Hotspot Italia

“The flora of neglected lands is not exclusive of its natural parade. It may host all the exotic pioneer flora that are compatible with the environment” [Gilles Clement]

Hotspot Italia is an ongoing investigation into the transformation of the Italian landscape, which constantly changing territory becomes more and more extreme and less welcoming. The research focuses specifically on the phenomenon of migration of plant, animal and bacteria species towards certain contexts, both native and invasive, where thanks to the alteration of climatic and environmental factors they found the conditions to develop and “occupy” parts of the landscape.

The evidence of the climate crisis is not the same in every part of planet Earth. There are “hot spots”, the so-called areas in which the consequences and effects of global warming are more perceptible and create more evident territorial transformations. Italy, due to the morphology of the territory and its particular geographical position, is considered one of these “environmental indicators” at a global level. The increasingly extreme weather conditions, with extended periods of drought and rainfall concentrated in a few days of the year, create the conditions for a radical landscape transformation. The metamorphosis is already underway, and it is possible to describe this transformation through catastrophic events.

Those dramatic events reflect the fragility of the moment we are living in and, at the same time, they show us the ability of nature to transform itself continuously, leaving room for other organisms to settle and replicate. The species analysed include Salicornia veneta, Xylella fastidiosa, and Ips typographus (commonly named bostrico). By exploiting the complexity of the analysed topic, Hotspot Italia wants to foster a reflection on environmental changes and outline a long-term research project within the landscape discipline.

1. Ips typographus (bostrico, bark beetle)

The bark beetle, known in Italy as bostrico, has become a phenomenon in recent years, considered responsible for one of the biggest epidemic infestations of forests in northern Italy. Its uncontrollable spread began right after the Vaia Storm in 2018, initiating a progressive mass extinction of trees that resulted in severe economic and natural losses. As an insect, it plays an important role as a wood decomposer, contributing to the healthy and natural management of the spruce forest ecosystem. It enters the inner bark of often damaged and weakened trees, creating labyrinths of tunnels where it reproduces. Native to coniferous forests of northern Asia and Europe, it naturally occurs in the alpine spruce forests.

However, the scale at which it appeared in the Italian Alps was so extensive that it quickly became labelled an invasive species. Several reasons behind the recent epidemic make up a more complex picture of the bostrico issue. Trees left on the ground after the Vaia storm provided a substantial environment for intense reproduction of bark beetles, which in time began to attack healthy trees as well. Rising temperatures and water stress related to climate change led to higher rates of beetle breeding, significantly affecting the already weakened and vulnerable natural defence mechanisms of trees as a consequence of Vaia. This chain reaction also had its roots in the monocultural structure of alpine spruce forests, planted after the Second World War to provide a raw material. As the spruce species is the main target of bark beetles, such a forest is naturally less resilient to natural events compared to a diversified one.

From a natural perspective, the bark beetle invasion may appear as an environmental adaptation strategy for a changing climate. A regular Bostrico invasion lasts 5-6 years, meaning that as of 2019, the peak has already occurred, and the epidemic in the Italian alpine area is on a downward trend. However, as the climate crisis becomes more tangible, the frequency of natural disasters and epidemics may increase in the coming years. The question of management strategies seems urgent, as does questioning the perspectives we have towards it.

2. Salicornia veneta (glasswort)

Salicornia veneta is a pioneering plant in lagoonal landscapes of the North Adriatic, particularly in Veneto, Emilia-Romagna, and Friuli-Venezia Giulia. During its short flowering period at the end of summer, it gradually changes colour from green to red, giving exclusive characteristics to the scenery where it appears. It occurs in limited quantities and has been included in the Annexes of the Habitats Directive for protection. Although it is not at risk of extinction, monitoring activities are carried out due to its unique and rare distribution. The recognition of Salicornia veneta as a distinct species is relatively recent, tracing back to 1969 when it was formally characterised by Sandro Pignatti and Duilio Lausi. This plant was initially spotted in the Venice lagoon, and subsequent studies revealed its substantial presence in the Friulian lagoon.

Glassworts lack what we typically think of as “real” flowers, instead they exhibit spike-like inflorescence. Differentiating Salicornia veneta from other salicornia types isn’t straightforward, however specific features render it genuinely distinctive and the key factor is its annual cycle. It emerges, produces fruit and flowers in late summer, undergoing a reddish transformation – this period serves as the optimal moment for unequivocal identification.

Due to climatic changes and the consequent lowering of the Po River’s harbour, which has become increasingly dry, we have witnessed the advancement of saltwater intrusion phenomenon, with disruptive effects, especially in the area of the river’s delta. During the period of the sea’s “rise” in the hinterland, mainly in the Po delta area, salicornia has managed to adapt to this territory through inland migration. The elevated internal osmotic pressure of the plant contributes to its great ability to absorb water from the ground and thrive in highly saline environments. This leads to an uncommon situation where salicornia begins to settle in previously unoccupied areas affected by the ebb and flow of seawater, raising interesting questions about the future of this species in the Venetian lagoon and its impact on the vegetation in the hinterlands.

3. Xylella fastidiosa (Philaenus spumarius, olive spittlebug)

Xylella fastidiosa became a focal point of attention when it was found infecting olive trees in Puglia in 2013, causing the death of thousands of trees in the following years. The significant economic and cultural heritage loss had an impact on further treating the endangered area and investigating the bacteria. Xylella is considered a plant pathogen that affects the water transport system, leading to disease and withering. In the Italian situation, it has been termed olive quick decline syndrome (OQDS). It originated in Costa Rica and entered Italy through infected coffee plants imported for ornamental purposes. The bacteria can affect various plant species, including citrus, almond, peach, and oleander trees, and it can be transported only by vector insects.

Philaenus spumarius, commonly known as the meadow spittlebug, was the primary cause of the Xylella epidemic spread in southern Italy, particularly in the olive agroecosystems of Salento. The most severely affected olives were the centenary trees of local cultivars Cellina di Nardò and Ogliarola Salentina. Various measures were taken to control the spread of infection, including the eradication of infected plants and those within a radius of 100 metres, weeding strategies, mechanical tillage of the soil, and phytosanitary treatments.

The European Union established special “infection”, “containment”, and “buffer” zones to limit the northward spread. Some strategies for regeneration after the loss of olives aimed at planting cultivars with better resilience to pathogens, such as Favolosa and Leccino, although not necessarily related to a place’s origins and landscape history. A recent study also showed that a zinc-copper-citric acid biocomplex improved the reduction of symptoms and bacterial concentration in olive trees. The treatment involves spray application, regular pruning of the plants, and soil mowing during certain periods of the year. This so-called eco-friendly technique significantly improved hectares of olive groves, while preserving the existing traditional specimens of trees.

There are discussions around Xylella being called a plant pathogen when it often constitutes only a part of the plant microbiome. It can settle in more than 350 types of plant species from different families, in most cases not being dangerous and causing diseases only in a few particularly susceptible plants due to the blockage of water flow in the xylem vessels. Similar to many other pathogens, the cultivation of extensive monocultures of a particular olive tree species emerges as a significant concern in this context.

Research team: Angelo Renna, Magdalena Smoter