ThePo Valley,Po Plain,Plain of the Po, orPadan Plain (Italian:Pianura Padana[pjaˈnuːrapaˈdaːna] orVal Padana) is a major geographical feature ofnorthern Italy. It extends approximately 650 km (400 mi) in an east-west direction, with an area of 46,000 km2 (18,000 square miles) including itsVenetic extension not actually related to thePo basin; it runs from the WesternAlps to theAdriatic Sea. The flatlands ofVeneto andFriuli are often considered apart since they do not drain into the Po, but they effectively combine into an unbroken plain, making it the largest inSouthern Europe. It has a population of 17 million, or a third of Italy's total population.[1]
The plain is the surface of an in-filled system of ancient canyons (the "Apennine Foredeep") extending from theApennines in the south to the Alps in the north, including the northern Adriatic. In addition to the Po and its affluents, the contemporary surface may be considered to include theSavio,Lamone andReno to the south, and theAdige,Brenta,Piave andTagliamento of theVenetian Plain to the north, among the many streams that empty into the north Adriatic from the west and north.
Geo-political definitions of the valley depend on the defining authority. The Po Basin Water Board (Autorità di bacino del fiume Po), authorized in 1989 by Law no. 183/89 to oversee "protection of lands, water rehabilitation, the use and management of hydro resources for the national economic and social development, and protection of related environment" within the Po basin, has authority in several administrative regions of north Italy, including the plain north of the Adriatic and the territory south of the lower Po, as shown in the regional depiction included with this article. The law defines the Po basin as "the territory from which rainwater or snow and glacier melt flows on the surface, gathers in streams of water either directly or via tributaries...".[2] The United Nations Environment Program includes the Alps and Apennines as far as the sources of the tributaries of the Po but excludes Veneto and that portion of Emilia-Romagna south of the lower Po; that is, it includes the region drained by the Po but only the Po and its tributaries.[3]
The Po Valley and the Adriatic overlay aforeland basin and a system of deeply buried ancient canyons surviving from thetectonic collision of an offshore land mass, Tyrrhenis, with the mainland, an incident within the collision of the African and Eurasian plates. Since theMessinian (7–5mya) the system has been filling with sediment mainly from the olderApennines but also from the Alps. The shoreline of the Adriatic depends on a balance between the sedimentation rate andisostatic factors. Until about 1950, the Po delta was prograding into the Adriatic. After that time due to human alteration of geologic factors, such as the sedimentation rate, the delta has been degrading and the coastline subsiding, resulting in ongoing contemporaneous crises in the city ofVenice.
The Malossagas condensate field was discovered in 1973 and produces at depths of 6 km (4 miles) from the UpperTriassic Dolomia Principaledolomite and the LowerJurassic Zandobbio dolomite, capped by the LowerCretaceous Marne di Bruntinomarl.[5]
The Po Valley is often regarded as asyncline, or dip in the crust due to compression at the edges. Regardless of whether this concept accurately describes its geology, the valley is manifestly a sediment-filled trough, or virtual syncline, continuous with the deeps of theAdriatic Sea. The surface terrain is therefore divided into two overall types oflandform: the plain, or flat surface of the fill, and theanticline at the edges, taking the form of hilly country in which theoutcrops of the original rock are visible along withalluvial fans formed from the outwash of the more severe anticlinal terrain; that is, the Apennines and the Alps.[6]
The valley is broadly divided into an upper, drier part, often not particularly suited for agriculture, and a lower, very fertile, and well-irrigated section, known inLombardy and westernEmilia asla Bassa, 'the low (plain)'. The upper areas of the Po valley take local names which reflect in their meanings their being modestly suited for farming. So we have the Piedmontesevaude andbaragge, the Lombardbrughiere andGroane, or, exiting from the Po valley proper, theFriulianmagredi, areas remote from easily reachable water tables and covered with dense woods or dry soils.
This specific meaning for 'lower plain' derive from a geologic feature called thefontanili line or zone, a band of springs around the Val Po, heaviest on the north, on the lowermost slopes of the anticline. It varies from a few kilometres to as much as 50 km (30 miles) wide. The fontanili line is the outcrop, or intersection, of the anticline'swater table with the surface at the edge of thebassa. The rock above the line is porous. Surface water in theintermittent streams of the mountains tends to disappear below ground only to spring out again in thespring zone.[7] The spring zone is often called "the middle valley."
