Pian di Spagna and Lago di Mezzola Nature Reserve was established with the resolution of the Regional Council no. 86 of 30/11/83: it was established to ensure, in the spirit of the Ramsar Convention (IRAN, 1971), the adequate environment for the stop and nesting of migratory birds, to safeguard and maintain the natural and landscape features of the wetland, to regulate the visit of the protected area with didactic-recreational purposes, and to bring under control the local social and economic activities, in the respect of the environment conservation needs.
The Nature Reserve covers an area that has been always disputed between the mainland and water; the particular geographical position makes this place rich in interesting naturalistic and historical-cultural features.
At the confluence of the two valleys, Val Chiavenna in the north-south direction and Valtellina in the east-west direction, an alluvial plain formed: it is delimited by Como Lake in the north and by Mezzola Lake. The surrounding mountains, abruptly joining up with the plain, form the picturesque setting of this stretch of plain, above all when they take on the showy autumn colors.
The place name Pian di Spagna derives from the succession of historical events involving this region: foreign invasions, battles, and a flourishing trade. However, the area is known and appreciated all over Lombardy above all for its precious landscape and environmental features.
Pian di Spagna is situated at about 200m a.s.l. and, except for Montecchi hillocks reaching the 300m a.s.l., it is an entirely flat area.
The territory of the Nature Reserve includes the Municipalities of Sorico and Gera Lario in the Province of Como and the Municipalities of Dubino, Verceia, and Novate Mezzola in the Province of Sondrio. The northern natural borders of the Protected Area are represented by the mountain massif of Mt. Berlinghera, belonging to Lepontine Alps in the north-west and to the granite summits of Rhaetian Alps in the north-east; in the south, Mt. Legnone, with its 2,609m, is one of the most imposing summits of Orobie Alps. The formation of Mezzola Lake and Pian di Spagna mainland is given to a series of geological events including the alpine orogeny of the Tertiary period and the more recent accumulation of clastic material of alluvial origin transported by the river Adda.
The existing stretches of water - the northern section of Como Lake, Mezzola Lake in the north, and the small Dascio Lake situated between the two - are the result of the separation of the big Lake covering this area after the withdrawal of the glaciers (12,000 years ago) and deeply penetrating along the course of the two tributaries, the rivers Adda and Mera. Such process took place after the accumulation of sediments at the bottom of the original lake and their subsequent outcropping: the current look of Pian di Spagna is rather recent, since for various centuries, until 700 AD, it was the theater of several river and lake floods, acquiring the features of a hostile and unhealthy marsh, only partially drained and cultivated.
The recovery and land reclamation measures of most of the territory were carried out by the Austrian during the 19th century: these measures included the adjustment of the last stretch of the river Adda and the excavation of Borgofrancone canal, whose waters come from the slopes of Mt. Legnone. The measures implemented by man to shape the territory have been combined with the non-stop natural silting up processes of Mezzola Lake made possible thanks to the proliferation of the characteristic canebrake vegetation.
Different plant species with the same ecological needs and sharing the same kind of habitat form vegetable formations that can be easily distinguished one from the other. The vegetation of Pian di Spagna is deeply linked to the presence of both lentic and lotic water systems: the former are still waters or the slightly rippled waters of the lakes, while the latter are the fast and turbulent waters of the rivers. In both habitats and during the floods soaking the soil with water, the various vegetable elements survive thanks to specific adaptation strategies enabling them to bear long-lasting plunging and anoxia periods of the roots.
Some of the floral species characteristic of open waters live anchored to the bottom, forming large submerged grasslands and swaying in the water thanks to the elasticity of the tissues forming their stalk. The best known species are Potamogeton and Helodea canadensis.
Other species float on the water and have expanded-lamina leaves: among them, the White Lotus (Nymphaea alba) and the Yellow Pond-Lily (Nuphar lutea), enriching in spring the whole course of some slow-flowing canals. Without a doubt, the most characteristic formation along the shores of Mezzola Lake is the canebrake. It is almost entirely formed by Phragmites australis, best known as Common Reed: it creates very thick formations, in particular along the southern lake shores, and often grows together with Typha latifolia, Typha angustifolia, Rorippa amphibia, and Myosotis scorpioides. The importance of the canebrake is mainly given to its role as shelter and adequate habitat for wild birds during the reproduction period, as well as to the gradual silting up action caused by the development of the vegetation covering. The most common floral species it is possible to find along the canals and ditches are Filipendula ulmaria, Stachys palustris, Calystegia sepium, Juncus effusus, Iris pseudacorus, and Alisma plantago-aquatica.
