FAQ
FAQ
Welcome to our FAQ!
Here we’ve compiled the most common questions we receive and the answers that will help you quickly find the information you need. Whether you want to learn more about our services, how we work, or practical details, we hope this page makes it easier for you to find what you’re looking for.
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i-Tree Eco is an American software program that allows users to specify the country, region, and city for which calculations are to be performed. Since 2019, it has been possible to use Sweden and Swedish cities as the basis for calculations, as well as to select specific SMHI weather stations located closest to the city or area included in the current calculation. The language used is English, regardless of whether the calculations are for a city in Sweden.
The calculation applies to the entire urban area. The economic calculations are based on the population figure specified in the Excel spreadsheet.
Becoming a good consultant in the tree industry requires solid professional experience. We at Trädkontoret are landscape engineers and horticultural engineers with backgrounds in both public administration and consulting. We are happy to share our expertise through lectures, articles, courses, and—soon—a knowledge base on our website.
Are you interested in working with us? We’re always interested in hearing from people who are curious about our industry. Please send a cover letter and your resume toinfo@tradkontoret.se
Every tree and every site is unique. We therefore always recommend conducting a root survey—for example, through test excavations or vacuum trenching—to determine the location of the roots. If this is not possible, for example for financial reasons, you can instead use one of the industry standards that are available.
Working Around Trees – Protecting Trees During Planning and Execution
SIS has developed a standard for the protection of trees during construction work (SS 990002:2025). The standard is intended for those involved in the planning, design, and execution of work near trees.
Below is an excerpt from this publication:
5.6 Tree Protection Zone
5.6.1 General
Tree protection zones must be assessed and established in order to protect the roots, crown, and surrounding soil of trees from damage and compaction during construction work.
5.6.2
The estimated tree protection area should be used as a starting point to indicate the size of the area around trees that may require protection.
Note: Crown diameter may be used instead of the tree crown’s extent.
The estimated tree protection area should be calculated using the following formula: Tree crown spread + 4 m in each direction
5.6.3
The designated tree protection zone shall be used to define the area to be protected.
A tree expert shall establish the tree protection zone.
To establish the tree protection zone, a site visit with a tree expert must be conducted, and root mapping must be performed if necessary.
When work needs to be performed within the designated tree protection zone, technical solutions should be used.
The County Administrative Board's Recommendations
- The roots are protected by marking off an area around the tree with a fence, concrete blocks, or similar barriers.
- The area should extend at least 2 meters beyond the outer edge of the crown, but preferably 15 times the diameter of the trunk.
- No excavation, driving of heavy vehicles, dumping of soil, or placement of sheds or construction equipment is permitted within the area.
- Gasoline, diesel, pesticides, or solvents must not be handled in this area either.
- If the marked-off area is less than 15 times the diameter of the trunk, special care should be taken with the roots during excavation.
- Larger roots should, as far as possible, not be damaged during digging, especially if they are thicker than 5 cm. One way to avoid damaging the roots is to dig around them by hand.
- Roots that need to be cut should be pruned with a pruning saw or pruning shears.
- The sides of the trench should be watered and covered while work is in progress, and the trench should be backfilled as soon as possible.
- Limit construction traffic to a few routes in the area. If traffic must pass near trees, slabs or other low-impact ground cover can be installed to reduce the risk of soil compaction.
The County Administrative Board's brochure can be downloaded viathe following link.
Measures to Preserve Trees During Excavation Work
Below is a brief summary of the protective measures we recommend to preserve trees where preservation is possible through such measures:
- Designate tree protection areas and divide them into different zones based on the activities that can be carried out there.
- Trees to be preserved within the construction site or at its boundary must be fenced off. The fence must be placed outside the tree protection zone. The fence must prevent work, storage, transportation, or other activities harmful to the tree from taking place within the tree protection zone. The fence must have a minimum height of 180 cm and be a permanent, non-movable structure. The installation of the fence must not damage the root system.
- When excavating in areas where roots are present, all excavation work must be carried out as gently as possible to avoid damaging the roots. By excavating carefully, roots can be detected before they are cut.
- In exceptional cases, roots must be removed. When excavating where larger roots (3 cm in diameter) must be removed, they should be cut with a sharp pruning tool (pruning shears or a saw).
- Exposed roots must not be exposed to drought, sunlight, or cold. Exposed roots should always be kept moist and, if necessary, watered until the excavation pit has been backfilled. A root curtain is a good way to keep roots protected.
