Tree Health in England

Question for Short Debate

Asked by

To ask Her Majesty’s Government what assessment they have made of the health of trees in England; and what progress they have made towards developing a variety of ash that is resistant to ash dieback.

I know that two fundamental assumptions will underly all the contributions to this debate by your Lordships: first, trees are absolutely essential for the environment, the future of the climate and human well-being; secondly, many of them are in a very poor state indeed. They are under threat, notably because of ash dieback.

In 2018 the Government produced their Tree Health Resilience Strategy. Four years later is a very good time to ask the Government what progress has been made on what they set out to do in that. What success has there been? I know your Lordships will want to focus on a range of issues, not least bio protection, but I want to concentrate on ash and elms.

We know how ash dieback came into the country, how rapidly it spread and how devastating its effect has been. But there is some good news to report. In 2009 it was reported that researchers from Queen Mary University of London and Kew sequenced the DNA from over 1,250 ash trees to find inherited genes associated with ash dieback resistance. About this, Professor Richard Nichols said:

“Now we have established which genes are important for resistance we can predict which trees will survive ash dieback. This will help identify susceptible trees that need to be removed from woodlands, and provide the foundations for breeding more resistant trees in future.”

This is obviously very hopeful, but the words are “This will help”. It would be good if the Minister could say anything more certain about how far it is now possible to identify resistant trees and whether they are being successfully developed.

There is more good news. Research from the Nornex project led by the John Innes Centre in Norfolk was reported in April. It has developed three genetic markers which enable it to predict whether a tree is likely to be tolerant of disease, and even whether it is likely to be mildly or strongly tolerant. In particular, it has developed a tree it has named Betty that shows strong tolerance. Again, it would be good if the Government could say any more about the timescale and when any significant proposals for replanting might come about.

All this is encouraging, and I recognise that this kind of research is complex and time consuming, but there is an urgency about this task. It is now some 50 years since the devastation caused by Dutch elm disease. It was once one of the most familiar and loved trees of the English landscape, painted by John Constable among others, but 25 million elms were wiped out: 90% of the population. Again, there is some good news to report here. Apparently, in 2019 some elms resistant to the disease had been developed, but the information is somewhat sparse.

More recently, nursery and garden centre company Hillier has described a variety of elm called Ulmus New Horizon that it states is 100% resistant to Dutch elm disease. It has been cultivated since the 1990s, but it took until 2019 to build enough stock to launch it commercially. This is not a native English elm and, from what has been said, it looks as though we will not be able to get native elms back, but it is a closely related hybrid.

My Lords, I think we are all extremely grateful to the noble and right reverend Lord for introducing this important debate. It is not just the loss of diseased trees that we need to consider but all the consequences. Ash holds a special place in the ecosystem of woodlands. Because of its characteristics, it is a good tree for reducing atmospheric CO₂, while 1,058 species from birds to lichens are associated with ash. As with elm trees, the large-scale loss of ash is having a significant impact on a range of species and habitats, as well as the economics of broad-leaved woodlands.

Much is known about the phenology of autumnal leaf fall, gene tolerance and microbial symbionts associated with resistance of ash, but progress on that alone will not solve the problem. Far too many in the forestry establishment still think that disease is an act of God and wilfully do not look at the influence of us humans and the effect we have on this situation. That influence is called management; more accurately, I call it bad management. We know that most of our woodlands in this country are in bad condition—what an indictment.

Planting blocks of the same species with a view to clear-felling is a recipe for increasing disease and pest problems and is unnatural. For over 50 years I have banged the drum for working with nature and for mixed, uneven-age forestry. Dense woods put the trees under pressure and ash, like oak, is very intolerant of lateral competition. Stressed trees are more susceptible to disease. Dense stands lead to quiet, humid conditions, which increase spore production and retention within the stand.

Some enlightened companies, such as SelectFor Ltd, have been pursuing irregular silviculture and continuous cover for many years. It has backed its belief with scientific research, using the universities of Salford and York. Initial results indicate that even with genetically tested trees other factors, such as environment and management, are involved in the trees’ ability to survive infection. The University of Birmingham’s work supports this: initial results show that ash survive better if planted alongside cherry but worse if planted alongside lime.

My Lords, hear, hear. I declare an interest as chairman of the Woodland Trust. Ash dieback is very serious. The study in 2019 showed that the long-term economic and environmental cost would be about £7 billion over the next 10 years. Ash supports more than 900 other species, of which 44 are entirely dependent on ash. They are very important—particularly, in my view, because they are the most prevalent form of standard trees in hedgerows, and hedgerows with standard trees are vital for the movement of species across the countryside that will be required with climate change.

