Rapidly spreading diseases, the kind that necessitate emergency removal or quarantine, represent a chilling reminder of our vulnerability in the face of biological threats. Whether it's a novel virus leaping from animal to human or a resurgent, drug-resistant strain of a familiar foe, these outbreaks can quickly overwhelm healthcare systems and disrupt the very fabric of society. The fear and uncertainty they engender are as contagious as the pathogens themselves.
Think of the chilling speed with which Ebola ravaged West African communities, or how the world held its breath as COVID-19 spread across continents. In such scenarios, emergency removal, while drastic, can be a vital tool for containing the spread and protecting the wider population. It's a difficult balancing act, weighing individual liberties against the collective good. Ethical considerations become paramount: How do we ensure fair and humane treatment for those removed from their homes and families? How do we minimize stigma and prevent discrimination?
The term "emergency removal" often evokes images of hazmat suits and hurried evacuations, but it encompasses a broader spectrum of actions. It could mean isolating a single infected individual in a hospital, or quarantining an entire cruise ship. It might involve relocating communities threatened by a vector-borne disease, like a mosquito-infested area harboring a deadly virus. Regardless of the scale, the underlying principle remains the same: to create a sanitary cordon, breaking the chain of transmission and buying precious time for researchers and healthcare workers to mount a response.
Of course, emergency removal is not a solution in itself. It's a stopgap measure, a desperate attempt to control the immediate crisis while we work towards long-term solutions. These solutions lie in strengthening public health infrastructure, developing effective treatments and vaccines, and fostering international collaboration to enhance surveillance and response capabilities. Ultimately, our best defense against rapidly spreading diseases isn't reactive removal, but proactive preparedness.
Insect infestations, while often considered a nuisance, can rapidly escalate into serious structural threats, posing immediate risks to the integrity of buildings and the safety of their occupants. Unlike slow-acting decay or gradual weathering, certain insect infestations can compromise structural elements within a surprisingly short timeframe. This necessitates swift action and highlights the importance of recognizing the signs of these destructive pests.
One of the most notorious culprits is the subterranean termite. These voracious insects feed on cellulose, the primary component of wood, and can silently hollow out support beams, floor joists, and wall studs, leaving behind a fragile shell. A seemingly minor infestation can quickly undermine a building's structural integrity, potentially leading to collapses, especially under stress like heavy snow loads or strong winds. The insidious nature of termite damage often means the problem goes unnoticed until significant weakening has already occurred.
Another wood-destroying insect posing an immediate threat is the carpenter ant. While they don't consume wood like termites, they excavate galleries within it to build their nests. This tunneling weakens the wood, making it susceptible to cracking and failure. Carpenter ants are particularly drawn to moist or decaying wood, exacerbating existing structural issues. Their presence often indicates underlying water damage, which itself can compromise structural integrity.
Powderpost beetles, though smaller than termites or carpenter ants, can also inflict significant structural damage. Their larvae bore into wood, creating a network of tunnels that reduce its strength and stability. Over time, heavily infested wood can become brittle and crumble, jeopardizing the structural components it supports.
The key to mitigating the risks posed by these insect infestations lies in early detection and rapid intervention. Regular inspections by qualified pest control professionals are crucial in identifying the subtle signs of infestation before significant damage occurs. These signs can include mud tubes built by termites, piles of sawdust-like frass produced by carpenter ants and powderpost beetles, or the presence of the insects themselves. Prompt treatment can effectively eliminate the infestation and prevent further structural damage, ensuring the safety and longevity of the building. Ignoring these warning signs can have devastating consequences, turning a seemingly minor pest problem into a major structural crisis.
Identifying high-risk pests and diseases that demand immediate action is crucial for protecting our crops, forests, and even our own health. We're not just talking about a few aphids on the roses here; we're talking about the threats that can decimate entire ecosystems or cause widespread illness if left unchecked. Think of it like a wildfire – a small spark can be manageable, but if you ignore it, it can quickly explode into an inferno. Similarly, a seemingly minor infestation can rapidly spiral out of control, leading to devastating consequences.
