Current concern about oak decline

 

Over the past five years, there have been a number of reports sent into the Forest Research Tree Health Diagnostic and Advisory Service about a resurgence in oak decline with trees showing symptoms of dieback.

The reported cases are widely distributed as shown on the map below and particularly since 2002 there has been a significant increase in reported sites with severe oak decline as shown by the graph.

Just as in the early 1990s, several reports comment on the acute nature of the dieback and decline. In some, very high proportions of trees are affected on individual sites and many trees have died or had to be removed within just a few years of the first foliar symptoms becoming apparent.

The exact reasons for the current episode of oak decline have yet to be elucidated, but an important trigger may have been reduced water availability in soils.  Some of the highest mean annual temperatures ever recorded have occurred over the last decade during 2002-2007. In addition, 2003 and 2006 were notable drought years and undoubtedly over the last few decades Britain has seen a trend of drier summers and warmer winters.