On June 17 we celebrate the World Day to Combat Desertification and Drought in order to make visible this serious environmental problem we are facing. The main effects of desertification are soil degradation and biodiversity loss. As a consequence, the territory's capacity to maintain the functionality of biological systems decreases and, therefore, the availability of natural resources is affected.
The Mediterranean region is one of the areas in Europe with the highest risk of suffering desertification processes. This is due to its particular environmental conditions. On the one hand, it has a dominant semi-arid climate with intense seasonal drought and a strong concentration of rainfall in short periods of time. On the other hand, it has a rugged relief and soils with a low organic matter content and a weak structure, which makes them erodible. These environmental conditions mean that vegetation cover is not high, which has been aggravated by centuries of agricultural, forestry and livestock use. Within the European Mediterranean region, the southeast of our country, specifically, the Autonomous Communities of Valencia, Murcia and some areas of Andalusia present high to very high desertification risk values, according to the Desertification Risk Map prepared by the Ministry for Ecological Transition and Demographic Challenge. Furthermore, in the last decades, the land use model in the region has changed due to agricultural intensification and the expansion of urban-industrial uses in the areas closest to the coast, including tourism. These changes in land use and the associated environmental repercussions (soil erosion, contamination and salinization, landscape deterioration and destruction of natural ecosystems, etc.) have increased soil degradation in large areas of the region, which has increased the risk of desertification.
At the gates of his retirement and having dedicated a good part of his life to research on Desertification, Professor Juan Sánchez Díaz, reviews the progress made in the knowledge of this complex process that represents a serious threat to our territory. Juan Sánchez is Professor of Soil Science at the University of Valencia, a place where he has been recognized as a promoter of Soil Science studies for several decades. He belongs, therefore, by training and experience to that small group of researchers who in the eighties opted for research oriented towards the study of the problems arising from soil degradation in the Mediterranean basin, at a time when these studies were scarce. He has been Director of the CIDE between July 1998 and January 2006 and Vice-Director on two occasions, one between September 1996 and July 1998 and the other from 2019 to the present, in parallel to his work as scientific correspondent of the Committee on Science and Technology (CST) established within the United Nations Convention to Combat Desertification. In the following lines, he shares his vision on the current situation of the study of Desertification and how it has evolved in the last decades.
In order to understand the scope of this process, it is first necessary to understand what exactly we are referring to when we talk about desertification.
The desertification process or phenomenon is a complex process in which a series of natural (climatic conditions, lithology or the presence of soils susceptible to degradation) and anthropogenic (deforestation, intensive agriculture, urbanization, etc.) causes or factors converge. This set of factors gives rise to a series of effects primarily on the environment (soil degradation, alteration of vegetation cover, impacts on the landscape) which ultimately have repercussions on the population (increase in poverty, forced migrations or worsening malnutrition).
What is the magnitude of this problem and to what extent can this process impact our lives?
According to the Secretariat for Combating Desertification, today, more than 2 billion hectares of previously productive land are degraded. By 2030, food production will require another 300 million hectares of land.
The use of more than 70% of natural ecosystems has been transformed. By 2050, the figure could reach 90%.
This phenomenon is not new. In fact, it has been a fundamental element in human history, contributing to the fall of great empires and displacing local populations. However, it is estimated that the rate of degradation of arable land is currently increasing at 30 to 35 times the historical rate.
The livelihoods of some 2 billion people, ninety percent of whom live in developing countries, depend on dryland ecosystems. Overpopulation in many underdeveloped countries creates the need to exploit drylands for livestock and agriculture. A downward spiral begins on these low-productivity lands, leading to the depletion of soil nutrients and groundwater aquifers.
This year's International Day focuses on changing public attitudes towards the main cause of desertification and land degradation: mankind's relentless production and consumption.
Population growth and urban population increase intensify the demand for land to produce food, fodder and textile fibers. Meanwhile, the health and productivity of existing arable land is declining, a decline that is worsened by climate change.
