Biosecurity: the inherent contradiction

THERE is a long-overdue focus on the planting of trees. It has become fashionable, at last, to recognise the benefits which trees provide, and encourage more tree planting across the UK and indeed mainland Europe. Politicians at both national and local level are increasingly supporting policies to stimulate and increase tree canopy cover.

As this welcome recognition of trees and their benefits becomes mainstream, there is a similar awareness about the importance of biosecurity and the threats to our tree populations from imported pests and disease. Injudicious planting of imported tree stock direct into the indigenous landscape has led to the spread of pests such as oak processionary moth and contributed to the almost universal spread of ash dieback in the UK.

The contradiction arises as the demand for trees increases. Tree nurseries cannot, overnight, produce large numbers of additional trees to satisfy the increased demand. It takes between five and seven years for a tree to reach the minimum 10–12 cm girth size considered as suitable for planting in the urban landscape. The numbers of trees available now and the species mix grown on UK nurseries were calculated five to seven years ago, based on market conditions at the time. Tree nurseries adjust their planting figures annually based on speculative predictive forecasting to anticipate what market conditions and demand are likely to be at the time those trees will be ready for sale. The same analysis applies to the number and variety of species to be grown, with a focus on a historic knowledge of which trees are likely to sell irrespective of market conditions. This is a very narrow palette. Market conditions five to seven years ago were different from the reality today, where the focus is on planting more and more trees – particularly in urban areas.

The government’s welcome initiative and commitment to plant an additional 100,000 new urban trees over a two-year period commencing this planting season through the Urban Tree Challenge Fund, coupled with initiatives from many local authorities and other land owners, has resulted in a position where demand is now beginning to exceed supply in terms of what the UK industry can provide. From this it is obvious that the deficit, if the ambitious planting plans are to be achieved, must be met from somewhere: this inevitably increases the pressure to import trees. With imported trees comes an increased risk of imported pests and diseases. The European market is equally stressed as the increased demand is not limited to the UK alone. Similar planting initiatives can be found – and are being implemented – across Europe and elsewhere. The Dutch tree nursery market has exported close to 100,000 trees to China this year, as well as for the past couple of years.

Canopy cover targets have to be realistic. It would take at least 40–50 12–14 cm girth newly planted trees to replace the canopy volume of these London Plane planted about 1947–1950.

In recent years, the work of DEFRA, the Forestry Commission and others, with regard to the biosecurity of the UK’s tree population, has been commendable. It is likely that a biosecurity accreditation scheme will be introduced in the coming months. This should increase awareness, strengthen the position of those who specify trees and make it possible for the judicious to ensure biosecure pathways into the UK. Unfortunately, this will not regulate mavericks or private individuals who will bring a few plants back from the continent in the boot of the car – with the inherent accompanying risk of diseases such as Xylella travelling as well. Essentially, regulation and accreditation are still going to be defined by the actions of individuals. It must be remembered that oak processionary moth, which is now beyond eradication – and some would say control – was brought into the UK on a single tree planted directly into the landscape. It is likely that one individual person or a small group of people were directly responsible, possibly reacting to a perceived urgent need to complete a landscaping scheme. A shortage in the number of trees available from UK nurseries caused by a sudden increase in demand fuelled by policy decisions, no matter how well meaning and justified, is only likely to increase the likelihood of similar scenarios occurring in the future.

So how can these two admirable initiatives appear to be in conflict, and thus to be working so ominously against each other?

It is important that biosecurity remains central to both local and political policy makers; and it is right that DEFRA, the Forestry Commission and others continue to advise and where appropriate regulate. An accreditation scheme for nurseries and other players within a complex supply chain is also a positive move and should be supported when it emerges. It is essential that individuals recognise and accept personal responsibility for their own actions when purchasing trees. It is also essential that no imported tree should be planted into the UK landscape without first spending at least one full growing season on a UK nursery where full precautionary biosecurity measures can be implemented.

Alongside these approaches, it is right that the number of trees planted, particularly in our urban environments, continues to increase. It is right to support national and local policy and funding initiatives which make this possible. But – and this is the big but – if this acceleration in planting is to be sustained and more trees are to be supplied by UK nurseries, either being grown in the UK or imported and effectively quarantined for a growing season, there has to be action which reconciles supply with demand.

At this moment in time it would seem we are entering into one of the recurring bubbles of political and social conscience where a course of action is deemed to be the right one and there is a burst of frenetic and spontaneous activity within a defined timescale – usually, in respect of trees, a ridiculously short one.

The number of ambitious targets being released into the public domain by politicians in both central and local government – and the claim that canopy cover will be increased by a certain percentage within a given number of years or that a certain number of trees will be planted within a two- or three-year period – are going up almost daily.

Trees sold into today’s market have been in the ground for at least five years and reflect market conditions at the time they were planted.

Yet most of these targets are ill-considered, and often unachievable. Tree population management is strategic and needs to be considered over 20, 30, 40 years and longer. There needs to be a coherent, realistic vision. What is the long-term objective of all this accelerated increased planting of trees? Where is the evidence that strategic goals have been considered in any of the initiatives which have so far emerged into the public domain? Are trees being planted to increase the level of ecosystem services provided within any given geographical area? Is the intention to improve health and well-being through the provision of more environmentally sound places where people live, work and play?  Or are politicians just providing a short-term visible response to enhanced environmental awareness in the general population? It is to be hoped that these questions and others will be answered when the proposed ‘Strategic Plan for UK Trees and Woodlands’ is published early in the new year.

Reconciliation between the need for more planting of trees and the need for improved biosecurity will be encouraged when the urban forest is managed by long-term strategic planning. With strategic planning, it is possible funding streams for new planting will be continuous and not subjected to a roller coaster which rises and falls from plenty to nothing on a repeated basis. Dependable funding and resource allocation according to a clear strategy, together with long-term consultation with the nursery industry, enables supply to be managed to meet planned demand, thereby reducing the necessity for pressurised imports to meet accentuated but irregular demand.

This is not to be critical of either the need for good biosecurity or the requirement to plant more trees. Never has the need for both been more readily apparent. Unfortunately, there is always someone, somewhere in the demand/supply chain who will put personal gain before more altruistic (and strategic) motivation.

It is possible to be biosecure and increase tree planting, but the whole issue surely must be on a strategic and long-term basis: ‘tree time’.