Veteranisation in Aboriculture

Background

Humans have deliberately damaged plants for centuries to mimic natural effects. Pollarding is one example.

Managing younger trees to accelerate the development of habitat features has occurred for decades (e.g., Italy, United Kingdom, United States).

Carey, Andrew B., and H. Reed Sanderson. 1981. “Routing to Accelerate Tree-Cavity Formation.” Wildlife Society Bulletin 9 (1): 14–21.

Habitat-tree protection, as a wider practice, dates back at least 200 years.

Mölder, Andreas, Marcus Schmidt, Tobias Plieninger, and Peter Meyer. 2020. “Habitat-Tree Protection Concepts over 200 Years.” Conservation Biology, ahead of print. https://doi.org/10/gg9zw3.

Importance

Old trees provide hollows, fissures, and decaying wood. These features support biodiversity, especially species that depend on mature or dead wood for nesting, roosting, or foraging. Where old trees are scarce due to logging, agriculture, or urbanisation, veteranisation can restore ecological functions and support threatened taxa.

Intent

Support existing taxa or reintroduce taxa by rewilding degraded areas.

Veteranisation aims to mimic natural damage and start decay processes that form cavities.

Techniques

Most techniques are subtractive, similar to manufacturing groupings (additive/subtractive).

Types:

Subtract to create a feature.
Redirect or initiate a process to create a feature.
Add a feature.
Hybrid.

Examples

Subtractive Techniques

In living trees, modifications must resist growth and healing.

In dead trees, modifications must resist decay and collapse.

Hollows carved with chainsaws.

Best, Katherine, Angie Haslem, Alex C. Maisey, Kristin Semmens, and Stephen R. Griffiths. 2022. “Occupancy of Chainsaw-Carved Hollows by an Australian Arboreal Mammal Is Influenced by Cavity Attributes and Surrounding Habitat.” Forest Ecology and Management 503: 119747. https://doi.org/10/gpk7ds.

Chainsaw hollows:

Mimic thermal properties of natural hollows better than boxes.
Marsupials may start using them rapidly.
Can be long-lasting.

Find inner decay by probing with a small hole, then create a larger access hole.

Ellis, Murray V., Jennifer E. Taylor, and Susan G. Rhind. 2022. “Creating Entrances to Tree Cavities Attracts Hollow-Dependent Fauna: Proof of Concept.” Restoration Ecology 30 (8): e13713. https://doi.org/10/gq3fjt.

Trials with:

Bats (see Griffiths)
Phascogale (Phascogale tapoatafa) and sugar glider (Petaurus notatus): 2.5-year test, species used chainsaw hollows more than boxes, some plates deformed, some calluses grew, maintenance needed, some potential.

Terry, William, Ross L. Goldingay, and Rodney van der Ree. 2021. “Can Chainsaw Carved Hollows Provide an Effective Solution to the Loss of Natural Tree Cavities for Arboreal Mammals?” Forest Ecology and Management 490: 119122. https://doi.org/10/gcrz.

Feathertail glider (Acrobates pygmaeus) (in 75% of hollows), brown antechinus (Antechinus stuartii) (75%), sugar glider (Petaurus breviceps) (63%), long-eared bat (Nyctophilus sp.) (50%), white-throated treecreeper (Cormobates leucophaea) (25%), 15-month study.

Rueegger, Niels N. 2017. “Artificial Tree Hollow Creation for Cavity-Using Wildlife – Trialling an Alternative Method to That of Nest Boxes.” Forest Ecology and Management 405: 404–12. https://doi.org/10/gchkkr.

Process-Initiating Techniques

These techniques create conditions that encourage natural physical, chemical, or biological processes to produce features over time. This approach fosters collaboration between humans and other organisms.

However, these processes often create short-lived features or may not achieve intended outcomes.

Chainsaw topping.
Mechanical wounding at the base.
Fungal inoculation.
Girdling or bark stripping and cambium removal, for example around woodpecker hollows to prevent occlusion.
Branch pruning or breaking.
Controlled burning or scorching.
Coronet cuts on branches to create water-collecting points that develop into holes by rot.
Ringbarking large branches.
Bruising with sledgehammers.

Bengtsson, Vikki, Phil Wheater, and Pro Natura. 2021. The Effects of Veteranisation of Quercus robur after Eight Years. No. 13. Länsstyrelsen Östergötland.

Additive Techniques

Advantages: do not depend on damage, can replace, enhance, or support trees. These techniques can be adjustable, reversible, or movable.

Artificial hollows, including traditional nesting boxes, sections of dead wood with existing hollows from other trees, and innovative designs.

Parker, Dan, Stanislav Roudavski, Therésa M. Jones, et al. 2022. “A Framework for Computer-Aided Design and Manufacturing of Habitat Structures for Cavity-Dependent Animals.” Methods in Ecology and Evolution 13 (4): 826–41. https://doi.org/10/gpggfj.

