Kveldssanger

13/04/16. Fact #190. The below relates to UK case law associated with the management of dangerous trees. Stemming originally (after the ruling of Rylands v Fletcher [1868] relating to a landowner’s duty of care) from Giles v Walker [1890] and Noble v Harrison [1926], the latter having the judge conclude that “I see no ground for holding that the owner is to become an insurer of nature, or that default is to be imputed to him until it appears, or would appear upon proper inspection, that nature can no longer be relied upon…“, and slightly more recent court cases, beginning with Brown v Harrison [1947] and Lambourn v London Brick Co Ltd [1950], both of which concluded in line with Noble v Harrison [1926], provide background guidance for modern-day court cases. Such modern-day cases also take the lead from the cases of Goldman v Hargrave [1967] and Leakey v National Trust [1980], of which the latter drew influence from the former. Before visiting more contemporary cases however, further exploration is warranted into older cases. As noted in the case of Rylands v Fletcher [1868], a landowner must accept that he or she has a duty of care to those using neighbouring parcels of land for their own purposes, by ensuring trees upon their land (that may affect adjacent properties) are as safe as is reasonably possible. This sentiment is echoed in Donoghue v Stevenson [1932], where the judge remarked that a tree owner has a duty of care to “avoid acts or omissions” that can be reasonably foreseen to, if allowed to persist, cause harm to a neighbour. Of course, only where a defect is outwardly evident to a reasonable and prudent landowner will a successful case be made, as was recognised in the case of Kent v Marquis of Bristol [1940]. In this instance, it was ruled that if the elm tree in question had been inspected, then it would have been outwardly recognisable that the cavity present upon the structure was a hazard, and therefore should have been dealt with prior to a subsequent incident occurring. A willow (Salix alba) with a significant hazard beam. Because of the target area beneath, the hazard was removed, in this instance. Adding to this, where a tree becomes defective as a result of vandalism or at the hands of a trespassing individual, as soon as the landowner becomes aware of the issue (or should be reasonably expected to already be aware of the issue) then the tree must be made safe. This was the case in Sedleigh-Denfield v O’Callaghan [1940], where the local authority trespassed onto a parcel of land and undertook works to ensure a ditch drained properly (by installing a culvert and grate), unbeknown to the landowner. However, such works proved to be ineffective because of the improper installation of a grate, which led to the culvert frequently being blocked. Because of this, the land frequently flooded, and eventually onto a neighbouring property where extensive damage was caused. The defendant on whose land the flooding emanated from claimed that he had no knowledge of the work being undertaken by the local authority, though the judge ruled that because the defendant had continued the allow the nuisance (which should have readily been identifiable) that he was to be liable for the damages. This has implications for the arboricultural industry, as it suggests that as soon as one is aware of a hazard relating to a dangerous tree, it must be appropriately actioned. Similarly, where a tree has had pruning operations undertaken unto its structure, which have had the impact of making the tree less structurally safe (such as topping causing an abundance of sprouts, though even if pruning the tree in accordance with BS 3998), there is added impetus to follow-up with further inspections to ensure the tree is not posing an unreasonable danger to the target zone beneath. Such a stance was held in the case of Chapman v Barking and Dagenham LBC [1997], and prior to this the case of Caminer v Northern & London Investment Trust ruled that whilst the lopping of the elm tree in that instance would be appropriate to remedy the situation that manifested when the tree failed and caused injury to the claimant, it would make the tree more dangerous in the long term and must therefore be expected more frequently. In addition to this ruling, the case also held magnitude because the judge ruled that, as the tree was outwardly not defective, there was no reasonable justification in expecting the landowner to have instigated further investigation into the tree’s state. However, if the tree had warranted further investigation to such a layperson, they would have been expected to employ an expert to assess the tree more vigorously. Reverting attention back towards more recent cases, Leakey v National Trust [1980] was concerned primarily over a landslip and who was liable, if anyone, for the damage caused. The court did however utilise the case to expand upon the issue of natural phenomena, which ultimately included relevant conclusions for trees. The court concluded that there is a general duty with regards to ensuring hazards, naturally-borne or man-made, do not stem from the land of the owner and affect neighbouring land owners or guests on the site. The duty is “to do what which is reasonable in all circumstances, and no more than what, if anything, is reasonable, to prevent or minimise the known risk of damage or injury to one’s neighbour or his property.” However, somewhat critically, it did determine that naturally-borne hazards that could have been be prevented can only having the ruling applied to them where “the defendant has, or ought to have had, knowledge of the existence of the defect and the danger thereby created.” As a result, one can expect that only hazards relating to trees that are relative to the expected knowledge of the owner of the land, or those employed to look after such land, to be actionable. Such a standard was in fact elucidated to in Khan & Khan v London Borough of Harrow & Helen Sheila Kane [2013], where the court ruled that the issue of reasonable foreseeability is not a subjective test depending on the peculiar characteristics of the particular defendant, but is an objective test as to what ought to have been known to a reasonable person in the position of the defendant: “In this case, the relevant person is a reasonably prudent landowner.” However, a defendant’s subjective knowledge can impose a higher standard, the court found. Therefore, local authorities and organisations who are responsible for trees may indeed be held to such a higher standard. Such a precedent has since been mirrored by many other more recent cases, including: - Corker v Wilson [2006], where as the defendant had carried out informal observations of the oak tree, which had seen one of its limbs fail and strike a passing motorist, injuring him and damaging the vehicle, on