Biodiversity is the abundance of life within a given area. Marine biodiversity is the variety of life found in the ocean. It includes all species from tiny phytoplankton to the mighty blue whale (Balaenoptera musculus). Places with a higher-than-average number of different species are considered biodiversity hotspots.

High biodiversity in Earth’s oceans is critical to a healthy planet. Biodiverse marine ecosystems produce half of the oxygen we breathe. The ocean is a massive carbon sink, offsetting carbon dioxide in the atmosphere. Coral reefs and mangrove forests protect coastlines from storms, a vital ecosystem service for the nearly 44% of the world’s human settlements living within 150 kilometers (93 miles) of the ocean. In addition to protection, the ocean provides food and income for millions of people through fishing and aquaculture.

However, biodiversity, marine and terrestrial, is in decline. The World Wildlife Fund estimated in a 2024 report that we experienced an average of 73% decline in global populations of mammals, fish, birds, amphibians and reptiles from 1970 to 2020. Things are so bad that some scientists suspect we are experiencing the sixth great extinction.

Humans impact marine biodiversity in many different ways, including overfishing, catching species we do not need (bycatch), polluting the ocean, introducing invasive species and contributing to climate change. Each species serves a purpose in its ecosystem. Removing one can have significant impacts that cause environmental changes or the disappearance of other species that were dependent on the function served. Removal of a keystone species, for example, could have a chain reaction on the ecosystem. Higher biodiversity may make ecosystems more resilient to change, something particularly important today as climate change alters the temperature and chemistry of the ocean.

You can make a difference to protect marine biodiversity. You can choose sustainable seafood options, reduce your use of single-use plastic and recycle when you can, reduce your carbon footprint, and volunteer with organizations that pick up litter, teach others about the ocean or advocate for the creation of marine protected areas like the National Geographic Pristine Seas project.

The data in this map layer was created by the National Geographic Society’s Pristine Seas team to help them prioritize what areas of the ocean to protect next. Their mission is to create more protected spaces for marine life so it will be there for future generations. The team examined the ocean in three areas: (1) species, (2) biogeographic provinces and (3) seamounts. For species, the team looked at habitat suitability maps for 4,242 species and examined them for threats such as habitat destruction and fishing that the creation of a marine protected area (MPA) would prevent. They then weighted each species on how likely they are to go extinct and how distinctive they are evolutionarily and functionally. Scientists then added in where in the ocean each species lived. For example, were they coastal? Did they live in the deep sea? Were they pelagic, or living in the open water? The final factor they added to this biodiversity model was the location of seamounts. Seamounts are underwater mountains and are known to be important and biodiverse habitats.

This data is organized into cells, also called pixels. Each cell was assigned a value based on the criteria the scientists set, from zero to one. The closer the value is to one, the more important the area is to protect. Places that have already been protected were assigned a higher value for comparison. Turn on the Pristine Seas or Protected Areas layers to explore them further.