The water cycle is essential for maintaining Earth's ecosystems because it regulates the distribution and availability of freshwater, which is critical for the survival of all living organisms. Through processes like evaporation, condensation, and precipitation, water circulates between the atmosphere, land, and oceans, replenishing groundwater supplies, nourishing plants, and sustaining animal life. The water cycle also helps regulate climate and temperature, supports nutrient cycling, and ensures the stability of ecosystems by maintaining habitats. Without this cycle, ecosystems would suffer from droughts, floods, and a lack of resources, disrupting life on Earth.