The noble and right reverend Lord, Lord Harries, outlined how some trees appear more resistant, or at least tolerant, of ash dieback, but there is a long way to go before we are in a position where we will have tolerant seed stock on a widespread scale and are able to plant trees that will persist in the environment. The reality is that we should not hold our breath on the research. We need to take steps now. One of them is not to cut down trees that have ash dieback unless they are a risk to human health and safety. We are unnecessarily destroying trees that may recover or show signs of tolerance or resistance.

Ash dieback is only one of the diseases that affects trees. There is now a pathogen, pest or disease for almost every single species of tree that we have in this country—and if not here already they are lurking somewhere on the continent, ready to come. It is vital that we take tree health and biosecurity seriously across the board, particularly in view of the fact that we are dashing to plant and regenerate trees in the face of climate change: there is no point in increasing the tree cover if it is promptly going to die.

In conclusion—I have already had two minutes and 15 seconds on my timer—I urge the Minister to think about three things in terms of tree health measures. First, let us really have a drive to reduce imports by promoting the UK nursery sector. Will he support—as he is already doing—and promote even more firmly the UK and Ireland Sourced and Grown accreditation system, which aims at all tree stock, from seed to mature tree, being grown in this country or Ireland?

My Lords, I must first declare my interest as co-chairman of the All-Party Parliamentary Gardening and Horticulture Group—and what a mouthful that is to say. I would like to make a general point first about the three types of trees: there are those that are involved with forestry; those involved with woodland management; and those involved with arboriculture—the amenity parts of trees. I have a suspicion that the Government take the arboricultural side of things less seriously, and I hope I can be told I am wrong by the Minister when he comes to sum up. But they are an extremely important aspect when dealing with the health of trees.

I will not dwell on the issue of ash dieback, as it has been so comprehensively dealt with by the noble and right reverend Lord, Lord Harries, and others before me. I want to concentrate now on threats to come. I have been told that there are at least 47 pests and diseases beyond our shores, at present, but which may reach our shores in the next decade. Therefore, it is extremely important that every measure possible is taken to deal with that issue.

I spoke a year or two back to the director of horticulture at Kew’s Royal Botanic Gardens and I thought that their policy on new trees was a lesson for us all. First, they seek to buy from British sources only—British nurseries. If that is impossible, they will buy imported trees but those are then, rather like dogs of old, quarantined for six months in a special area before they are allowed out into the wider community.

That may be a counsel of perfection not possible for all, but it chimes with the point made by the noble Baroness, Lady Young, that we need to increase production in tree nurseries by helping and supporting them. I guess there is a limit to the number of sites on which they can produce, but it is important that they have some knowledge of the future orders that might be placed by local authorities or the Government. They need good warning, because it takes up to five years to produce the sorts of trees required for such schemes.

My Lords, I begin by declaring my interests in the register and explaining that I own some ash trees. One of my abiding memories of the Platinum Jubilee weekend was the obvious impact of ash dieback on the tree cover of Cumbria: everywhere were black, skeletal twigs protruding through the tree canopy. This pandemic predates Covid and moves more slowly, but it is a real pestilence just the same. We have not talked about it as much as Covid-19, fortunately, but the noble and right reverend Lord, Lord Harries, has done us a good turn in bringing this debate.

We should not be surprised by something such as this happening. After all, Dutch elm disease occurred in this country’s living memory and, before that, in the 1930s. Pundits have predicted this kind of thing and historians of nature, ecology and the environment have chronicled this kind of happening regularly, from time to time over the centuries. That is not to say it is not sad. We regret that the landscape, as we know it, is losing a very important component and is dying in front of our eyes. But something else will emerge. While it is destroying part of our living world, it is not destroying the world itself.

As other noble Lords have said, I understand that some trees are likely to be resistant. As long as they are spared the woodman’s axe and their natural offspring are allowed to grow, we, in partnership with plant breeders, will be able to replenish our countryside’s ash trees. As has been said, the life cycle of trees is long. It is not the end of the ash, any more than Dutch elm disease completely wiped out the English elm or wych elm.

It seems to be agreed that tree nurseries spread the disease from spores contained in stock raised on the continent. In this context, we need to be clear that we have always had phytosanitary arrangements and being in the single market did not affect that. As others have said, we have to tighten them up. I suspect that, in addition to a number of pernicious plant diseases, we will see more invasive species that are likely to carry out a lot of damage. I put it to your Lordships that the grey squirrel has probably done more damage to British tree cover than ash dieback has. We have to plan for this happening. The problem is that, like generals, we are always tempted to fight the last war. It has also been suggested that spores may have blown over the North Sea. If that sort of thing happens again, it will be rather more difficult to deal with.

My Lords, like us all, I have a great love of trees and have been involved with them one way or another all my working life. I attended a meeting at the Forestry Commission’s headquarters in Savile Row in the 1960s, called to discuss Dutch elm disease. Despite the testimony of a roomful of experts in both arboriculture and silviculture, the Government insisted that the situation was not serious. They maintained that Dutch elm disease had been with us since the 1930s, that there had been many peaks and troughs and that this was just another peak. How wrong they were and how tragically that illustrates the need for government to maintain the closest possible contact with organisations that have experts in the field, such as the Arboricultural Association and the Woodland Trust.

