Seeing and managing forests as functional complex networks – an interview with Christian Messier

In September 2017 I participated to a very dynamic field-week that took place in Tuscany, Italy. Here international students had the chance to discuss new concepts in forest management, such as viewing forest ecosystems as complex adaptive systems. One of the organisers, Prof. Christian Messier form the University of Quebec, recently published an article proposing a novel approach for managing forested landscapes at multiple spatial scales.

First, thank you Prof Messier for this interview and for sharing your expertise with the readers of Forest Monitor. You have been recently appointed with the prestigious Canada Research Chair in Forest Resilience to Global Changes. Can you tell us what is the focus of your research and why is it crucial in these uncertain times? 

Yes, the Canada Chair aims at increasing our understanding of the current and future threats to forests, both biotic such as exotic insects and disease and abiotic such as pollution and climate change, and to develop management practices that could increase their resilience. The aim is not to predict all possible threats since many are very uncertain or unknown, but to consider different possible scenarios (even the worst one) and develop management plan accordingly. Me and my team of post-docs and graduate students are trying to demonstrate that forest management, through the harvesting of trees, could be used for improving its resilience and not only to harvest trees to make money and to establish tree species that industry or foresters think are important.  To do so we are using simulation models and the latest tools and approaches in spatial and functional ecology.

Based on your experience, what are the major challenges for forest ecosystems in the near and long-term future? 

Well, this should be obvious from the title of my Canada Chair. I believe that our forests are under threats from a multitude of factors such as fragmentation, pollution, rapid climate change, inadequate forest management and new invasive insects and pests that results from our increase globalization. I co-wrote a paper a few years ago with David Lindenmayer about how to avoid forest ecosystem collapse in the world because we both felt that many of our forests are losing their resilience due to the simplification of our managed forest and the increasing threats I just mentioned. We need to reverse this trend otherwise I am afraid that we will see an increase in forest ecosystem degradation all over the world and that we will not have the time and/or money to intervene to reverse it. It is much less costly to avoid a collapse than to reserve it, so I believe it is URGENT to use forest management to increase resilience before it is too late.

Now, let’s enter the topic of your recently published paper. Can you tell us in brief why do you think forest resilience can be improved by managing forests at landscape scale and by seeing them as functional complex networks?

The idea of using functional complex network to improve forest resilience is based on my belief that we cannot intervene everywhere on the landscape to increase resilience where forests are currently threatened by climate change, exotic pests and diseases and their abusive simplification. So, by knowing how different patches of forests are functionally connected (through seed dispersal) and what functional traits (important biological characteristics of trees) might be missing at the landscape scale to make the landscape as functionally diverse as possible, we can then intervene efficiently to make the territory more resilient to know and unknown threats. The approach allows us to determine how and where to intervene most efficiently in the landscape to facilitate an efficient and rapid recovery of the forest if and when catastrophic disturbances will hit. Because, I do not believe the question is if, but when and where these catastrophic disturbances will hit. I often used the word “immunization” to describe the approach. Using a functional complex network approach, one could determine which areas in the landscape should be managed in priority to have the most effect like when we want to immunize a population against a disease, we first target those individual the most connected so to reduce the spread of the disease.

In 2005 you started an ambitious research project to manage large forest units based on the principle of functional zoning (TRIAD). The approach has been very successful, and it now widely applied in forest management plans in Quebec and other Canadian provinces. How the approach based on the functional complex network differ from this?

The functional zoning or TRIAD approach is a relatively old idea that I was able to test operationally in a large territory in central Québec. The basic idea is that one might be better able to achieve our multifunctional objectives in a large landscape if we do not try to achieve the same level or type of multifunctionality everywhere. So, in a TRIAD approach, a part of the landscape is protected, a part is allocated to intensive forest management and the largest part is allocated to extensive low intensity forestry. When I started to work on this project, I was not familiar with complexity and complex adaptive system and so now we are trying to adapt the TRIAD approach to incorporate functional complex network, adaptive complex system and uncertainty into our approach. I believe that the functional complex network approach can be very useful to implement a more resilient TRIAD approach where the three functional zones are located in the landscape in a way that maximize functional connectivity and modularity of the landscape. I believe that both approaches can be merged to facilitate multifunctionality and increase resilience to global change factors.

(a) Conceptual diagrams of forestry operations that can be applied at multiple scales (stand, ownership, landscape) and (b) view of the landscape as a functional complex network composed of nodes (stands) and edges (functional links) in which a harmonised management plan could enhance resilience by increasing functional diversity, connectivity, centrality and modularity. Modified from Messier et al. 2019.

Harmonising multiple silvicultural practices in large landscapes sounds exciting but perhaps quite challenging in the real world. What can we do to achieve this objective? What tools can we use to assess multiple scenarios and management strategies?

Yes, this is very challenging and one cannot do that without some help. This is where simulation models come handy! There are now many good simulation models that have been used and tested today and we parameterized one for the area. We were then able to evaluate how different scenarios and management strategies affected the most important ecosystem services that forests provide. By doing that, we showed that TRIAD scenarios were better at providing multiple ecosystem services compared to non-TRIAD scenarios. Simulation models are not the reality but they can help forest managers evaluate different scenarios over long period of time BEFORE implementing one in the field.

To conclude, in 2017 you were awarded the “Humboldt Research Award” by the Alexander von Humboldt Foundation that funded stays in Germany and travels in Europe and gave you the possibility to foster your collaboration. Do you think that also scientific research should be seen as a functional complex network and how important is networking for you in research? 

Ah, ah! Yes, indeed human interactions are like a complex network and one important objective I have been trying to do in my career is to foster exchanges and collaborations among researchers all over the world. My stay in Germany has been important in strengthening another important forest research node (Germany). We can always learn from others in the same field in other country, but also from others in other fields. So, I see networking as multi-dimensional where by working with researchers from various countries and from different research fields or disciplines we then create a kind of rich functional network of research ideas and students that help us foster a more innovative and resilient research environment world-wide.

Christian Messier is professor of Forest Ecology and Urban Forestry and scientific director at ISFORT at the University of Quebec, in Canada (UQO and UQAM). He obtained his PhD from the University of British Columbia, followed by a post-doc at the University of Helsinki. His research interests range from the basic understanding of tree growth and mortality, forest community and ecosystem functioning to decision-making tools to better manage and conserve natural and urban forests. He has published more than 300 referee papers, reports, book chapters and books. He holds an industrial-NSERC research Chair on tree growth since 2010 and a Canada Research Chair on the resilience of managed forest to global change since 2017.

Read here the open access paper:

Messier, C., Bauhus, J., Doyon, F., Maure, F., Sousa-Silva, R., Nolet, P., Mina, M., Aquilué, N., Fortin, M.-J., Puettmann, K. (2019). The functional complex network approach to foster forest resilience to global changes. Forest Ecosystems. 6:21.

Main photo: The complexity in species and functional traits of southern Quebec’s forests. Author of the photo: Marco Mina

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