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Ecological corridor management is a medium-term sustainable maintenance concept for the vegetation in the protective strip of the high-voltage lines. The initial focus of ecological corridor management is on the care and design of the growing and predominant vegetation.
This requires a coordinated maintenance concept that primarily considers the ongoing security of supply but also pursues the relevant ecological goals (nature/species protection), the concerns of the various stakeholders and, finally, the economic goals (maintenance costs of the TSO/DSO).
Why Corridor Maintenance Matters
Continuity in maintenance measures over many years is the key to success. A transformation of nature towards biodiversity, both of flora and fauna, can only be achieved through targeted but extensive vegetation care over several years.
All processes in nature that need to be designed for ecological sustainability, in addition to a locally coordinated concept, monitoring of measures (observation) and, above all, time and patience.
This “long breath” / "staying power" is always a point of discussion in companies for economic reasons, as in the minds of decision-makers, success must always be achieved in the short term (< 5 years).
It often happens that good ECM projects are prematurely terminated after 2-3 years because only costs could be generated but no success.
In these cases, the development goal of the corridor vegetation had not yet been achieved, e.g. there is still far too much fast-growing vegetation, which should displace slow and low-growing tree and shrub species.
As a result of this cancellation, all the "initial investments" made in the first few years in redesigning the corridor have become pointless (ad absurdum), as the once dominant vegetation returns in a short time. This means that everything is back to square one, the financial investment is lost and the entire ECM package has failed miserably from the point of view of those responsible for the process.
The consistent implementation of the implementation concepts until the development goal is achieved must be understood and supported by everyone; it is an important part of the ECM mindset. As a rule, these visible successes only appear after 5-7 years, only then will you find a species-rich route that guarantees security of supply, accessibility and considers the concerns of species and nature conservation.
Understanding Corridor Maintenance
Corridor management - regardless of the type - must primarily be designed in such a way that trees growing vertically or falling from the side do not pose a threat to the line operation and that an uninterrupted supply of electrical energy is always guaranteed.
It is also important to avoid dense and poorly penetrable vegetation so that inspection, maintenance and repair work can be carried out without problems.
The creation of 4-5 m wide meandering mulch strips (walkways and driveways) in the central axis of the protective strip is of great importance here. These paths serve the line operator as excellent inspection and maintenance routes, and these open areas within protected forest routes also represent excellent "hiking trails" for numerous animal species.
This technically desired measure of keeping the corridor clear serves essentially to habitat networking and thus contributes significantly to the population and thus to species protection.
The development and maintenance of low forest structures alternating with open landscapes is only possible through continuous, but rather extensive care over several years. These measures have the character of classic natural regeneration, which is particularly important in times of climate change.
Young and small plants are more vital and therefore more resilient, their capillary root system defies the ever-increasing soil erosion. The vegetation close to the ground provides more shade for the species-rich topsoil, the moisture in the soil is conserved and drying out in the hot seasons is significantly counteracted.
Importance of Ongoing Maintenance
Each DSO/TSO has been given operational responsibility by its government for the trouble-free operation of high-voltage systems. It must also definitely fulfil this obligation in order to avert major operational and economic damage to the economy and society.
Depending on the grid configuration, a ground fault in a high-voltage line caused by contact with a tree that is too close, or falls can lead to network outages in larger regions or even to cross-border blackouts.
This happened in Italy in 2003, where over 50 million people were without power for several hours because branches encountered an important interconnector. Or in California in 2018, where trees were pushed into the line by the wind, causing forest fires, 86 people died in the flames and damage amounting to 12 billion euros.
Such accidents, which have the potential to lead to a widespread blackout, occur again and again around the world; in most cases, poor vegetation care is identified as the main cause. Under these premises, continuous, preventive corridor management and the additional costs incurred for it pay for themselves very quickly.
This is especially true when the importance of the route is rated high and a significant increase in storms is to be expected with increasingly unstable forest edges. Especially in times of prevailing supply bottlenecks due to various network restructuring measures due to decentralized producers, neither mechanical nor electrical faults must occur.
