More than 100 people showed up to a meeting in Oamaru on Tuesday to raise concerns about a large scale forest farm being developed in the area.
A 2500 hectare sheep and beef farm at the headwaters of the Kakanui River has been bought by New Zealand Carbon Farming.
The company establishes permanent forests to mitigate climate change through carbon credits.
Locals say the company already has one farm in the Waitaki region which is already showing adverse environmental effects.
Natural resources engineer at environmental consultancy group Irricon Keri Johnston, who spoke at the meeting, said the community is not against forestry but just wants a better understanding of what is going on.
"The Kakanui River is already considered to be water short - so the presence of forestry over such a large area in the headwaters of the catchment will impact the amount of water which makes its way into the river."
She said landowners in the region around the carbon farm already established by the same company have noticed the effects of the forest.
"The quality of little waterways which run through the farm have deteriorated, pests have become a big problem, they now have wallabies in that area which they didn't have before and the company did things like blanket spray and cleared a lot of vegetation when the forest was being established."
She wants regulations put in place to ensure the forests do not have negative effects on the environment.
"Like I said, no one is anti-forestry - we just want to make sure the right trees are planted in the right place."
Waitaki District mayor Gary Kircher said there is not a lot the council can do apart from monitor if the company is complying with the district plan.
New Zealand Carbon Farming said as the owner and manager of the largest New Zealand-owned conservation estate of permanent forests, it significantly contributes to the country's climate goals.
"Our trees are never harvested. Instead they are actively managed to return, over time, to a 100 percent indigenous and biodiverse conservation estate - providing a rich habitat for Aotearoa's unique native flora and fauna.
"Over 95 percent of New Zealand Carbon Farming's 66.7 million trees under management for carbon are planted on marginal land (grade 6 and above) - often in steep and erosion prone areas," the company said.
It said it carefully manages its forests - employing local people to work year-round on tree and estate management and pest control.