César Pérez Cruzado: «Slight changes in forest management can greatly affect the global balance»
Why do forests already play a critical role in the fight against climate change? Why is it so essential to understand and take care of our forests? How can trees help us to capture carbon? César Pérez Cruzado, Ph.D. in Forestry Engineering and head of the Laboratory on Forest Monitoring and Carbon Projects of the Projects and Planning research group (PROEPLA) of the Department of Forest Production and Engineering Projects of Campus Terra, addresses each of these questions with a fantastic pedagogical vocation.
To understand his reflections, to reflect on them, is an exercise that is more than recommendable. His work matters to all of us for its social relevance and ability to provide solutions to one of those problems that no one can avoid: in short, what we are doing with our planet.
After four years working as a researcher at the University of Göttingen, within one of the most relevant research groups worldwide in the field of forest monitoring, in 2016, he rejoined the Universidade de Santiago de Compostela, first with a Juan de la Cierva contract, then with a Marie Skłodowska-Curie Action of the European Commission and finally, in 2020, with a Ramón y Cajal contract, the governmental program to recover talent.
Today, he devotes his time to understanding how to monitor and manage our forests, sequester carbon, and develop methodologies that contribute to building a better, more viable planet. It is a titanic task that he combines with his 4-year-old daughter, the mistress of his free time, with whom today, like so many parents, he shares hobbies and experiences.
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-After finishing your doctoral thesis at the University of Santiago in 2011, you packed your bags and traveled to Germany for postdoctoral research. What motivated you to choose the University of Göttingen?
-Before going to Germany, I spent a year as a Postdoctoral Researcher at ICIFOR-INIA of CSIC in Madrid, working, among other things, on the scientific assignment of the Ministry in the National Forest Inventory. That was my first contact with large-scale forest monitoring.
In 2012, I applied to a selection process at the University of Göttingen for a contract as a teaching and research staff in the Department of Forest Inventory and Remote Sensing, and I was lucky enough to be selected. What motivated me to apply for this position was the possibility of working in one of the best research groups in the world in the field of forest monitoring and maintaining the link with university teaching.
This experience in Germany has been enriching professionally, as it has allowed me to work on international projects of great responsibility, such as the design and implementation of National Forest Inventories and carbon sequestration projects on a massive scale in Europe, South America, Africa, and Asia. The German research system is very committed to young researchers, which allowed me to gain experience directing research projects as a principal investigator, which would have been very difficult in Spain. In addition, German universities have a high degree of internationalization in their teaching, which has also been a very instructive experience.
-Getting a Ramón y Cajal contract allowed you to create your research laboratory at Campus Terra in 2020, associated with the PROEPLA group at the Polytechnic School of Engineering. What projects are you currently focused on?
-One of the most exciting aspects of the Ramón y Cajal call is the possibility of establishing emerging research lines in already consolidated research groups. In my case, I joined the Projects and Planning research group (PROEPLA), where I was allowed to establish a Laboratory on Forest Monitoring and Carbon Projects.
We are currently six people working on these lines of research, and we have research projects related to carbon dynamics in forest systems, forest management oriented to carbon sequestration, reverse mining, and development of methodologies for carbon quantification and establishment of baseline in improved forest management.
We also have research projects related to forest monitoring at various scales, including a development project on designing and implementing the Continuous Forest Inventory of Galicia. We have also participated in large-scale projects with FAO on monitoring carbon emission reductions in managed forests and with the United Nations Intergovernmental Panel on Climate Change to establish methodologies for greenhouse gas inventories.
-In recent years, there has been an increased interest in forest monitoring systems. Why do you think this is?
-The field of forest monitoring has traditionally been immobile because comparability with historical estimates has taken precedence over the improvements that changes in methodologies and technologies could bring.
However, during the last few years, there have been such essential advances that practically all forest monitoring systems are being renewed. These changes are ultimately driven by society's increasingly demanding need for information on forests.
This means that the European Commission has recently promoted a common regulation for the EU that requires significant changes in the National Forest Inventories, an important scientific challenge for the research groups in this area. In addition, forest monitoring systems have become critical elements for the entry into carbon markets, so there is an increasing interest in having these types of tools.
PROEPLA has become a reference in forest carbon cycle monitoring. What technologies do you use daily, and what innovations could revolutionize this field in the coming decades?
