The Arthur Clough Oak, shown in a sequence of photographs over a century. (Images: Philip Stewart)

The Arthur Clough Oak: A photographic tale of tree time

The famous collection of images of the tree known as the Arthur Clough Oak provides a remarkable demonstration of the resilience of trees, and how their shape and form can change, and be changed, over their lifetime. If shown only the most recent picture of the tree, who could imagine its actual form a century earlier?

As we know, ‘tree time’ operates at a completely different pace – we view trees through the limited window of our human lifespan, often from only a short inspection over a few minutes.

While historical photos from long ago can’t show us everything, this tree tells its own story, part of which we can understand through the morphophysiology of trees and the genetic blueprint that produces a tree’s crown architecture.

As is often the case with veteran trees, there are also interesting stories about the human connections to this fascinating specimen, including how it came to be so named and how the extraordinary photographic record of the tree came to be available to us.

In this presentation I will explore the history of the tree using these images and share additional details gathered through investigative research (and reasoned speculation where necessary!) to elaborate on the compelling story of this wonderful, and seemingly unique visual example of tree time.

Trees and homeowners’ insurance: Adoption of climate-smart tree risk assessment in coastal communities

The threat of tree failure damage to coastal communities is related to increasing frequency and intensity of storms. Preliminary evidence suggests that insurance companies are implementing policies that could influence community forest management decisions. These policies include increasing premiums, denying coverage, or suggesting the removal of trees, all of which represent a negative adaptation to climate change because not all trees are vulnerable to storms. Proper management activities, such as appropriate species selection and placement, pruning and tree healthcare, can mitigate risk. In turn, a healthy and abundant tree canopy is a critical step towards climate change resilience.

To this end, our research will: (1) describe current trends in insurance-motivated tree risk reduction activities; (2) identify the industry’s risk assessment methods and communication of risk to arborists and homeowners; (3) document homeowner response to tree risk. The study uses a mixed methods approach of interviews with insurance professionals and Certified Arborists across the US South to identify trends and risk communication. In addition, homeowners, insurers and arborists will complete surveys measuring risk perceptions and relationships with insurance and tree management.

The disconnect in tree risk knowledge and decision-making among insurers, and the lack of communication between professionals, has created an atmosphere of distrust. Despite the rift that exists between many arborists and insurance carriers, several interview participants from both industries expressed a desire to bridge gaps and create better working relationships. My presentation will identify the policies and practices used by the insurance industry to mitigate its risk, and develop opportunities for the insurance and tree care industries to increase their knowledge about tree risk and management as well as improve working relationships.

Tree allometry: What is it and how can we use it to improve arboriculture?

In 2024, we produced the Handbook of UK Urban Tree Allometric Equations and Size Characteristics.

This was the product of analysing a large set of measured tree data contributed by Treework Environmental Partnership and other organisations. The allometric equations presented in the Handbook enable the production of 2D and 3D models of trees, including projected growth, derived from one or two measured attributes.

Our presentation will explore:

• What is allometry?
• How the study arrived at the calculations.
• What are the issues with the data that we will overcome with future studies?
• A visual presentation of how the allometric equations are used to model 2D and 3D trees and tree canopy growth, CAVAT value and carbon sequestration over time.

It will also be call to action: the arboricultural profession has an amazing opportunity to utilise the data that we have collected on trees to improve our knowledge and practice of tree care.

Flying in the face of oak processionary moth

It has been nearly 20 years since oak processionary moth (OPM) was introduced to the UK. With it came fears of tree damage and human health risks. Despite many millions of pounds being spent on its management, OPM is now naturalised in Greater London and will continue to spread. For many tree managers within the established zone OPM has become a normal part of risk management.

Since 2015, the team of conservation arborists at Hampstead Heath have been managing OPM in a busy urban open space. In 2018 we began monitoring the numbers of parasitoid insects, predominantly tachinid flies emerging from OPM nests. Initially this was to investigate any possible links between populations of OPM and the predatory tachinid fly Carcelia iliaca. Some years later, the number of species we have found predating OPM has increased, producing more questions than firm answers. However, the main question that we are asking is will nature-based solutions generally prove to be the most satisfactory method for controlling OPM?

Oak processionary moth has not been the major problem we feared it could be. I would like to share some of the findings from our seven-year ongoing parasitism study and ask you join me in looking to explore the possibilities of implementing a risk- and nature-based approach to managing OPM.

Riyadh: Urban forestry in the extremes

What happens when a city at the heart of one of the world’s driest regions sets out to plant millions of trees and transform the cityscape – when public space is reimagined to cater for the needs of its residents? Riyadh is not just greening. The Saudi capital is rewriting what urban forestry means in the face of climate extremes.

Where summer temperatures regularly exceed 45°C, rainfall is minimal and irregular, and humidity is very low for most of the year, there are plenty of challenges. Yet over the past few years, the Saudi capital has moved at remarkable speed in its urban afforestation efforts. Green Riyadh, a city-wide strategy, has acted as a key enabler since 2019 by catalysing tree planting and a rethinking of what public realm design can achieve. Massive initiatives have followed which are reshaping the urban canvas.

Through a vivid photographic journey, we will explore how urban forestry is being developed and implemented at an extraordinary pace. Across thousands of square kilometres where conditions are extreme, almost every conventional rule has to be relearned, or broken to be rewritten. From species selection and the quality of nursery production through to landscape management both new and established, we will look at the ambitions to turn this arid desert capital into a city of lush gardens and shaded active travel-ways and the challenges they face. While the outcomes are still evolving, Riyadh’s experience offers valuable insights and will continue to do so long into the future, into how urban forestry can adapt, scale and take root even under the most testing conditions.