Many threats exist to the life of an oak tree and if we find one that is very big and has perhaps lived for 800 years it has been rather lucky. A great number of oaks of its 'generation' are already dead. If circumstances remain favourable for oaks in an area, we may assume that there are younger oaks which will progress to become veteran and then ancient, and the number of ancient oaks would remain more or less constant over time. But if circumstances change to the detriment of oak trees, not enough survivors may remain to become very old and we will see a decline.

For the nation as a whole it is difficult to know if the numbers are in decline, constant, or increasing. But we have records of large ancient oaks in England from the 19th century and from these we know that many have disappeared. However, many other large ancient oaks were not mentioned then, and several of these were probably not big enough to draw much attention. There were no systematic surveys which recorded all large trees, not even in places well known to have had them for a long time such as Blenheim Park or Windsor Great Park. We must look at other evidence to infer the historical losses or otherwise of ancient oaks.

One factor that has played a detrimental role for ancient oaks is forestry. We can more or less forget the cutting of oaks for ship building, although it has played a part in the demise of ancient oaks in the Forest of Dean and a reduction of numbers in the New Forest. More importantly, it was plantation forestry that has threatened the ancient oaks and often destroyed them. Especially planting with conifers was destructive: the old hollow trees, worthless for good straight timber, were either removed or shaded out by the fast growing conifers. There are many sites where this has happened. A more recent valuation of what remains has set off rescue attempts, but for many oaks this has come too late.

Conversion of ancient deer parks is another important factor in the demise of ancient oaks. This went all the way from landscaping to golf courses to arable farmland and the oaks may have been only partly preserved or completely destroyed as a result of these conversions. In landscaped parks ancient trees could be preserved, but just as well removed if they did not fit with the design of the visual landscape that was intended. Golf courses have the additional negative effect of altering the ecosystems in which the ancient oaks grew by draining, fertilizers and chemicals, removal of dead (risky) wood and in some instances soil compaction. Farming has often resulted in outright removal of the ancient trees and especially arable use can do damage to those that are left standing.

There is greater awareness among landowners and the public of the value of ancient trees now than in the past. The most important sites for ancient oaks are now often designated as SSSI with restrictions of use and guidelines for management aimed at the ancient trees. Conifers are no longer planted among them and farmers often try to protect the trees from damage by animals or the plough. But more needs to be done, especially to stimulate and help with protection of individual trees on farms. No new golf courses should be planned on sites with ancient oaks. For biodiversity, a >9.00 m girth oak is possibly as important as an entire nature reserve and as Ted Green has said, it should be an SSSI in its own right.