an ongoing basis, and all the evidence was that the tree was in good health. The judge ruled that there was nothing about the tree which should have alerted the defendant or led him to obtain a more detailed inspection by an arboriculturalist. - Atkins v Scott [2008], where the judge ruled that it was “neither probable nor reasonably possible for a competent inspector to have observed the crack in the branch that failed“, after the branch of an oak tree failed and struck and injured a passing motorist during windy weather. - Selwyn-Smith v Gompels [2009], where an ordinary landowner’s tree fell onto a neighbouring garage. The claim was rejected as the judge deemed that the defendant had no requirement to engage with an arboricultural expert “unless and until reasonable inspection by the standards of that [the defendant’s] knowledge discloses or should disclose that the tree might be unsafe”. - Ulsterbus Ltd v Sufferin [2010], in a case where a double decker bus carrying school children collided with a branch within the crown of a tree and caused both damage to the bus and injury to some passengers, after it veered slightly to the left to allow for a large van to pass heading the other way, saw the court rule that “the defendant in this case was not aware of the risk” and “should not have become aware with reasonable care of any danger posed by the branch with which the bus collided.” The court drew influence from British Road Services v Slater [1964], where the court ruled that the case should fail based on the fact that the claimant had pulled into his nearside to enable an oncoming vehicle to pass, thereby leaving the carriageway in part, in addition to the fact that both the claimant and the defendant had not, until this point, considered the tree a hazard. - Micklewright v Surrey County Council [2011], where it was found that extensive internal decay was a major factor in the failure of a large branch of a mature oak tree. The judge found that nobody had seen any external signs of decay and ruled that, even if the local authority had had in place a proper system of inspection, the extent of the decay, and the danger it posed, would not have been revealed. - Bowen (A Child) & Ors v The National Trust [2011], where the court ruled that a “risk assessment in any context is by its very nature liable to be proved wrong by events, especially when as here the process of judging the integrity of a tree is an art not a science, as all agree. [The court] accept these inspectors used all the care to be expected of reasonably competent persons doing their job, and the defendant had given them adequate training and instruction in how to approach their task. To require more would serve the desirable end of compensating these claimants for their grievous loss and injuries. But it would also be requiring the defendant to do more than was reasonable to see that the children enjoying the use of this wood were reasonably safe to do so. I regretfully conclude that I cannot find that the defendant was negligent or in breach of its duty in respect of this tragedy.“ - Stagecoach South Western Trains Ltd v Hind & Anor [2014], where it was determined that “there was nothing that should have alerted her [the defendant], or put her on notice, that the tree was anything other than healthy, or required a closer inspection by an arboriculturalist.” This case related to a 150-year old ash tree, whose stem had fallen onto the railway line from the garden of the property, which then resulted in a collision with an oncoming train. The court in this case drew influence from both Corker v Wilson [2006] and Selwyn-Smith v Gompels [2009], concluding that a system of informal observations by the landowner was adequate, and that an inspection by an expert arboriculturalist was only necessary if there was something revealed by the informal inspection which suggested that a more detailed inspection was required. The arboriculturalist was also found to not be liable for any wrongdoing, having worked on the tree more than one time prior to the incident. Again, there were no outward signs to suggest to him that there was evident risk associated with the ash’s presence. This veteran beech (Fagus sylvatica) lapsed pollard is riddled with Ganoderma, and thus it has received a slight crown reduction to reduce the level of risk associated with the fungal decay and the sheer weight of the many stems. However, in specific instances, it has been deemed that the land owners have not done enough to prevent hazards from materialising. Such cases include: - Quinn v Scott [1965], where it was decided upon that because the decay of the tree was so visibly apparent, it should have been felled in response to the clear hazard presented. The judge stated: “The duty of the Trust is to take such care as a reasonable landowner – and that means a prudent landowner – would take to prevent unnecessary danger to users of the highway adjoining the Trust’s land. There is not to be imputed in the ordinary landowner the knowledge possessed by the skilled expert in forestry… But, in my opinion, there may be circumstances in which it is incumbent on a landowner to call in somebody skilled in forestry to advise him, and I have no doubt but that a landowner on whose land this belt of trees stood, adjoining a busy highway, was under a duty to provide himself with skilled advice about the safety of the trees”. - Chapman v Barking & Dagenham LBC [1997], where it was concluded that “the defendant council did not at any relevant time appreciate the distinction between making lists of trees and routine tree maintenance, and systematic expert inspection as often as would reasonably be required”, thereby finding them liable of negligence and not remedying a hazard that could have readily been identified. - Poll v Bartholomew [2006]. This High Court case covered the standard of the duty of care and decided that, in this set of circumstances, a drive-by check was not a sufficient level of inspection and the claimant succeeded. The claimant had collided with a fallen tree that had extensive decay, though this was not picked up on by inspectors given the poor extent of inspection. This case is particularly important as it suggests different levels of inspection and competence are to be applied, depending upon the knowledge extent of the owner. However, the case of Stovin v Wise [1996] raises an interesting point, in that “The mere existence of statutory power to remedy a defect cannot of itself create a duty of care to do so. A highway authority need not have a duty of care to highway users because of its duty to maintain the highway“. For example, under Section 154 of The Highways Act 1981, a local authority is not necessarily to be held liable if they do not exercise the power under Section 154 to remove a threat to the highway and its users.

