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Assisted Natural Regeneration, a complementary solution to tree planting to restore degraded forests


Assisted Natural Regeneration (ANR) is a complementary solution to planting. This solution consists of a soft forest management method that preserves and strengthens existing forests through forest maintenance work that respects and mimics the natural reproduction cycle of trees. This method favors the progressive regeneration of the forest and thus the preservation of biodiversity and the carbon storage function of the soil throughout the process. Within a degraded forest plot that needs to be restored, how is the choice of silvicultural itinerary made between planting, ANR or a combination of these two solutions? In concrete terms, what does ANR work consist of? Why is ANR becoming more and more popular? These are some of the questions that Reforest'Action, an expert in forest restoration around the world, can answer.

What is ANR?

Assisted Natural Regeneration (ANR) is a method of restoring forest ecosystems that consists of intervening in existing forests that show signs of regeneration, but that are insufficient to guarantee the renewal of the forest and the conservation of its ecosystem services. It is a soft method of silvicultural management that respects the natural cycle of the forest, preserves the soil and the existing biodiversity, and is less expensive than planting.

In concrete terms, what does the ANR work involve?

In concrete terms, ANR work involves identifying young shoots of different species already naturally present in the soil, and protecting them so that they can grow, by eliminating obstacles that threaten their growth. The assisted natural regeneration of a forest takes place over time and requires about fifteen years. It makes the forest more diverse and resilient in the future.

Respect and mimic the natural reproduction cycle of trees

In the spring and summer, the forest ensures the fertilization of the trees through flowering. The fruits that appear later fall from the tree when they are mature. The seeds contained in the fruits are lodged in the soil and germinate when the ideal conditions of light, temperature and humidity are met. These seeds give rise to numerous tree seedlings a few centimeters high. However, depending on the size and density of the adult trees above the seedlings, the seedlings may lack space and light, preventing them from growing.

The accompaniment of the forester in the regeneration of the forest

Within the framework of an ANR project, the forester accompanies the forest to allow it to regenerate under optimal conditions. His objective is to encourage young shoots of good quality and to provide them with the necessary light and space, so that they develop as well as possible. While taking care to maintain minority species to preserve the diversity of the forest, work is also done to orient the selection of species in favor of those that have a better probability of evolution and are the most adapted to climate change. To do this, the forester will carefully observe the evolution of the forest and carry out over time various forestry works (clearing, pruning, removal of aging trees...) that will allow the most promising shoots to grow thanks to the gain of space and light.

Why is ANR preferred in some degraded forest plots?

The choice between the planting method or the ANR method depends on the type of forest plot and the history of the forest to be restored. In France, and more generally in Europe, the challenge is to deal with forest degradation, not deforestation, which implies bare plots. In the face of worsening natural and climatic hazards and their increasing frequency, ANR, when the situation permits, appears to be the most suitable method for restoring degraded forests. The financing of ANR work also encourages longer cycles and more sustainable management. It is therefore common for Reforest'Action to support ANR projects in temperate zones.

In what situations is tree planting necessary?

ANR work cannot take place in a plot that does not have the capacity to regenerate naturally, i.e., a plot that is devoid of seedlings from the fallen seeds of mature trees. In addition, some forests require the incorporation of new species to enable them to adapt to climate change and better cope with drought and disease. The planting of trees from nurseries is therefore necessary, as well as in parcels severely degraded by fire or insect attacks, which cannot regenerate naturally. In some cases (e.g., drought-affected forests), ANR can be combined with stand enrichment by planting a variety of species.

When and why should ANR be used to regenerate a forest?

ANR is favored to accompany the lengthening of silvicultural cycles within the framework of a more progressive management, and to regenerate degraded stands that still show signs of natural renewal. This method promotes the growth of young shoots and ensures a mix of species present in the plots, with the aim of improving biodiversity and the resilience of the forest to hazards and diseases. In terms of impact, ANR is the most gentle method and respects the natural reproduction cycle of trees. It allows to enhance what is already existing to preserve and strengthen the forest heritage. Compared to planting, ANR has a more favorable impact on the preservation of biodiversity and soil.

What are the benefits of ANR?

ANR plays a critical role in achieving global climate, biodiversity and ecosystem restoration goals. According to World Resources Institute (WRI) estimates, forests can be restored through ANR at less than one-third the cost of planting, more quickly and with a greater chance of success by leveraging what is already existing.

ANR is more suitable than planting in certain situations

Within plots already showing signs of natural regeneration, ANR is more suitable than planting to restore forest ecosystems. In France and in Europe, where forests are affected by degradation due to climatic or natural hazards, it is frequent that a forest plot is partially affected by these hazards but still shows signs of regeneration. In this case, ANR is relevant to support this regeneration. It is also possible to opt for a combination of ANR and planting to preserve and restore degraded forests.

ANR is more viable and less risky than planting

In a forest restoration project through tree planting, the risk of tree mortality is higher than in a ANR project, which aims to protect future trees already present in the soil as young shoots, and which are carefully identified by the forester to increase the success of the project. The ANR also makes it possible to avoid shortages and fluctuations in the price of seedlings in nurseries, as well as the increasingly frequent and violent climatic hazards, such as droughts or floods, which sometimes penalize traditional planting projects.

ANR makes it possible to strengthen the multifunctionality of forests without disturbing their natural cycle

ANR avoids clear-cutting and bare soil, thus preserving biodiversity and the carbon storage function of soils throughout the process. Within a ANR project, Reforest'Action also encourages foresters to leave volumes of dead wood within the plot, so that they can contribute to the development of biodiversity of fauna and flora. In this way, ANR helps to reinforce the multifunctionality of forests - that is, all the environmental, social and economic benefits they produce - without disrupting their natural cycle.

ANR is an eco-responsible approach to forest management, which allows the restoration and strengthening of forest ecosystems. On the one hand, this method avoids clear-cutting and bare soil, and favors the progressive regeneration of the forest, thus preserving biodiversity and the carbon storage function of the soil throughout the process. On the other hand, it allows for the recreation of true multifunctional forests, which are sources of many benefits beyond the maintenance of biodiversity: wood production, carbon storage, regulation of the water cycle...

At Reforest'Action, the diversity of solutions meets the diversity of forest needs, with common objectives: to make forests more resilient, to develop their multifunctionality, and to preserve and develop the carbon and biodiversity sinks of tomorrow. ANR therefore fully corresponds to the environmental and ecological ambitions of Reforest'Action and the foresters with whom we collaborate. Our objective is to accompany the ANR approach over several years within our projects to ensure their proper development, while prioritizing the diversity of tree species represented within the regenerating forest.