At least 30,000 ash trees are due to be felled by the National Trust this year at a cost of £3m due to dieback, as the charity warns of a “catastrophic” increase in tree and plant disease because of climate breakdown.
Changing weather patterns are expected to cause pests and diseases that destroy trees to thrive, which could bring dramatic change to British landscapes.
The charity has released aerial images showing how this is already happening with some species. For example, tens of thousands of larch trees will be felled due to Phytophthora ramorum, affecting views such as Tarn Hows in the Lake District. The spread of the fungus-based pathogen is accelerating across the Lakes and in some sites it is predicted that 75% of larch in the woodland will be lost. Foresters in the area expect 95% of their time will be spent dealing with the disease.
Just this autumn, two fresh threats to plant health have been identified in the UK – a new disease, Phytophthora pluvialis, and a new outbreak of the eight-toothed spruce bark beetle has been found in south-east England, meaning restrictions have been placed on the movement of trees, bark, wood chipping and cut foliage in various parts of the country.
Phytophthora pluvialis was discovered last month in an area of Cornwall – the first time the disease has been identified in Europe. The disease has since been found in Devon and Cumbria. Although it has not yet been found on National Trust land, experts are keeping a close eye on western hemlock, Douglas fir and several pine species.
The National Trust says it is trying to build “woodlands of the future” that are resilient to climate change, including using species from warmer climates, which are less likely to be affected by disease – for example, by replacing ash trees with walnut.
Ash dieback is also taking up resources, with the cost of removing diseased ash trees having risen from £1m to £3m over the past year. It is expected that 75–95% of the UK’s ash trees will be lost in the next 20 to 30 years.
Scientists are also braced for an outbreak of Xylella, an incurable plant disease that can cause serious stress and death in over 150 species including oak, cherries, hollies and walnuts. It has not yet hit the UK but there have been major outbreaks elsewhere in Europe, with olive groves ravaged. It is likely that the disease will come to the UK on an imported plant, much like other pathogens that have been brought over by the horticulture trade.
The National Trust has also warned that an increase in the incidence of storms such as Arwen last week is disrupting disease management efforts and costing millions of pounds to clear up. Thousands of trees are also being lost to the extreme weather events, further adding to decimation of the UK’s woodlands.
Trees lost due to disease and pests need to be replaced to help Britain meet its climate change commitments, the National Trust argues, as they are crucial in effectively sequestering carbon as well as continuing to provide homes for wildlife and public access to nature.