The bark beetle epidemic in the forests impacted by Vaia storm continues: as many trees are at risk as those felled by the storm.

In just two days, between 28 and 29 October 2018, 42,800 hectares of forest were damaged in 494 municipalities in Lombardy, Veneto, Trentino Alto Adige and Friuli Venezia Giulia for a total of two billion in damage between infrastructure, buildings and environmental heritage.

Five years ago, storm Vaia, with winds at speeds of over 200 km/h, destroyed in a few hours the seven-year working potential of all Italian sawmills put together and a forest heritage of inestimable value for the communities that live and care for those areas every day.

Bark beetle emergency: another storm

To date, the situation is still tragic: at least 25,000 hectares of forest and around 5 million cubic metres of timber have been damaged in the areas already devastated by storm Vaia. The cause is the bark beetle, a naturally occurring forest beetle that prefers spruce but can also attack other species. The insect digs tunnels under the bark, leading in a short time to the tree’s death, which dries up after losing its needles and bark. It usually chooses weak and brittle, crashed or broken trees, and the abundance of wood caused by the storm provided a fertile breeding ground for it. Once the dead and damaged trees decay too much, the insect population attacks the healthy trees, damaging the forest stands that had been saved. Thus, from an equilibrium situation, we move to a bark beetle epidemic.

Since 2019, an extensive monitoring network of the insect has been set up in the areas affected by the storm thanks to special traps scattered throughout the territory. To indicate an epidemic phase of the infestation, it is sufficient to count the number of insects per trap. Eight thousand insects per trap is a threshold value, but in many forest districts, this value is far exceeded. In the province of Trento, for example, average catches were above 8,000 in all forest districts, with averages between 20,000 and 30,000 insects per trap for 2022. In some specific districts, bark beetle damage has already doubled that of Vaia: for every tree felled by the storm, two healthy trees were attacked by the bark beetle. It is estimated that this emergency will take another five years.

The consequences for forests

There are many impacts, more challenging to quantify, that Vaia and the bark beetle have on the ability of forests to retain sediment, regulate water, protect against avalanches, guarantee clean water and good air, but also the value of the landscape, and recreational tourism, which are fundamental for many mountain economies that, thanks to the tourism system, represent a pillar of the local economy.

The epidemic brings with it several critical issues: expansion of outbreaks in the next few years, mainly because of the fragility of the surviving stands, expansion of denuded areas on entire steep slopes with a consequent accentuation of hydrogeological instability and ground instability phenomena, repercussions on the safety of paths and the landscape aspect, hence on the usability of the territory progressive impoverishment of the wood resource and disruptive effects on future forest planning and finally increased risk of infestation development due to weather situations favouring the insect, such as prolonged drought and higher average temperatures.

What are the possible solutions?

Against the bark beetle, the most effective form of control is the removal of crashed and infested material in good time. This stops the larvae in their development phase, although, unfortunately, this route is not always feasible. In reality, various approaches defined according to the context are applied. One can envisage clearing dead trees, removing them, or maintaining them to encourage the development of insects and animals antagonistic to the bark beetle and protect trees that are still alive. In contexts with human presence, intervention is necessary to mitigate the problem and favour the restoration of forest functions.
Various prevention and restoration interventions are helpful in the medium term (thinning in the densest forests with the elimination of the weakest trees; punctual planting under the bark beetle trees of other species suited to the local context but not attractive to the insect). In the long term, on the other hand, the multi-layered structure of the forest must be favoured: a forest structure capable of responding to both epidemics and climatic crises includes trees of different ages, species and functions.

Etifor, thanks to the wownature platform, enables public bodies, companies and individuals to actively support the owners of some of the affected lands on which action is urgently needed with on-the-ground economic, social and reforestation and environmental restoration projects.