- Excavations should be as narrow as possible to avoid digging into the surface soil layers, which contain the most roots. Sheet pile structures that reinforce the walls of the excavation and thus allow for narrower excavations can be used to good effect.
- For long trenches where many roots need to be removed, a root barrier should be installed. A root barrier protects the trench and provides the tree with good conditions to recover after an intrusion into the tree protection zone.
- An economic value should be assigned to each tree. This economic value should be used to calculate penalties if the trees are damaged. The value should be determined using the Alnarp Model 2.2.
- All tree pruning must be performed by an ETW-certified arborist.
Calculating the socioeconomic benefits that trees provide by delaying stormwater runoff cannot be done in the same way as in most international projects, since the vast majority of Swedish cities have separate systems for stormwater management rather than combined systems. The former means that stormwater flows through a separate pipeline from storm drains directly to the receiving body of water and never passes through a wastewater treatment plant. Consequently, it is not possible to calculate the economic cost incurred by wastewater treatment plants when both sewage and stormwater are combined. Even the stormwater fee applicable to property owners in Sweden has proven difficult to use for economic comparisons, as it is based on units entirely different from those used in i-Tree Eco. It is suggested that an economic assessment regarding stormwater retention in Swedish i-Tree projects could instead be based on a cost comparison with engineering structures. This refers to the construction cost per cubic meter of water applicable to, for example, a swale, a rain garden, or an underground storage reservoir.
The economic analysis of trees’ carbon sequestration and carbon storage is typically conducted at the global level. This primarily refers to climate impacts and the cost of carbon dioxide. i-Tree Eco calculates the amount of carbon sequestration and carbon storage in annual weight units of metric tons—that is, metric tons per year. This unit is also converted to carbon dioxide and expressed in metric tons. The economic valuation of trees’ contribution through carbon sequestration, carbon storage, and consequently carbon dioxide is linked to reduced climate impact; thus, the economic valuation takes a global perspective. To convert the amount of carbon dioxide into Swedish kronor and öre and to determine what this means for global benefits, it is possible to conduct an economic valuation based on the analytical method described in the Swedish Transport Administration’s report “Analytical Method and Socioeconomic Calculation Values for the Transportation Sector” (ASEK 6.1).
For the economic assessment of the impact of trees on reducing air pollution, it is recommended to analyze the amount of air pollution using the method described in the Swedish Transport Administration’s report “Analysis Method and Socioeconomic Calculation Values for the Transportation Sector” (ASEK 6.1). The calculations in this type of analysis are performed at the local level and take into account, among other things, the number of people exposed to air pollution in the specified area as well as the ventilation conditions. The regional level is not included in the economic valuation because it is based on compliance with the national environmental objective and does not provide an economic estimate.
The economic calculation generated by i-Tree Eco—which is included in the report automatically sent after a calculation is performed on the U.S. server—is based on U.S. conditions. The economic calculation in SEK included in this report is thus a free conversion from U.S. dollars and is based on U.S. GDP as well as U.S. perspectives on, for example, the population’s willingness to pay to avoid illnesses caused by air pollution. To provide as accurate an economic translation as possible of the monetary benefits of trees in Swedish cities, the results need to be analyzed based on Swedish conditions.
Yes, planting trees on top of floor joists has been done since the “Million Program” began in Sweden. In many cases, concerns about root intrusion and excessive loads are unwarranted, but it is important that projects involving trees on floor joists undergo quality assurance with expert support throughout all project phases. The weights of both plant beds and vegetation must be calculated, and waterproofing must be protected against root intrusion. Another important aspect is selecting the right substrate and ensuring that drainage functions properly.
Trädkontoret has extensive experience planting trees on wooden decking, both on open green roofs and in enclosed courtyards above parking garages. Please contact us if you need assistance with your project.
A complete inventory means that all trees within the area in question are inventoried.
Tree-lined avenues are protected under the general biotope protection provisions. This is regulated under Section 5 of the “Ordinance (1998:1252) on Area Protection,” which designates as protected certain small, easily recognizable land or water areas that, due to their special characteristics, serve as valuable habitats for endangered animal or plant species or are otherwise particularly worthy of protection. In addition to tree-lined avenues, the following biotopes are also generally protected:
- Spring with surrounding wetlands on farmland
- Cultivation mound on farmland
- Pilevall
- Small bodies of water and wetlands on agricultural land
- Stone wall on farmland
- Åkerholme
What counts as a tree-lined avenue?
