Esperanza Álvarez: «We need to educate and raise awareness of the importance of soil, to give it its rightful place: we need to know that without soil, there is no life»

"Out of the long list of nature's gifts to man, none is perhaps so utterly essential to human life as soil." Behind this quote from soil conservation pioneer Hugh Hammond Bennet lies a reality unknown to many today. Soil is the basis and sustenance of life, forming an essential element for the development of most human activities, different ecosystems, and global biodiversity.

Even so, its functions and the importance of protecting it continue to occupy a secondary educational, social and media role, which is why it is critical to focus on the work of professional experts in this field, such as Esperanza Álvarez Rodríguez, a university professor at Campus Terra, researcher and coordinator of the UXAFORES group, among many other things.

With over 30 years of professional experience and over 250 publications under her signature, her voice enjoys a great authority on soil in its multiple facets: chemistry, fertility, conservation, restoration, and contamination. Her research focuses on topics such as reducing soil pollution, recovering degraded areas and applying the circular economy in soil restoration processes.

In commemorating the figure of H.H. Bennet, considered the "father of soil conservation", World Soil Conservation Day has been celebrated every 7 July for over 60 years. Today, we take the opportunity to talk to Esperanza Álvarez about this subject, the importance of education about the value of soil from an early age and the ways we have as a society to take care of this essential resource for life.

-This week the World Soil Conservation Day takes place: why is soil so crucial for life, and what role does soil play in the fight against climate change?

-Soil performs multiple ecosystem services essential for life on Earth. It is the basis for many human activities, including agriculture and forestry production, construction and recreation. It is the physical support for plants, providing stability and support so they can settle properly. It is a source of essential nutrients for plant growth, which come from rock alteration or the decomposition of organic matter by soil micro-organisms. Thanks to the colloids in the soil (clays and organic matter), these nutrients can be stored and released when the plant needs them; this kind of pantry is of utmost importance for plant nutrition.

Soil can retain water, which is essential for plant growth and maintaining water balance in ecosystems. In addition, the soil has a high purification power, filtering water and retaining pollutants, preventing them from reaching underground aquifers and surface water bodies. It is also home to a great diversity of organisms, from microscopic bacteria and fungi to earthworms and arthropods, which play an essential role in the decomposition of organic matter and release of nutrients, in the humification process, bioturbation (soil mixing) and pest control.

In short, soil is a complex environment where numerous chemical reactions occur. Interactions between minerals, organic matter, water and air determine the availability of nutrients and the mobility and toxicity of pollutants, affecting ecosystem health, food security and water quality.

Soil also contributes to climate regulation through the carbon cycle. It acts as a carbon sink, storing large amounts of organic carbon. Proper soil management can increase this storage capacity, thus mitigating climate change. Organic matter also influences soil temperature and soil moisture, having a high-water retention capacity.

Soil is, therefore, essential for life on Earth, but it is a finite resource that needs to be cared for. Its conservation and sustainable management are crucial to ensure the continuity of ecosystem services. Soil degradation, on the other hand, can lead to loss of agricultural and forest productivity, desertification, declining water quality and pollution that will affect ecosystem health and human life.

-Professor at the University of Santiago de Compostela, researcher, coordinator of two courses and subjects, director of multiple doctoral theses and final degree projects, teacher and coordinator of the research group UXAFORES. Tell us, what is the day-to-day life of such a busy person with many responsibilities?

-Very similar to that of most university lecturers. You must combine teaching with research and with management. On a day-to-day basis, you have to teach the theoretical and practical subjects assigned to you and plan and supervise the laboratory work of the students doing their final dissertations, Master's theses or PhD theses. Students must also be taught how to process, interpret and discuss the data obtained to prepare their papers or theses and articles for publication in international journals. Supervising PhD theses of pre-doctoral students in other countries (in my case, Panama, Tunisia, Morocco, and Mozambique) requires a greater effort than those in our team.

Another part of the work consists of attracting resources to do research, so I have to draw up project proposals to present to the different national and international competitive calls for proposals or attract resources through contracts with companies. I also have to dedicate time to proofreading articles, as I am a reviewer for several international journals, or to editorial work. In addition, there is the coordination of the research group, the coordination of courses and subjects I teach, and attending teaching and research meetings.
 

-The UXAFORES group comprises many researchers interested in forest management, wood applications, the impact of forest fires, and soil rehabilitation, among other things. What are your functions as a coordinator of the group? What is the importance of transversal and multidisciplinary research?

-We are a multidisciplinary team, with members belonging to three departments: Agroforestry Engineering, Plant Production and Soil Science and Agricultural Chemistry.

We have 15 permanent members, in addition to pre-doctoral contract staff and technical personnel. We also have national and international collaborators from universities, administrations, research centers, and companies. The coordination work focuses on looking for synergies and collaborations between the group members in different topics of interest within environmental and sustainable forestry management. The coordinator also acts as a liaison between the group and other external actors and, together with the group manager, is responsible for regular and detailed reporting on the group's progress, challenges and achievements and for maintaining accurate and up-to-date documentation of all activities.

We are a forestry and environmental group conducting research activities funded by public and company projects. Our research in this field ranges from soils (fertility, contamination, rehabilitation, carbon sequestration, waste valorization) to forest planning and management, forest modeling, silviculture, forest fires, forest health, mycological production, and the properties and applications of wood, which allows us to address very broad topics in this field.

The multidisciplinary research we can carry out is essential for the challenges facing sustainable environmental and forest management, trying to achieve a balance between environmental conservation, social welfare and economic development.

