56% of the world’s oceans have turned green over the past two decades, study finds

Over the billions of years that the Earth has been around in the solar system, it “survived” multiple extinction events. As the dominant force in our planet, the oceans cover over 70% of the entire planet, and less than 10% has been explored – scientists have more knowledge about space than the seas, as human limitations could lead to an eventual tragic event since we can only dive to certain depths due to the water pressure, but still scientists were able to find something that involves NASA and the Voyager 1.

Oceans are still a mystery: Only one thing can hit the bottom

With the lack of research and interest in exploring the oceans, also being limited by nature, every discovery amazes scientists and researchers, because there is still a lot more to come, and they are not even at the tip of the iceberg. As technologies advance and people can go down to the Mariana Trench – the deepest point on Earth – new theories about the ocean come up.

Differently from other theories, this one points out an aspect of the surface that might have been very different in the past, at a point when the human species did not even come close to existing, before even the dinosaurs. Some studies show that comets were responsible for bringing water to our planet, but it wasn’t blue like it is today. It had another color.

NASA’s project unveiled the color of our planet: It wasn’t like this

When NASA launched the Voyager 1 in 1977, at Carl Sagan’s request, controllers turned the spacecraft around one last time in 1990 to photograph Earth from a distance, and from that moment on, one of the most iconic quotes in science was said by Carl Sagan as he referred to our planet as “Pale blue dot”.

But for most of Earth’s past, it would not have looked blue at all. For billions of years, an alien traveler might have called it the Pale Green Dot. Between about 3 billion and 600 million years ago, right before complex life began to flourish, the oceans carried a strong green tint. A team from Nagoya University in Japan traced that color back to cyanobacteria, microorganisms that once ruled the seas. Their findings appeared in Nature Ecology & Evolution.

Chemicals changed the colors of the oceans: It’s telling us something.

The color of early Earth wasn’t random—it came down to what filled its oceans. In the planet’s first few billion years, those waters carried large amounts of iron hydroxide, a compound that soaks up blue light. At the same time, the water itself absorbed the red wavelengths. What slipped through was green, leaving the seas with their strange tint, explained Taro Matsuo, the study’s lead author.

From 2003 to 2021, photosynthesis across the planet saw a steady rise, thanks mostly to the growing activity of plants on land. By 2023, a follow-up study found that 56 percent of the world’s oceans had turned green over the past two decades. The oceans, however, told a slightly different story. Marine algae showed a small decline in photosynthetic activity, which trimmed back some of the overall gains. The study was published on August 1 in Nature Climate Change.

Separated, but should be studied as one: The scientific “mistake”

Earlier studies of net primary production usually looked at land and ocean ecosystems separately. That left scientists without a clear sense of how carbon is cycled across the planet as a whole—and what that means for efforts to slow climate change. In the new study, researchers tracked year-to-year shifts in global net primary production, with a focus on how changes on land connect to what’s happening in the sea.