Graffiti, Paintings and Other Modifications of Tree Bark

Version	Summary	Created by	Modification	Content Size	Created at	Operation
1		Giovanni Nicola Roviello	--	1786	2023-03-01 09:30:10	\|
2	format correct	Catherine Yang	Meta information modification	1786	2023-03-02 02:26:05	\| \|
3	format correct	Catherine Yang	-1 word(s)	1785	2023-03-02 02:42:59	\|

This entry is adapted from the peer-reviewed paper 10.3390/su15054022

By the word ‘graffiti’ one usually indicates messages, scribbles, patterns, or drawings written, carved, or painted on different types of surfaces including walls, monuments, and tree bark. Consequently, a ‘graffitist’ is a person who creates graffiti. Graffiti has existed as long as human society but has become a public issue in recent decades, being often considered as a recurrent and unacceptable form of vandalism especially when the victims are trees. The entry reports the problem of graffiti on tree barks and reviews some methodologies proposed by urban forestry specialists to remove graffiti and other paintings from the trees without damaging the plant itself.

graffiti tree-bark: paintings vandalism nature conservation

1. Culturally Modified Trees (CMTs)

According to English police ^[1], spraying graffiti is a major offense in a list that starts with littering and ends with vandalism and violence. When graffiti appears, the vast majority of local residents find it objectionable and want it to be permanently removed from the vandalized surface, especially when the victim is a mature urban tree. The hope that the vandalism will not reappear is frequently in vain, but this does not justify the renouncing of the difficult and onerous work of graffiti removal. Volunteers can accomplish a variety of environmental improvements efficiently and with enjoyment but graffiti cleaning from trees does not fall within this category of activities and should be regarded as a task for experts. In fact, it could require dangerous chemicals and, in some cases, it endangers tree bark and inner tissues, as well as environmental and public health. Trees that have been intentionally sculpted by a range of human activities are collectively referred to as Culturally Modified Trees (CMTs). The debarking of planks, felling of logs, testing of strength, and other operations may be shown in CMTs. Arborglyphs ^[2]^[3]^[4]^[5]^[6]^[7] are a subtype of CMTs that comprise pictures or text painted on or etched into tree bark or into wood after the bark has been removed from the tree. There are many distinct tree species that feature arborglyphs, and they are found on different continents at locations as disparate as some sites in Peru, Ecuadorian Andes, Hawaii, and New Zealand, where graffiti can be observed also on woody bushes or on the broad leaves or bodies of cactus, agaves, or other succulents ^[8]. The US is home to the carved quaking aspen (Populous tremuloides), whose reconstructed, white-colored bark offers a clean canvas. There is a lot of graffiti on well-known 20th-century poplars in the area that were made by Irish, Basque, and Hispanic shepherds. Additionally, since arborglyphs may date back to very early periods, there are numerous pre-Columbian CMTs in North America and other parts of the continent. As for European CMTs, there is a story about a shepherd carving his name into a beech tree in the Bucolics in the pastoral poems written by the Roman poet Virgil in the first century before the Common Era. On the other hand, native people, immigrants, pilgrims, and infatuated individuals are still carving graffiti into trees today ^[8]. Tree bark paintings produced and commercialized by the community living in Asei village, East Sentani District, Papua are an example in which artistic objects obtained from tree bark are used by local communities to sustain their economy. The quality of bark paintings coming from Asei village is considered high because these people, who still live in symbiosis with nature, have a clear identity, which is evident in their unique product motifs. The bark painting products of the Asei village community and a brief profile of the artists were also displayed on a website that can be accessed by the global community in order to promote them more effectively and efficiently with a larger coverage area ^[9].

