<P> The gradual breakdown and transformation of economic and social linkages and infrastructure resulted in increasingly localized outlooks . This breakdown was often fast and dramatic as it became unsafe to travel or carry goods over any distance; there was a consequent collapse in trade and manufacture for export . Major industries that depended on trade, such as large - scale pottery manufacture, vanished almost overnight in places like Britain . Tintagel in Cornwall, as well as several other centres, managed to obtain supplies of Mediterranean luxury goods well into the 6th century, but then lost their trading links . Administrative, educational and military infrastructure quickly vanished, and the loss of the established cursus honorum led to the collapse of the schools and to a rise of illiteracy even among the leadership . The careers of Cassiodorus (died c. 585) at the beginning of this period and of Alcuin of York (died 804) at its close were founded alike on their valued literacy . For the formerly Roman area, there was another 20 per cent decline in population between 400 and 600, or a one - third decline for 150 - 600 . In the 8th century, the volume of trade reached its lowest level . The very small number of shipwrecks found that dated from the 8th century supports this (which represents less than 2 per cent of the number of shipwrecks dated from the 1st century). There were also reforestation and a retreat of agriculture centred around 500 . </P> <P> The Romans had practiced two - field agriculture, with a crop grown in one field and the other left fallow and ploughed under to eliminate weeds . Systematic agriculture largely disappeared and yields declined . It is estimated that the Plague of Justinian which began in 541 and recurred periodically for 150 years thereafter killed as many as 100 million people across the world . Some historians such as Josiah C. Russell (1958) have suggested a total European population loss of 50 to 60 per cent between 541 and 700 . After the year 750, major epidemic diseases did not appear again in Europe until the Black Death of the 14th century . The disease Smallpox which was eradicated in the late 20th Century did not definitively enter Western Europe until about 581 when Bishop Gregory of Tours provided an eyewitness account that describes the characteristic findings of smallpox . Waves of epidemics wiped out large rural populations . Most of the details about the epidemics are lost, probably due to the scarcity of surviving written records . </P> <P> For almost a thousand years, Rome was the most politically important, richest and largest city in Europe . Around 100 CE, it had a population of about 450,000, and declined to a mere 20,000 during the Early Middle Ages, reducing the sprawling city to groups of inhabited buildings interspersed among large areas of ruins and vegetation . </P> <Ul> <Li> Under Emperor Justinian (r . 527 - 65), the Byzantines were able to reestablish Roman rule in Italy and most of North Africa </Li> </Ul>

What city was the center of imperial life in the roman empire in the early fifth century