The main factor that drives terrestrial biomes is climate, specifically temperature and precipitation patterns. These climatic conditions determine the types of vegetation that can thrive in a particular area, ultimately shaping the ecosystem's structure and function. For example, tropical rainforests flourish in warm, moist conditions, while deserts arise in areas with low rainfall and high temperatures. Additionally, factors such as elevation and soil type can influence biome characteristics. Understanding these driving forces is crucial for studying biodiversity, ecosystem services, and the impacts of climate change on global ecosystems.