So, how do we pinpoint these ticking time bombs in the natural world? One key aspect is understanding the potential for rapid spread and severe impact. For example, a new invasive insect species with a voracious appetite and no natural predators could quickly wipe out native plants. Similarly, a highly contagious disease with a long latency period could spread widely before symptoms even appear, making containment extremely difficult. We need to be especially vigilant about these “sleeper agents” of the biological world.
Another critical factor is vulnerability. A pest or disease might not pose a significant threat in one area but could be devastating in another. Consider a forest already weakened by drought; it's far more susceptible to insect infestations or fungal diseases than a healthy, resilient forest. Similarly, a community with limited access to healthcare is more vulnerable to the rapid spread of infectious diseases. Context matters.
Finally, we need to consider the potential for cascading effects. The sudden disappearance of a keystone species due to disease can disrupt entire food webs, impacting populations of other plants and animals. Similarly, a widespread crop failure caused by a pest outbreak can lead to food shortages and economic instability. These ripple effects highlight the interconnectedness of ecosystems and the importance of early detection and rapid response.
Identifying these high-risk threats is not just an academic exercise; it's a vital step in safeguarding our environment and our future. By prioritizing surveillance, rapid diagnostics, and proactive intervention strategies, we can effectively mitigate the risks posed by these biological wildfires and protect the health of our planet.
Disease and insect infestations can quickly transform from a nuisance to a full-blown crisis, demanding immediate action to protect the health and safety of individuals and the wider community. Sometimes, this necessitates emergency removals – a drastic measure with significant social, economic, and emotional consequences. Examining case studies of such events reveals the complex interplay of factors that contribute to these situations and the challenges involved in managing them effectively.
One example is the sudden outbreak of a highly contagious disease, like measles, within a densely populated refugee camp. Lack of sanitation, malnutrition, and compromised immune systems can create a perfect storm for rapid disease transmission. In such a scenario, emergency removal of infected individuals to quarantine facilities becomes critical to contain the spread and provide necessary medical care. However, these actions are fraught with difficulties. Identifying and isolating infected individuals can be challenging in overcrowded settings. Furthermore, cultural sensitivities and mistrust of authorities can hinder cooperation, making the removal process even more complex. The ethical dilemmas surrounding forced removals and potential stigmatization also require careful consideration.
Another case study involves a severe insect infestation, such as a large-scale termite infestation in a public housing complex. While termites might not pose an immediate health risk like a contagious disease, their destructive impact on building structures can quickly create unsafe living conditions. Collapsed ceilings, weakened floors, and compromised electrical wiring can put residents at risk of injury or even death. In these cases, emergency relocation of residents is necessary to ensure their safety while the infestation is addressed. However, finding suitable temporary housing for a large number of displaced individuals can be a significant logistical challenge, particularly for vulnerable populations with limited resources. The financial burden of repairs and relocation can also strain local authorities and create long-term housing instability.
These case studies highlight the importance of proactive measures to prevent such crises. Robust public health infrastructure, including vaccination programs and disease surveillance, can mitigate the risk of widespread outbreaks. Regular building inspections and pest control measures can identify and address insect infestations before they escalate into emergencies. Furthermore, having contingency plans in place for emergency removals, including pre-identified temporary housing options and clear communication protocols, can help streamline the response and minimize the negative impact on affected communities. Ultimately, a multi-faceted approach that emphasizes prevention, preparedness, and a compassionate response is essential for effectively managing the complex challenges posed by disease and insect infestations that necessitate emergency removals.
Arboriculture (/ˈɑËÂÂÂÂrbÉ™rɪˌkÊŒltʃər, É‘ËÂÂÂÂrˈbÉâ€ÂÂÂËÂÂÂÂr-/)[1] is the cultivation, management, and study of individual trees, shrubs, vines, and other perennial woody plants. The science of arboriculture studies how these plants grow and respond to cultural practices and to their environment. The practice of arboriculture includes cultural techniques such as selection, planting, training, fertilization, pest and pathogen control, pruning, shaping, and removal.
