"The oceans are in a state of emergency," he started.
"Entire marine ecosystems are vanishing with the warming of the seas, and as the waste of our world empties into our waters, we face the devastating crisis of plastic pollution." He went on to call the amount of plastic in the oceans "shameful", pointing out the shocking reality that there are now more plastic particles in the seas than there are stars in our galaxy.
"We are a disease that is infecting our planet. As a human species we need the earth to survive. But make no mistake – the earth doesn’t need us."
Hawaii-born Momoa also touched on how Small Island Developing States (SIDS) such as Barbados, Samoa and Haiti are copping the brunt of the damage and how his first-hand experiences have motivated him to do more.
"Island nations contribute the least to this disaster, but are made to suffer the weight of its consequences," he continued.
"The people will hold our governments and corporate powers accountable for the destruction you are allowing to our environment."
It's not the first time Momoa has stepped in on behalf of the environment. Previously, the 40-year-old took to insta to let followers know he was ditching the beard to raise awareness for climate action.