What on absolute... wow. Shameful. Poor tree! How's it doing now?

The presence of trees in the urban environment is certainly beneficial for the health and well-being of local residents, who will, generally-speaking, benefit more than they suffer as a result of the trees’ presence. Somewhat anecdotally, it has also been shown that it is the presence of healthy trees that has such beneficial impacts. In this sense, if tree populations suffer at the hands of a biotic or abiotic stressor, visibly decline in health, and potentially die in time (even on a massive scale), then the impact will also be ‘felt’ by the local residents. As a means of adding weighting to this statement, we can look at a US-based study that assessed whether the presence of the tree pest emerald ash borer (Agrilus planipennis), as it ravaged urban ash (Fraxinus spp.) populations, brought about adverse health responses in humans as well. The beetle has spread quite rapidly in the US since its arrival in 2002, and now occupies an area of land quite massive in scale (as shown by the map below). Specifically, the study looked at whether the presence of emerald ash borer had associations with the rate of mortality caused by cardiovascular and lower-respiratory-tract issues. The authors of this study selected these causes of death, because they are the first and third highest causes of death, respectively. Furthermore, there is reason to suggest that these two causes of death can be influenced by the presence (or lack) of trees. A map of where the emerald ash borer has been found in the USA, on a county level. In all of the US states that had at least one case of the emerald ash borer, the authors analysed information, from 1990-2007, outlining the cause of death for citizens. With this data, the authors looked at whether the presence of the beetle, and how long it had existed in a state, had any influence upon the mortality rates associated with the two causes of death mentioned. These comparisons were then related to the estimated abundance of ash trees in the states, and demographic data obtained via census records. Following on from data analysis, the authors identified that the presence of the beetle had a more significant impact upon respiratory-related mortality rates in wealthier counties (where there was a greater access to ash trees, compared to poorer counties) and, on average, there were 6.8 more deaths per 100,000 individuals in states host to the pest than prior to the state’s date of infestation. However, the impact of its presence increased over time, therefore meaning that areas that have been infested for longer will experience a higher average mortality rate than those areas more recently infected (as can be seen in the below table). At the time of the study, the authors therefore estimated that 6,113 respiratory-related human deaths had been caused by the presence of the emerald ash borer between 2002-2007, because of its impact upon its host ash trees (which almost always will die, or are cut down upon detection of them being infected). Therefore, we can perhaps observe that dying trees (and an increasing lack of trees) means dying humans. However, the fact that there is an anticipated 2-5 year lag associated with beetle presence and human mortality rates, the real effects of the ash borer upon human health may not yet be fully appreciated. Curiously, the authors also suggest that the media coverage of the ash borer’s presence may induce stress in some individuals, and such stress may potentially exacerbate (or create) health issues. Perhaps this highlights the emotional relationship people have with trees, and at times there may even be a sort of cross-kingdom empathy (and associated grief). The impact upon respiratory-related human mortality rates caused by the emerald ash borer. The observed impacts upon cardiovascular-related mortality rates per 100,000 individuals was even higher. In counties host to the emerald ash borer, an additional 16.7 deaths per 100,000 can be attributed to the pest’s presence. Therefore, 15,080 deaths can be directly linked to the effects of the borer, meaning that a total of 21,193 individuals have suffered mortality, between 2002-2007. Much like with respiratory-related deaths, the duration of time for which the beetle has been present has an impact upon the rate of mortality (see the below table). It was also found that individuals in counties with moderate levels of average income were most markedly affected. The impact upon cardiovascular-related human mortality rates caused by the emerald ash borer. Not provided in the journal, I decided to plot both sets of figures relating to the mortality rate increase observed with the presence of the borer, and assess the two lines (as shown below). What we can crudely see is that, as the years progress, the dispiraity increases between the two data sets, in favour of cardiovascular-related deaths. However, respiratory-related deaths consistently remain, across the six year period, 39-41% lower than cardiovascular-related deaths. Therefore, enriching cardiovascular health may likely be a more significant focal point with regards to any mitigation measures that may take place, though we must obviously be aware that there is likely going to be a levelling-off threshold, by where no more ash trees exist and therefore the mortality rate cannot suffer any further (accompanied by lag times). During this time, re-planting may of course occur, and offset any adverse impacts associated with ash mortality. Of course, these new trees will take time to mature, and therefore it may be many decades before health impacts begin to markedly reverse. Comparing the two data sets (blue line: cardiovascular mortality rates; orange line: respiratory mortality rates). There is no question that such data is indeed very interesting, and the results don’t necessarily remain limited to the emerald ash borer. Across the world, we can observe trees dying or being removed because of pest or disease outbreaks, so one can suspect that similar impacts may be associated with, for example, ash removal because of ash dieback, elm removal because of Dutch elm disease, or tree removal caused by Xylella fastidiosa. Granted, the actual impacts may differ (either be more severe, or less severe), though there will certainly be impacts. The findings that more affluent individuals were more adversely impacted by the emerald ash borer is very interesting, though perhaps not surprising, as environmental inequality certainly exists within urban districts (with more affluent areas having a more abundant tree presence). In this sense, less affluent neighbourhoods may already be suffering as a result of other stressors, and the lack of ash trees in the near locality means that they simply aren’t impacted by their death, because they are not directly experiencing such significant tree mortality. Other socio-demographic issues may also be implicated in this equation, such as the highest level of education an individual has. Similarly, the reduction is ecosystem sevices (pollution removal, encouragement to exercise outdoors, and so on) associated with the death of ash trees may have an impact upon respiratory and cardiovascular health, and this impact will be most pronounced where the most trees have been lost, which is (in this case) in the more affluent areas. ATTENTION: Have you seen this pest? It is wanted for the death of over some 100,000,000 ash trees, in the USA. Source: Aetree. Source: Donovan, G., Butry, D., Michael, Y., Prestemon, J., Liebhold, A., Gatziolis, D., & Mao, M. (2013) The relationship between trees and human health: evidence from the spread of the emerald ash borer. American Journal of Preventive Medicine. 44 (2). p139-145.