A person who practices or studies arboriculture can be termed an arborist or an arboriculturist. A tree surgeon is more typically someone who is trained in the physical maintenance and manipulation of trees and therefore more a part of the arboriculture process rather than an arborist. Risk management, legal issues, and aesthetic considerations have come to play prominent roles in the practice of arboriculture. Businesses often need to hire arboriculturists to complete "tree hazard surveys" and generally manage the trees on-site to fulfill occupational safety and health obligations.[citation needed]
Arboriculture is primarily focused on individual woody plants and trees maintained for permanent landscape and amenity purposes, usually in gardens, parks or other populated settings, by arborists, for the enjoyment, protection, and benefit of people.[citation needed]
Arboricultural matters are also considered to be within the practice of urban forestry yet the clear and separate divisions are not distinct or discreet.[citation needed]
Tree benefits are the economic, ecological, social and aesthetic use, function purpose, or services of a tree (or group of trees), in its situational context in the landscape.
A tree defect is any feature, condition, or deformity of a tree that indicates weak structure or instability that could contribute to tree failure.
Common types of tree defects:
Codominant stems: two or more stems that grow upward from a single point of origin and compete with one another.
Included bark: bark is incorporated in the joint between two limbs, creating a weak attachment
Dead, diseased, or broken branches:
Cracks
Cavity and hollows: sunken or open areas wherein a tree has suffered injury followed by decay. Further indications include: fungal fruiting structures, insect or animal nests.
Lean: a lean of more than 40% from vertical presents a risk of tree failure
Taper: change in diameter over the length of trunks branches and roots
Epicormic branches (water sprouts in canopy or suckers from root system): often grow in response to major damage or excessive pruning
Roots:
Proper tree installation ensures the long-term viability of the tree and reduces the risk of tree failure.
Quality nursery stock must be used. There must be no visible damage or sign of disease. Ideally the tree should have good crown structure. A healthy root ball should not have circling roots and new fibrous roots should be present at the soil perimeter. Girdling or circling roots should be pruned out. Excess soil above the root flare should be removed immediately, since it presents a risk of disease ingress into the trunk.
Appropriate time of year to plant: generally fall or early spring in temperate regions of the northern hemisphere.
Planting hole: the planting hole should be 3 times the width of the root ball. The hole should be dug deep enough that when the root ball is placed on the substrate, the root flare is 3–5cm above the surrounding soil grade. If soil is left against the trunk, it may lead to bark, cambium and wood decay. Angular sides to the planting hole will encourage roots to grow radially from the trunk, rather than circling the planting hole. In urban settings, soil preparation may include the use of:
Tree wells: a zone of mulch can be installed around the tree trunk to: limit root zone competition (from turf or weeds), reduce soil compaction, improve soil structure, conserve moisture, and keep lawn equipment at a distance. No more than 5–10cm of mulch should be used to avoid suffocating the roots. Mulch must be kept approximately 20cm from the trunk to avoid burying the root flare. With city trees additional tree well preparation includes:
Tree grates/grill and frames: limit compaction on root zone and mechanical damage to roots and trunk
Root barriers: forces roots to grow down under surface asphalt/concrete/pavers to limit infrastructure damage from roots
Staking: newly planted, immature trees should be staked for one growing season to allow for the root system to establish. Staking for longer than one season should only be considered in situations where the root system has failed to establish sufficient structural support. Guy wires can be used for larger, newly planted trees. Care must be used to avoid stem girdling from the support system ties.
Irrigation: irrigation infrastructure may be installed to ensure a regular water supply throughout the lifetime of the tree. Wicking beds are an underground reservoir from which water is wicked into soil. Watering bags may be temporarily installed around tree stakes to provide water until the root system becomes established. Permeable paving allows for water infiltration in paved urban settings, such as parks and walkways.
Within the United Kingdom trees are considered as a material consideration within the town planning system and may be conserved as amenity landscape[2] features.
The role of the Arborist or Local Government Arboricultural Officer is likely to have a great effect on such matters. Identification of trees of high quality which may have extensive longevity is a key element in the preservation of trees.
Urban and rural trees may benefit from statutory protection under the Town and Country Planning[3] system. Such protection can result in the conservation and improvement of the urban forest as well as rural settlements.