Surface runoff water (the Po and its affluents) is not of much value to the valley's dense population for drinking and other immediate uses, being unreliable, often destructive, and heavily polluted by sewage and fertilizers. Its main anthropic value is for hydro-electric power, irrigation, and industrial transport. The cost of purifying it for human consumption makes that process less feasible. The fresh drinking water comes from hundreds of thousands of wells concentrated especially in the fontanili zone. The major settlements, therefore, are also in that zone, which has become the centre of economic development andindustry in Italy, and now is an almost continuousmegalopolis stretching fromTurin toTrieste.[8]
Thebassa Padana was settled and farmed earliest, in Etruscan and Roman times. After the collapse of theRoman Empire (5th century AD), lack of maintenance of the irrigation systems[9] associated with a cooling climate phase (i.e. the so-called Migration Period orThe Dark Age Cold Period[10][11]) led to the progressive waterlogging of the Po Valley and the natural depressions on the right side of thePo turned in vast swamp basins.[12] The waterlogging process of the area continued until the 10th-century influencing the human sustenance and settling practices. According to historical-archaeological data, indeed, thewetlands were exploited for fishing as well as for transport by boat while theearly medieval sites settled on the fluvial ridges, in topographically higher and strategic position[13] in the surrounding swampy meadows.
The Po Valley has been completely turned to agriculture since theMiddle Ages, when efforts from monastic orders, feudal lords and freecommunes converged. The older and smaller cities deriving from ancient times are still located there.
According to historical maps and documents the land reclamation of the Po Valley reached its peak during theRenaissance (15th–16th centuries) and continued in theModern Age (17th–18th centuries), with the last marsh areas only being reclaimed in the 20th century: channels and drainage system are still active and allow the Po Valley to be drained and be cultivatable.
Natural vegetation (central-European broadleaved trees) of the Padan Plain
The Po Valley has a generallyhumid subtropical (Köppen:Cfa) climate. The conformation of the plain, surrounded by theAlps and theApennines, and the influence of theAdriatic Sea cause high levels ofrelative humidity throughout the year. The climate is increasingly warmer and more humid farther south and east.
Winters are cool and damp, with January mean temperatures ranging between 0 and 5 °C (32 and 41 °F).Fog andmist are frequent, although theurban heat effect has made winters less foggy and cold than before in some areas. Snow and winterdroughts can deny sufficient moisture to the soil for agriculture. Summers are hot and humid, with July mean temperatures ranging between 22 and 25 °C (72 and 77 °F) (1971–2000 averages). Frequentthunderstorms and suddenhailstorms can produce large hail, dump large quantities of rain, and destroy crops.Supercell thunderstorms produce large hail, with significant agricultural costs.[14]Tornadoes are common in the plains of the valley. TheFriuli-Venezia Giulia, beyond the Po plain itself, is downwind of the mountains and upwind of moisture sources from nearby is an exception. Spring and autumn are well-marked and pleasant. Both winter and summer are less mild in the lower parts along the Po, while theAdriatic Sea and the great lakes moderate the local climate in their proximity.
Rainfall varies between 700 and 1,200 mm (30 and 45 inches) and equally distributed during the year. Rainfall maximums are during autumn and spring. Winds are usually weak, although sudden bursts offoehn or thunderstorms can sweep the air clean. The almost enclosed nature of the Padan basin with much road traffic, makes it prone to a high level of pollution in winter,when cold air clings to the soil. The natural potentialvegetation of the Po basin is a mixed broadleaf forest ofpedunculate oak,poplars,European hornbeam,alders,elderberry,elms,willows,maples,ash, and other central-European trees. The largest remaining fragments of forest are located around the River Ticino and are protected by a Biosphere Reserve.[15]
The Po Valley has had traces of inhabitation since at least 780,000 years ago, when the first big glaciation of pleistocene took place. Sites such as Monte Poggiolo may have served as refuges of human populations fleeing the terribly cold conditions ofNorthern Europe during the subsequent glaciations along pleistocene.[16] The valley was covered by sea level in warm times, but glaciations could cause a lower sea level that allowed big mammals and humans to migrate from Africa and the Middle East to central and Western Europe through an empty and open Po valley, avoiding the barrier of the Alps, reaching the Loire Valley, and Iberian Peninsula, and then, when glaciation retreated, the rest of continental Europe.
