Final answer:
Nomads typically stay in an area until resources are depleted, and they move due to factors like depleted pastures, climate, and conflicts. In the modern era, challenges like climate change and industrialization threaten their way of life, leading to shifts towards semi-nomadic practices or urban living.
Step-by-step explanation:
Nomadic pastoralists typically stay in an area until the resources, particularly pastures for their herds, are depleted. Factors such as availability of food for their herds, water sources, weather conditions, and conflicts with other communities can cause them to move on. These groups, including the Bedouins and the Mongolians, have faced both historical and contemporary challenges such as political upheaval, climate change, and national borders that affect their nomadic lifestyles. Due to these challenges, some have transitioned to semi-nomadic practices like transhumance or have settled in urban areas.
In the twenty-first century, nomadic lifestyles are increasingly under threat due to climate change, conflicts over resources, and the encroachment of industrialized and settled lifestyles on nomadic lands. This has led to a decline in the number of people living as nomads and a cultural shift towards more settled ways of life. However, it also poses questions about the sustainability of their traditional practices and the preservation of their cultural identity.