In order to have enough productive land to meet the demand of 10 billion people in 2050, it is necessary to change our lifestyle. Through the Day to Combat Desertification and Drought, celebrated under the slogan “Food. Fodder. Fiber,” aims to educate people on how to reduce their individual impact.
The Mediterranean region in which we find ourselves is seriously threatened by climate change, with forecasts of an increase in aridity, what is the current situation and how do you think these forecasts may influence the risk of desertification in this area?
Most of the results offered by the different General Circulation Models of the atmosphere (GCMs) agree that the Mediterranean region will be particularly sensitive to changes in precipitation and temperatures. If the aforementioned predictions are confirmed, drought stages and floods will be more intense and longer and, therefore, the aridity of Mediterranean landscapes will increase. Therefore, desertification would be more extensive and intense, induced directly by climate change and indirectly by the higher incidence of forest fires, increased erosion and soil salinization, etc.
From your experience, how has the study of this problem evolved in the academic field and where do you consider the greatest difficulties in its approach?
Desertification was taught as a doctoral program at the CIDE within the third cycle program of the University of Valencia. The teaching staff were researchers of the Center and the students, mostly scholarship holders of projects linked to the Center, were mostly biologists, geographers and agronomists. It fulfilled its function partially, since most of them culminated with the reading and defense of their doctoral thesis. However, the program could not continue since the location in Albal, outside the university campuses, made it undesirable for most of the students.
With respect to teaching in the degrees, Soil science, to cite the subject that is very close to me, has remained practically testimonial in the degree of Environmental Sciences. I do not understand the permanent rejection by those responsible for the modification of the curricula in the last two decades, preventing biologists to be trained in Soil Science. With this lack of knowledge, it is not possible to approach with guarantees the studies of soil degradation such as salinization, sealing, contamination and soil erosion, i.e. Desertification.
What lessons have you learned in your study?
After more than 40 years of studies (global and regional, integrated and sectoral), debates and discussions, the term Desertification remains under conceptual discussion, due to the numerous ambiguities it presents, especially in the differentiation of natural processes from induced ones, but above all in the integration of physical-natural and socio-economic aspects. Proposals for indicators are recurrent and there is currently no body of doctrine that is accepted by all.
It is true that there is consensus on the indissoluble association between desertification and land degradation, as recognized by most scientists and institutions. The problem lies in the fact that the meaning of the term “land degradation” is not defined from a scientific point of view either. This has been contributed to by studies that, based on a conceptual confusion about the term, have applied inadequate criteria to measure desertification: important extensions of semi-arid soils are considered as degraded soils when in fact they are zonal soils and in equilibrium with those environmental conditions. It has also occurred when production has been confused with productivity, and consequently, the advance of desertification has been reflected on the basis of a decrease in vegetation cover, without having carried out an analysis of the state and evolution of soil productivity and, on the other hand, when emphasis has been placed on the decrease of water resources (both in quantity and quality), either due to climate or anthropic pressure, as the cause of land degradation, without having looked at the real water possibilities of the community or the potential of the soil resources to manage the available water.
Climate change prospects, according to existing models and the predicted increase in temperatures for this century, point in the direction of increased desertification. Drought and flooding processes will be important considering the irregular rainfall predictions. Feasible scenarios should be considered in order to have prior knowledge of the socio-economic future of the region, if we take into account the degree of impact it may have on important sectors such as agriculture and tourism, and to integrate adaptation to climate change in forest planning and management to guarantee the provision of ecosystem goods and services.
And at the level of citizenship, how do you think attention could be drawn to this problem, as is already being achieved with other issues such as the loss of diversity or climate change?
A study carried out within the framework of the National Plan for Adaptation to Climate Change analyzed the impact of climate change on the risk of desertification in Spain. Considering together the effects of the evolution of aridity and erosion, the study revealed that, by the end of the present century, the area subject to desertification risk would increase for all the established categories, with the greatest projected change in the very high risk (+45%) and high risk (+82%) categories. The matter therefore requires significant attention.
This interview serves as a recognition of Juan Sánchez's research work, for his great contribution to the scientific bases of natural resource management and territorial planning in our country and his commitment to the defense of the environment.
CIDE Communication
