Are our trees having their own health crisis?

You have to go to Melbourne now to see an avenue of elms like this

Our trees have flourished and are abundant with wildlife. However, within the green landscape some of our long-term assets are in a serious state of decline.

2020 and 2021 will be remembered for the COVID pandemic. A locked down society was the new normal, but along the counties’ silent roads, Oxfordshire’s trees have continued to fight a host of new and historic diseases.

  • Dutch Elm disease (DED): is a fungal disease that is spread by wood boring beetles. Large outbreaks occurred in the mid to late 20th century with the disease still affecting elms today.
  • Ash Dieback (ADB): is a fungal disease which causes leaf death and canopy dieback, first reported in Oxfordshire in 2012. Approximately 90% of ash trees are expected to die as a result. Ash dieback is now widely apparent in the entire Oxfordshire landscape, shown by the trees’ sparse canopies.
  • Oak Processionary Moth (OPM): is a novel species in Oxfordshire. The caterpillars from this species of moth rely on oak leaves as a food source. Caterpillars attack in large numbers and have the ability to eat an entire tree canopy in one season, damaging the trees ability to create energy. The pest also poses a threat to public health when caterpillars release toxic hairs which cause severe rashes. Current data indicates the pest is spreading out from London and unfortunately may arrive in Oxfordshire.

This list is by no means exhaustive and provides a snapshot of only three issues within our treescape in the past, present and future.

Treescapes: focal points of the landscape.

Oxfordshire has a high density of trees within field boundary hedgerows. These are sometimes dubbed “sentinel trees” and form part the distinctive Oxfordshire landscape as well as creating a wide range of habitats.

The felling of these trees is sometimes unavoidable when structural integrity makes them dangerous.  Is this the end for ash trees?  Answering this leaves us with the option of trying to preserve ash in the landscape for as long as possible, with the short answer being only removing trees exhibiting significant decline. Could pollarding or coppicing trees in certain situations be possible or even better? The longer we can leave trees in the landscape the longer we can enable wildlife to adapt and prevent further losses.

Emerging problems or shared opportunity? The loss of trees due to pest and disease is spread by globalisation. We need to encourage replanting when trees are removed, both in private and public settings. This will ensure future generations will continue to enjoy Oxfordshire’s treescapes.

Edward Whorwood
Treetech Arboricultural Services Ltd

August-September 2021