Historically the profession divides into the operational and professional areas. These might be further subdivided into the private and public sectors. The profession is broadly considered as having one trade body known as the Arboricultural Association, although the Institute of Chartered Foresters offers a route for professional recognition and chartered arboriculturist status.
The qualifications associated with the industry range from vocational to Doctorate. Arboriculture is a comparatively young industry.
Pruning is a horticultural, arboricultural, and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots.
The practice entails the targeted removal of diseased, damaged, dead, non-productive, structurally unsound, or otherwise unwanted plant material from crop and landscape plants. In general, the smaller the branch that is cut, the easier it is for a woody plant to compartmentalize the wound and thus limit the potential for pathogen intrusion and decay. It is therefore preferable to make any necessary formative structural pruning cuts to young plants, rather than removing large, poorly placed branches from mature plants.
Woody plants may undergo a process referred to as "self-pruning", where they will drop twigs or branches which are no longer producing more energy than they require. It is theorized that this process can also occur in response to lack of water, in order to reduce the surface area where water can be lost.[1] This natural shedding of branches is called cladoptosis.
Specialized pruning practices may be applied to certain plants, such as roses, fruit trees, and grapevines. Different pruning techniques may be used on herbaceous plants than those used on perennial woody plants.
Reasons to prune plants include deadwood removal, shaping (by controlling or redirecting growth), improving or sustaining health, reducing risk from falling branches, preparing nursery specimens for transplanting, and both harvesting and increasing the yield or quality of flowers and fruits.
Branch wood is an individual stem that grows off of another stem.
Trunk wood is the main stem of a tree which individual stems grow out of.
This refers to the area below the union of where branch wood attaches with the trunk/stem wood. This can often appear raised.
This refers to the junction between branch wood and trunk/stem wood. It usually looks raised. [2]
Pruning in an urban setting is crucial due to the tree being in drastically different conditions than where it naturally grows.[3]
Arborists, orchardists, and gardeners use various garden tools and tree cutting tools designed for the purpose, such as secateurs, loppers, handsaws, or chainsaws.[4] Additionally in forestry, pole pruners (averruncators in British English) and pole saws are commonly used, and these are often attached to poles that reach up to 5–6 m (16–20 ft). This is a more efficient and safer way of pruning than with ladders. These bush saws on polls have also been motorized as chainsaws which is even more efficient. Older technology used Billhooks, Kaiser blades, and pruning knives. Although still used in some coppicing, they are not used so much in commercial forestry due to the difficulty of cutting flush with the stem. Flush cuts happen when a pruner cuts into the cambium layer of the main trunk, which can happen when a pruner is not precise with pruning cuts, and removes a portion of the branch collar, which can put the tree at risk of entry cords from forest pathogens.
Although there are several different types of pruning, they can be simplified into two categories. One of which is cutting the branch back to a specific and intermediate point, called a "reduction cut", and the other of which is completely removing a branch back to the union where the branch connects which the main trunk, called "removal cut".[5]
A "reduction cut" is when one removes a portion of a growing stem down to a set of desirable buds or side-branching stems. This is commonly performed in well trained plants for a variety of reasons, for example to stimulate growth of flowers, fruit or branches, as a preventive measure to wind and snow damage on long stems and branches, and finally to encourage growth of the stems in a desirable direction.
In orchards, fruit trees are often lopped to encourage regrowth and to maintain a smaller tree for ease of picking fruit. The pruning regime in orchards is more planned, and the productivity of each tree is an important factor.
Branches die off for a number of reasons including sunlight deficiency, pest and disease damage, and root structure damage. A dead branch will at some point decay back to the parent stem and fall off. This is normally a slow process but can be hastened by high winds or extreme temperatures. The main reason deadwooding is performed is safety. Situations that usually demand removal of deadwood include trees that overhang public roads, houses, public areas, power lines, telephone cables and gardens. Trees located in wooded areas are usually assessed as lower risk but assessments consider the number of visitors. Trees adjacent to footpaths and access roads are often considered for deadwood removal.[8]
Another reason for deadwooding is amenity value, i.e. a tree with a large amount of deadwood throughout the crown will look more aesthetically pleasing with the deadwood removed. The physical practice of deadwooding can be carried out most of the year though should be avoided when the tree is coming into leaf. The deadwooding process speeds up the tree's natural abscission process. It also reduces unwanted weight and wind resistance and can help overall balance.
