Forestry is moving from being a carbon sink to a carbon source as trees planted in the 1990s start being harvested.
In the five years to 2012, New Zealand's 25 percent increase in carbon emissions was masked by carbon stored in forests.
Forest Owners' Association chief executive David Rhodes said forestry would never provide a permanent solution to carbon emissions, although it was giving the country a breathing space while it sorted out how to lower emissions.
But trees had only been a temporary measure, he said.
"Certainly we have cycles going on in forestry as well. So whilst we have a lot of trees growing from when they were planted, say, back 10 years ago, then there's an awful lot of carbon being absorbed.
"Unfortunately, our profile is such that we do have dips as well as peaks and what we really need is some new planting to fill in those dips."
However, the trend in not re-planting forest blocks was gathering pace, Mr Rhodes said.