"He cleaned up the gorge over a month using nothing but his time and hands. Please be more respectful of our beautiful country and be a tidy Kiwi."
Along with collecting rubbish, he also uncovered more than 60 tyres and lots of wood dumped in the area.
Within seven hours of the post going up, more than 770 people have commented, praising him.
Keep Waihi Beautiful said he was "a local hero, keeping Karangahake Gorge beautiful". "Hopefully this encourages people to keep their rubbish in their cars until they can find a bin, and not chuck it out their car windows!"
Another person spotted him at work on Sunday in the scorching heat and said they were shocked to see how much rubbish he had collected.
"It was scorching hot and he was out doing his thing. My husband counted the bags - 55!!!! Some less than three meters apart. Comeon Waikato, let's keep our country clean and green. Mate you're a legend!!!! Thanks for being bloody awesome!!!"
Others have called him amazing, a bloody legend and said he deserved a medal for keeping that part of paradise pristine.
In response, Barker posted on Facebook: "Wowee you guys don't know how much this means to me!"
He said he was in the process of editing a documentary on the issue and hoped to have it online by the end of the week.
"... We need to make a difference and keep New Zealand beautiful as Kiwis and this is a stepping stone on the right track.
"You have all manavated me to do the mahi and keep Aotearoa ātaahua!..."
READ MORE:
• Remember 'Be a tidy Kiwi'? Keep NZ Beautiful is back in campaign-mode
• Premium - Letters: Being a tidy Kiwi is becoming more and more expensive
• How AI and tidy Kiwis are cleaning up our beaches
• Rubbish is no match for tidy Kiwis