Urban development began in the Po Valley much later than in southern Italy or Greece. The first known ancient inhabitants of the thick forests and swamps were theLigurians, who may have been anIndo-European people. After the progressive immigration in the 7th century BC ofCeltic peoples known as theInsubres (hence the name ofInsubria sometimes being given to northwesternLombardy), the southern and central regions were conquered and colonised here and there by apre-Indo-European people, theEtruscans, who left names such asParma,Ravenna and Felsina, the ancient name ofBologna. The Etruscan domination left significant marks and introduced urban civilisation, but was short-lived.[citation needed] Its inhabitants, theVenetics, probably being a distinct group who, being skillful merchants, were, in time, also culturally influenced by bothEtruscans andGreeks. By 500 BC the Etruscans were gradually displaced from the region by migrating Gauls.[17]
Once the longPax Romana showed signs of weakening, and after enduring the passage of several Germanic invaders, and even that ofAttila and hisHuns, the Po valley was to find no peace. TheGothic War andJustinian's plague devastated the Padan population. In this scenario of desolation, from which many people had fled to the mountains for safety (making them fairly populated till the 20th century) came theGermanicLombards, a warrior people who gave their name to almost the whole of the Po valley:Lombardy. In the Middle Ages the term was used to indicate all of northern Italy. The Lombards divided their domain induchies, often contending for the throne;Turin and Friuli, in the extreme west and east end respectively, seem to have been the most powerful, whereas the capital soon shifted fromVerona toPavia.Monza also was an important town in that time, more so than ruinedMilan. The Lombards' harsh,caste-like rule over the natives softened somewhat with their conversion fromArianism toCatholicism.
TheLombard kingdom was overthrown in 774 byCharlemagne and hisFrankish armies, becoming a prized part of theCarolingian Empire, forming thekingdom of Italy, always with its capital in Pavia.[18] The affirmation of large landownership from the eighth/ninth centuries accelerated the process of land reclamation and intensified land use, transforming the landscape of the Po Valley.[19] After the chaotic feudal dissolution of the empire and much fighting among pretenders to the imperial crown,Otto I ofSaxony set the stage for the following phase of the region's history by adding the Po Valley to theHoly Roman Empire of the Germanic nation in 962. InVeneto, the lagoon capital ofVenice, emerged a great sea power in alliance with its old master, theByzantine Empire. In time theComuni emerged, as towns thrived in commerce. SoonMilan became the most powerful city of the central plain of Lombardy proper, and despite being razed in 1162, it was a Milan-drivenLombard League withPapal benediction that defeated emperorFrederick Barbarossa at theBattle of Legnano in 1176.
Between the 10th and 13th centuries, concurrent with theMedieval Warm Period climate phase, the European population grew substantially, almost tripling (in northern and central Italy, the urban population doubled), and increasing the demand for cultivated lands. Cereals became a more significant constituent in the average diet and in the agrarian regime compared to the centuries before, leading populations to reconfigure the medieval natural landscape for agricultural purposes. In creating new land for cultivation and settlement, the European communities triggered a massive landscape transformation through woodland clearance, arable intensification, the development of irrigation systems and the drainage of wetlands. Land reclamations works profoundly modified many European regions. In central Po Plain the earliest evidence of attempts to clear the forests and drain the wetlands is mentioned in historical documents from the late 8th century, but only from the 10th to 13th centuries were land and water management activities actually carried out widely.[20][21][22]
Further civil wars escalated in theGuelph-Ghibelline reciprocate bloodbath of the 13th and 14th centuries. The Signorie came from spent out Communal institutions. WithVenice's expansion on the eastern mainland in the first half of the 15th century andMilan's supremacy in the center and west the region (not significantly diminished by theBlack Death of 1348) reached unprecedented peaks of prosperity. Vast areas were irrigated and cultivated with the most modern techniques available. The population averaged some 50 people per square kilometer, a very high standard for those times.
In 1494, the ruinousItalian Wars began betweenFrance andSpain, which lasted for decades. Land changed hands frequently. EvenSwitzerland received some Italian-speaking lands in the north (Canton Ticino, not technically a part of the Padan region), and theVenetian domain was invaded, forcingVenice into neutrality as an independent power. In the end, Spain prevailed withCharles V's victory overFrancis I of France at theBattle of Pavia in 1525.
WhenNapoleon I entered the Po Valley during some of his brightest campaigns (1796 and 1800, culminating in the historicalBattle of Marengo), he found an advanced country and made it into hisKingdom of Italy. With Napoleon's final defeat the Austrians came back, but they were no longer welcome. In the west, inPiedmont, theSavoy dynasty would emerge to serve as a springboard for Italian unification.
TheRisorgimento, after an unsuccessful start in 1848 and 1849, triumphed ten years later inLombardy, which was conquered by a Franco-Piedmontese army. In 1866Veneto joined young Italy, thanks toPrussia's defeat ofAustria. Poverty in the countryside increased emigration to theAmericas, a phenomenon which subsided in the central region towards the end of the 19th century, but persisted inVeneto well into the 20th century. Industry grew rapidly, thanks to an abundance of water and literate manpower.
TheWorld Wars did not significantly damage the area, despite the destruction caused byAlliedaerial bombing of many cities and heavy frontline fighting inRomagna. TheResistance protected the main industries, which theThird Reich was using for war production, preventing their destruction: on 25 April 1945 a general insurrection in the wake of the German defeat was a huge success. Most cities and towns, notably Milan and Turin, were freed by the partisans days before the Allies arrived.
