Oceans and other wetlands cover approximately 70% of the Earth's surface and represent some of the most vital and dynamic ecosystems on the planet. These aquatic environments provide essential functions that support both planetary and human well-being - from regulating climate through carbon sequestration and influencing weather patterns, to sustaining biodiversity and supplying food and livelihoods to billions of people. They act as buffers against extreme weather events, nurseries for marine life, and crucial components of global nutrient and water cycles. Despite their critical role, however, oceans and wetlands remain underrepresented in the One Health discourse, which traditionally focuses more on terrestrial ecosystems such as rainforests, agricultural zones, and urban environments. The resilience of these aquatic systems is therefore deeply interlinked with human and animal health and marine pollution. Overfishing, climate-induced ocean acidification, and the spread of aquatic-borne diseases are all pressing issues that have direct and indirect impacts on public health, food security, and socio-economic stability - particularly for coastal and island communities. Recognizing oceans and wetlands as central components of the One Health framework is therefore essential for developing holistic and effective strategies to address public health challenges, and integrating One Health into research, policy, and practice is scientifically necessary and crucial for achieving long-term sustainability and resilience in a rapidly changing world. This book addresses that disparity of integration and tackles the main concepts of One Health using aquatic environments. It thus covers: - Definitions of One Health concepts and the use of One Health in practice; - The value of water-based environments and their importance in the implementation of One Health programs; - Important cross-sectoral topics such as epidemiology, health economics and statistics, biosecurity, governmental policy, food security, and underreported zoonoses. This textbook explores the interconnectedness between aquatic ecosystems and human health through the lens of the One Health approach. It also aligns with a number of the United Nations' Sustainable Development Goals and has been written as an accessible resource for students, researchers, and practitioners working within the One Health framework.
