Final answer:
Silk traders used land-based routes over sea routes due to the high risks of piracy, poor weather conditions, and navigational challenges on maritime routes. The overland Silk Road was seen as more predictable and safer, with oasis towns providing vital rest points for merchants, despite the added costs and the presence of bandits.
Step-by-step explanation:
Based on the map and our knowledge of the Silk Road trade routes, silk traders preferred to use land-based trade routes instead of sea routes mainly due to the hazards associated with maritime travel. Piracy, unpredictable weather, and the threat of shipwrecks along poorly charted waters made the sea route significantly riskier. In contrast, despite the geographic and environmental hazards along the Silk Road, the development of caravansaries and the relatively more predictable nature of land travel made it the preferred choice. The growth of stable land empires like the Sasanian Persians' realm also increased the appeal of the overland route.
Land-based trade along the Silk Road involved a series of interconnected stations and oasis towns where goods could change hands and merchants could rest. Despite the presence of taxes, fees, and the threat of banditry, these routes were crucial for trade and cultural exchange. This network enabled not only commerce but also the spread of ideas and religions, profoundly impacting large regions. Long-distance trade during the early and later Middle Ages was difficult and expensive. Europeans eventually sought other routes to procure the desired commodities, culminating in ages of exploration aimed at establishing direct trade links with Asia and the East Indies.