After the war, the Padan area took the lead in theeconomic miracle of the 1950s and 60s. Since 1989,Lega Nord, a federation of Northern regionalist parties, has promoted eithersecession or largerautonomy for the Padan area which they callPadania.
The Po Valley is one of the most important industrial and agricultural areas in Europe. Hydroelectricity is produced by the flow of the Po. The river is extensively used for irrigation for the region's agriculture.[23]
Po valley is considered the worst area in Europe for air quality.[24] In March 2019, theEuropean Space Agency (ESA)[25] published images ofnitrogen dioxide concentrations taken from theSentinel-5P satellite. These images show a big red area, made of nitrogen dioxide and fine particles, situated above the Po Valley area, which incorporates the city ofMilan,Turin, andBologna. Milan and Turin share high levels ofozone andnitrogen oxides, which are mainly produced by cars' diesel and petrol engines. To shed light on the danger for humans living polluted environments, Chicago Energy Policy Institute[26] has developed the Air Quality Life Index (AQLI), a system capable of analyzing air pollution worldwide. According to AQLI findings, Po valley air pollution affects inhabitants so hard that it cuts off about half a year of their life expectancy. The main reasons for the high amount of air pollution over the Po valley are strictly connected to livestock and factories. The so-called "NPK fertilizers", made of nitrogen, phosphorus and potassium, along with manure emissions from intensive breeding and high levels of nitrogen dioxide released by diesel and petrol engines are all accountable for this disastrous air condition in northern Italy. The region ofLombardy produces also vast amounts of animal waste, a big contributor to pollution. It delivers more than 40 percent of Italy's milk production, for example, while over half of the Italian pig production is located in the Po Valley.[27]
According to research published inThe Lancet Planetary Health[28] in January 2021, which estimates the death rate associated with fine particulate matter (PM2.5) and nitrogen dioxide (NO2) pollution in 1000 European cities,Brescia andBergamo inLombardy have the highest death rate from fine particulate matter (PM2.5) in Europe.Vicenza (Veneto) andSaronno (Lombardy) are in fourth and eighth place, respectively, in a top ten of ten cities.Turin andMilan are also at the top of the European ranking—3rd and 5th respectively—in terms of increased mortality from nitrogen dioxide, a gas that is produced mainly from traffic and in particular from diesel vehicles, whileVerona,Treviso,Padova,Como andVenice rank eleventh, fourteenth, fifteenth, seventeenth and twenty-third respectively.
The data show that many cities in the Po Valley suffer the most serious impact at European level due to poor air quality, first of all the metropolitan area of Milan, thirteenth in the ranking in terms of fine particulate impact, where any year 3967 premature deaths occur—approximately 9% of the total.
^"Po". United Nations Environment Programme, Division of Early Warning and Assessment (DEWA), Global Resource Information Database (GRID) - Europe. Archived fromthe original on 1 August 2009. Retrieved4 June 2009.
^Errico, G., Groppi, G., Savelli, S., and Vaghi, G.C., 1980, Malossa Field: A deep Discovery in the Po Valley, Italy, in Giant Oil and Gas Fields of the decade: 1968-1978, AAPG Memoir 30, Halbouty, M.T., editor, Tulsa: American Association of Petroleum Geologists,ISBN0891813063, pp. 525–538.
^Bridges, Edwin Michael (1990).World geomorphology. Cambridge; New York: Cambridge University Press. p. 225.ISBN978-0-521-28965-8.
^Squatriti, Paolo (2002).Water and society in early medieval Italy, AD 400-1000. Cambridge: Cambridge University Press.ISBN978-0521522069.OCLC49550805.
^Brandolini, F.; Trombino, L.; Sibilia, E.; Cremaschi, M. (August 2018). "Micromorphology and site formation processes in the Castrum Popilii Medieval Motte (N Italy)".Journal of Archaeological Science: Reports.20:18–32.Bibcode:2018JArSR..20...18B.doi:10.1016/j.jasrep.2018.04.017.ISSN2352-409X.
^Human migration into Europe during the late Early Pleistocene climate transition Article in Palaeogeography, Palaeoclimatology, Palaeoecology · October 2010
^Authors, Several (2015-12-17).Roman legion. Self-Publish. p. 167.
^Campopiano, Michele (January 2013). "The evolution of the landscape and the social and political organisation of water management: the Po Valley in the Middle Ages (fifth to fourteenth centuries)".Landscapes or Seascapes?. Comparative Rural History of the North Sea Area.13:313–332.doi:10.1484/M.CORN.1.101558.ISBN978-2-503-54058-0.
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