Dothistroma needle blight (DNB) is now “endemic” across the country and represents a “significant threat” to Caledonian pinewoods, according to the UK’s independent Committee on Climate Change.
Caused by a fungus, the disease affects the needles of infected trees. As it progresses, the needles eventually shed, weakening the trees and sometimes killing them.
The report said there was evidence that a trend towards warmer springs in Scotland, coupled with more summer rainfall, was “optimising conditions” for the spread of DNB.
It said in recent years there had been a “rapid increase” in the potential exposure of Caledonian pinewoods, Scotland’s only native coniferous forests, to the disease.
The committee’s report into how Scotland is coping with the threats posed by climate change said statistics from Forestry Commission Scotland showed that the presence of DNB was increasing in “all species surveyed”.
It warned that DNB is now more prevalent in Scots pine, Corsican pine and lodgepole pine than it was in 2016, when the last assessment was carried out.
“The distribution of these sites indicates that the disease is now endemic,” the report said.
Warning the Scottish Government’s goals for woodland restoration were “not being met”, the report’s authors called for “urgent efforts” to reduce forests’ vulnerability to pests and diseases.
George Anderson of conservation charity Woodland Trust Scotland welcomed the report, which he said highlighted the need for authorities to look more closely at the threat posed by DNB.
“Native Scots pine was thought less susceptible but it now seems to be worsening, which raises concerns for the few remaining fragments of ancient native Caledonian pinewoods,” he added.
“Lodgepole or Corsican pine next to ancient native woods present a particular threat of infection and we think it is important these be removed.
“If that is done and good airflow maintained, then the Scots pine can remain resilient. But with climate change it is harder to predict what lies ahead.”
A spokesman for Forestry Commission Scotland said DNB had been present in Scotland for nine years, with action being taken to prevent its spread.
The body is also fighting other tree health threats, including several that are already present in the south of England but have not yet travelled north.
“The new Forestry Strategy for Scotland, which will come into effect on 1 April with the launch of two new forestry agencies, has ‘increasing the adaptability and resilience of forests and woodlands’ as a top priority,” the spokesman added.
Environment secretary Roseanna Cunningham said: “The Scottish Government takes the threats posed by climate change very seriously. That is why we have published a Climate Change Bill that includes the strictest targets in the world for 2020, 2030 and 2040 and will mean Scotland is carbon neutral by 2050. But we also need to be ready to adapt to the changing climate.
“Today, the adaptation sub-committee of the UK Climate Change Committee published its final independent assessment on our first statutory Scottish Climate Change Adaptation Programme 2014-19.
“There are many positives in the report, which highlights that many of our policies and actions have progressed since the adaptation committee’s first assessment in 2016. Notable progress has been made managing current and future climate risk, particularly on peatland restoration, actions to increase marine resilience and an improved understanding of the number of people in Scotland living in areas at flood risk.
“The report also provides a number of recommendations for our next five-year programme. These, together with the responses to the Climate Change Adaptation Programme 2019-2024 consultation, will inform our plans ahead of its publication later in the year.”