“Dangerous” trees are to be cleared as part of an 18-month project to help keep motorists and pedestrians safe.
Natural Resources Wales has announced plans for a £3m project to harvest unstable trees growing above a section of the trunk road between Machynlleth and Dolgellau.
The work will remove approximately 22 hectares of woodland, which is roughly the size of 30 football pitches.
The Bont Evans Tree Works and Stabilisation project, or BETWS, has been set up by NRW to protect people by removing the trees and stabilising the steep bank.
The work on a hillside above the A487 near Ceinws, is due to start in the autumn and will take around 18 months to complete.
It has to be done because the trees have become unstable and would be dangerous to people and traffic if they fell during a storm.
Steve Cresswell, operational resources manager for Natural Resources Wales, said: “Some of them were planted before the Second World War and they have become unstable because of their age, height, weight and steepness of the bank.
“The risk that they could fall onto the road is increasing each year, and this could lead to unplanned road closures, or potentially a major accident.”
Safely removing the larger trees, which weigh up to 12 tonnes, above the main road is “complex”.
It is likely to take around 18 months to complete and will cause some traffic disruption.