Section 4 of the third World Ocean Assessment is focused on providing details of the changes that have occurred in the ocean since the period covered by the second Assessment, i.e. between 2018 and 2023, relating directly to the corresponding chapters in the second Assessment. All relevant information is described with respect to various geographical ocean regions.
Chapter 1 (Drivers) of section 4 provides a list of drivers updated since the second World Ocean Assessment. Chapter 2 (Scientific understanding) is focused on improvements and advancements in ocean science and technology, including various human-ocean interactions and relationships. Chapters 3 (Trends in the physical and chemical state of the ocean), 4 (Biodiversity) and 5 (Habitats) provide updates since the second Assessment. A subchapter on cephalopods has been incorporated into chapter 4 and a subchapter on fjord systems has been added to chapter 5. Furthermore, the subchapter entitled "Open ocean" in the second Assessment has been replaced by the subchapter "Pelagic domain", which also includes shelf areas. Chapter 6 (Pressures) provides a cross-cutting analysis of changes in pressures, such as erosion and sedimentation, and cumulative effects.
