They explained what climate change and environmental damage meant to them.
"There is a ticking clock to protect our planet - with climate change, the deterioration of our natural resources, endangerment of sacred wildlife, the impact of plastics and microplastics, and fossil fuel emissions, we are jeopardising this beautiful place we call home - for ourselves and for future generations. Let’s save it. Let’s do our part," they posted.
And even went on to personally quote Harry, Duke of Sussex.
“Environmental damage has been treated as a necessary by-product of economic growth. So deeply ingrained is this thinking that it has been considered part of the natural order that humankind’s development comes at the expense of our planet," Harry said.
"Only now are we starting to notice and understand the damage that we’ve been causing. With nearly 7.7 billion people inhabiting this Earth, every choice, every footprint, every action makes a difference.”
And while some royal fans commended Harry and Meghan for shining a light on these important issues, others called out the couple for not setting a good example when it came to their own CO2 emissions.
"Wait guys. You can’t fly private jets in your personal life and then post this kind of thing. Either live it or don’t. Truly. Walk the talk. Otherwise it’s hypocrisy," one follower said.
"Great initiative, but what about all the flying and driving done by the entire royal family? What about the outrageous size of the housing, the cost of the clothing etc. Perhaps it’s time to set an example. Be the change the our planet needs," said another.
Another added: "Fly commercial planes if you have to rather than private jets if you truly believe what you’re posting."
While other fans were annoyed at being "lectured" by the Duke and Duchess.
"Why does it feel like I’m being lectured every time I read this account?" a fan wrote.