-One of your main lines of research is focused on reducing the presence of antibiotics in soils. You have recently published a paper on eliminating Azithromycin through pine bark, oak ash and mussel shells. How do these drugs end up in soils? What does the presence of these drugs in our soils mean?

-Antibiotics are widely used worldwide as therapeutic agents. Still, they are poorly absorbed, so a high proportion (up to 80%) is excreted in feces and urine and ends up in sewage sludge, in the case of those for human consumption, and the slurry pit, in the case of those used in veterinary medicine. Incorporating sludge or slurry into the soil can lead to the entry of these drugs into the environment, and depending on the soil's capacity to retain them, they can pass through water, into crops and enter the food chain. Their presence in the environment increases the risk of the emergence and spread of resistant pathogenic bacteria, which cause infections in animals and humans, thus affecting their health.

-You also do research on the use of bioadsorbents for the adsorption of emerging pollutants and heavy metals. What are these elements, and how do they work? What role do the circular economy and the use of waste play in the production and use of bioadsorbents?

-Soil can retain emerging pollutants such as antibiotics or other pollutants such as heavy metals, preventing them from entering the water, crops and thus the food chain. This retention capacity depends on the characteristics of the soil and those of the pollutant, so some soils have a low retention capacity for certain toxins. To increase this retention or adsorption capacity, waste materials or by-products with a solid capacity to adsorb them irreversibly, i.e. bioadsorbent materials, can be used. 

For example, these materials could be added to the soil or installed in sewage treatment units associated with slurry pits. We are using mussel shells, slope bark or biomass ashes, and waste/by-products that are abundant in Galicia and being studied by our research team in relation to the adsorption of heavy metals and antibiotics with very positive results. Some of these wastes/by-products, in our case mussel shells and ashes, can also act by correcting the acidity of acid soils in Galicia, improving their fertility on a physical, chemical and biological level. This also contributes to valorizing these wastes/by-products within a circular economy context, as they go from problematic materials to products of great interest at agroforestry and environmental levels.

-A few weeks ago, we spoke with your colleague Pablo Souza Alonso about soil health and the impact of intensive agriculture on it. How is the process of recovering soil damaged by this type of practice or other human activities?

-Recovering soil degraded by intensive agriculture and other human activities is fundamental to restoring its productivity and long-term sustainability. Soil degradation can manifest in loss of organic matter, erosion, compaction, increased acidity, salinization, contamination and loss of microbial biodiversity, among other problems. To restore these soils, integrated strategies can be employed to improve soil structure, water and nutrient holding capacity, and overall soil health.

When faced with a loss of the soil's capacity to produce goods and services, the first thing to do is conduct a soil analysis to diagnose the degree and type of degradation and establish recovery strategies. In any case, the incorporation of organic matter (manure, compost, crop residues...) is essential, as it improves soil structure, is a source of nutrients from its mineralization, increases the soil's capacity to store nutrients and give them to the plant when it needs them (called cation exchange capacity), increases water retention, adsorbs pollutants and prevents them from entering the food chain, and also promotes biological activity.

Balanced fertilization adapted to the crop's specific needs is also vital as it minimizes nutrient leaching and environmental pollution, thus promoting more sustainable agriculture. Also, as mentioned above, bioadsorbents based on waste materials or by-products, such as mussel shells, biomass ashes or pine bark, can be used to adsorb pollutants from the soil and improve soil quality. In addition to retaining contaminants, the first two can also act as soil acidity correctors. Soil conservation techniques, which reduce erosion and the loss of fertile soil, may also be used in some cases.

Therefore, restoring degraded soils requires sustainable agricultural practices combined with certain techniques to restore agricultural productivity, promote environmental health and ensure long-term resilience.

-As a society, what can we do to take better care of our soils? How can we act to conserve the properties that make soil such an essential element of nature?

-Caring for our soils is essential to maintain their productive capacity and ecosystem services. As a society, we can act responsibly to care for and conserve the properties of our soils. The first thing is to educate and raise awareness about the importance of soil, to give it its rightful place, and to know that without soil, there is no life. That is why soil must be part of the thematic content from the earliest stages of education; we must know its importance in acting responsibly. Educational programs and awareness-raising campaigns can also help spread knowledge about how to care for soils and why it is important. This includes farmers, who can benefit from training and technical advice to adopt more sustainable practices.

It is very important to promote sustainable agricultural practices to maintain the ecosystem services of soils, including (a) proper management of organic matter; (b) responsible use of fertilizers and pesticides, applying them in a balanced way and based on soil analysis to reduce nutrient leaching and environmental pollution, thus protecting water and soil quality; (c) crop rotation, which diversifies vegetation and improves soil fertility by interrupting pest and disease cycles; d) biodiversity conservation practices in agricultural systems such as vegetation strips or ecological corridors increase biodiversity (including soil micro-organisms and fauna), which is essential for maintaining processes such as organic matter decomposition or nitrogen fixation.

Public policies also play a crucial role in soil protection. Regulations that promote sustainable use and provide incentives for sustainable agricultural practices must be implemented. Policies that support soil conservation research can significantly impact long-term soil health.

Ultimately, caring for our soils requires an integrated approach that combines education, sustainable agricultural practices, proper fertilization management, biodiversity conservation, and effective public policies. If we act responsibly, our soils will maintain their services, such as healthy food production, climate regulation, or biodiversity support, ensuring their ability to sustain life and maintain environmental health.