Light and dark elements emerge from the "Environmental Data Survey" in the cities that ISTAT carries out annually. The data for 2020, just released by the Institute, show an environmental and climate situation rather worrying for the main Italian cities. The only positive element is that of urban forestation, which is constantly increasing.
In 2020, the average temperature is equal to +16.3°C (calculated as the average of the values of thermopluviometric stations of the 24 regional capitals and metropolitan cities), an increase of 0.3°C on the corresponding average value of the decade 2006-2015. Considering only the regional capitals, for which large and complete data sets are available, the average temperature, equal to +15.8°C, shows an anomaly of +1.2°C over the 1971-2000 climate value.
In all cities the average temperature anomalies are positive and due to temperature increases, both minimum and maximum: the highest are found in Perugia (+2.1°C), Rome (+2°C), Milan (+1.9°C), Bologna (+1.8°C) and Turin (+1.7°C).
2020 is presented as the least rainy year of the last ten, together with 2011, with a total annual precipitation of 661 mm (average of the observed stations). In the main cities, superimposed on the trend of generalized increase in average temperature, the decrease in precipitation is -132 mm on the corresponding average value of the period 2006-2015.
Negative precipitation anomalies affect 22 cities, with peaks in Naples (-423.5 mm), Catanzaro (-416) and Catania (-359.7). In the regional capitals, the anomaly averages 91 mm less than the climatic value 1971-2000 and affects 15 cities: in the lead Naples (-439.6 mm) followed by Genoa (-276.9 mm), Catanzaro (-262.1 mm), Florence (-221.6 mm), Bologna (-211.9 mm) and Milan (-196).
It is confirmed the phenomenon of Urban Heat Island (UHI): in cities the temperature is higher than in the external areas, with a temperature differential of 1-3 ° C in those of large size, due to the concentration of structures consisting of radiative surfaces of different materials (concrete, metals, asphalt, etc..).
Istat devotes ample space in the report to the analysis of urban forestry in Italy, which is confirmed to be growing: the interventions of urban forestry, useful for mitigation, are increasingly widespread and present in 47 capitals (31 in 2011), for a total area of 11.6 million m2.
"The protection and promotion of urban green areas - says ISTAT - is a natural solution that, by increasing the resilience of cities, can play an important role in strategies to combat climate change and, more generally, in improving the sustainability of urban systems and the quality of life of citizens".
In Milan, the total coverage of green areas is equal to 13.8% of the municipal area (over 25 million m2) and consists almost entirely of urban green areas: 5.7% of urban parks, 3.9% of small parks and neighborhood gardens and the rest mainly of historical green areas and street furniture. Rome has a much higher overall coverage of green areas, equal to 35.8% of the municipal territory, made up only for 3.6% by urban green areas (over 46 million m2) and 32.2% by protected natural areas (415 million m2), a small part of which also falls within the perimeter of the urban area. Naples, like Rome, has a very high green coverage, equal to 31.5% of the municipal area (over 37 million m2), but only partly due to urban green areas (10.1%) and, to a higher percentage, to protected natural areas, among which the Metropolitan Park of the Hills of Naples stands out (over 22 million m2).
In the capital cities, where about 30% of the Italian population lives (17.7 million inhabitants), the extension of urban green areas is over 550 km2, equal to 2.8% of the municipal territory, corresponding to an availability of 31 m2 per inhabitant. Considering also protected natural areas, the incidence reaches 19.3% of the territory (3,775 km2). The total surface area of urban green areas is continuously increasing: on average +0.4% per year since 2011 (+0.6% in metropolitan capitals). The availability of green areas is highest in the capitals of the North-East (62.2 m2 per inhabitant, against 27.2 in the Centre and 25.1 in the North-West), lowest in those of the South (20.8 m2 per inhabitant in the South and 19.5 in the Islands).
According to ISTAT, "urban and peri-urban forestation is becoming increasingly widespread in the capital cities, consisting in the creation of new forests with natural development, aimed at mitigating one of the most significant effects of climatic alterations in the urban environment, the aforementioned "heat islands".The area dedicated to urban forestry amounts to over 11.6 million m2, or an average of 30 m2 per hectare of urbanized area. The distribution is far from uniform, in fact less than half of the capitals are above average, with the North having much higher values than the other regions: 71.2 m2 per hectare in the Northeast and 40.4 in the Northwest, 13.1 in the Center, 6.8 in the South and 5.2 in the Islands. In the last 10 years the area dedicated to urban forestry has progressively increased (+14.9%). The most marked increases have been registered in the capital cities of the Islands (+31.0%), followed by those of the North (16.3%). Decidedly less significant increases were registered in the Center (up 6.0%) and the South (up 2.5%). Compared with an average increase of 15% since 2011, the increases were higher among the capitals of metropolitan cities (+22.7%) than among the other provincial capitals (+12.6%).