Karst ecosystems from 2022 to 2024: what changed after the big fires

A new investigation by the Universities of Udine and Trieste shows the effects of rewilding on Karst ecosystems between Italy and Slovenia after the large 2022 fires. The research results were shared in a conference organised by Italy’s National Biodiversity Centre, funded by the National Recovery and Resilience Plan, and WILDCARD.

The 2022 Karst fires between Italy and Slovenia led to the loss, on average, of almost 50% of the biomass present in the area affected by the fire, with considerable differences depending on the composition of the forest. The fires were also favoured by the dry plant biomass accumulated following repeated dry summers. The forest, however, is already regenerating massively.

As far as animals are concerned, since the spring following the fire, burnt areas have been used intensively for food by some species of herbivores such as roe deer and hares, and less so by deer and wild boar, which are, however, increasing strongly in the non-fire areas. The various bird communities in the burnt areas also show changes compared to those in the non-affected areas.

These are some of the main results of the surveys carried out by the Universities of Udine and Trieste, with the support of Legambiente volunteers, on the territory affected by the fires that almost two years ago incinerated about 4,100 hectares of forest area between Italy and Slovenia. A balance of the situation was made on the 1st of March in the Italian town of Gorizia with the conference “Rising from the ashes? Ecological and management consequences and prospects of the 2022 Karst fire“. Speakers included scholars from various disciplines of the two universities and technicians from the Friuli Venezia Giulia Region’s Forestry Corps.

Credit: Sara Pischedda
Credit: Domen Stanič
Credit: Domen Stanič
Credit: Sara Pischedda
Credit: Domen Stanič
Credit: Domen Stanič

The forest and biodiversity – By combining ground measurements with satellite surveys, it was possible to quantify the extent of damage to the forest and the post-event reaction. The greatest damage was found in areas dominated by scotanus and manna ash, while downy oak showed greater resistance to fire. However, the forest is already vigorously reproducing through stump regrowth and seed regeneration, particularly where the fire intensity was lower. The specific post-fire composition is closely linked to the intensity of the event. The data, presented by Giorgio Alberti and Francesco Boscutti of the University of Udine, ‘show that species richness increases linearly with the latter, regardless of whether native or allochthonous (exotic) species are taken into account’. In addition, thanks to the surveys carried out, it was possible to investigate in detail the adaptive strategies implemented by the different species in regaining space after the event, highlighting functional traits that are profoundly different depending on the species and the characteristics of the environment after the fire.

Mammals – Specific research is currently underway to assess the presence and use of burnt and unburnt areas by medium and large mammals and their behaviour. Initial results show very dynamic and specific processes in different areas and for different species. In the spring following the fire, the burnt areas were used with great intensity by some herbivore species such as roe deer and hares for food, and less so by deer and wild boar, which nonetheless show a strong increase especially in the non-fire-affected areas. The golden jackal, a typical species of this area, where it shows very high densities, appears to be more present in the non-fire areas, although a few months after the fire it had shown an apparent increase in the frequentation of the area affected by the fires. For this species it seems interesting to understand the phenomenon that has affected the Gorizia karst, where there was a sharp increase in mortality from road and rail accidents in 2023, and whether or not this can be directly or indirectly linked to the large fires of 2022 and/or other factors The different areas compared in terms of the structure and composition of tree species, type of undergrowth and intensity of the fire they have suffered, show their own specific dynamics in terms of the presence of animals, as well as the behaviour of the animals detected with the phototraps.

The Friulian University’s Fauna Management and Conservation research group has been carrying out research on mammals in the area of the Gorizia and Trieste Karst for over ten years. “In this context,” explains the group’s coordinator, Stefano Filacorda, “the great fire of 2022 provided, in the dramatic nature of the event, an opportunity to study and compare the dynamics of the presence and behaviour of many mammal species present on the Karst”.

Habitats – Through the processes of ecological succession, fire-affected habitats can reconstitute themselves spontaneously, but climate change and the expansion of exotic and invasive species can lead to a change in the floristic composition, characteristics and dynamism of habitats. This is what emerged from the first monitoring results developed to analyse the consequences of fires on the species composition and dynamic processes of the main Karst habitats presented by Miris Castello from the University of Trieste.

Water in vegetation – The possibility of estimating the water content of vegetation remotely is fundamental for monitoring the risk of fire propagation on a large scale. In the Karst region, the NDWI index obtained from satellite images – which uses infrared wavelengths to monitor changes in the water content of leaves – was found to be correlated with water content measurements taken in experimental areas. Thus, Francesco Petruzzellis, from the University of Trieste, pointed out that ‘the development of a model for predicting the water content of vegetation specific to the Karst area could be a relevant tool for determining fire risk during dry periods’.

Woody species and fire risk – The fires of 2022 were favoured by dry vegetation biomass accumulated following repeated dry summers. The analysis of the water stress tolerance of the different native and invasive woody species present on the Karst, combined with the characterisation of the flammability of their biomass at different water contents, makes it possible, explained Andrea Nardini, of the University of Trieste, “to identify the level of fire risk associated with the presence and abundance of each species in future climate scenarios”.

The consequences on ornithological communities – Almost two years after the fires, the ornithological communities of the Italian and Slovenian Karst show changes compared to those present in non-affected areas. Davide Scridel from the University of Trieste explored which biological and ecological characteristics of each species may determine their position as ‘winners’ or ‘losers’. “Although burnt areas host fewer species and individuals,” Scridel said, “the effects vary between different species and habitats.

The contribution of the Forestry Department – The Regional Forestry Department of the Friuli Venezia Giulia Region operates at various levels in the regional system of forest fire protection. Dario Cancian, of the Regional Forestry Service and Corps of Foresters, explained that its operations “are not limited to the so-called ‘active fight’ against fires, but include forecasting and prevention activities, implemented through surveillance, land management, the granting of contributions and investigative actions. The survey of areas covered by fire and the collection of numerous data related to the events that occurred also contribute to research and statistical processing of the phenomenon’.

This text was originally published in Italian by the University of Udine