Only 0.001 percent of the seabed has been explored

It is a common truism that we know more about the moon or Mars than about the world's oceans. A team from the Ocean Discovery League has investigated how much of the ocean floor humanity has explored. According to the study, the seabed in the deep sea is not only largely unknown to us, but practically completely unknown.

70 percent of the Earth's surface is covered by oceans. The majority of this is considered deep sea, which means deeper than 200 meters below the surface. These areas make up 66 percent of the Earth's surface, a total of almost 336 million square kilometers.

"Our data show that we have visually examined less than 0.001 percent," writes Katherine Bell and her team in the journal Science Advances. This corresponds roughly to the size of Rhode Island -– the smallest US state has an area of 3100 square kilometers.

44,000 diving expeditions in over 60 years

For the study, the team analyzed data from almost 44,000 diving expeditions that have been undertaken in these regions since 1958. Most of these took place in 120 national Exclusive Economic Zones (EEZs), also known as 200-mile zones.

Only just under a fifth of the expeditions were carried out on the high seas, although these make up 58 percent of the deep sea. And there are fewer and fewer of them: in the 1960s, just over half of the expeditions were on the high seas. In the 2010s, the figure was just under 15 percent.

The distribution is also extremely limited, the team complains: 65 percent of expeditions took place in the EEZs of three countries: Japan, New Zealand and the USA. Some areas, such as canyons or mountain ridges, have been well researched, while others, such as plains or seamounts, have hardly been explored at all.

In any case, only very few countries conduct deep-sea research: 97 percent of the expeditions were carried out by five countries: Germany. France, Japan, New Zealand and the USA. The reason for this is the high cost of such expeditions.

Better understanding of the deep sea

"Given the increasing threats to the deep sea – from climate change to the possibility of mining and resource exploitation –, the limited exploration of such a vast region is becoming a major problem for science and policy", said Bell, head of the Ocean Discovery League and lead author of the study. "We need a much better understanding of deep-sea ecosystems and processes to make informed decisions about resource management and conservation."

The deep sea, i.e. the area from 200 meters below the ocean surface, plays an important role in maintaining the health of our planet, such as oxygen production or climate regulation. The life forms could also serve as food or as potential suppliers of new medicines. It is therefore important to continue researching this area, the researchers conclude. Visual imaging is one of the most important methods here.

However, this is a difficult undertaking given the area involved: Even if 1000 research teams were to examine three square kilometers every year, it would take more than 100,000 years to survey and document the entire seabed.

"So much of our oceans remains a mystery," said Ian Miller, Chief Scientific Officer of the National Geographic Society. "Deep-sea exploration led by scientists and local communities is critical to better understanding Earth's largest ecosystem."

(wpl)