Ancient trees are suffering "unsustainable" losses because of worries about failure, but a lack of data on large trees being felled is preventing campaigners from making their case.
"More places are closing so they don't have to intervene with their trees so much," said Woodland Trust ancient trees expert Jill Butler.
"Incidents where there are casualties and publicity put a lot of pressure on other sites if they can't close to the public. We'd like the public to be more responsible so these accidents don't happen in the first place and not go into sites where they're putting themselves at risk.
"We feel there is a high rate of loss and it isn't sustainable, and our concerns are about rate of loss because of natural events, health and safety and lack of knowledge."
She said an ancient tree such as the Duke of Wellington cedar (HW, 10 January), recently felled by the National Trust at Kingston Lacy in Dorset is irreplaceable and planting young trees is like destroying a Chippendale and "replacing it with a reproduction".
Butler recommended Government funding for top-quality tree advice for landowners and a national register of trees, similar to listed buildings, to stop more ancient tree loss.
Tree consultant Jeremy Barrell said he is frustrated because "we know it is happening, but cannot substantiate it".
On the "rapidly depleting heritage of old trees" he added that "risk assessment has become so complicated that arborists are so confused they are taking the easy option and felling rather than taking the risk.
"I am seeing case after case where trees have just been felled when there was an obvious and easy management option." Barrell said he advocates crown reduction or fencing off.
Jeremy Barrell, managing director, Barrell Tree Consultancy
"I am aware from general practice that many large trees are being removed and these are the ones that will eventually become our future heritage trees. What seems to be happening is that the loss of these intermediate trees is diminishing the future stock of heritage trees. The reality seems to be that we do not know where a lot of these trees are, which is why we need a national register like the listed buildings schedule, which is why the Tree Council Green Monuments initiative is so important. Until we know what we have got, we really will have no idea of what we are losing."