Tropical and subtropical oceanic regions

The Earth is tilted by 23.5 degrees and it rotates on its axis. This results in seasons because of the exposed sun angle. Some regions remain less affected and are exposed to the sunlight in a more constant fashion. The regions between the Tropics of Cancer and Capricorn (23.5 degrees north and south latitude) make up the tropics. Its center is the equator, with the Intertropical Convergence Zone (ITCZ) at its core. In concert with the polar regions, it is a global weather engine. Many ocean and wind currents are also found in this region. The tropics are bound in the north and in the south by the subtropical region, where much of the rain falls that is created by the ITCZ. Both regions, tropical and subtropical, make for areas where a rather high biodiversity can be found. A diversity of human life can also be found there.

Humans fared in this ocean region very well because of the warm temperatures and the superabundance of food and resources, including plants and fish. Approximately 20 percent of the tropical and subtropical region is covered by land, including Polynesia, Greece, Papua New Guinea, Melanesia, and Japan. The historic use of ocean vessels was commonly found in these regions, for example, off Chile, in Polynesia, Portugal, Spain, and in ancient Greece.

Coastal fisheries have been a mainstay of human life in the tropical and subtropical ocean regions. The coastal wetlands of this region, including estuaries and mangroves, play a major role for global well-being. The mangroves of this region are a major contributor when it comes to global carbon cycling. Mangroves are also nurseries for fish, and host congs (shells that were harvested) and marine mammals like dugongs and manatees (many of these species are now endangered, or even extinct). Further, the Amazon, Nile, Congo basin, Ganges, Jangtsekiang, and Mekong Rivers all drain into tropical and subtropical oceans, and are major global hot spots because of sediment inflow, mixing, and fish nurseries. Marine mammals can be found there (indicative of rich food chains), as well as many human population centers (now often expressed as modern port locations).

The tropical seas are the hot spots of mankind. Most people live in the tropics, and there, most of them actually live near the coast. Coastal fisheries play a major role. Famous interfaces between islands and oceans are found, for instance, in the southeast Pacific with its millions of islands, the Florida Keys, the Caribbean islands, and the Seychelles. Such ocean–land interfaces include entire cultures and nations like the Philippines, Indonesia, Papua New Guinea, Jamaica, Madagascar, Japan, and northern Australia. Subtropical examples are found in New Zealand, the Azores, the Baleares, and Easter Island.

Examples of tropical and subtropical oceans can be found in the Yellow Sea, Indian Ocean, Caribbean Sea, Sargasso Sea, Central Atlantic, and the Central Pacific Ocean. More landlocked seas of such water bodies are represented by the Mediterranean, Black Sea, Red Sea, Gulf of Mexico, and Sea of Japan. These ocean regions include such famous and diverse ecosystems as the coral reefs (e.g., the Great Barrier Reef, Caribbean Reefs, and Coral Reef Triangle), the deepest ocean floor (Mariana Trench), seagrass (Sargasso Sea), the Ring of Fire (a Pacific chain of tectonic plates and volcanoes), and some of the most remote islands of the world (e.g., Easter Island and Hawaii).

The tropical and subtropical oceans are a large resource of biodiversity, and many sea mammal and seabird species can be found there. Much of the marine benthos still awaits its description, as do many plankton and fish species. However, the biodiversity and habitat loss is already a major problem. Invasive species and diseases are on the rise. Marine protected areas (MPA) are planned, but these initiatives will hardly protect relevant areas. The well-being of these oceans and their sophisticated and evolved land- and seascapes, ecosystems, and human cultures have declined rapidly in less than 50 years. Overfishing is occurring on a global level. Illegal fishing and piracy are also big unresolved issues. The freedom of the international seas cannot be upheld.

The approach of single-species management fisheries has been criticized for decades. Top predators disappear (e.g., marine mammals such as sharks and tuna) in the study area. Dynamite fishing is still practiced, destroying entire ecosystems. Coral reefs are bleaching on a massive scale. Hypoxias occur, and so does ocean acidification. Plastic pollution has been raised as another major issue. Shipping, ports, marinas, oil pollution, and offshore gas and oil development are further unresolved problems. Many of the destructions are directly linked with the promotion of economic growth, poverty increase, political heritages, and the rise of neocolonialism schemes. Policies set by the Rio Convention or the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) will not be able to stop these destructions alone, judged by the results thus far. The situation has become worse in most areas, including missed biodiversity targets, widening poverty gaps, economic crises, and increased human populations. The tropic and subtropic ocean regions and their web of life will not disappear any time soon, but with the increase of climate change, sea-level rise, a population of more than 9 billion people projected by 2050, and an increase of consumption of products and goods, the outlook for the tropical and subtropical ocean regions, and thus the future for the world, seem rather grim.