Trascrizione
Five million years ago, just 18 and a half days in the life of our person-Earth, Gea, the forces that caused the convergence of the European and African plates and gave rise to the Alps, ceased.
At this point, the Alpine landscape began to be shaped by erosion, to which every rock, every slope, every valley, reacted differently, bringing to the incredible variety of environmental conditions and ecosystems we know today. One of the most important agents of this transformation, the very soul of Valtellina, is its river, the Adda, which originates to the east in Val Alpisella, in the Rhaetian Alps, and flows for 313 kilometres westward until it joins the Po River at Castelnuovo Bocca d'Adda.
Its east-west course follows the valley's alignment and, as we saw in the previous room, that of the fault known as the Insubric Line. From a rushing torrent in the Livigno area, the Adda becomes calm at its mouth in Lake Como, where, accumulating sediments, it gives rise to the Pian di Spagna, only to become forceful again, as depicted in Leonardo da Vinci's works (it indeed serves as the backdrop for several paintings by the great master, including the Mona Lisa), when it exits from Lecco.
From an environmental perspective, the Adda is a very rich river. In the valley floor, despite numerous reclamation efforts, some wetland areas remain - some backwaters, which are river sections separated from the main channel, and small ponds - as well as actual swamps at the confluence of the Adda and the Mera, within the Natural Reserve of Pian di Spagna. These are places of great biodiversity, that is, rich in various species: from the common water frog to the Italian crested newt, from the Italian tree frog - with its unmistakable sound - to the snakes that prey on it, such as the grass snake and the dice snake.
However, the river also has historical and cultural significance. The Adda has played an important role in the economic and industrial development of the region, providing hydropower and supporting activities such as the textile industry and navigation.
Moving slightly up the better-exposed slopes of Valtellina, specifically on the Rhaetian side, where forests have been replaced by often terraced crops supported by dry stone walls, there thrives a warm, even dry, vegetation unique in the province of Sondrio. Here, the fauna, almost Mediterranean, includes species such as the wall lizard, the western lizard, and the rat snake, a non-venomous snake that spends long hours basking in the sun to store energy. It seems that the green toad also lived in this area, and efforts are being made to preserve its habitat by promoting sustainable agricultural practices.
On the opposite side, on the Orobic slope, one encounters broadleaf forests that extend up to 1300-1500 metres in altitude. The original forests have been transformed into chestnut groves or mowed meadows, a practice that has multiplied the variety of environments. As a matter of fact, in the undergrowth of a chestnut grove, at night or during rain, you can find the common fire salamander and the common toad. At the edges of the woods and clearings, there is the slowworm, a legless lizard that resembles a snake, while the Aesculapian snake, a very long and fast snake entirely harmless, moves within the dense vegetation, sometimes even climbing trees. You surely know this snake, because it was considered a symbol of life force that heals ailments, and even today, it is represented together with the staff of Asclepius, the Greek god of medicine, in all our pharmacies!
Continuing to ascend in altitude, living conditions become increasingly extreme, and the last isolated larches or Swiss stone pines gradually yield to rhododendron and blueberry shrubs, the habitat of the common viper and the smooth snake. At high altitudes, alpine meadows prevail, where the viviparous lizard and the alpine salamander reside. All four of these species do not lay eggs but give birth to fully developed offspring, an adaptation to the harsh climates of the high mountains. Beyond the limits of the alpine meadows, we find the pools of the alpine pastures, glacial ponds, and alpine lakes, moist environments with sparse vegetation, except for peat bogs, swampy areas where sphagnum mosses, also known as peat mosses, thrive. In the pools and ponds, the alpine newt and the common frog reproduce, while among the sphagnum mosses, you may sometimes find the European adder, a viper that does not disdain wet and cold environments.
Until a few decades ago, here, as further down, on Pian di Spagna, the yellow-bellied toad could still be found, an amphibian similar to a toad, with a typical… well, howling sound! Continue your visit by going upstairs, where the larger animals that inhabit these areas are on display.