The definition of a tree-lined avenue is:
“Deciduous trees planted in a single or double row consisting of at least five trees along a road or what was previously a road, or in an otherwise open landscape. The trees must consist predominantly of mature trees.” According to the Swedish Environmental Protection Agency’s handbook, a mature tree is defined as one with a diameter of 20 cm at breast height or, if this occurs earlier, an age of 30 years.
All tree-lined avenues are protected as soon as they meet the definition; in other words, they do not need to be designated to be protected.
Recent court rulings have made it clear that the protection of tree-lined avenues applies to avenues consisting of trees that were not planted (but were intentionally preserved), to trees planted as replacements for avenue trees as part of a compensation measure (but which have not yet grown large enough to be considered mature), as well as in cases where the tree-lined avenue has significant gaps—for example, where a roundabout separates trees from the rest of the avenue.
Since rows of trees in an “otherwise open landscape” are protected, tree rings and tree-lined avenues adjacent to and within cemeteries and church grounds may be subject to biotope protection. Similarly, tree-lined avenues in towns and cities may meet the criteria of being situated in an open landscape or along a road (Figure 1).
However, the general biotope protection does not apply to trees located in the immediate vicinity of buildings. Measures may therefore be carried out there without an exemption, regardless of whether they would harm the natural environment. Please note that it
- This applies only to the individual trees located in the immediate vicinity of the buildings. The other trees in the avenue remain protected.
- must be in theimmediatevicinity of residential areas. This is evident from recently published court rulings. The exact meaning of “immediate” is interpreted differently by various county administrative boards pending further clarifying court rulings.
General habitat protection also does not apply in areas covered by a zoning plan adopted before 1994, or if the zoning plan specifies something else—such as “nature,” “park,” or similar—for the area where the tree-lined avenue is located.
What is prohibited?
According to Chapter 7, Section 11, second paragraph, of the Environmental Code:
“Within a biotope protection area, one may not engage in any activity or take any action that could harm the natural environment.”
What constitutes damage to the natural environment in a tree-lined avenue depends on the specific circumstances of each case. The natural environment as a whole is protected within the biotope, and it is the potential damage that the measure may cause to the natural environment and the living conditions of species in the biotope that is significant and must be assessed. This means that, in some cases, the removal of individual trees does not necessarily constitute damage to the natural environment (though in other cases it may), but that severe pruning (topping) can constitute such damage, even if the tree is spared.
The biotope protection regulations do not prevent the implementation of management and other measures that promote the long-term survival of a biotope (and the species found there).
According to the provision, the prohibition applies to actions that may harm the natural environment. Thus, the mere existence of a risk of harm is sufficient for the action to be prohibited.
According to the Swedish Environmental Protection Agency’s handbook on biotope protection areas, “A single tree or branches that pose an obvious and significant immediate risk of harm to people, animals, or property may be removed at one’s own risk without an exemption, if the risk of harm is so imminent that an exemption review cannot be awaited. However, an application for an exemption should be submitted at the same time. It is advisable to contact the county administrative board before felling a tree, especially if the tree is old or large, to assess whether it is necessary to fell the entire tree, whether it might be appropriate to leave a high stump, or whether felling the tree could result in the loss of protection for the tree-lined avenue.”
Exemptions, Special Circumstances, and Compensatory Measures
There are no specific regulations defining what constitutes a “special reason,” but, for example, the fact that a tree-lined avenue entails extra work or additional costs in the form of raking leaves is generally never considered a special reason. Possible special reasons may include development in the public interest, other nature conservation or cultural heritage interests, research and investigation, health and safety, tree diseases, or restoration needs. If the county administrative board has determined that the biotope protection regulations and the continuity of the trees’ biological values have been taken into account in a tree care plan—or, alternatively, a care and maintenance plan—the plan may constitute a special reason for an exemption for measures that could harm the natural environment, provided they are carried out in accordance with the plan.
A prerequisite for granting an exemption is the existence of special reasons. It is the assessment in each individual case—weighing the significance of the damage against the weight of the reason for taking the action that causes the damage—that determines whether an exemption can be granted or not. This means that greater damage may be accepted if the reason for causing the damage is compelling. When weighing these factors, consideration must also be given to whether there are other suitable alternatives that do not cause damage to the protected biotope.
