Tree Pests and Diseases

Earl of Cork and Orrery Excerpts

Thursday 13th February 2020 Lords Chamber

[The Earl of Cork and Orrery (CB)]

My Lords, I echo the thanks to my noble and learned friend Lord Hope and my noble friend Lord Kinnoull for procuring this valuable debate. I declare an interest as a trustee of the International Dendrology Society. It is an honour to follow so many knowledgeable noble Lords, but it must be said that at this point in the debate, 10 speakers in, we are all likely to be crossing similar paths in various areas, so please forgive me when I cross ground that has already been touched on.

Trees are such an integral part of our landscape, both urban and rural. They support biodiversity by housing a wide range of animals and providing them with food. They help make towns and cities attractive places to live and boost mental health. Imagine cities without the plane, platanus hispanica, or the common sycamore, acer pseudoplatanus—note the relationship—or even the flowering cherries and magnolias, silver birches and horse chestnuts which line our streets, fill our parks and keep us cool in summer, while also marking the passing of the seasons.

Imagine, too, the countryside of Britain without those crowning glories among our common trees: ash, oak, beech, chestnuts—both horse and sweet—birch and alder. The list goes on, but one is missing: the English elm. Much reference has already been made to this wonderful tree, and the fact that many of us in this House are old enough to remember the majestic columns of ulmus procera dominating the countryside. There are now only a few thousand healthy specimens of this variety left in the UK, mainly in urban environments and, surprisingly, most in Brighton, after the ravages of Dutch elm disease killed an estimated 25 million trees. This pest, a beetle, was first identified in 1918 in Holland by some very well resourced and clever microbiologists; that epidemic died out and a second and more virulent attack hit the whole of northern Europe in the 1960s. This appears to have originated in Canada on imported logs, so it is not fair to blame the poor Dutch. However, this pest showed us in sobering fashion what could happen if insufficient measures were taken to control it. We do not seem to have learned that lesson.

This brings me to the disaster facing one of our best loved and most numerous native trees: Fraxinus excelsior, the European ash. In this case, the problem is a fungus rather than a beetle, although the Americans are facing a similar disaster caused by a beetle, the emerald ash borer, which has not yet made an appearance in this country. Our ash dieback is caused by the fungus Chalara fraxinea, which originated in Asia. Recent estimates suggest that this disease will kill around 70% of our native ash, which will amount to something in the order of 70 million trees. Some surveys put the total number of mature trees in the country as high as 130 million. When you consider the size and visual impact of this species, that will leave an even bigger hole in our landscapes than the elm.

The fungus arrived here by various means, including wind spread, but one of those routes was undoubtedly the major trade in young plants imported from Holland. The Dutch nursery trade is hugely successful, and I have no problem with that, but it flies in the face of common sense to import ash whips and saplings from a known disease-ridden environment to plant in our gardens and parks. Ash both seeds and grows prolifically in this country, as anyone who has had to pull up ash seedlings around ash trees knows only too well. Why then do we need to allow the import of such plant material? However, unreported so far by other commentators, I am told that Queen Mary University has managed to isolate the genome of disease-resistant ash trees they have found. This gives us hope that maybe we can go forward with a method of planting ash that will remain resistant.

On a related point, a great many of these ash trees we will lose are in hedgerows and parks around the country. When they die, as they assuredly will, it is a known fact that they become brittle and if left standing are likely to drop limbs or even fall over altogether. The idea of leaving them, as elms were left, simply does not stand up—sorry for the bad pun. This makes them dangerous and those responsible for them, be they in public or private ownership, will be liable. This will entail felling and removal of any tree within 60 to 70 feet of a road or footpath.

This process will be very costly; the cost to the economy has already been estimated at £15 billion. Will the Government be prepared to assist local authorities and landowners in the removal of this vast stock of dead wood? Some form of grant linked to the number of trees to be dealt with and a specific timescale would be a good starting point. The silver lining is that ash is an excellent firewood and can be turned into woodchips for biomass fuel plants. Perhaps the Government could go further and incentivise the building or conversion of such plants to ensure that this unfortunate source of energy is not wasted.

In my own small patch of west Sussex, surrounded by unmanaged woodland, I have in the region of 50 ash trees in a patch of less than three acres. All are affected to a greater or lesser extent. Extraction will involve heavy machinery and, with the Wealden clay underfoot, it would be impossible for about nine months of the year. With no road close by, it will be extremely difficult, not to mention messy and unsightly. Scale that up to the size of the ash woods prevalent in the south of England and you can see the problem.

In the current wave of enthusiasm for planting trees to offset our carbon emissions, some words of caution should be voiced. Politicians like big numbers; Jeremy Corbyn promised to plant 2 billion trees over the next 20 years. This would be the equivalent of 100 million a year. That is the equivalent of 270,000 for every day of the year, or nearly 200 per minute. This is, however, only about twice the estimated requirement for carbon neutrality by 2050 to be achieved. This would require UK woodland cover to increase from about 13% of total land area to about 20%, but much of that increase would have to be on land currently used for farming purposes. The conflicts of interest are obvious. These trees should be UK native species and not so-called non-natives. A native species arrived here before or during the last ice age; non-natives, by definition, arrived over the last 8,000 years. This should not include exotics, such as the fast-growing conifer types which have been imported, largely from North America, to provide the so-called battery hens of the arbori- cultural world.

With Brexit, we have an ideal opportunity to strengthen our phytosanitary regulations. We have talked about invasive plant and animal species; these regimes must be strengthened and enforced, and we should certainly stop the import of plant varieties which have a history of disease and can be grown from seed or cutting successfully within our own industry. Further appropriate funding for the Animal and Plant Health Agency would be a start.

Sadly, it is too late for the ash, but it may still be possible to save and protect other species such as oak and chestnut. The Government’s tree health resilience strategy of 2018 was a good start, but can the Minister outline the measures being taken to improve our protective shield in the wake of Brexit and inform us of progress made in achieving the aims of that strategy in the two years since publication?