Short answers, pulled from the story.
The Po Valley began as a system of deeply buried ancient canyons formed by the tectonic collision between the African plate and the Eurasian mainland. This geological event created an offshore land mass that crashed into the continent during the Messinian period from 7 to 5 million years ago.
Until about 1950, the Po delta prograded outward into the Adriatic Sea before human activity shifted the sedimentation rate causing degradation instead of growth. The coastline now subsides while Venice faces ongoing contemporaneous crises due to these changes.
The first known ancient inhabitants were the Ligurians who may have been an Indo-European people. Celtic peoples known as the Insubres immigrated progressively during the 7th century BC followed by Pre-Indo-European Etruscans and migrating Gauls by 500 BC.
The region delivers more than 40 percent of Italy's milk production according to recent data. Over half of the Italian pig production is also located within the Po Valley boundaries supporting a population of 17 million people.
Brescia and Bergamo in Lombardy have the highest death rate from fine particulate matter PM2.5 in Europe based on research published in The Lancet Planetary Health. Vicenza ranks fourth and Saronno eighth in a top ten list of cities with severe mortality impacts.