Plenty of reading to do.

I fully understand that problem posed to LA people. In the case of removal, was there a letter drop at the time explaining why the stem was to be left as it was, or was the stem just left and nobody told the reasons why?

Anthropocentric = human-oriented. So basically focussed on the benefit to humans, usually in the directest of senses.

Onwards and upwards! Nice job. It's something that would quite literally have to be a paradigm shift, though for those of us that are aware of the need of conserving biodiversity there is no justification in not spreading information. If people don't want to consider another point of view then that's their prerogative, but I won't allow myself to not try and expose them to such a way of thinking.

Evening Alistair, I'm after any response, frankly. I posted this with the aim of discussing why we value urban trees, so I'm not expecting people to fully agree (if at all). With regards to your comments, I would pretty much wholly agree with what you say. A concern I have is the little drive, in the mainstream media (which influences so many, for good and for bad), to bring attention to trees, and instead to focus on sports, celebrities, and other superficial matters that distract from more important issues. Your comparison to humanity being in an infantile stage is a good one, though my question to that would be why? Is humanity conditioned to be in that state for broader socio-political reasons, or is it simply not able to mature because of a lack of something (or somethings)? Taking off my tin foil hat, and putting on my Fomes hat, I hope it doesn't take a crisis to highlight our downward slide, but, like you, I fear it will. The concern for me is that once biodiversity drops it's hard to get it back (lag times, etc). If we don't pick up enough momentum going downhill, we struggle to reach the top of the next steep hill without furiously burning resources and effort that we may not even have. Better to keep up the momentum than seek to regain it.

That's not a problem. I guess a tl;dr would be: we spend too much time focussing on the amenity value trees provide, or other benefits they provide to humans, that we forget that trees also exit to serve biodiversity, and we should be paying for attention to ensuring urban forests are managed in a way that enables for them to support healthy and species-rich ecosystems.

Get it all while it's still freely available. Some cracking articles in there! No idea if it'll be permanent open access. Urban Forestry & Urban Greening | Vol 15, Pgs 1-236, (2016) | ScienceDirect.com

Does nobody have any thoughts?

Probably something akin to this! [ame] [/ame]

That's some dryad-level magic!

