Fundamentals of Ecosystem Science provides a compact and comprehensive introduction to modern ecosystem science. This book covers major concepts of ecosystem science, biogeochemistry, and energetics. It addresses, contrasts, and compares both terrestrial and aquatic ecosystems. It combines general lessons, concepts, frameworks, and challenges in highly accessible synthesis chapters. It presents firsthand case studies, written by leaders in the field, offering personal insights into how adopting an ecosystem approach led to innovations, new understanding, management changes, and policy solutions. This book is ideal for advanced undergraduate and graduate students who have had a general biology course, but not further training in ecosystems as well as researchers and professionals in ecology and environmental sciences.