The clearing of ancient woodland to make way for the HS2 high-speed rail line is to be delayed while the project is reviewed, the government says.
The project has already been put back five years and could run more than £20bn over budget but a “go or no-go” decision is due by the end of the year.
Transport Secretary Grant Shapps said it must be recognised that some works “cannot be undone later”.
The Woodland Trust described the announcement as “a welcome step”.
It said at least 108 ancient woods would be affected by HS2 as a whole, with 63 suffering “direct loss” and damage due to noise, vibration, changes to lighting and dust.
There are 34 affected sites in the first phase of the project from London to Birmingham.
Clearance work on eight sites in Warwickshire and three in Staffordshire this autumn has now been halted, the trust said.
£7.4bnAlready spent on the project
9,000Jobs supported by the railway
345 milesNew high-speed track
50 minutesJourney time saving between London and Manchester
The London to Birmingham section of the line was due to open at the end of 2026, but it could now be between 2028 and 2031.
The cost of the project, which is to go on to Manchester and Leeds, has also risen from £62bn to between £81bn and £88bn, it was revealed earlier this month.
The review, led by Douglas Oakervee, a civil engineer and former chair of HS2 Ltd, will consider whether and how it should proceed.
Mr Shapps said the project faced challenges and difficult decisions.
“So, as Douglas Oakervee’s review continues, we must take a sensible approach and recognise that some works simply cannot be undone later.”
Delaying the woodland clearances “ensures we avoid irreversible decisions without major impacts on cost and schedule”, he said.
“HS2 may be a complex project overall but I think this request is just common sense.”
An HS2 Ltd spokesman said it was committed to reducing the new high speed railway’s impact on ancient woodlands and agreed a “sensible balance” was required.
The firm has said it is planting more than four times as much new woodland on the route to compensate.
Follow BBC West Midlands on Facebook, on Twitter, and sign up for local news updates direct to your phone.