RICHNESS AND RED LIST STATUS OF ANIMAL SPECIES

Italy has a great richness of animal species, with a high incidence of endemic species. The Italian fauna is estimated at over 58,000 species, including approximately 55,000 invertebrates and 1,812 protozoa (Table 1), which together account for about 98% of the total species richness, as well as 1,258 vertebrate species, representing 2%. If subspecies are also considered, the total number reaches around 60,000 taxa. arthropods is the richest phylum , with over 46,000 species, largely belonging to the class of insects (Table 1). The richness of marine fauna is also noteworthy, with 10,313 entities recorded (Table 2). Among vertebrates, apart from cartilaginous fish and birds—highly mobile species groups whose distribution extends beyond national borders—several classes include endemic Italian species. Notably, significant endemism rates are found in amphibians (31.8%) and freshwater bony fish (18.3%) (Table 3).

To date, Italian IUCN Red Lists have been published for five invertebrate groups (corals, dragonflies, saproxylic beetles, butterflies, and bees), for all vertebrates, and for breeding birds, for which two assessments have been conducted (Figures 1-3).

Among invertebrates, the following species are extinct or probably extinct: one dragonfly, two beetles, one butterfly, and five bee species. Species threatened with extinction (CR+EN+VU) include 9% of corals (10 species), 11% of dragonflies (10 species), 21% of saproxylic beetles (418 species), 6% of butterflies (18 species), and 11% of the evaluated bees (16 species). The percentage of species for which data is unavailable is very high for corals (60%, corresponding to 67 DD species) and wild bees, as 117 out of the 151 species suspected of decline, were found to be data deficient or not threatened (Figure 1).

Among the 672 Italian vertebrate species (576 terrestrial and 96 marine), six are extinct in Italy (two sturgeons, three birds, and one bat), while 161 species are threatened with extinction (138 terrestrial and 23 marine species), representing 28% of the assessed species. About 50% of Italian vertebrates are not at immediate risk, while for 12% there is insufficient data for an evaluation. Counting together the endangered species (CR+EN+VU), vertebrate show different extinction risk percentages: 2% in marine bony fish, 19% in reptiles, 21% in cartilaginous fish, 23% in mammals, 36% in amphibians, 48% in freshwater bony fish (Figure 2).

Breeding birds are the only group for which two IUCN assessments have been conducted (Rondinini et al., 2013; Gustin et al., 2019), seven years apart, allowing for an evaluation of extinction risk trends over time. Of the 278 species assessed in 2019, five are "Regionally Extinct" (one in recent times). In 2019 threatened species (CR+EN+VU) are 67, equal to 26% of the assessed species (percentage calculated on 278 species, excluding the 21 NA species)(Figure 3). Half of the Italian breeding bird are not at imminent risk of extinction. Excluding non-genuine changes between 2012 and 2019 (e.g., changes due to improved knowledge), the overall extinction risk for Italian breeding birds has decreased. Specifically, 17 species are no longer at risk of extinction, while six species have entered a higher risk category (Gustin et al., 2019). However, this decrease is not particularly significant when analyzing the percentage distribution of IUCN categories in the two assessments (Figure 3).

An analysis of demographic trends in populations (evaluated in the Red Lists for some groups) shows that terrestrial and marine vertebrates are declining by 27% and 22%, respectively, while marine bony fish exhibit better trends (Figure 4). On both land and sea, the number of declining species is about twice that of increasing species, while the percentage of species with stable populations is much higher on land (43% compared to just 4% in marine environments). Overall, 28% of Italian breeding bird populations are stable, and 34% are increasing. About a quarter (24%) of populations are in decline, while for 14% of species, demographic trends are unknown (Gustin et al., 2019). Data on coral population trends are scarce (absent for 68% of species), while for the remaining species, 11% are declining, 20% are stable, and almost none are increasing. The percentage of declining dragonfly populations is 16%, five times higher than those increasing (3%). For butterflies, demographic trends (estimated based on the number of sites from which species have disappeared in recent periods) indicate that most populations are stable, 9% of species have shown significant declines in occupied sites, and 1% is currently increasing.

A summary of the main pressures affecting different groups is shown in Figure 5 (note that the number of species assessed for each group varies widely). A comprehensive reading of the graph highlights that the most common and widespread pressure across taxonomic groups is urban and commercial expansion, along with habitat loss and fragmentation, followed by pollution.

The following sections examine in more detail the pressures affecting different groups.

The main pressures on terrestrial vertebrates (excluding birds, which are analyzed separately) include habitat loss and degradation (affecting about 120 species) and pollution (just under 80 species).Only a small number of species are threatened by direct harvesting (just over 20 species) or persecution (fewer than 10), while nearly 60 terrestrial vertebrate species are not threatened by any specific pressure.

For breeding birds, the primary threat is changes in natural systems, followed by pollution, climate change, agriculture, and aquaculture (Figure 5). The number of native species threatened by invasive alien species remains relatively low. For over 30 species, threats from biological resource use are linked to poaching. Climate change poses an even greater threat to several species, especially in wetland and mountain regions (Gustin et al., 2019).

For marine vertebrates (excluding bony fish), the most significant threat is accidental mortality (reported for 65 species), due to the dataset excluding bony fish and the fact that most evaluated species (sharks, rays, and chimeras) have low commercial interest (Rondinini et al., 2013). This is followed by harvesting, which is a significant pressure for 16 marine vertebrate species.

For marine bony fish, the main pressure is overfishing, both direct (for targeted species) and indirect (bycatch, where species are unintentionally captured by fishing gear targeting other species). This is followed by coastal urban development and water pollution. Most marine bony fish are not subject to significant threats (Relini et al., 2017), but this is not reflected in Figure 5, as the "No Pressure" category was not used in the Red List.

The primary threat to Italian corals is accidental mortality due to fishing gear that can mechanically damage colonies or degrade their habitat. For many species, this threat interacts with biological traits (intrinsic factors) such as low dispersal capacity or adaptation to life on heterogeneous rocky seabeds, which are increasingly rare with greater depth and sediment expansion, making them inherently vulnerable (Salvati et al., 2014). One species, the red coral, is at risk of extinction due to direct harvesting.

Dragonflies are threatened by habitat loss (affecting 10 species) and pollution (9 species), as well as intrinsic factors such as low tolerance to human disturbance (Riservato et al., 2014).

The primary threats to Italian saproxylic beetles include habitat loss and fragmentation, light pollution, predation by invasive corvids, and competition from imported xylophagous and saproxylic species.

Butterflies are mainly threatened by changes in natural systems, habitat loss due to land-use changes, agricultural practices, and climate change.

For bees, the main pressures include agricultural expansion and intensification, urbanization, land-use changes, and, for some species, natural reforestation due to rural abandonment. Moreover, some species (11) could be sensitive to climate change (Figure 5). For completeness of information, it is worth noting the widespread and generalized decline of the honeybee (Apis mellifera), which is attributed to the parasitic mite Varroa destructor, the use of agrochemicals, changes in agricultural practices, urbanization, pollution, climate change, and the spread of diseases and natural enemies introduced by new species (Quaranta et al., 2018).