Planting trees is one of the most important responses to the climate crisis that we are currently facing. To be successful, sourcing these trees has to be done with care. An international model of plant trade has developed over the last 30 years which has made the import of trees more cost effective than growing them in the UK. This increased reliance on imported trees has led to at least 20 serious tree pests and diseases being inadvertently imported into the UK, resulting in the loss of tens of millions of trees, reveals the Woodland Trust.

Between 1992 and 2019 tree imports have increased from £6 million to £93 million. That’s a 1450% increase. As post EU policy is drawn up, the charity is calling for significant improvements in biosecurity. The risks of the accidental importation of new pests, diseases and invasive species on imported plants need to be acknowledged. Trees planted in the UK should preferably be UK grown in order to quash the chances of further mass loss that would scupper the Government’s aims to achieve net zero by 2050 to tackle climate change.

Dr Matt Elliot, tree health policy advisor for the Woodland Trust warned:

“There are at least 127 tree pests and diseases that are considered high risk to the UK. If imported into Britain, 47 of these could cost over £1 billion each to tackle and wipe out millions of trees. The evidence is clear, the importation of trees carries a very high degree of risk and a UK grown model of plant production would significantly reduce this risk.

“We need investment now in new tree production technology to increase capacity in UK nurseries so that the trees required for government tree planting targets can be produced without importing more pests and diseases. This investment would also create much needed long-term stability and jobs in the sector. Given the climate emergency we find ourselves in, this issue needs to be tackled with urgency.”

Dutch elm disease and ash dieback have already wiped out tens of millions of trees. For context, only around 4 million trees were planted by government in England, Wales and Northern Ireland last year. Scotland fared a little better, planting around 16 million.

Dr Elliot continued: “Prevention is far cheaper than cure because once a new pest or disease is discovered it is often too late to remove it. As we leave the EU, the UK Government is developing a new GB Biosecurity Strategy. There is a significant risk that the wish to maintain the free flow of plants could be prioritised over protecting the environment long-term through stringent new biosecurity procedures. For example, between 1 January 2021 and 1 July 2021, the physical checking of priority plants will not take place at the border but rather at places of destination inland. This move has been designed to reduce the risk of disruption to trade at the border and is extremely concerning and profoundly risky.”

The Trust also warns that a lack of action on stemming the flow of tree pests and disease into the country could prove a massive blow to the UK’s strategy to meet its climate change targets. 

Dr Elliot adds: “The Government’s own climate change plan to achieve net zero carbon emissions by 2050 requires planting a minimum of 30,000 hectares a year to increase the UK’s tree cover from 13% to 17%. Achieving this is made much more challenging because of the trees we are losing to pests and diseases. Accidentally importing more pests and diseases would further hamper efforts to reach these targets as well as permanently damaging important native habitats.”

The charity also warns of the potential financial impact on councils and private landowners of managing pests and diseases.

“If more diseases took hold, landowners would be expected to foot the bill of managing or removing affected trees. We are already aware of the financial burden on landowners of dealing with ash dieback. Our own bill for managing disease on our estate will top £500,000 this year.”

In order to ensure that the trees that the Woodland Trust plant and sell are not imported, the charity established its own assurance scheme, known as UK & Ireland Sourced and Grown (UKISG). This enables the Trust to work with UK nurseries to ensure a secure supply of trees that have been produced within the UK and Ireland (required for planting projects in Northern Ireland). The charity now urges government and others to specify UKISG trees to help reduce the risk of importing new pests and diseases.

The Government is currently drafting new policy on its strategy for trees and woods in England. Its first draft is expected in the spring.

Notes to editors

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The Woodland Trust is the largest woodland conservation charity in the UK. It has over 500,000 supporters.

The Trust has three key aims:

  1. protect ancient woodland which is rare, unique and irreplaceable
  2. restoration of damaged ancient woodland, bringing precious pieces of our natural history back to life
  3. plant native trees and woods with the aim of creating resilient landscapes for people and wildlife.

Established in 1972, the Woodland Trust now has over 1,000 sites in its care covering over 29,000 hectares. Access to its woods is free.

Policy change

From 1 January 2021 until 1 July 2021, instead of border inspections, businesses can register to become a “Place of Destination” in order to accept goods directly and carry out inspections, should they be deemed necessary. This means that plant pests and disease have an opportunity to enter the country and not be detected until they are at the nursery. This gives them the increased opportunity to escape and spread.

Examples of the current tree disease crisis in the UK

Native oak trees could be grown in the UK but have been frequently imported despite the known risks of pests such as oak processionary moth (OPM). Between 2013 and 2015 alone, 1,117,696 oak trees were imported. As a result, OPM has been repeatedly imported with over 70 new interceptions during the 2018/19 planting season on trees that had already been planted. The plant health authorities traced most of these trees and destroyed them but some moths may well have escaped - only time will tell.

Ash dieback is another example. This disease will kill millions of ash trees across the UK (approximately 80% of ash trees are predicted to be lost) with an environmental, cultural and economic cost of £15 billion. In addition to ash dieback, land managers are now managing a myriad of introduced invaders including Dutch elm disease, oak processionary moth, horse chestnut bleeding canker, sweet chestnut blight and Phytophthora blight of juniper and alder.

According to the UK Plant Health Risk Register hosted by Defra, there are over 100 other serious tree pests and diseases that would cause devastation if they got into the UK. Examples include a number of bark boring beetles of ash, birch and chestnut, and diseases such as oak wilt and Xylella fastidiosa.

Relevant blogs:

Further reading on tree disease