11/04/16. Fact #189. The presence of trees in the urban environment is certainly beneficial for the health and well-being of local residents, who will, generally-speaking, benefit more than they suffer as a result of the trees’ presence. Somewhat anecdotally, it has also been shown that it is the presence of healthy trees that has such beneficial impacts. In this sense, if tree populations suffer at the hands of a biotic or abiotic stressor, visibly decline in health, and potentially die in time (even on a massive scale), then the impact will also be ‘felt’ by the local residents. As a means of adding weighting to this statement, we can look at a US-based study that assessed whether the presence of the tree pest emerald ash borer (Agrilus planipennis), as it ravaged urban ash (Fraxinus spp.) populations, brought about adverse health responses in humans as well. The beetle has spread quite rapidly in the US since its arrival in 2002, and now occupies an area of land quite massive in scale (as shown by the map below). Specifically, the study looked at whether the presence of emerald ash borer had associations with the rate of mortality caused by cardiovascular and lower-respiratory-tract issues. The authors of this study selected these causes of death, because they are the first and third highest causes of death, respectively. Furthermore, there is reason to suggest that these two causes of death can be influenced by the presence (or lack) of trees. A map of where the emerald ash borer has been found in the USA, on a county level. In all of the US states that had at least one case of the emerald ash borer, the authors analysed information, from 1990-2007, outlining the cause of death for citizens. With this data, the authors looked at whether the presence of the beetle, and how long it had existed in a state, had any influence upon the mortality rates associated with the two causes of death mentioned. These comparisons were then related to the estimated abundance of ash trees in the states, and demographic data obtained via census records. Following on from data analysis, the authors identified that the presence of the beetle had a more significant impact upon respiratory-related mortality rates in wealthier counties (where there was a greater access to ash trees, compared to poorer counties) and, on average, there were 6.8 more deaths per 100,000 individuals in states host to the pest than prior to the state’s date of infestation. However, the impact of its presence increased over time, therefore meaning that areas that have been infested for longer will experience a higher average mortality rate than those areas more recently infected (as can be seen in the below table). At the time of the study, the authors therefore estimated that 6,113 respiratory-related human deaths had been caused by the presence of the emerald ash borer between 2002-2007, because of its impact upon its host ash trees (which almost always will die, or are cut down upon detection of them being infected). Therefore, we can perhaps observe that dying trees (and an increasing lack of trees) means dying humans. However, the fact that there is an anticipated 2-5 year lag associated with beetle presence and human mortality rates, the real effects of the ash borer upon human health may not yet be fully appreciated. Curiously, the authors also suggest that the media coverage of the ash borer’s presence may induce stress in some individuals, and such stress may potentially exacerbate (or create) health issues. Perhaps this highlights the emotional relationship people have with trees, and at times there may even be a sort of cross-kingdom empathy (and associated grief). The impact upon respiratory-related human mortality rates caused by the emerald ash borer. The observed impacts upon cardiovascular-related mortality rates per 100,000 individuals was even higher. In counties host to the emerald ash borer, an additional 16.7 deaths per 100,000 can be attributed to the pest’s presence. Therefore, 15,080 deaths can be directly linked to the effects of the borer, meaning that a total of 21,193 individuals have suffered mortality, between 2002-2007. Much like with respiratory-related deaths, the duration of time for which the beetle has been present has an impact upon the rate of mortality (see the below table). It was also found that individuals in counties with moderate levels of average income were most markedly affected. The impact upon cardiovascular-related human mortality rates caused by the emerald ash borer. Not provided in the journal, I decided to plot both sets of figures relating to the mortality rate increase observed with the presence of the borer, and assess the two lines (as shown below). What we can crudely see is that, as the years progress, the dispiraity increases between the two data sets, in favour of cardiovascular-related deaths. However, respiratory-related deaths consistently remain, across the six year period, 39-41% lower than cardiovascular-related deaths. Therefore, enriching cardiovascular health may likely be a more significant focal point with regards to any mitigation measures that may take place, though we must obviously be aware that there is likely going to be a levelling-off threshold, by where no more ash trees exist and therefore the mortality rate cannot suffer any further (accompanied by lag times). During this time, re-planting may of course occur, and offset any adverse impacts associated with ash mortality. Of course, these new trees will take time to mature, and therefore it may be many decades before health impacts begin to markedly reverse. Comparing the two data sets (blue line: cardiovascular mortality rates; orange line: respiratory mortality rates). There is no question that such data is indeed very interesting, and the results don’t necessarily remain limited to the emerald ash borer. Across the world, we can observe trees dying or being removed because of pest or disease outbreaks, so one can suspect that similar impacts may be associated with, for example, ash removal because of ash dieback, elm removal because of Dutch elm disease, or tree removal caused by Xylella fastidiosa. Granted, the actual impacts may differ (either be more severe, or less severe), though there will certainly be impacts. The findings that more affluent individuals were more adversely impacted by the emerald ash borer is very interesting, though perhaps not surprising, as environmental inequality certainly exists within urban districts (with more affluent areas having a more abundant tree presence). In this sense, less affluent neighbourhoods may already be suffering as a result of other stressors, and the lack of ash trees in the near locality means that they simply aren’t impacted by their death, because they are not directly experiencing such significant tree mortality. Other socio-demographic issues may also be implicated in this equation, such as the highest level of education an individual has. Similarly, the reduction is ecosystem sevices (pollution removal, encouragement to exercise outdoors, and so on) associated with the death of ash trees may have an impact upon respiratory and cardiovascular health, and this impact will be most pronounced where the most trees have been lost, which is (in this case) in the more affluent areas. ATTENTION: Have you seen this pest? It is wanted for the death of over some 100,000,000 ash trees, in the USA. Source: Aetree. Source: Donovan, G., Butry, D., Michael, Y., Prestemon, J., Liebhold, A., Gatziolis, D., & Mao, M. (2013) The relationship between trees and human health: evidence from the spread of the emerald ash borer. American Journal of Preventive Medicine. 44 (2). p139-145.

How polite of those leaves to reveal the fungus!

01010111011010010110111000100001 (Paul may appreciate that ^^) Thanks for help on this one and, as always, it's hugely appreciated. I hadn't considered D. confragosa because the morphology on the upper surface (and the size / arrangement) was just too 'off' from what I usually have seen. Have you seen them adopt such a form prior to this?

Managed to get a few spores and they came out white. The belowside of the bracket also bruised upon touch (both on Friday and today), so probably D. confragosa would you say? Some images from today:

