More than a billion trees would cover an area 25 times the size of Edinburgh
Scotland must plant more than a billion trees if it is to meet a target of having 25% woodland cover by 2050, Forestry Commission Scotland has said.
It said enough new saplings must be planted to cover an area 25 times the size of Edinburgh.
The figures emerged as the Scottish Government unveiled a paper proposing a new strategy to expand forests.
One option out for consultation is to lease some of the national forest estate to other companies to manage.
Environment Minster Michael Russell said the income from leasing out woodland could generate about £200m and would enable woodland creation rates to more than double to 24,000 acres (10,000 hectares) a year.
He added: "Rates of woodland creation have generally declined since the high levels up to 1990.
"To continue this trend in the current climate is not an option - an increase in woodland creation must happen.
"More woodlands can help tackle greenhouse gas emissions and importantly supports local businesses and farm diversification."
But Liberal Democrat environment spokesman Jim Hume, who has led the campaign against leasing out Scotland's forests to private investment companies, disputed the government's figures.
He said: "Despite widespread opposition from forestry unions, environmental groups, timber companies, tourism and leisure businesses, and almost 10,000 signatories to the Liberal Democrat petition, the Scottish Government continues to peddle this ridiculous plan.
"The environment minister thinks he'll net £200m profit from this plan. But under his plans the Forestry Commission could lose up to £20m a year for the 75-year term of the lease."