The County Administrative Board has the right to impose conditions when granting an exemption. Examples of conditions include the timing of the work (work is usually not permitted during the breeding season), the requirement to preserve tall stumps, or the replanting of new trees (including the species and size). The care of the newly planted trees may also be subject to conditions.
The County Administrative Board also has the right to request compensatory measures for the natural value lost as a result of the project. Examples of compensatory measures include planting more trees than the original number and preserving dead wood in wildlife refuges.
"Hazardous tree" is a term that many people use when they are concerned that a tree might fall. However, for a tree to be classified as a hazardous tree, three different factors must be present:
- There must be a target—such as a person or a car—that could be injured in the vicinity of the tree.
- The tree must have some kind of damage or weakness, such as dead branches or a severe rottenness.
- The consequences of the target being hit by the tree part must be significant.
The consequences of an incident—such as a large branch breaking off—can be significant if there are buildings or people near the tree. The consequences, and thus the risk, are therefore less severe if the tree is located in a place that is rarely or never visited. The consequences can also vary depending on the size and force of the falling tree part. A damaged tree deep in a forest cannot, therefore, be classified as a hazardous tree because there is neither property nor people in the vicinity at risk of injury. This is often overlooked, leading to all trees with various types of damage—regardless of where they are located—being associated with high risk.
A risk assessment is always time-limited because uncertainty increases the longer the time horizon used, and because all trees collapse sooner or later. A validity period of 3–5 years is often used. This means that the specified risk level applies only within this time period, provided that no significant changes occur. Such changes could include pruning the tree or felling neighboring trees. Furthermore, the risk assessment applies under normal weather conditions and not during extreme weather events.
Risk Tree Assessment
Many trees are cut down due to a lack of knowledge about which trees pose a risk. A hollow in the trunk or dead branches in the crown may be interpreted as a sign that the tree is dying or about to fall, but that is not necessarily true. Trees with extensive damage and fungal infestation may still be considered safe due to factors such as the tree’s location or the stability of the remaining wood. There are a number of different publications and methods that have been developed to assess hazardous trees, and training courses are also offered on the subject. To accurately assess a tree’s vitality, damage, and potential risks, the inspection or inventory of the trees should be conducted by a qualified professional with relevant training and experience, such as a consulting arborist, tree specialist, or someone with equivalent qualifications.
The County Administrative Board's Recommendations
The County Administrative Board has produced a brochure describing risk assessments and the relevant legal framework. The brochure can be downloaded viathe following link. The brochure also explains the provisions of the Public Procurement Act (LOU), and below are suggested text passages that can be used in procurement processes.
“Training in risk assessment, such as TRAQ—Tree Risk Assessment Qualification—or QTRA—Quantified Tree Risk Assessment—or the equivalent.”
It is important to note that, for example, TRAQ and QTRA are different types of systems; however, if you, as a property manager, are primarily interested in risk assessment and not in how the system is structured, both systems can be included in the procurement process. In Sweden, however, TRAQ is by far the dominant method for risk assessments.
The Swedish Environmental Protection Agency has recently issued new guidelines stating that measures taken on trees of special conservation value are interpreted as a significant alteration of a natural environment, which, according to the Environmental Code, requires consultation under Chapter 12, Section 6. Many people refer to this as “12:6 consultation.” This clarification was necessary because different county administrative boards had previously interpreted the provisions of the Environmental Code in various ways. The Code states that “an activity or measure that may significantly alter the natural environment, and that is not subject to a permit or notification requirement under other provisions of the Environmental Code, shall be reported for consultation pursuant to Chapter 12, Section 6 of the Environmental Code.”” The notification for consultation must be submitted to the supervisory authority, which in this case is the county administrative board.
Many municipalities have begun to use this new interpretation to discourage private tree owners from cutting down trees. At the same time, the new interpretation means that more trees may be protected during development, but of course it increases the bureaucracy surrounding trees and the burden on the country’s county administrative boards.
What is a tree worthy of special protection?
Sincetrees deemed “particularly worthy of protection”now always require what is known as a “12:6 consultation,” it is important to know which trees the Swedish Environmental Protection Agency has classified as such. The trees in question must meet one or more of the criteria listed below:
- Giant trees:Living or dead trees that are more than one meter in diameter at their narrowest point at chest height.
- Very old trees: Livingor dead spruce, pine, oak, and beech trees that are older than 200 years. Other tree species that are older than 140 years.
