The biggest challenge of the present times is how to bridge the gap between the quick population increase, from one hand, and the soil-limited space that looks not capable to satisfy the food production of human needs, from the other hand. It is expected that by 2050 the world population will reach the 9 billion people and the concern is about the food security issues since there is no possibility to increase the cultivated land.

Globally the per capita arable land was 0.45 ha in 1950 and decreased to 0.35 ha in 1970, 0.28 ha in 1990, and 0.22 in 2000 and it is expected to be 0.15 ha in 2050. In some very densely populated countries the per capita land is estimated to be in 2025 less than 0.1 ha such in Bangladesh (0.05 ha), in China (0.06 ha), in Egypt (0.03 ha), in Pakistan (0.07 ha) and in Tanzania (0.05 ha) (Lal and Stewart, 2010). It is estimated that about 1 billion people are food insecure and the goal of UN Millennium Development of reducing hunger by 50% until 2015 was not achieved. 

Food is obtained by agricultural activities, which are mainly based on soil. So, since humans depend on food, the sound management of soils is a prerequisite of human survival. However, since agriculture may cause a serious environmental pollution if it is not well practiced, we must be very careful in using the new technology and inputs (fertilizers, pesticides) to avoid environmental degradation. 

Soil degradation constitutes a severe threat of the Earth. It is estimated that so far, about 1965 Mha of soil have been degraded in a significant degree (Oldeman, 1994). The vulnerable area to desertification is estimated to be about 1/3 of the Earth’s land area (4320 Mha) from which 1170 Mha in regions with a high population density of >41 persons/km2. About 23.5 % of the Earth’s land area has been degraded and the number of people impacted by land degradation is estimated to be 1.5 billion i.e. (Eswaran et al. 2001; Bai et al., 2008). 

Another serious threat of the agricultural land is urbanization. Taking into account that for accommodation of 1 million people is required about 40.000 ha of land for housing, infrastructure and waste disposal and considering an annual increase in world population of about 80 million, an additional land area of about 3 Mha/year is needed (Lal, 2010). Thus, urbanization decreases substantially land resources something that should be seriously taken into account when we schedule soil management.

WATER SECURITY
Another serious concern is the water security, which is a fast-growing challenge since agriculture uses about 85% of fresh water. In some arid or semiarid areas water stress will be a bigger challenge than land scarcity. About 1 billion don’t have access to fresh water (Gleick, 2003). The irrigated land area increased from 8 Mha in 1800 to 280 in 2000 and is projected to increase to 529 Mha in 2050 (Tilman et al., 2001).

The total world population in 2050 will increase water demand for agriculture by about 60-70% (Moldern, 2007). Analogous is the water demand industrial and urban uses. Water footprint of wheat, soybean, rice, chicken, and beef are estimated to about 1500, 1500, 3500, 4200, and 50000 L per kg of each of these products respectively (Clay, 2004). Furthermore, the problems related to water pollution must be considered. It is noticed that soil can store about 2% of this amount of water but much of the agricultural use goes through soil. 

ENERGY SUSTAINABILITY

Another facing challenge is energy sustainability. It is estimated that the global energy demand increases at a rate of 2.5-3.0% per year. The global daily oil consumption is estimated to 2.8 L/person, which corresponds to about 19 billion L/day and is expected to increase dramatically with the increase of living standards in countries like China and India, where the per capita energy consumption today is by fossil fuel combustion only 20% and 13% than in the USA respectively (Marland et al., 2001). So, the expected increase in per capita energy consumption in emerging economies like China and India will have very strong impact on global energy consumption that will affect climate change. It is well known that agriculture and forestry via soil can produce renewable energy non-carbon fuel sources. Carbon sequestration in long-lived sinks such as soils and biota must be seriously considered.

From the other hand, climate change needs a sustainable solution. Soils can mitigate greenhouse gases which cause global warming. It is estimated that in the 20th century the Earth’s temperature increased by 0.6±0.2 ºC (IPCC, 2001). If the rate of increase in temperature is 1 ºC per century the ecosystems cannot adjust. The attainable potential of terrestrial carbon sequestration in agricultural and forest ecosystems at 2.5 Pg C/year, which corresponds to a net increase of only 0.5 to 0.7 Pg C/year in atmospheric concentration (IPCC, 2000). Soils store 2700 Pg carbon which is twice the carbon of the atmosphere (789 Pg) and biomass (575 Pg) combined. 

Soil acts as a buffer against extreme climate events, protecting thus the society. All the above mentioned are linked directly or indirectly to human health through nutrition and disease prevention.  Improving soil quality through soil carbon sequestration is a good strategy for both adaptive and mitigative options.

Photo*: Results of dismanagement of agricultural soils
(erosion due to bad practice in soil ploughing -erosion across the contour lines)

BIODIVERSITY PROTECTION
Another important function of soils is biodiversity protection. About 25% of biodiversity is in soil and there is probably a much undiscovered biodiversity that has been already lost. Soil biodiversity besides its influence on the quality and quality of the food we eat, the air we breathe, and water we drink, also seriously affects human health providing disease control. 

The maintenance of these important functions depends on the careful and sustainable use of soil as a resource. Poor land management and climate change reduce species richness, the functional diversity and biotic interactions leading to loss of ecosystem functioning and service provision such as water infiltration, regulation of pest and pathogens, erosion control and nutrient release. All they lead to increase of soil-born pathogen and pest load from one hand and to reduction of food supply and finally impact the human health by increasing risk of diseases caused by pest and pathogens, reduction of nutritious food and decreasing clean water and air (Wall et al., 2015).

All those already mentioned above i.e. food security, water security, climate change, biodiversity protection, human health and energy sustainability are linked through soil security which is the nexus of the them.

SO WHY SOIL SECURITY?
If we search for concepts describing how humanity values and cares for soil, we will meet a great number of concepts including biophysical concepts (soil horizons, profiles, pedons, landscape etc.), scientific concepts (science of soil, soil science or science of soil materials, and societal concepts valuing and caring for soil for humanity.

Several concepts of the past such as soil conservation, land evaluation and capability and soil care as well as many from the present such as soil function, soil quality, soil health, soil condition, soil change, soil resilience and soil ecosystem services are used for soil services. However, some of them were similar such as soil quality ≡ soil health ≡ soil condition. In fact, there are a plethora of concepts usually fairly narrow and sometimes unclear and in general biophysical. 

Therefore, there is a need to coalesce and generalize by creating a concept that should incorporate the economic, social and policy settings and the biophysical concepts, a wider-ranging concept these manifold settings and at the same time recognizing the role of the earlier concepts.  This is the concept of Soil Security which gains more and more recognition. 

The concept Soil Security has the following dimensions: Capability with biophysical dimensions (soil functions, capability), Condition with also biophysical dimensions (soil health, quality, condition, change), Capital with economic dimensions (soil ecosystems services, natural capital), Connectivity with social dimensions (soil care, awareness) and Codification with policy and governance dimensions (soil conservation, governance).

But what soils can do or what are the soils functions? They can be summarized to the following: biomass production, storage, filtering and transforming of nutrient and water, biodiversity pool, physical and cultural environment, source of raw materials, acting as carbon pool and archiving of geological and cultural heritage.

CONCLUSIÓN

Soil Security is a timely, strategic concept arising from global challenge and societal value considerations. It is homologous to food and water security and it must start to be measured and managed its dimensions.

REFERENCES

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*Article published in the 2017 annual journal of the Veterinary Sciences Academy of Catalonia