Nathalie Bréda: managing and adapting forests to impending pressures and challenges

Nathalie Breda’s professional career began following an open house day at the INRA centre in Champenoux (near Nancy). “I toured the centre for a whole day, learning about everything from the seeds used in reforesting to evaluating plank quality. The researchers in each lab were so passionate that I found everything interesting. That was where I wanted to work.”

With her forestry engineering degree in hand and after completing a thesis on forest ecophysiology on the response of oak trees to drought and thinning, Nathalie joined the Joint Research Unit for Forest Ecology and Ecophysiology (INRA, Henri Poincaré University) as a researcher. In early 2018, the unit became SILVA (INRAE, Université de Lorraine, AgroParisTech), where Nathalie works in the EcoSilva team (Ecology of little anthropised forests and ecosystems).

Nathalie served as the deputy head of the Forest, Grassland and Freshwater Ecology (EFPA) division from 2010 to 2013, and then ran the INRA metaprogramme Adapting agriculture and the forest to climate change (ACCAF). By shifting her attention to non-forest agricultural ecosystems, she has been able to test the general applicability of the concepts of adaptation to change and crisis resilience.

Tackling new challenges in forestry research

Today, Nathalie shares her experience with her colleagues to help them take on new challenges facing forestry research: developing sustainable production within ecological systems wherever possible, analysing and managing crises to increase collective capacities for advance adaptation, and characterising and optimising the services provided by forests and natural environments. The recent climate context has made these issues more prominent.

Trees that are both resilient and vulnerable

The resistance of trees and their growth performance is her main research focus: “We look at the growth rings in the tree trunk to determine the years where growth is disturbed. Problems may appear during several successive years or be a one-time issue. In this case, a narrow annual ring means that the tree hardly grew at all. After the droughts of 2003 to 2005, many dieback cases were studied for the project DRYADE – Vulnerability of forests to climate change: from trees to bioclimatic areas (ANR, 2007-2011), which Nathalie coordinated. Direct forest productivity losses were evaluated for the different species in French forests. But the most original findings had to do with mortality. “Within a stand, we were able to show that the trees that were most vulnerable during droughts and did not survive were often those that had grown most either in their early years or in the years before the drought.” This is a puzzle for foresters and geneticists, who have always sought to produce the best-growing trees. With the spreading climate and biotic crises, the aim is to now balance growth performance and drought resistance when selecting trees.

Complex ecosystems exposed to multiple pressures

Nathalie works mainly in natural conditions, where there are multiple pressures, complex interactions between communities and considerable diversity. “That’s what is so exciting. Each new dysfunction questions our knowledge and tests the generality of the mechanisms we study.” Changes – sometimes long established – in practices, forestry, fertility or climate and pest-related pressures are dissected, dated, quantified and ranked. A rigorous investigation is carried out to find the cause(s) of the dysfunctions and tree deaths. “Sometimes, the most difficult thing,” says Nathalie, “is to understand the mechanisms behind the extraordinary capacity of ecosystems to recover – what we call resilience.” Her work has also shown the nearly systematic involvement of water deficit episodes in triggering dysfunctions. For several years now, her team has been creating online tools such as BILJOU© which others can use to better understand the concepts and calculate forest water balances. Soon, maps of water deficits calculated since 1959 will be published on this website so anyone can find the characteristics of the drought episodes in a particular forest.

Using teamwork to leverage diverse disciplines and partnerships

Forest ecosystem complexity requires harnessing a wide range of technical and scientific skills. “This is a real challenge for moving our research forward. Getting geneticists and ecophysiologists, ecologists and foresters, pathologists and bioclimatologists, modellers and statisticians to work together is difficult but incredibly effective! And we also work with non-scientific partners: forest managers, departments responsible for forest inventories and health surveillance, etc. This is what modern ecological research is all about.” 

On a more personal level, Nathalie used her many skills to help produce the updated and enhanced edition of the guide to managing health crises in forests, alongside the French National Forest Office (ONF), the Department of Forest Health (DSF) under the French Ministry of Agriculture and Food, and the Joint Technology Network for adaptation of forests to climate change (RMT AFORCE). She has also been involved in INRAE foresight studies on risk. Finally, she recently participated in drafting the roadmap on adapting forests to climate change for the Ministry of Agriculture and Food.

Rethinking forestry and forest management in an uncertain context

The recent findings by Nathalie’s team on tree and stand vulnerability imply major consequences for private and public forest managers. Despite climate uncertainties, changes are underway and forest ecosystems will have to adapt spontaneously, sometimes at the expense of sudden deaths during extreme events such as storms, droughts, epidemics and pest outbreaks. “Our aim is to help managers make the right choices so they can support these changes now, by promoting planned adaptation rather than just reacting during crises, and by transforming our forests when the soil and climate conditions are or will be too difficult for the established ecosystems.” Certain compromises will have to be made regarding some forest functions, which are productive, diverse and sustainable.

Recognition for enthusiastic commitment and pragmatic responses

The constant questioning that characterises the life of a researcher is not always easy, but it is what drives Nathalie, who happily throws herself into her research with the same passion she brings to her public outreach activities.

A subtle mix of research and purpose

Nathalie’s eagerness and her commitment to science and its dissemination earned her the Researcher’s Award from the Lorraine Regional Council in 2004. “The Lorraine region told me that they appreciated this subtle mix of research and purpose. This award recognised the approach that INRAE is taking more generally in its research.” In 2006, she was once again honoured for the innovative interdisciplinary approach she developed to explain forest dieback and determine the essential role of drought when she received the Jean Dufresnoy Prize from the French Academy of Agriculture. Her team received the Science and Society prize from the Lorraine region in 2015 and the educational innovation prize from the Meurthe-et-Moselle Academy in 2016 for their involvement in a citizen science project called “Survivors” with secondary school students, based on a scientific programme on the mechanisms implicated in beech tree survival.

She is modest when she speaks of these accolades, forgetting even that she was named a Knight of the French Legion of Honour in 2015 for her scientific commitment in the field of forest adaptation to climate change. What she enjoys most is sharing science with those around her.