The repair of lines/infrastructure is expensive and time-consuming and further weakens the grid quality. The use of ECM in the corridors is a classic preventive measure, as the maintenance measures are frequent but extensive. In the past, this "too early cutting" of vegetation was not accepted by society.
It is only in recent years that the advantages of this forward-looking maintenance have been recognized by society. Important stakeholders and NGOs are even demanding this more and more, as it makes a significant contribution to the promotion and development of biodiversity.
Read also: Guide to Designing Ecological Corridors
Best Practices for Corridor Maintenance
Corridor Mapping
An important component in the ECM process is a good mapping of the areas in the protective strips of the high-voltage lines.
This must be done by biologists who document the biotope types found using a suitable mapping key.
It is not necessary to record every biotope, no matter how small, because this only increases the costs of mapping, but no added value is created, since the later operational implementation of these detailed measures is not possible.
It is much more effective to be able to document the boundaries of the biotopes in the corridors as precisely as possible in the plan. The mappers must have a good knowledge of the value of the detected biotopes for the region, because they must be qualified to determine which flora should be promoted and which flora should be displaced in the medium term. This is written down as a development goal for each biotope in the corridor in the ECM plan.
Experience shows that the mapped areas should generally have an area of 400-500 m².
Only if very high-quality biotopes are found that need to be promoted or species that should be intensively displaced (invasive species) can small areas be included in the ECM development plan.
The following applies: First and foremost, the vegetation should be mapped.
However, if the biologist notices rare and protected animal species when mapping the corridor or there are indications of this in maps or from regional conservationists (e.g. about the existence of cavity nesters in dead wood, rare xylobionte beetles, forest bees, insects, bird species, small mammals) that have the status of "red list species", it is sensible to document these as well.
It is necessary that the area mapping process is also carried out on site in the corridors by experienced biologists. Statements that these measures will be obtained in equivalent quality with satellite or drone images are not realistic at the current stage.
The soil and shrub vegetation, wetlands and many rare animal and plant species that are important for nature and species conservation cannot be detected from a distance. Statements to the contrary are dubious and could constitute "greenwashing" by experts and external consultants.
Of course, geographical support (satellites, drones, GIS systems) that serve to orientate and identify biotope boundaries and tree species in the corridors accelerate the ECM mapping and planning process and can ultimately contribute significantly to cost reduction.
Vegetation Management
In most cases, maintenance measures are implemented by service providers (forestry contractors).
Based on the maintenance specifications in the ECM plan, the corresponding measures should be implemented over several years. These measures include the selective felling of individual trees or extensive measures such as clearing bushes or forest edge design and the creation of flower meadows and open areas by mowing or mulching.
If special woody plants are to be preserved or promoted, special maintenance measures may also be necessary, such as "ringing" trees to develop standing deadwood or complex cuts to create pollard willows. Planting trees and shrubs in the corridor should generally be avoided but can make sense in a few exceptional cases. However, this always requires an economic and strategic assessment of the measure.
"Caring out" valuable woody plants that occur in these areas and are therefore resilient is always preferable to planting.
Compliance with Regulations
During the mapping and planning phase, the planning office must obtain information about existing or planned protected areas using maps or by consulting the central registers of the states and take these into account when planning measures.
In addition, both the client (TSO/DSO) and the service provider (forestry contractor) must obtain knowledge about protected areas and be aware of and apply the careful handling of nature, especially in these zones.
These qualifications are part of an annual instruction and training of all service employees involved in the process and should be checked by the client as part of external audits.
Community and Stakeholder Engagement
Right from the start of mapping ECM areas, it is advisable to coordinate the measures and development goals with the authorities and with the major property owners.
Due to the large number of properties under the high-voltage lines, this is not possible with all owners; that is unrealistic.