Cross-posted from my blog, as hopefully there'll be some interest here in discussing what I have written. This post is essentially a thought-piece, so in place of a referenced post it’s more of a ‘brain dump’ (of which I cannot promise absolute coherency and flow). I suppose the purpose of this post is therefore to stimulate some form of discussion, at least internally (though ideally also externally) – this discussion will, ideally, be laden with academic references and personal experiences. Over the last year in particular, as I have begun to really begin researching the role urban trees have, and what they are perceived to provide in the planning stages of developments, I have become increasingly concerned with the seemingly over-riding desire to use trees for the benfits of humans. In this sense, their role is one of a sort of dynamic ‘furniture’, be it a street that is furnished wth trees, a garden, an urban park, or even an urban woodland or forest. Attention is paid to what trees give humans, and this may range from the already-mentioned aesthetic aspects, to the social ecology of humans (promoting integration between individuals, and outdoor recreation), and to the economic benefits (reduced recovery times in hospitals, a better sense of self-esteem and associated lower levels of stress, the encouragement of consumer spending, raising the value of a property, and so on). The list, with regards to the anthropocentric provisionings of trees, is quite literally vast. However, at least anecdotally, there seems to be little desire to utilise trees in the urban environment for the benefit of biodiversity and, even if there is a desire, it seems to rank beneath the value trees directly provide to humans. We can even see this with (peri-)urban woodlands, which are utilised generally for recreational purposes, and these (usually intensive) recreational activities are very much damaging to lower tier plants and soil flora and fauna. In turn, these adverse impacts cause the tree populations to suffer (be it from seedling recruitment, reduced nutrient uptake, water uptake, and so on). Whilst I fully understand why trees are viewed in such an anthropocentric manner, we must not forget that our urban and peri-urban environments reside within a mosaic of habitats at the landscape-scale, and biodiversity does not stop at the doorstep of our ever-expanding towns and cities. By-and-large, native faunal biodiversity has evolved alongside the presence of native floral biodiversity, and this relationship over many millennia has produced thousands of obligate associations, and has formed the basis of functioning terrestrial ecosystems. In our urban areas, this relationship is sometimes aggressively severed by the abundant presence of exotic tree species that lack any obligate associations with native fauna (and have the potential to be invasive), a lack of tree species diversity, and fragmentation that creates many ‘urban tree islands’ (oft found in tree-less streets and estates), which are somewhat akin to their ‘forest island’ counterparts. At the same time, ivy stems are removed from trees, and usually under the guise of the ivy reducing amenity value in an urban system that thrives off of order and uniformity, or the concern that the ivy will kill the tree (which is usually not going to be the case). Even where the means of servance is risk-based, is there justification in severing the stem at the base? Probably not. Granted, with the fact that many invasive pests and pathogens are wiping-out native tree and plant species with relative ease, the ideal reliance upon native tree species is perhaps going to become an ever-growing problem. For example, ash dieback (an oriental plant pathogen) is expected to cause massive mortality of the European ash (Fraxinus excelsior), of which there is currently no means of remedy. It is suspected that oriental ash species will possess resistance to the pathogen, as they have evolved alongside the pathogen and thus have developed means of effectively limiting its impact on the population level (the same applies to ash trees and the insect pest emerald ash borer), though the introduction of such exotic ash species will not reverse, by any stretch, the intricate associations European ash have sustained with, for instance, obligate lichen species (of which many are endangered and will go extinct if the European ash die). One means of retaining the presence of native urban tree species is to create cultivars that are resistant, at least partially, and in the short-term this is ideal. However, once the pathogen has been exposed to the specific cultivar(s) over a period of time, it will itself adapt to the change in host type and likely once again ravage the (genetically undiverse, as many cultivars share some, or even all, genetic qualities) tree population(s). Even in recognising this, there still appears to be little consideration given to selecting resistant exotic tree species that can provide marked ecological benefits for urban biodiversity, with more focus instead being simply on sustaining a form of urban forest that gives benefits to humans (who generally don’t discriminate between tree species, but simply demand tree presence). An avenue of ash being killed by the insect pest Agrilus planipennis (emerald ash borer). Once these ash are removed, the entire area will be significantly lacking in large trees, which will have significantly adverse impacts upon biodiversity. Source: ACTrees. Beyond tree breeding for resistance, other cultivars and clones exist that have ‘urban form’, and these cultivars may also be at huge risk if exposed to an associated pest or pathogen. As urban environments suffer from in-fill and denser developments, restricted space leads to specific cultivars being selected that have fastigiate form, can tolerate root compaction, and so on. Where these cultivars exist as monocultured avenues, there may be an even more marked problem. Of course, standard tree avenues of a signle species are also very susceptible (notably if they are very similar, on a genetic level), and could quickly cease to be. This would then mean any biodiversity associated with the avenues is lost, too – notably, as dead trees are usually removed entirely from an urban site, even in spite of deadwood