Moving from the canebrake areas to the inland, we find hygrophilous grasslands mainly formed by the Carex species: they have different thickness and shape according to the duration and frequency of the flood periods; from the luxuriant and isolated tufts consisting of Carex elata, characteristic species of the areas where the water stagnation is very frequent and abundant, to the meadows with short-term floods, more homogeneous and compact, characterized by Carex vesicaria, Carex acutiformis, Carex hirta, and Carex distans.
Pian di Spagna and Lago di Mezzola Nature Reserve is characterized by various habitats: lake, rivers, streams, canals, ditches, ponds and pools, urban areas, cultivated lands (permanent pastures, corn), not very cultivated areas (fen formations), canebrake areas, a few woodlands, tree rows, hedges, and uncultivated lands.
In each of these habitats it is possible to observe very different bird species.
Around the lakes, it is generally possible to observe various species of diving ducks (Tufted Duck, Common Pochard, Ferruginous Duck, Common Goldeneye) or dabbling ducks (Mallard, Common Teal, Garganey, Wigeon), Swans, Rails (Coot), a few rare sea ducks (Velvet Scoter), Grebes, Divers, Cormorants, Mergansers, Seagulls, and Black Terns. Along the rivers it is easy to observe both diving and dabbling ducks, Swans, Coots, Grebes, Cormorants, Seagulls, and Black Terns.
Dippers, Kingfishers, and Gray Wagtails are common along the streams, while the canals are populated by dabbling ducks, Rails (Coots, Moorhens, Spotted Crakes, Water Rails, Little Crakes), and some wading birds like the Common Sandpiper, Green Sandpiper, Wood Sandpiper, Snipe, Herons, Eurasian Bittern, White Wagtail, Gray Wagtail, Gray Crested Grebe, and Little Grebe); along the ditches, it is possible to sight Gray Herons, Snipes, and Wagtails.
The beaches are rich in Wading Birds, Charadriidae (Snipes, Little Ringed Plovers, Dotterels) and Scolopacidae (Curlews, Black-tailed Godwits, Northern Lapwing, Sandpipers), Seagulls and Cormorants.
The canebrakes represent the ideal habitat for Rails, Bitterns, some birds of prey, Reed Buntings, Blue Tits, Starlings, Penduline Tits, Swallows, Sand Martins, and dabbling ducks.
Tree rows and hedges offer food to Shrikes, Thrushes, Finches, Crows, Tits, Woodpeckers, and Blackcaps.
Although it covers 1,586 ha, the territory is not large and peaceful enough to favor the nesting of particularly precious species, for instance Wading Birds, Ducks, Herons, or Birds of Prey. However, the following species are nesting in the area: at least one couple of Purple Herons, Corn Crakes, Savi's Warblers, Barred Warblers, Golden Orioles, Hoopoes, Long-eared Owls, Wagtails, Bitterns, and Spotted Crakes.
Pian di Spagna is one of the most important areas in Italy and Europe for the wintering of hundreds of ducks that can be observed on Mezzola Lake, along the river Mera, and in the north of Como Lake.
However, the essential role of the protected area is to enable thousands of birds to rest and feed during the spring and autumn migrations. Bad weather conditions with wind, fog, rain, or snow are frequent in the Alps in March and April: therefore, migratory birds are forced to stop in the plains, waiting for a better weather. In these periods, it is possible to sight various species of birds which, already tired after crossing in some cases the Sahara desert and the Mediterranean Sea, wait to cross the Alps and finally reach their nesting areas. In autumn, after crossing the Alps, many tired and hungry birds stop in Pian di Spagna to recover their strength.
Not all the birds migrate: for instance, Woodpeckers and Tits move only a little, the Alpine Accentor moves from the mountains to the valley, the Dipper follows the watercourse according to the gradual frost. Some birds like Thrushes and Chaffinches reach Africa but do not go beyond the Sahara, others carry out very long journeys of 8,000-9,000 km, like Storks, Swallows, Northern Wheatears, and Willow Warblers. The mountains surrounding the Nature Reserve house some birds of prey, like the Black Kite, the Eagle Owl, the Tawny Owl, the Goshawk, and the Buzzard.