The English elm has gone, destroyed by a shipload of logs from Canada. No longer can we enjoy that great majestic cauliflower-crowned tree, so beloved by landscape painters and an intrinsic part of our English countryside. We tried to save it: we pruned it and injected, but all to no avail. However, there is a glimmer of hope. Every year, the elm produces large amounts of new growth in our hedgerows. It increases in size until trunks are about as thick as your wrist and then they succumb again, but it keeps coming. It is tenacious, so there is hope that resistance will come.

The same fate has now befallen our ash trees—again an integral part of our countryside and our lives. They are not just beautiful to look at but very much part of our daily lives, from Morris Minor Traveller woodwork to hockey sticks. There is no cure available: just prune, fell if dangerous and hope for resistant strains to emerge. It is spread by the wind, they say, but it was undoubtedly ably assisted by us importing infected trees and distributing them around the country—unforgivable. Emerald ash borer has already been mentioned—another nasty. It has not yet arrived but is waiting in the wings, if there are any ash trees left to infect.

My Lords, I declare my interest as a woodland owner, sadly with far too many dead and dying ash trees in the woods. Shortly after the then Prime Minister David Cameron asked us all to hug a hoodie, I was told that hugging an ash tree was an indication as to whether the tree was mature enough to withstand Chalara. The thinking was that if you embraced an ash tree and your fingers could meet around its back, it was deemed small and immature, and thus susceptible to the disease. If your fingers could not touch, it might be robust enough to resist. I have to report, with much sadness, that this unscientific approach has not proved accurate and that many of the trees I tried to embrace and thought might survive have not.

I mention this because it is no less plausible an approach to identifying those vulnerable to the disease than many others that have been put forward. I am told that approximately 10% of the ash on the continent are surviving the disease, not 20% as the Woodland Trust states. Consequently, there should be a similar percentage of trees surviving here in England but, notwithstanding what the Minister will no doubt say, there seems to be a woeful lack of science currently at work.

Dutch elm disease occurred decades ago and it is only now that inward trials are taking place with resistant whips from UK stock—one site, I am delighted to say, is located in my own county of Kent. At the end of this month, a symposium is taking place at Kew on elm trees and their associated diseases. Given how long it has taken for such a symposium to come about, what does this mean for ash trees? Can the Minister tell us how long we will have to wait before we have similar developments at work on ash?

The Tree Council says that the ash population may recover over 50 years. I fear that this is fanciful; it has not proved to be the case with elms, and there is no prospect of an indigenation of elms regrowing yet. Is there really any meaningful difference between ash and elm? Forest Research says that its ash seed orchard should begin producing resistant trees from the mid-2030s, which really does seem a lifetime away.

My Lords, I thank the noble and right reverend Lord, Lord Harries of Pentregarth, for securing this really important and interesting debate. Like the noble Baroness, Lady Fookes, I am going to concentrate on what she labelled as amenity trees—what I might call street trees or urban trees in general. That is because I want to put some positive spin in here. We need to think about some positive news; we have heard lots of negative news and there is certainly a lot of that around on tree health.

I can attribute campaigners in Sheffield as playing a really important role in raising understanding of the importance of street trees, in particular to public health and well-being, as well as to biodiversity and in cooling our climate emergency-heated cities as well. I note that 19 cities in the UK have now taken the Tree Cities of the World award. A number of these were awarded last month. Sheffield was among them and it is notable that Leeds, Hull and Bradford were too, perhaps influenced by all the public interest in the news that came out of Sheffield, so we are really seeing the valuing of street trees.

But just as we need trees for healthy cities, trees need a healthy environment to flourish in cities. I pick up the point of the noble Earl, Lord Caithness, who talked of the need to a healthy phytobiome of a diversity of trees. Of course, what we also need is clean air; it is good for us and for the trees. I have to point here to my noble friend Lady Jones of Moulsecoomb’s Ella’s law clean air Bill, which is now in your Lordships’ House.

Hard surfaces make trees chronically stressed if they are not given sufficient space, so we desperately need to think about the planning and design of our cities for people and trees. Taking note of the point the noble Earl, Lord Caithness, made, I am not going to say “the right tree in the right place”, but I am going to say that we need the right tree in the nursery. Lots of people have been saying how much we need to grow so many more of our own trees, but we need to think about what kind of trees we are propagating in our nurseries to be street trees. What kind of signals are we giving to the industry? At the moment lots of the street tree plantings are very small rowans and birches, but we want to see the addition of some of those magnificent trees the Victorians planted—the big specimens that truly shade and enrich our cities in ways that little saplings meant to be lollipop trees are never going to.