Artificial perches such as poles or platforms, often attached to artificial structures. These can be standard industrial artefacts or dead wood branches.

Hannan, Lucy, Darren S. Le Roux, Richard N. C. Milner, and Philip Gibbons. 2019. “Erecting Dead Trees and Utility Poles to Offset the Loss of Mature Trees.” Biological Conservation 236: 340–46. https://doi.org/10/ggbjtk.

Split logs to construct buttress-like features.

Steel, Daniel. 2025. “An Observational Case Study, Monitoring the Efficacy of a Habitat Structure Aimed at Replicating Ancient and Veteran Tree Characteristics.” Arboricultural Journal 47 (2): 134–49. https://doi.org/10/g9wfhg.

Other translocated deadwood (not strictly additive, but additive to the target site).

Tranberg, Olov, Anne-Maarit Hekkala, Ola Lindroos, et al. 2024. “Translocation of Deadwood in Ecological Compensation: A Novel Way to Compensate for Habitat Loss.” Ambio 53 (3): 482–96. https://doi.org/10/gthvp6.

Hybrid Techniques

Types of Places and Ecosystems

Old growth forests where veteran trees have been removed by logging.
Restoration sites on former agricultural land with few or no trees.
Newly established woodlands or parks.
Urban trees.

Target Taxa and Behaviours

Birds.
Bats.
Insects such as saproxylic beetles.

Cizek, Lukas, Petr Kozel, David Hauck, et al. 2025. “Artificial Tree Microhabitats: Wound Depth and Position Affect Saproxylic Beetles Attracted to Freshly Veteranised Trees.” Insect Conservation and Diversity 18 (1): 69–79. https://doi.org/10/g9wdfn.

Use of habitat features is complex and difficult to study. For example, bats in European forests may prefer only cavities in main healthy branches, rejecting peeling bark, cavities on secondary branches, or cavities covered by spider webs. Retaining healthy old trees is has to remain the primary recommendation.

Desired Functions, Structures, Systems, and Attributes

Functions:

Thermal comfort.
Shelter from wind and rain.
Shelter from predators.
Opportunities for social interactions.
Opportunities for incubation and raising young.

Structures:

Microhabitats
Fissures
Hollows
Snags

Attributes:

Reliability
Adaptability
Efficiency
Effectiveness

Important Characteristics

Wound depth and position affect saproxylic beetles.

Cizek, Lukas, Petr Kozel, David Hauck, et al. 2025. “Artificial Tree Microhabitats: Wound Depth and Position Affect Saproxylic Beetles Attracted to Freshly Veteranised Trees.” Insect Conservation and Diversity 18 (1): 69–79. https://doi.org/10/g9wdfn.

Challenges

Fissures can close within months with sap or years through growth.
Target species may not use the features.

Griffiths, Stephen R., Pia E. Lentini, Kristin Semmens, and Kylie A. Robert. 2022. “‘Set and Forget’ Does Not Work When It Comes to Fissure Roosts Carved into Live Trees for Bats.” Restoration Ecology 31 (1): e13751. https://doi.org/10/gqxpgr.

Mechanical wounding and fungal inoculation can fail to produce snags.

Rivers, James W. 2024. “Fungal Inoculations and Mechanical Wounding of Trees Have Limited Efficacy for Snag Creation Two Decades after Treatment.” Forest Ecology and Management 553: 121651. https://doi.org/10/g9wdfk.

Ethical concerns: tree health and longevity may suffer to compensate for human-caused problems. Long-term effects on arboreal ecosystems remain unclear.

Needs

Further research required.
Persistent management needed (see lifecycle approaches).

Parker, Dan, Stanislav Roudavski, Chiara Bettega, et al. 2025. “Which Design Is Better? A Lifecycle Approach to the Sustainable Management of Artificial Habitat–Structures.” Conservation Science and Practice, e70084. https://doi.org/10/px29.

Holland, Alexander, Philip Gibbons, Jason Thompson, and Stanislav Roudavski. 2023. “Modelling and Design of Habitat Features: Will Manufactured Poles Replace Living Trees as Perch Sites for Birds?” Sustainability 15 (9): 7588. https://doi.org/10/gr7jqf.

Recommendations

Collaborate to ensure structures meet requirements and remain viable.
Collect empirical data across designs to assess effectiveness.

Martin, Maxence, Yoan Paillet, Laurent Larrieu, et al. 2022. “Tree-Related Microhabitats Are Promising yet Underused Tools for Biodiversity and Nature Conservation: A Systematic Review for International Perspectives.” Frontiers in Forests and Global Change 5: 818474. https://doi.org/10/jmkb.