- Large hollow trees:Living or dead trees with a diameter at breast height greater than 40 cm and a well-developed cavity in the main trunk.
Please note that sometimes trees that do not meet these criteria may have significant natural value and require consultation, for example, if a rare moss or lichen grows on them.
What requires consultation?
According to the Swedish Environmental Protection Agency’s new interpretation, tree owners must contact the county administrative board if measures that damage a tree worthy of protection are to be carried out. This includes, for example, felling, topping, or other severe pruning. Even measures that are not directly related to the trees but still affect them require consultation. A good example of this is digging a ditch or laying utility lines near a tree, as this affects the tree’s roots.
Notice of 12:6 Consultation
A notification regarding a 12:6 consultation is not an application; rather, as a tree owner, you must submit this notification to the county administrative board. The processing period is time-limited, and the county administrative board has six weeks to process the application once all required documentation has been submitted.
Keep in mind that trees may be protected in other ways, such as if they are part of a tree-lined avenue, if they are home to protected species, or if they are located in a cemetery.
GIS stands for Geographic Information System and refers to any type of data that can be integrated into maps. This includes everything from Google Maps to a municipality’s or housing company’s digital tree database in map format.
Having your tree inventory in GIS format makes it both easy to manage and simple to update.
We’ll help you collect the data in the format that works best for you.
A tree inventory can be used for many purposes. Generally, however, the goal is for the person managing the trees to gain an overview of the strengths and weaknesses of the tree stand. With a properly conducted tree inventory, it is easy for the manager to focus on the right things in order to strengthen the tree stand in a long-term and sustainable way. A good tree inventory follows Swedish standards and can be easily updated.
A sample plot can be likened to a projected circle over an area where the trees within the circle’s perimeter are inventoried. The plot’s diameter is 22.6 meters and covers 0.04 hectares. To ensure that the inventory provides a good representation of the city’s total tree population, approximately one hundred sample plots are inventoried. According to i-Tree, an inventory of 200 sample plots is required to create a reasonable representation that corresponds to reality and the total number of trees actually present in the city.
A sample plot inventory provides a representative picture of the city’s tree population, and the results serve as a clear basis for policy regarding current ecosystem services as well as future development needs. A comprehensive inventory contributes to a foundation for future management and maintenance, while also enabling site-specific calculations of ecosystem services.
In i-Tree Eco, stormwater is calculated in cubic meters, and it is the proportion of cubic meters of water captured by a tree’s foliage and branches that is counted as an ecosystem service. The calculation is divided into the trees’ ability to both delay and capture water in their needles, leaves, and branches (interception), and through evaporation and water loss via the stomata in the leaves (transpiration).
Trädkontoret can assist with all forms of data collection, analysis, and communication related to trees and other vegetation. This includes, for example, risk assessments, tree evaluations based on the Alnarp model, tree inventories, action plans, tree management plans, and more. You can learn more about our various services by clicking onthe following link.
Carbon uptake refers to the proportion of carbon in the form of carbon dioxide and how it is sequestered through annual growth. The larger and healthier the trees, the greater the carbon uptake. Carbon storage, on the other hand, refers to the amount of carbon bound in the tree’s biomass itself, regardless of time.
The structural value of a forest stand is based on its physical composition, such as the number of trees, species, size, and amount of leaf mass. These characteristics have a direct impact on ecosystem services and the extent of those services.
In Sweden, all weather data comes from local SMHI stations, and information on air pollution is based on measurements from the European Environment Agency.
i-Tree Eco calculates regulatory ecosystem services such as carbon storage, carbon sequestration, stormwater retention, and the amount of air pollutants that trees reduce (these include nitrogen oxides, sulfur dioxide, VOCs (volatile organic compounds), and PM₂.₅ particles).
What tree inventory data does the user need to provide in order to perform an i-Tree Eco assessment?
The program contains data on climate and air composition for various geographic areas, as well as a tree database that is matched to the trees entered by the user. The minimum required input is the tree species name (scientific or American name) and the diameter at breast height (DBH). To achieve the most accurate calculation possible, there are additional parameters that the user can provide—for example, crown diameter, the tree’s total height, height to the crown base, percentage of missing crown, how many sides of the crown have access to light, etc. The more information available regarding the specific extent and vitality of the tree crown, the more reliable the calculation of the tree’s ecosystem services will be.
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