Preventative and structural pruning can be done to mitigate several issues young trees may have in the future. The structural pruning can reduce tree stress, increase the lifespan of trees, and promotes resistance to damage due to natural weather events. Attributes of trees with good structure include excurrent growth by having a single dominant leader, branch unions without included bark, and a balanced canopy. Structural pruning does this by developing or maintaining a dominant leader, identify the lowest branches in the canopy, prevent branches below the permanent canopy from growing too large, keeping all branches less than one half the trunk diameter, space main branches along one dominant trunk, and suppress growth on branches with included bark. [9]
Subordination pruning is done on limbs that will exceed 50% percent of the stem diameter. A reduction cut may be performed while still allowing about 50% of the branch. This is done to help maintain form and deter the formation of co-dominant leaders. Temporary branches may be too large for a removal cut so subordination pruning should be done to slowly reduce a limb by 50% each year to allow the tree to properly heal from the cut. As a tree becomes larger the slower it grows. Reducing the larger limbs for eventual removal will allow for the tree to promote new growth rather than using energy in encouraging unwanted limbs to continue to grow. Removing a large branch increases the likelihood of the cut to not heal properly which also may attract insects, diseases and fungus. [9][10]
Crown thinning is the removal of live healthy branches which increases light penetration, air circulation and reduces wind resistance which reduces risks from damage and the possibility of pest infestation. [11]
Crown raising involves the removal of the lower branches to a given height. The height is achieved by the removal of whole branches or removing the parts of branches which extend below the desired height. The branches are normally not lifted to more than one third of the tree's total height.
Crown lifting is done for access; these being pedestrian, vehicle or space for buildings and street furniture. Lifting the crown will allow traffic and pedestrians to pass underneath safely. This pruning technique is usually used in the urban environment as it is for public safety and aesthetics rather than tree form and timber value.
Crown lifting introduces light to the lower part of the trunk; this, in some species can encourage epicormic growth from dormant buds. To reduce this sometimes smaller branches are left on the lower part of the trunk. Excessive removal of the lower branches can displace the canopy weight, this will make the tree top heavy, therefore adding stress to the tree. When a branch is removed from the trunk, it creates a large wound. This wound is susceptible to disease and decay, and could lead to reduced trunk stability. Therefore, much time and consideration must be taken when choosing the height the crown is to be lifted to.
This would be an inappropriate operation if the tree species’ form was of a shrubby nature. This would therefore remove most of the foliage and would also largely unbalance the tree. This procedure should not be carried out if the tree is in decline, poor health or dead, dying or dangerous (DDD) as the operation will remove some of the photosynthetic area the tree uses. This will increase the decline rate of the tree and could lead to death.
If the tree is of great importance to an area or town, (i.e. veteran or ancient) then an alternative solution to crown lifting would be to move the target or object so it is not in range. For example, diverting a footpath around a tree's drip line so the crown lift is not needed. Another solution would be to prop up or cable-brace the low hanging branch. This is a non-invasive solution which in some situations may be more economical and environmentally friendly. [12]
Selectively pruning a window of view in a tree.
Reducing the height and or spread of a tree by selectively cutting back to smaller branches and in fruit trees for increasing of light interception and enhancing fruit quality.
A regular form of pruning where certain deciduous species are pruned back to pollard heads every year in the dormant period. This practice is usually commenced on juvenile trees so they can adapt to the harshness of the practice. This practice can be used for tree shaping but is also used in specific species which young branches can be sold for floral arrangements.
Deadheading is the act of removing spent flowers or flowerheads for aesthetics, to prolong bloom for up to several weeks or promote rebloom, or to prevent seeding.
In general, pruning deadwood and small branches can be done at any time of year. Depending on the species, many temperate plants can be pruned either during dormancy in winter, or, for species where winter frost can harm a recently pruned plant, after flowering is completed. In the temperate areas of the northern hemisphere autumn pruning should be avoided, as the spores of disease and decay fungi are abundant at this time of year.