However, important and known sensitive owners, authorities, NGOs and stakeholders should be informally involved in the ECM planning; in most cases, these contacts are personally known to the energy suppliers. In addition, good and honest communication with all stakeholders is a guarantee for a successful ECM transformation.
Regular exchange and the incorporation of desired adjustments to the measures and goals forms the basis for a trusting relationship. In addition, it is still a good idea to announce the maintenance measures by email or telephone before the measures are implemented.
This is where another benefit of ECM pays off: since the authorities usually have the digital version of the ECM planning, a simple informal note that the maintenance work - analogous to the ECM concept - will begin shortly is sufficient.
You might also like: Strategies for Effective Corridor Management: Stakeholder Collaborations
Tools and Technologies for Effective Maintenance
From a scientific and biological point of view, high-quality mapping of the corridors can only be done manually - i.e. by on-site mapping by biologists.
Currently, GIS and satellite images serve as the basis for mapping and support the experts in local recording by geographically displaying the biotope boundaries.
In the future, software, AI-supported, tools will be able to derive even more detailed information from the satellite photos, such as tree species, growth rates, tree diseases, distances, etc.
This will significantly streamline the mapping and planning process. However, this data also serves another economic and ecological purpose, the monitoring of measures.
Intelligent referencing of photos and data will show whether the right trees were removed during implementation, in sufficient quality, at the right time and whether the development goal can be achieved.
Challenges in Corridor Maintenance
Increasing extreme weather conditions, e.g. storms or long periods of drought, have a significant impact on the stability of our forests and vegetation.
The unconditional resilience of the stocks in the power lines is becoming increasingly important, as the interruption of the supply of electrical energy causes considerable business and economic damage.
In times of energy transition, companies must make more budget and personnel resources available for this, especially given that the operation of high-voltage systems must also be ecological and sustainable.
The transformation to ecological route management makes an immensely important contribution here, increasing the security of supply while at the same time incorporating species and nature conservation projects.
Measuring the Success of Maintenance Programs
Evidence of the success of an ECM transformation in terms of supply interruptions, compliance rates, and increases in biodiversity has not yet been scientifically documented.
This is not trivial either, since interruptions due to vegetation, for example, are rather rare and not sufficiently documented in the companies, but the impact is devastating, both for life and limb and financially.
Comparisons within the E.ON Group show, however, that companies that have been practicing ECM for decades have significantly lower failure rates due to tree approaches or tree falls.
In terms of biology, a scientific study from 2015 found that biodiversity in an ECM route is between 5-8 times higher than in the adjacent natural area.
Proactive Corridor Maintenance: Case Study
The DSO "Westnetz" in the E. ON Group began the conceptual conversion of its forest routes into ECM routes back in 1992. Over 6,000 hectares were mapped and operationally implemented within 15 years.
On average, intelligent maintenance resulted in excellent and biologically valuable powerline corridors within 5-7 years.
Rare animal and plant species, such as the smooth snake, hazel grouse, wild cat, numerous insect species, wood-eating beetles, wild bees, white and blackthorn hedges, etc. have re-established themselves and have been able to receive targeted support.
In some cases, these areas have even been declared show and viewing areas for nature conservation organizations and universities.
Conclusions
The care of vegetation in powerline corridors is unavoidable and will continue to exist if there are overhead lines for the transmission of electrical energy. That is why sustainable and intelligent corridor management measures, such as ECM, must be proactively promoted both within the TSO/DSO and demanded by authorities and NGOs.
This is not a contradiction at this point, but rather a win-win situation for the energy supplier, society and of course for our environment and nature. Fossil fuels will have to be pushed back in the short term so that climate neutrality can be achieved in 2050.
Our energy needs can only be met by cleanly produced electricity, which requires a significant expansion of the supply networks, especially in non-urban areas, i.e. in the middle of nature.
ECM has the potential to become an enormously important building block of the energy transition; it can increase acceptance for necessary new line construction measures or upgrading of existing lines and turn parties into partners.
