Mathematics for Planet Earth is an online lecture series initiated by the Department of Computer Science, CHRIST (Deemed to be University), Pune Lavasa Campus, to showcase the role of mathematics in understanding the world around us. The inaugural lecture, "Mathematics of Planet Earth: A Wide Spectrum of Ideas and Possibilities," marks the first session of this series and will be delivered by Prof. Christiane Rousseau, Professor Emerita, Department of Mathematics and Statistics, Université de Montréal, Canada. An internationally renowned mathematician, Prof. Rousseau is the instigator and international coordinator of the Mathematics of Planet Earth (MPE2013) initiative and has played a significant role in promoting mathematics globally. In this lecture, she will explore how mathematics helps us understand natural systems, environmental challenges, and complex societal issues through modelling, analysis, and interdisciplinary collaboration. The session is intended for students, faculty members, researchers, and mathematics enthusiasts, offering participants an inspiring perspective on the relevance of mathematics in today's world.