Editorial: extreme weather continues to take a toll and to lead discussions

The latter half of 2023 continued the trend of extreme weather conditions around the globe but especially here in Great Britain. An extended drought over the previous period was followed by almost continual storms with strong winds and heavy (torrential) rainfall. Although the winter included early snowfall and, in some places, heavy snow accumulations, the general trend has been towards mild and wet. A warm autumn and winter has meant plant, animal, and fungal species increasingly out of sync. and a broadscale blurring of traditional seasons. Many summer-flowering wildflowers can now be seen in bloom almost year-round. Furthermore, environmental stresses including floods, droughts, unseasonal weather trends and the like, combine with urbanisation, globalisation, and atmospheric pollution (particularly nitrogen fallout), to exacerbate or even cause, outbreaks of pests and diseases worldwide. This situation becomes a recipe for serious and escalating, long-term problems.

An obvious question from the above descriptive account is what this means for our trees and for tree professionals. Excessive soil moisture combined with storm winds clearly causes treefall and fracture across the country and tree professionals responding to the consequent need to remove, tidy up, and make safe. Similarly, heavy snowfall combined with periods of relatively mild weather and high wind may generate catastrophic factures and collapse of large branches from big trees. Of course, an additional consequence of the above observations is that there will be further questions raised about matters of safety, of costs incurred, and necessary guidance on things like routine inspections, etc. Trees, especially big trees, help provide carbon sinks to help mitigate climate change and they also generate resilience at a landscape level. However, these same trees near buildings or, for example, transport infrastructure (specifically highways and railways), bring associated hazards and cause potential disruption. Furthermore, at a time when local authority and government agency budgets continue to be inexorably squeezed, there are important questions about the ability to respond in order to minimise danger and disruption and clear up the mess when disaster strikes. To address these growing challenges requires responsive best practice guidance underpinned by the necessary good science.

In this issue of the Arboricultural Journal, we bring together three research papers and a Research Note. Pertinent to the above discussion, Emerick et al. (2024) address issues of tree failure with a case-study of Spathodea campanulate in Viçosa (Minas Gerais, Brazil). The site they chose to evaluate was a university campus where urban trees were impacted on by a bad storm in October 2019. The analysis took stock of the damaged trees to assess the degree of impact and the extent to which this was recoverable or permanent. The case-study provides findings and recommendations transferable to other scenarios. Indeed, other examples of post-event tree assessments would be interesting to see.

Pyne et al. (2024) examine the development of fungal communities in veteranised branches of oaks. This work relates to the unique importance of the fungal communities in deadwood and in decaying wood in ancient and veteran trees in the context, of course, of tree decline, death, and loss. Associated biodiversity is a widely threatened resource and the continuity of the characteristics inherent in veteran and ancient trees such as old oak, is of particular interest. The concept and practice of veteranisation of mature trees that are not yet “veterans” has been of interest to conservation managers for several decades and this enthusiasm has grown in recent years. Whilst intuitively we expect biodiversity benefits from such interventions, the actual evidence of impacts may be harder to ascertain. With this in mind, a paper reporting research into the ecology of veteranisation is especially welcome. Whilst much further work remains to be done into veteranisation this study adds considerably to the current knowledge. The overall finding was that there were “significant differences in fungal species composition between veteranised branches and branches that had died naturally”. The authors suggest that the differences might affect future fungal community development and that tree managers should take the implications into account if veteranisation projects are proposed.

Also, relevant to understanding climate change and taking effective actions to combat adverse impacts, is the need to capture carbon. Addressing opportunities for carbon-capture in both urban and rural situations is increasingly considered and so examining the balance between different spatial areas is important. Considering these matters, Shrestha et al. (2024) assessed the issues of tree species-richness and phytomass outside Kathmandu, Nepal. Species-richness tended to fall from the urban, through the suburban and into the rural probably associated with exotic, planted species. The average phytomass carbon stock only varied significantly between native and exotic species in the urban area sampled but not in suburban or rural zones. The findings will be of interest to urban greenspace planners.

Finally for this issue, we present a Research Note from Kristina Sodomkova which is a review of Chapter 1 of the new Manual 5 of Blue-Green Infrastructure published by the Institution of Civil Engineers (ICE) (Sodomkova, 2024; Washbourne & Wansbury, 2023). The article usefully reviews this important publication and highlights that Chapter 1 introduces key matters such as the origin, definitions, and typologies of this relatively recent umbrella concept. Helpfully for professional arboriculturists who may increasingly come across the concept, the report’s authors present key aspects of blue-green infrastructure, and its function, value, and overall importance. In working alongside planners, engineers, and project designers, these are terms that will undoubtedly become more familiar to those working on trees and in forestry in the years to come.

For those arborists and others whose passion includes veteran and ancient trees, the extreme weather, associated storms and the vagaries of climate change combine to generate major and ongoing threats to the resource. Additionally, the specific biodiversity associated with these demands continuity in both time and space, and current environmental change makes the connections more tenuous. As biological entities, perhaps with the exceptions of some long-lived clonal or self-coppicing tree species, ancient trees eventually die. Climate change and other stresses may well be speeding their passing, and so we need ways to extend life where possible, to grow better temporal and spatial links, and to foster the veteran character of younger specimens so they can temporarily fill the gap. If we fail to achieve better connection across the tree generations then we stand to lose much irreplaceable biodiversity. Along with programmes of veteranisation as described earlier, for viable populations of future veterans there will be a need to establish specimens at landscape level and somehow to mimic the eco-cultural processes that generated our current and diminishing stock. There is much more work to be done and time is not on our side.

As so often the case with the Arboricultural Journal, we have a selection of papers and topics highly pertinent to current and emerging issues. This editorial began with comments about extreme weather and climate change both of which are embedded in matters of biodiversity extinction, and socio-economic or political trends in society. Within all of these matters we know that trees are hugely important, and for local communities often of major importance for health and wellbeing, and in generating a “sense of place”. Delivering genuinely long-term sustainability in an increasingly urbanised and globalised world must be one of our society’s greatest ever challenges, and the arboriculture profession must be at the core of any realistic vision.

We are also pleased to announce a new section to the journal, called ‘SOUNDINGS: Views from the Urban Forest’ (Rotherham, 2024) and I have kicked off this innovative, interactive idea to engage with current issues, challenges, and expert opinions. Please see page 67 for the first entry to the new section.