being of huge ecological importance. Excessive risk management in urban settings, primarily out of the fear of litigation, is another huge issue that does not reconcile with the need for urban forests to provide for biodiversity. Older trees are usually going to present the greatest risk, due to their stag-headedness and other retrenchment processes that see them become what is considered ‘strucurally unsafe’, though it is these trees that give the most benefits to biodiversity – namely, saproxylic insects and fungi, though also other species that have had dozens (or hundreds, or even thousands) of generations exposed to the specific old trees in situ. Such risk to humans generally sees the trees managed, perhaps via crown reduction (or even felling), and in the case of reduction (and felling) work deadwood (which is ecologically crucial) may likely be removed if a target area exists beneath. At times, this deadwood won’t even remain at the base of the tree (if only reduction work is set), even in large parks (where retention is particular feasible), and this essentially creates an ecosystem (from single tree scale up to city-wide scale) with a huge void of deadwood-associated species. Outside of parks, the grabbing of large pieces of deadwood by members of the public that are destined solely for the log burner is a similar ecological travesty (this is an education issue). A line of five Salix alba within a well-used urban park that were monolithed, as a result of extensive fungal decay caused by Ganoderma australe. These willows could easily have been felled, though the retention of the very large decaying stems is of marked benefit to saproxylic species. Leaving trees themselves temporarily, the observation of most (if not all) urban cities having a fascination with intensively-cut amenity grass is another ecological issue. Large tracts of grass are usually cut for no reason other than to enable for the scene to look formal, and whilst this may be understandable in areas in parks where sports recreation is undertaken (which means management isn’t solely for formality), huge roadside verges are also cut in the same manner. Such verges, or even areas of parks not used for sports recreation, really need not be cut, and instead could be left unmowed for most of the growing season and allowed to ‘wild’ for the benefit of biodiversity (arthropods and small mammals, namely). Scope exists to keep grass long beneath many trees, in fact. Such a practice would in part resolve the issue of ground compaction around trees, and if the tree harbours many insect species, the wildflowers and ‘weeds’ may provide a source of nectar for such insects, and providing the conditions for a small micro-ecosystem to manifest on the single-tree level. During urban development processes, we also observe areas of woodland, pasture, parkland, or otherwise, removed for housing and other forms of development. At times, relicts of former land use (namely trees) are retained, though not always in good conditon and certainly in isolation from their once more diverse ecological setting. The general bias in governmental (worldwide) plans for economic development sees attention to the ecological aspects associated with such developments lacking, and the lack of desire, scope, and ability to ensure tree planting, protection, and retention measures are properly developed, understood, practiced, and enforced, means that many new urban developments lack mature trees and are graced by only an insufficient number of new trees that are usually improperly cared for, and are often unable to provide, even long-term (if they survive), for local biodiversity. Small gardens so highly common in newer developments, compiled with a lack of roadside verges (maximising space for housing and off-road parking) and an abundance of aerial and subterranean services, means that scope for planting large (or even small) trees may not even exist. What hope is there ever going to be for these settings, on an ecological level? Rarely is there scope for demolishing these areas and entirely re-building, given the costs involved. The fragmented nature of the development process also doesn’t serve to aid with the provisioning for biodiversity, with horticultural and arboricultural measures usually only being considered during the latter stages of the process. Even when they are considered, it is questionable as to what weight they have, unless the site is particularly contentious or the potential customers are very affluent and demanding of high-quality landscaping and an associated mature tree presence. A quite newly-built housing development that is largely void of space that can accommodate trees. We can see a few large trees in the background, though a lack of a roadside verge (on the property side), and a front garden of any decent size, severely limits the potential for any sort of tree planting. Source: Architecture Photos. Not wanting to continue and make this post into something akin to War and Peace, I’ll round up here. There is no way I can cover everything I want to without making the post much longer, and that would go against the point of a blog post. I suppose the real crux behind all of my points here is that there is a general desire for amenity and human practicality when it comes to creating and managing tree populations, in place of the desire being to principally provide on an ecological level. In my eyes, this is counter-productive, as whilst it satisfies the need for humans it neglects needs of the ecosystem, which we, as humans, can never escape. Our urban environments are ecosystems just as much as our forests are, and if the health of the ecosystem declines then our own health will decline alongside. Trees, across the world, form the basis of many terrestrial ecosystems, and therefore they must also form the basis of our urban ones, and it is important that this is recognised and held in the highest of regards by those in the realm of decision-making and influence (this extends to pretty much every individual). It is also important that the tree species chosen are chosen for ecological reasons, as if they are chosen primarily for other reasons then the area will fall foul to ecological decline (in comparison to an area developed with ecology in the highest mind).