2. Persistence of Paintings on Tree Bark: The Studies of Frank Nigel Hepper

Once painted, a tree’s bark can show the signs of this anthropic intervention for a long time, as shown in the studies conducted by the English botanist Frank Nigel Hepper. In a work presented by Dr. Hepper in 1981, great attention was paid to the remarkable longevity of white markings on several species of trees along Kew Road, in Kew, UK ^[10]. Interestingly, surplus tree stock was given away by the nearby Royal Botanic Gardens at the beginning of the 20th century, and this probably accounts for the wide range of tree species which Hepper found along Kew Road. To increase their visibility during the blackouts, these street trees were painted (white-washed with lime) with transverse white stripes during World War II (1939–1945). More precisely, the white lines on the street trees of Kew dated back to 1945 and were useful for both drivers and pedestrians because the streets were often unlighted and car headlights were obscured. The practice of tree-painting was discontinued once hostilities ended. After 35 years, the original banding’s vestiges were still visible in Hepper’s study, where his observations provided interesting insight into bark behavior according to the different tree species over these first 35 years; the trees having been under almost daily observation for 28 years. ^[10]. Trees showing white color were photographed in 1958 and re-photographed in 1979, i.e., 34 years after they were last painted. It was unlikely that anyone could have imagined the markings to persist for so long on tree bark, with some even lasting into the new millennium. By 1939 the street trees had trunks sufficiently large to be painted which led Hepper to estimate their initial age as 30 to 40 years. At the time of his study, published in 1981, these trees were likely 70–80 years old while during his last observations described in his publication of 2006 ^[11] they were about a century old and some of them still showed white markings. Looking at the findings in more detail, while no evident markings were present on Acer pseudoplatanus (Sycamore); Castanea sativa (Spanish Chestnut), Platanus X hispanica (London Plane), or Platanus orientalis (Eastern Plane), white lines could be clearly seen on trunks of Acer platanoides (Norway Maple), Aesculus hippocastanum (Horse Chestnut), Fraxinus excelsior (Ash), Juglans nigra (Black Walnut), and Tilia x vulgaris (x europaea) (Common Lime). This last species was particularly noteworthy with most of the 13 specimens still showing some paint, and one specific tree photographed in 1979 (Figure 1a) and then in 2006 (Figure 1b) showing bold markings even during the last observation. This is particularly evident in the inverted colors images of Figure 1.

Figure 1. Stripes painted on the trunk of a Tilia x vulgaris European Lime examined by Frank Nigel Hepper in November 1979 ^[10] (a) and January 2006 ^[11] (b). Inverted colors are displayed for better clarity.

Remarkably, Hepper’s work showed that after more than 60 years, all the white markings had persisted while one would have expected the disappearance of all signs of paint not only as an effect of general erosion but also by replacement of the bark by the tree itself. In this regard, even tree species with flaking bark retained small flecks of paint. Overall, the findings of these two studies led the author to conclude that a tree could be visually harmed for decades by ‘a moment’s daubing’ ^[11].

