A B.C. government initiative to plant trees as a way to offset greenhouse gas emissions is facing criticism from environmentalists.

The provincial government is looking to spend up to $5 million on projects to plant trees or make existing ones grow faster through fertilizer and other means.

The idea is that trees remove carbon from the atmosphere as they grow, and that that reduction in greenhouse gases can make up for pollution from whoever pays for the offset.

The program will be used to offset emissions from the public sector and the 2010 Winter Olympics.

However, Nicholas Heap of the Vancouver-based David Suzuki Foundation is critical of carbon credit schemes based on tree planting.

It can take decades for the trees to grow enough to make a difference, he said, and the trees will eventually rot and release the greenhouse gas back into the atmosphere.

"Environmentalists like ourselves have been talking about the wonderful myriad benefits of trees and planting forests," Heap said.

"But when you're planting trees primarily or only as a carbon offset, we're not playing to the greatest strength of trees. There are other means of producing offsets that actually out-compete planting forests."

Forests Minister Pat Bell vowed B.C. would make sure its carbon credits meet a high standard.

"We only want to do things that we can scientifically defend, that can be accounted for and that people support and know is a very real carbon offset," Bell said.

"We can either… help make the rules and ensure that the rules are open, transparent and accountable, or you can let someone else develop the rules. For my money I'd rather be the ones that are driving the bus [in] developing the rules."

Bell said B.C.'s forests have the potential to keep millions of tonnes of greenhouse gases out of the atmosphere.

But Heap said the province would be better off investing in other projects, like ones that reduce the use of fossil fuels, to offset carbon emissions.