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Adrià Descals’ study on phenology, vegetation and warming, Award for Relevant Doctoral Theses from the CSIC

Adrià Descals' award-winning thesis covers a variety of scenarios, taking global change as its axis and using images captured by satellite. Image: Sentinel-2 (Copernicus).
Adrià Descals' award-winning thesis covers a variety of scenarios, taking global change as its axis and using images captured by satellite. Image: Sentinel-2 (Copernicus).

In a situation of global warming, phenology becomes essential scientific knowledge to understand the environment’s behaviour in the medium and long term. Beyond changes as ephemeral and visible as the evolution of the colour of tree leaves, phenology studies the relationship between the cycles of living beings and the climate, linked to the annual course of meteorology in a specific place.

The doctoral thesis of CREAF researcher Adrià Descals Ferrando seeks to understand the phenological behaviour of vegetation and determine the climatic factors that limit its growth, given the situation of increasing temperatures in the world. The first conclusion – and the most simplified – is that the responses of vegetation to the rise in the thermometer are uncertain, which raises questions about its capacity to absorb atmospheric CO2 to compensate for its emissions. The thesis – titled “Spatio-temporal variability of vegetation phenology and its drivers at global scale“, carried out at CREAF under the supervision of Josep Peñuelas Reixach and Aleixandre Verger Ten – has received the CSIC Relevant Doctoral Theses Award in the field of global life. In total, in this second edition of the award, 20 theses have been awarded among a total of 190 applications presented, distributed in the areas of Life, Society and Matter.

The distinction recognizes the key work of researchers to advance scientific knowledge, in addition to contributing to advancing their professional careers. According to CSIC, “the level of the 190 applications received has been very high, which is a source of pride” and their quality, impact and relevance stand out.

“I will continue doing the same work, perhaps with a little more confidence that I am doing things right. In practice nothing changes: what motivates me about research is answering a question, not even publishing in prestigious journals”.

ADRIÀ DESCALS FERRANDO, CREAF researcher.

According to Adrià Descals Ferrando, the distinction implies “recognition of the immense effort involved in writing a doctoral thesis and, for that reason, I am very grateful and appreciate it, especially for the prestige of the entity that grants it”. And he assures that it is part of a professional journey marked by the will to grow in his scientific dedication. “I will continue doing the same work, perhaps with a little more confidence that I am doing things right,” he says. “In practice nothing changes: what motivates me to dedicate myself to research is answering a research question, not even publishing in major journals or receiving an award”.

CO2 absorption and heat waves

The work confirms that the capacity of vegetation to absorb atmospheric carbon may be saturated with future climate warming. And the reasons that explain this are radiation and water restrictions. This means that climate warming will limit the capacity of vegetation to absorb terrestrial carbon, to compensate for emissions into the atmosphere.

The work confirms that the capacity of vegetation to absorb atmospheric CO2 can be saturated with climate warming, as well as that heat waves accelerate leaf fall in deciduous forests.

The results of the thesis demonstrate different spatial restrictions on both temperature, light and water availability at the beginning and end of the growing season, suggesting that vegetation phenology will respond heterogeneously to climate warming depending on location and climate.

In direct connection with phenology, the thesis confirms that heat waves are advancing leaf fall in deciduous forests, demonstrating that these impacts are more recurrent than previously thought.

Global change via satellite

Adrià Descals’s research covers a variety of scenarios, taking global change as the axis and using images captured by satellite. His study developed innovative algorithms to characterize phenology with high-resolution satellite images and using new cloud computing platforms. For this reason, he integrates interdisciplinary knowledge and methods in remote sensing, global ecology, cloud computing, big data and machine learning, keys to processing large amounts of data obtained via satellite in all chapters of the thesis.

Descals has developed innovative algorithms to characterize phenology with satellite images, integrating interdisciplinary methods in remote sensing, global ecology, cloud computing, big data and machine learning. All documentation generated has been published under open science licenses.

The data and maps produced were published under an open license on Zenodo and Google EarthEngine and include, among others, the first high-resolution phenology map in the Arctic and global phenology maps for the period 2001-2021. In addition, to guarantee transparency and the ability to replicate, the computer code generated during the thesis is also available on GitHub. Another notable result is the publication of the first algorithm to estimate phenology maps from high-resolution satellites (Sentinel-2). Of the six publications derived from the thesis, four articles were published in open source journals and one of the collaborations led to him signing as first author in the scientific journal Science.

The CSIC distinction recognizes the key work of researchers to advance scientific knowledge, in addition to contributing to advancing their professional careers. According to what was stated by the Consejo Superior de Investigaciones Científicas, “the level of the 190 applications received has been very high, which is a source of pride for the institution”, given that the selected works stand out for their quality, impact and relevance.

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