Some woody plants tend to bleed profusely from cuts, such as mesquite and maple. Some callus over slowly, such as magnolia. In this case, they are better pruned during active growth when they can more readily heal. Woody plants that flower early in the season, on spurs that form on wood that has matured the year before, such as apples, should be pruned right after flowering as later pruning will sacrifice flowers the following season. Forsythia, azaleas and lilacs all fall into this category.
An arborist, or (less commonly) arboriculturist, is a professional in the practice of arboriculture, which is the cultivation, management, and study of individual trees, shrubs, vines, and other perennial woody plants in dendrology and horticulture.[citation needed]
Arborists generally focus on the health and safety of individual plants and trees, rather than managing forests or harvesting wood (silviculture or forestry). An arborist's scope of work is therefore distinct from that of either a forester or a logger.[citation needed]
In order for arborists to work near power wires, either additional training is required or they need to be certified as a Qualified Line Clearance Arborist or Utility Arborist (there may be different terminology for various countries). There is a variety of minimum distances that must be kept from power wires depending on voltage, however the common distance for low voltage lines in urban settings is 10 feet (about 3 metres).[1]
Arborists who climb (as not all do) can use a variety of techniques to ascend into the tree. The least invasive, and most popular technique used is to ascend on rope. There are two common methods of climbing, Single Rope System (SRS) and Moving Rope System (MRS). When personal safety is an issue, or the tree is being removed, arborists may use 'spikes', (also known as 'gaffs' or 'spurs') attached to their chainsaw boots with straps to ascend and work. Spikes wound the tree, leaving small holes where each step has been.[citation needed]
An arborist's work may involve very large and complex trees, or ecological communities and their abiotic components in the context of the landscape ecosystem. These may require monitoring and treatment to ensure they are healthy, safe, and suitable to property owners or community standards. This work may include some or all of the following: planting; transplanting; pruning; structural support; preventing, or diagnosing and treating phytopathology or parasitism; preventing or interrupting grazing or predation; installing lightning protection; and removing vegetation deemed as hazardous, an invasive species, a disease vector, or a weed.[citation needed]
Arborists may also plan, consult, write reports and give legal testimony. While some aspects of this work are done on the ground or in an office, much of it is done by arborists who perform tree services and who climb the trees with ropes, harnesses and other equipment. Lifts and cranes may be used too. The work of all arborists is not the same. Some may just provide a consulting service; others may perform climbing, pruning and planting: whilst others may provide a combination of all of these services.[2]
Arborists gain qualifications to practice arboriculture in a variety of ways and some arborists are more qualified than others. Experience working safely and effectively in and around trees is essential. Arborists tend to specialize in one or more disciplines of arboriculture, such as diagnosis and treatment of pests, diseases and nutritional deficiencies in trees, climbing and pruning, cabling and lightning protection, or consultation and report writing. All these disciplines are related to one another and some arborists are very well experienced in all areas of tree work, however not all arborists have the training or experience to properly practice every discipline.[citation needed]
Arborists choose to pursue formal certification, which is available in some countries and varies somewhat by location. An arborist who holds certification in one or more disciplines may be expected to participate in rigorous continuing education requirements to ensure constant improvement of skills and techniques.[citation needed]
In Australia, arboricultural education and training are streamlined countrywide through a multi-disciplinary vocational education, training, and qualification authority called the Australian Qualifications Framework, which offers varying levels of professional qualification. Government institutions including Technical and Further Education TAFE offer Certificate III or a diploma in arboriculture as well as some universities.[3][4] There are also many private institutions covering similar educational framework in each state. Recognition of prior learning is also an option for practicing arborists with 10 or more years of experience with no prior formal training. It allows them to be assessed and fast track their certification.[citation needed]
In France, a qualified arborist must hold a Management of Ornamental Trees certificate, and a qualified arborist climber must hold a Pruning and Care of Trees certificate; both delivered by the French Ministry of Agriculture.[5][6]
In the UK, an arborist can gain qualifications up to and including a master's degree. College-based courses include further education qualifications, such as national certificate, national diploma, while higher education courses in arboriculture include foundation degree, bachelor's degree and master's degree.[citation needed]
In the US, a Certified Arborist (CA) is a professional who has over three years of documented and verified experience and has passed a rigorous written test from the International Society of Arboriculture. Other designations include Municipal Specialist, Utility Specialist and Board Certified Master Arborist (BCMA). The USA and Canada additionally have college-based training which, if passed, will give the certificate of Qualified Arborist. The Qualified Arborist can then be used to offset partial experience towards the Certified Arborist.