I shall return tomorrow, on the way to seeing the missus! Should I just get a cutting and then place the bracket on paper and get a print, or just tap the bracket onto some paper and keep the brackets all in situ?

Paul said that earlier, actually. He pinched some of the underside and it appeared to 'blush'. If I get some spores, what do I do with them?

08/04/16. Fact #188. Courtesy of forestry practices, and also the general clearance of ageing trees either to facilitate development or to remove a high level of supposed risk from their retained presence in urban and woodland environments, there is a growing lack of a future veteran / ancient tree population. This is concerning, as such trees have huge ecological value, and typically a value that is far greater to biodiversity than younger trees (notably for saproxylic insects and cavity-nesting birds). At this moment in time, the majority of existing veteran and ancient trees are likely native species, by sheer virtue of the fact that introduced species likely do not predate the 1600s-1700s (and those that are of marked age are generally few and far between, having been planted only in high-profile areas). However, given many environments now feature tree species that have been introduced artificially, future veteran and ancient tree populations may have to exist beyond just those species which are native to an environment. Similarly, if veteranisation techniques are to be practiced in order to artificially bridge the gap between two generations of ‘true’ veteran trees, such practices may have to also be undertaken on introduced tree species. This will in fact be particularly important, as many native tree species suffer from high mortality rates associated with exotic pests and diseases (Dutch elm disease, ash dieback, acute oak decline, and so on, in the realm that is the UK), which may increase our reliance upon exotic tree species. In order to assess whether an introduced tree species can support native biodiversity, the authors of this study sought to ascertain whether veteranisation techniques (the creation of basal water-filled cavities and trunk cavities for nesting birds) undertaken to the London plane (Platanus x acerifolia) would yield positive results for select bird species, and for how long. This species was chosen as, in the study site of northern Italy (Bosco Fontana), the plane is considered a pest that is damaging the native ancient and semi-natural Quercus robur stands (alongside an invasive tree species: Quecus rubra). Ecologically, the implications of such an un-natural stand formation and succession could be considered highly significant, as there are almost certainly going to be a huge number of obligate associates to the native oak species, which in turn attract predators and parasitoids, and so on and so forth. Conversely, no species will have co-evolved with the London plane or red oak, and thus associations may very well be few and far between. A map of the site, with the green dots being individual plane trees used in the study. The 112 plane trees featured in the study were all of a DBH between 40-75cm, and spaced at least 20m apart from one another, in many segments of the study location (see above map). On each tree, between two and three basal pockets and one larger nesting cavity upon the trunk (1-5m up) were created. The basal pockets were designed to accumulate water and slowly rot (for the benefit of water-reliant fauna), and the largest slits were at the bottom of the trunk and decreased in size as they progressed upwards (unfortunately, no data is provided as to their benefits for biodiversity in the study). Upper nesting cavities were designed to house secondary cavity-nesting birds, and resemble naturally-occurring cavities frequent in veteran trees. Their sizes varied, in accordance with the intended bird species that would use the cavity as a nesting site, and these cavity types (and abundance) are listed in the table below. Tree cavities and the intended nesting birds – an overview of the study cavity types. For each tree, the artificial stem cavities noted in the above table were routinely monitored over three years for signs of habitation, and in a select few trunk cavities the internal cavity temperature was recorded for a period of six moths during 2001. Internal cavity temperatures were compared to nest boxes also installed on some trees. Two additional (partial) investigations were also conducted on the plane trees, in 2008 and 2010. The DBH of all trees was measured, to determine whether the veteranisation techniques had harmed the tree in any marked manner. After a period of 8 years following on from the creation of the habitats, 77% of the plane trees remained alive, and the treatment type (trunk cavity sizes) and the size of the tree had an impact upon the mortality rate. Those that did die most routinely failed along the main stem, suggesting that the decay initiated by the habitat creation practices was a possible cause (though, not a significant attributing factor). Of the cavities within the main stem, the most constant temperatures were recorded for the large nesting cavity created for Strix aluco, suggesting that conditions within the host stem were optimal for habitation. Temperatures were also far more constant than those within nest boxes, which means that, wherever feasible, nest boxes should be avoided and instead nesting cavities constructed within the tree (even for exotic tree species). Looking at bird species that colonised the cavities, it was found that five of the nine bird species targeted utilised the 87 (80%) of the artificial habitats (M. striata, P. caeruleus, P. major, S. aluca, S. europaea). For P. caeruleus and P. major, their presence significantly increased with time, and they were even found to use cavities created for other bird species. This trend (increased abundance as time progressed) was also observed for many other of the bird species found, as can be seen in the graphs below. However, by the eighth year, the cavities were largely unsuitable for nesting birds, perhaps because of the decay around the cavities. The different graphs relate to the cavity sizes listed in the table earlier in this post. Evidently, the use of the tree cavities by nesting birds means that exotic tree species can be relied upon to provide for some habitat, assuming they are continually created as the previous ‘batch’ become unsuitable (due to decay, insect infestation, and so on). Of course, some bird species didn’t use the cavities even though they were locally present, though given over half of the bird species did use the cavities it shows a good level of willingness by the bird species to associate themselves with the planes. From this, we can recognise that there is value in exotic tree species, and that veteranisation techniques should not necessarily be isolated solely to native tree species (if native tree species are even available, that is!). The authors do however note that this practice should be limited to broadleaved species, as the traumatic resin canals created by conifers flood the cavities with resin and this makes the cavities unsuitable for nesting birds. By a similar token, such practices should take place away from well-used locations, meaning that if the practices are undertaken in a woodland then they should be done away from pathways. This benefits both the need for risk management and nesting birds, which would generally be more suited to locations that are less disturbed. Source: Zapponi, L., Minari, E., Longo, L., Toni, I., Mason, F., & Campanaro, A. (2014) The Habitat-Trees experiment: using exotic tree species as new microhabitats for the native fauna. iForest-Biogeosciences and Forestry. 8 (1). p464-470.

Indeed. Got to arrange for the trees to be felled now at the necessary heights, though I'll share some photos from today prior to that. Props to Paul, might I add - great guy, and that's an expensive piece of kit he has. Enjoyable day, and seemingly so for members of the public as well, who were quite drawn to the Arbotom!

Four. A douglas fir with Phaeolus, that horse chestnut with Kretz, a willow with a lovely crack and two D. confragosa sporophores, and a Prunus sp. with Ganoderma sp. Once Paul gets over some of the cross-sections I'll sort out some photos.

I'll get them to fell the beech. In all seriousness, I'll go back (I'll go up probably during June - coming back up to the Heath as well, to explore for a day) and try and get a bit of the fungus.

I don't rank Wikipedia for such things, though thought I'd raise the point as evidently that article is wrong. Paul was down today with the Arbotom and I had an apprentice with me (I drive him home some days) who had to carry with him 5kg of chicken, so I couldn't resist the opportunity to be childish!