Which of the following factors helps explain the rise of urban centers and the increase in trade in Afro Eurasia during the second half of the 13th century?

SILK ROAD NETWORK:  The Silk Roads continued to focus on luxury items such as silk and other items whose weight to value ratio was low. In the post-classical age, however, the Silk Roads diffused important technologies such as paper-making and gunpowder. Continuing a phenomenon from the classical age, they would also spread disease; the Black Death would spread from Asia to Western Europe along Silk Road and maritime routes eventually killing about one third of the people there. Despite these continuities, the Silk Road network would be transformed by cultural, technological and political developments. By 600 C.E., the classical empires of China, India and Rome had all crashed. Silk Road trade declined with them. The rise of the Islamic Abbasid Caliphate would invigorate trade along the Silk Roads once again. Sharia law, which gave protection to merchants, was established across the Dar al-Islam. Indian, Armenian, Christian and Jewish merchants alike took advantage of Muslim legal protection. Courts and Islamic jurists called qadis presided over legal and trade disputes. All of this enabled trade by decreasing the risks associated with commerce. A more important boost to Silk Road trade in this era was the rise of the Mongol Empire. The Mongols defeated the Abbasid Caliphate in 1258 and the vast Pax Mongolica soon placed the majority of the Silk Roads under one administrative empire. Merchants were more likely to experience safe travel.[3] The Mongol code of law, known as the Yassa, imposed strict punishments on those disturbing trade.[4] The rule of the Mongols in central Asia coincided with the peak of Silk Road trade between 600 and 1450 C.E.

MEDITERRANEAN NETWORK:   In the previous period (600 B.C.E. to 600 C.E.) the Mediterranean saw its heyday of trade under the territorial height of the Roman Empire. Like the Silk Road trade, this network declined when Rome weakened. However, the rapid spread of Islam across north Africa and the continuation of Roman civilization in the Byzantine Empire would revive trade in the post-classical age. As with all networks in this era, the religion of Islam had a positive impact on trade. Sharia law, the establishing of qadis and courts, along with the high regard with which Islam holds merchants (Muhammad was a merchant) all led to an increase of commercial activity where Islam had a significant presence. The Egyptian cities of Cairo and Alexandria, now under Muslim rule, became powerful commercial centers of the Mediterranean network. Muslim and Jews established trading firms in Cairo which benefited from the lucrative trade in silk yarn and cotton textiles.[5] Into the Mediterranean flowed precious gems and perfumes from India, along with the long standing trade items of olive oil and glassware. Constantinople, the capital of the Byzantine Empire, became an important hub of trade owing to its location between Europe and Asia. A major portion of the Silk Roads ended on the Black Sea, where goods would be loaded onto ships and carried through the Bosporus into the Mediterranean. The city's control of trade provoked the jealousy of the merchants of Venice, a powerful commercial city-state that thrived on the Italian peninsula at this time. Venetian merchants helped steer the Fourth Crusade toward Constantinople in order to gain a larger share of this trade.

TRANS-SAHARAN NETWORK:   The Trans-Saharan trade routes that formed in the classical age grew enormously in the period from 600 to 1450 C.E. Here again, Islam played a primary role in this increase. During the Umayyad Caliphate Islam came to north Africa and reinvigorated trade. Caravan crossings of the Sahara desert increased the trade in gold, salt, ivory and slaves. Along these same routes, Islam spread to sub-Saharan portions of west Africa. For the first time, empires emerged under the Sarah desert, in large part because Islam brought the means to empower local kings and provide a point of unity. Mansa Musa's famous and extravagant pilgrimage to Mecca gave his kingdom of Mali wide recognition across the Dar al-Islam and served to increase trade connections across the Sahara.

INDIAN OCEAN NETWORK:   Despite the growth of these important trade routes, Indian Ocean trade was the dominate network of trade in the post-classical period. In terms of the volume of trade, the number of people involved, and the interaction of various cultures, the Indian Ocean network was unrivaled in this period. It did, however, bears some continuities with the previous period (600 BCE to 600 CE). For example, it remained closely tied to environmental conditions, namely the monsoon winds that merchants had to consider while scheduling their departures. This meant that the port cities along the rim of the Indian Ocean at any given time had large numbers of non-citizens waiting for changes in the monsoon winds. Thus these cities were cosmopolitan and exuded a great deal of cultural tolerance. Because this is a maritime network, Indian Ocean trade continued to be the ideal network for exchanging bulk items, such as timber, ivory, spices, cotton textiles, and other things that would be difficult to move on land routes. Finally, Indian Ocean trade continued to be free from the domination of any state or empire. The seas were open to all merchants and not until the arrival of the Europeans would any single power attempt hegemony.

Indian Ocean trade also experienced major changes during the post-classical age. The volume of exchange increased dramatically and the number of civilizations participating increased. The coming of Islam played a significant role in the increase of trade in the Indian Ocean. We have seen already how the civilization of Islam encourages trade, and the Muslim city-states along the Swahili coast of east Africa contributed enormously to maritime trade. Gold, ivory, and exotic animals made their way from sub-Saharan and southern Africa to these cities, through which they entered the busy sea routes of the Indian Ocean. Islam followed the path of goods, making converts across the network, particularly southeast Asia. On the Malay peninsula in southeast Asia, the Buddhist kingdom of Srivijaya thrived on the lucrative spice trade that flowed through the straits of Malacca. Srivijaya became an important kingdom for the diffusion of Buddhism across the region. Another political development that increased Indian Ocean trade was the recovery and economic flourishing of China. During the Song Dynasty, Chinese maritime trade exceeded Silk Road trade, and Chinese porcelain has been found as far away as the Swahili coast of Africa.[6] The efficiency and volume of trade in the Indian Ocean was also facilitated by the introduction of new maritime technologies. The Chinese introduced the compass and massive trading ships called Junks which were able to carry larger cargoes. The Arabs popularized the Dhow ship which was able to tack against the wind because of its advanced lateen sail. Finally, an instrument called the astrolabe allowed skilled sailors to determine their latitude at sea. All of these advancements increased participation, facilitated navigation, and removed some of the risks of maritime trade.

As a member of the Hanseatic League, the northern Russian city of Novgorod was vital in connecting European merchants with their Arab and Byzantine counterparts. Its surrounding marshes and thick forests protected it from the Mongol conquests allowing its importance for the coveted trade in fine furs to be uninterrupted

In southeast Asia Malacca (Melaka)  became an important city in the spice trade. It was a collection point for spices grown on tiny islands across Indonesia. In Malacca they were packaged and sold in bulk on the Indian Ocean. The city's location on the straits of Malacca allowed it to collect tolls and control passage

The location of Timbuktu on the southern rim of the Sahara Desert raised its importance for trans-Saharan caravan trade. It became an exchange point for west African gold and north African salt. Because of the trade in books, the city also became an important city for Islamic scholarship and education.

Hangzhou was located near China's southern coast and on the Grand Canal which connected it across 1000 kilometers to Beijing. It was a departure point for Chinese goods to Korea, Japan, southeast Asia, and the Indian Ocean trade network. It became the capital of China during the Southern Song Dynasty.

Mississippi River Valley

Mesoamerica Trade Networks

Inca Road Network

Examples of luxury goods: 

• Silk and cotton textiles
• Porcelain
• Spices
• Precious metals and gems
• Slaves
• Exotic animals

Examples of commercial and transportation technologies:

• compass
• astrolabe
• larger ship design in travel

Examples of new forms of credit and monetization:

• Bills of exchange
• Credit
• Checks
• Banking houses