Tree Risk Assessment Qualified credential (TRAQ), designed by the International Society of Arboriculture, was launched in 2013. At that time people holding the TRACE credential were transferred over to the TRAQ credential.[citation needed]
In Canada, there are provincially governed apprenticeship programs that allow arborists' to work near power lines upon completion. These apprenticeship programs must meet the provincial reregulations (For example, in B.C. they must meet WorkSafeBC G19.30), and individuals must ensure they meet the requirements of the owner of the power system.[citation needed]
Trees in urban landscape settings are often subject to disturbances, whether human or natural, both above and below ground. They may require care to improve their chances of survival following damage from either biotic or abiotic causes. Arborists can provide appropriate solutions, such as pruning trees for health and good structure, for aesthetic reasons, and to permit people to walk under them (a technique often referred to as "crown raising"), or to keep them away from wires, fences and buildings (a technique referred to as "crown reduction").[7] Timing and methods of treatment depend on the species of tree and the purpose of the work. To determine the best practices, a thorough knowledge of local species and environments is essential.[citation needed]
There can be a vast difference between the techniques and practices of professional arborists and those of inadequately trained tree workers. Some commonly offered "services" are considered unacceptable by modern arboricultural standards and may seriously damage, disfigure, weaken, or even kill trees. One such example is tree topping, lopping, or "hat-racking", where entire tops of trees or main stems are removed, generally by cross-cutting the main stem(s) or leaders, leaving large unsightly stubs. Trees that manage to survive such treatment are left prone to a spectrum of detrimental effects, including vigorous but weakly attached regrowth, pest susceptibility, pathogen intrusion, and internal decay.[8]
Pruning should only be done with a specific purpose in mind. Every cut is a wound, and every leaf lost is removal of photosynthetic potential. Proper pruning can be helpful in many ways, but should always be done with the minimum amount of live tissue removed.[9]
In recent years, research has proven that wound dressings such as paint, tar or other coverings are unnecessary and may harm trees. The coverings may encourage growth of decay-causing fungi. Proper pruning, by cutting through branches at the right location, can do more to limit decay than wound dressing [10]
Chemicals can be applied to trees for insect or disease control through soil application, stem injections or spraying. Compacted or disturbed soils can be improved in various ways.[citation needed]
Arborists can also assess trees to determine the health, structure, safety or feasibility within a landscape and in proximity to humans. Modern arboriculture has progressed in technology and sophistication from practices of the past. Many current practices are based on knowledge gained through recent research, including that of Alex Shigo, considered one "father" of modern arboriculture.[11]
Depending on the jurisdiction, there may be a number of legal issues surrounding the practices of arborists, including boundary issues, public safety issues, "heritage" trees of community value, and "neighbour" issues such as ownership, obstruction of views, impacts of roots crossing boundaries, nuisance problems, disease or insect quarantines, and safety of nearby trees or plants that may be affected.[citation needed]
Arborists are frequently consulted to establish the factual basis of disputes involving trees, or by private property owners seeking to avoid legal liability through the duty of care.[12] Arborists may be asked to assess the value of a tree[13] in the process of an insurance claim for trees damaged or destroyed,[14] or to recover damages resulting from tree theft or vandalism.[15] In cities with tree preservation orders an arborist's evaluation of tree hazard may be required before a property owner may remove a tree, or to assure the protection of trees in development plans and during construction operations. Carrying out work on protected trees and hedges is illegal without express permission from local authorities,[16] and can result in legal action including fines.[17] Homeowners who have entered into contracts with a Homeowner's association (see also Restrictive covenants) may need an arborists' professional opinion of a hazardous condition prior to removing a tree, or may be obligated to assure the protection of the views of neighboring properties prior to planting a tree or in the course of pruning.[18] Arborists may be consulted in forensic investigations where the evidence of a crime can be determined within the growth rings of a tree, for example. Arborists may be engaged by one member of a dispute in order to identify factual information about trees useful to that member of the dispute, or they can be engaged as an expert witness providing unbiased scientific knowledge in a court case. Homeowners associations seeking to write restrictive covenants, or legislative bodies seeking to write laws involving trees, may seek the counsel of arborists in order to avoid future difficulties.[19]
