The sanctuary had been used for grazing and was in a terrible state, Mr Maister said.
Hundreds of volunteers have worked hard for more than a decade to eradicate pests, regenerate native bush, build a 600m predator-proof fence and create walking tracks through the reserve.
As well as his environmental work, Mr Maister also volunteers as chairman for the Picton Smart and Connected group and represents New Zealand on the International Olympic Committee.
He has been selected as a regional finalist in the Pride of New Zealand Awards in the Environment category for his dedication to the Picton community.
"He is a true leader and does all of this without the fanfare and with a huge degree of humility," his nominator said.
Mr Maister believes it is important to try and give each community an "identity, positivity, enthusiasm and purpose".