. (2016). Map of soil erosion in Mexico and possible implications for soil organic carbon storage. Latin American Earth 34:271-288.

FAO. (2015). How soils are formed. http://www.fao.org/resources/infographics/infographics-details/es/c/294318/

FAO. (May 10, 2019). Let's stop soil erosion to ensure future food security. http://www.fao.org/fao-stories/article/es/c/1193735/

FAO. (2015a). Soil is a non-renewable resource. http://www.fao.org/3/i4373s/i4373s.pdf

FAO. (2015b). The functions of the soil. http://www.fao.org/resources/infographics/infographics-details/es/c/294325/

FAO. (2015c). Status of World's Soil Resources (SWSR) - Main Report. Rome, FAO.

FAO. (2021). FAO/UNESCO World Soil Map. http://www.fao.org/soils-portal/soil-survey/mapas-historicos-de-suelos-y-bases-de-datos/mapa-mundial-de-suelos-de-faounesco/es/

SEMARNAT. (2008). National Sustainable Land Management Program to Combat Land Degradation and Desertification in Mexico. Mexico, SINADES. https://www.gob.mx/cms/uploads/attachment/file/31167/pnacdd.pdf