Before undertaking works in the UK, arborists have a legal responsibility to survey trees for wildlife, especially bats, which are given particular legal protection. In addition, any tree in the UK can be covered by a tree preservation order and it is illegal to conduct any work on a tree, including deadwooding or pruning, before permission has been sought from the local council.[citation needed]
The protagonist in Italo Calvino's novel The Baron in the Trees lives life on the ground as a boy and spends the rest of his life swinging from tree to tree in the Italian countryside. As a young man he helps the local fruit farmers by pruning their trees.[citation needed]
Some noteworthy arborists include:
Tree care is the application of arboricultural methods like pruning, trimming, and felling/thinning[1] in built environments. Road verge, greenways, backyard and park woody vegetation are at the center of attention for the tree care industry. Landscape architecture and urban forestry[2][3] also set high demands on professional tree care. High safety standards against the dangers of tree care have helped the industry evolve. Especially felling in space-limited environments poses significant risks: the vicinity of power or telephone lines, insufficient protective gear (against falling dead wood, chainsaw wounds, etc.) and narrow felling zones with endangered nearby buildings, parking cars, etc.. The required equipment and experience usually transcends private means and is often considered too costly as a permanent part of the public infrastructure. In singular cases, traditional tools like handsaws may suffice, but large-scale tree care usually calls for heavy machinery like cranes, bucket trucks, harvesters, and woodchippers.
Road side trees are especially prone to abiotic stress by exhaust fumes, toxic road debris, soil compaction, and drought which makes them susceptible to fungal infections and various plant pests[4] like the spotted lantern fly.[5] When tree removal is not an option, because of road ecology considerations, the main challenge is to achieve road safety (visibility of road signs, blockage-free lanes, etc.) while maintaining tree health.
While the perceived risk of death by falling trees (a part of the "tree risk" complex) is influenced by media and often hyped (the objective risk has been reported to be close to 1 : 10.000.000, almost as low as death by lightning),[6] singular events have encouraged a "proactive" stance so that even lightly damaged trees are likely to be removed in urban and public traffic surroundings.[3] As a tree ages and nears the end of its safe useful life expectancy (SULE),[7] its perceived amenity value is decreased greatly. A risk assessment normally carried out by local council's arborist to determine the best course of action.[8][9] As with all public green spaces, trees in green urban spaces and their careful conservation is sometimes in conflict with aggressive urban development even though it is often understood how urban trees contribute to liveability of suburbs and cities both objectively (reduction of urban heat island effect, etc.) and subjectively.[10][11][12][13] Tree planting programs implemented by a growing number of cities, local councils and organizations is mitigating the losses and in most cases increasing the number of trees in suburbia.[14] Programs include the planting of 2 trees for every 1 tree removed, while some councils are paying land owners to keep trees instead of removing them for farming or construction.[15]
The voluntary industry consensus standards developed by TCIA, resulted in the ANSI A300 standard, the generally accepted industry standard for tree care practices including trees, shrubs, and other woody plants.[16] It includes the following parts:
Urban Forestry maintains 4.1 million trees on public property, which includes an estimated 3.5 million trees within Toronto's parks and ravines, and approximately 600,000 trees on City streets. ... The focus of our maintenance service is shifting progressively from reactive maintenance to proactive maintenance.
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Ho Chi Minh City has announced a plan to move and cut down 300 trees on Ton Duc Thang Street in District 1 to make space for a bridge connecting to District 2 and a metro station.