The color of the ocean is derived from the materials found in its upper layers. Tropical oceans close to the equator in particular have become greener in the past two decades, reflecting changes in their ecosystems, according to the study published Wednesday in the journal Nature. More than 56% of the world’s oceans have changed color to an extent that cannot be explained by natural variability, said a team of researchers, led by scientists from the National Oceanography Center in the UK and the Massachusetts Institute of Technology in the US, in a statement.

The color of the ocean has changed significantly over the last 20 years and human-caused climate change is likely responsible, according to a new study.