According to the passage, the rise in population is one of the key factors contributing to the scarcity of freshwater. As populations grow, the demand for water increases, making freshwater resources more scarce. This increased demand, coupled with the loss of wetlands and poor water management, further exacerbates the situation. The passage suggests that unless there is better water conservation and allocation, water shortages will worsen, especially in certain regions like Africa, the Middle East, and South Asia.