Final answer:
Nomadic tribes move to different areas to prevent resource depletion and preserve the environment. Their migrations allow ecosystems to regenerate, maintaining biodiversity and preventing grassland degradation. Modern challenges, however, are threatening their way of life.
Step-by-step explanation:
Nomadic tribes need to move from one place to another primarily to preserve the environment. Their movement involves following resource availability, specifically targeting regions where the ecosystem can support their herds and their own subsistence needs without depleting the natural resources. This continuous movement helps prevent over-grazing and allows time for the environment to recover in areas they have previously used.
Additionally, nomadic lifestyles facilitate a symbiotic relationship with the environment as they rely on the health of ecosystems for their livelihood. The advantages to the environment with such movements include the maintenance of biodiversity, the prevention of grassland degradation, and the support of ecological processes. Thus, the correct answer is (d) Nomadic tribes move to preserve the environment.
It is also important to note that modern challenges such as climate change and political conflicts are increasingly making the nomadic life more difficult, threatening their existence and forcing many to adapt or abandon their traditional ways. Herders must now navigate issues like desertification, severe weather, and competition for land, sometimes resulting in violent conflicts and mass displacements.