3. Removal of graffiti from Tree Bark

The removal of graffiti and the maintenance of cities in general are processes governed by specific laws and important regulations, but without workers, interventions, and extraordinary measures, especially for urban parks, they would fall by the wayside. The types of interventions must cope with urban environmental conditions, such as weather, that prevent the use of some graffiti removal methods. The cleaning practice is also susceptible to changes, with new graffiti removal methods being tested in the most difficult situations such as on porous surfaces. Even though most graffiti do not harm trees, in some cases oil-based paints can damage tree life support systems by killing cambium tissue and clogging lenticels. In particular, paint and other chemical applications that reach cambium tissue can compromise tree health, while spray-derived coverings can clog the lenticels (tiny openings on the epidermis of different plant organs) which allow trees to release CO₂ and take in O₂ for respiration. In addition, paint may interfere with photoreceptors embedded in the plant stem, covering them and ultimately interfering with the plant’s ability to sense changes in light intensity, duration, and quality, in turn disrupting the tree’s natural biological processes. Just as importantly, the cambium layers and bark can be damaged by paint chemicals, especially those found in oil-based paints, which are able to heavily damage or even kill thin-barked trees. Different methods to remove graffiti from trees were reported by the urban agriculturist Bonnie L. Grant, (https://www.gardeningknowhow.com/ornamental/trees/tgen/graffiti-paint-removal-tips.htm, accessed on 10 January 2023). These included both mechanical interventions, such as scrubbing or pressure washing, and natural methods. For the mentioned mechanical methods, pressure washing can be employed to remove graffiti paints on trees with large trunk girths and thick bark such as chestnut (Castanea sativa), hornbeam (Carpinus betulus), different oaks, and cottonwoods (Populus deltoids), while smaller trees need to be gently hand scrubbed or subjected to pressure washing using a washer on low setting. In general, pressure washing, as suggested by Grant, should be accomplished with the washer on medium to low from a distance of at least 1 m away from the tree trunk, always assessing for any tree bark or cambium damage. Other than pressure washing and scrubbing, another method to clean tree barks is sanding using light abrasive papers, such as a 400-grit (20.6–23.6 μm) sandpaper, to hand sand the graffiti painted area. On the other hand, using a power sander is not recommended as more tree bark and other plant tissues will be damaged than necessary. Since mechanical methods can damage and remove the outer bark layer of trees, exposing the tree inner tissues to fungi and bacteria that may cause the plant to be irreversibly damaged, less invasive systems are clearly desirable. In this context, natural tree graffiti cleaners such as citrus-based graffiti removers or degreasers, whose active ingredients like orange oil are completely natural, have the advantage of cleaning the tree bark without doing harm to the plant or the environment and are commercially available ( https://www.gardeningknowhow.com/ornamental/trees/tgen/graffiti-paint-removal-tips.htm, accessed on 10 January 2023).

4. Conclusion

In conclusion tree bark is often subjected to graffiti and other forms of vandalisms in urban settings and this requires more attention from institutions to protect the monumental tree patriarchs even because once painted the tree can show the signs of the graffiti for long times as the studies of the botanist F.N. Hepper showed. The most suitable cleaners to remove paintings from tree barks are based on Citrus ingredients and should be applied gently following carefully the instructions of the urban forestry specialists in order to preserve the health of not only plants but also of the workers and the surrounding environment.

References

Whitford, M.J.; Ashworth, G. Getting Rid of Graffiti: A Practical Guide to Graffiti Removal and Anti-Graffiti Protection; Routledge: London, UK, 2017.
Connolly, N.J. Environmental Variables Associated with the Location of Arborglyphs in the Eastern Sierra Nevada, Alpine County, California; University of Nevada: Reno, NV, USA, 2012.
Summerfield, C. Trees as a Living Museum: Arborglyphs and Conflict on Salisbury Plain. In Beyond the Dead Horizon’: Studies in Modern Conflict Archaeology; Oxbow Books: Oxford, UK, 2012; pp. 159–171.
Lorås, J.; Storaunet, K. Bark Peeled Scots Pine Prees and Arborglyphs in a Pite Sami Area of Norway. 2012; Upublisert manus.
Kobiałka, D. Living monuments of the Second World War: Terrestrial laser scanning and trees with carvings. Int. J. Hist. Archaeol. 2019, 23, 129–152.
Hoyt, A. History in the Trees: The Basque Arborglyphs of Idaho and “The Grove” on Grove Street; Boise State University: Boise, ID, USA, 2007.
Gulliford, A. Reading the Trees: Colorado’s Endangered Arborglyphs and Aspen Art. Colo. Herit. 2007, 18–28.
Lovata, R.M.A.T. Marked trees: Exploring the context of Southern Rocky Mountain arborglyphs. In Understanding Graffiti; Routledge: Oxfordshire, UK, 2016; pp. 91–104.
Peradantha, I.B.G.S.; Suryati, S.; Putra, I.B.H.K. E-catalogue based promotional media for tree bark painting in Asei village, Papua. In Proceedings of the International Conference on Information Technology, Multimedia, Architecture, Design, and E-Business, Virtual, 18–20 December 2020; pp. 477–482.
Hepper, F.N. Changes in street tree bark during 35 years. Arboric. J. 1981, 5, 39–43.
Hepper, F.N. Changes in Street Tree Bark During 60 Years. Arboric. J. 2006, 29, 291–295.

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