-We have specialized in inference modeling, an area that is entirely new in its use in forest monitoring systems and has many advantages over classical inference methods. We have also made significant advances in terrestrial remote sensing for forestry applications, mainly through terrestrial laser scanning (TLS), and we are starting to work with synthetic aperture radar.
We are currently in a period of change in all monitoring systems, leading to a high demand for innovation from the sectors concerned, not only in the forestry and environmental fields but in many others as well. Incorporating these innovations to their full extent will require changes in the training programs of universities since some of the contents are outside the curricula of their degrees.
-How could forest management improve carbon sequestration? This is a critical task because of the climate crisis facing the planet.
-Forest management has great potential for carbon sequestration. To give some figures, annual global carbon emissions from fossil fuel consumption are 4.5 Giga Tons of C per year (GTmC/year). In contrast, the yearly photosynthetic capacity for carbon sequestration would be 110 GTmC/year, which should discount the respiration of living beings, the decomposition of organic matter in the soil, and deforestation and forest degradation, among other factors.
Overall, there is a negative annual balance of 6 GTmC of emissions. The potential of forest management in the carbon cycle is, therefore, very large since the net yearly balance of emissions is 5.45% of the photosynthetic potential, so slight changes in forest management can significantly affect the global balance.
These numbers invite optimism, but it is unrealistic to suggest that all carbon sequestration efforts should be directed to forestry since carbon neutrality requires reducing emissions in other sectors that are transparent emitters, such as transport or energy.
-Does the age of the trees influence carbon capture and storage? And the species?
-Both factors have an influence. Generally, the older a tree grows, the more carbon it captures, so maintaining forest stands in active growth states is conducive to carbon sequestration. But it is not only the absorption that is important in the process but also the permanent fixation of this carbon.
In this respect, mature stands play an essential role because of the co-benefits of such stands, but so do the forest products generated based on forest management. There are management systems where the most significant carbon sequestration occurs via forest products, both because of the carbon retained in them and the substitution effect on alternative products with more unfavorable carbon balances.
-How is it determined how much carbon a tree sequesters and for how long it stores it?
-The procedures for estimating carbon in any sector are defined in the greenhouse gas inventory guidelines of the United Nations Intergovernmental Panel on Climate Change, a document in which we have participated in the development and scientific review. These guidelines also establish different methodologies depending on national competencies and the availability of information.
In the case of Galicia, the highest level of detail (Tier 3) would be applicable, so the estimation of carbon in trees is carried out employing models that first estimate the biomass in different fractions and then transform these values into carbon based on coefficients that vary slightly depending on the species and the fraction. The retained carbon time depends on managing the forest stands and the products generated from them so that no generic value can be given.
Generally, the highest values of permanence are given by using and promoting forest products. The carbon accounting process in forestry projects is typically complex and depends significantly on the specific mechanisms of the carbon sequestration projects. One of the lines we have open right now is the development of calculators for carbon sequestration projects. We have been working with Wageningen University (Netherlands) since 2009.
-Machines capable of capturing carbon have already been developed. What advantages and disadvantages do they have over trees?
-The main advantage of these artificial procedures is the permanence of the carbon, which is much more manageable than carbon sequestered by natural processes. These synthetic sequestration processes must be combined with long-term sequestration plans through reverse mining-type projects.
We are currently participating in a research project on this topic. However, artificial carbon sequestration processes have many uncertainties, such as their high energy consumption, their limited capacity to act on atmospheric carbon stocks, or the interactions between the chemical form in which the carbon is stored and natural systems.
-What challenges will you face in your discipline in the coming years? Within forestry engineering, what profiles will the market demand?
-The biggest challenge is the lack of qualified personnel at all levels. There is a very high demand for forestry engineers, which graduates from engineering schools do not cover. Even foreign forestry engineering consulting companies are conducting recruitment campaigns in Spain due to the need for more professionals at the international level.
The next challenge, in order of importance, is the adaptation of the contents of forestry engineering degrees to the advances that have taken place during the last years in central topics of the degree. These changes are essential since the most technical profiles are in demand.
-And finally, how did your interest in this field arise?
-Positive experiences create vocation, and they are contagious. I have been fortunate to have had professors in subjects related to my field of work with a tremendous vocation who have been able to transmit to me their passion for the specific subjects of forestry engineering.