Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review
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Open access Subject review
https://doi.org/10.5552/crojfe.2022.1179
Essential Issues Related to Construction
Phases of Road Networks in Protected Areas:
A Review
Dursun Şakar, Abdurrahim Aydin, Abdullah Emin Akay
Abstract
Protected areas play an active role in protecting natural resources and wildlife habitat. These
areas must be accessible within protection-use balance. For this reason, road networks in
protected areas are one of the main functions of sustainable infrastructure services. The con-
struction phases of road networks in these sensitive areas should be considered in planning
within the balance of protection-use with interdisciplinary studies. Especially during the
construction of the road network, it is necessary to pay attention to the construction machin-
ery used, geotextile materials, hydraulic and ecological road structures, plantation of the slopes,
fences that increase the visual quality and work schedule. Based on a related literature survey,
the issues to be considered during the construction phases of road networks (i.e. road planning,
tree felling and removing, excavation and embankment, subgrade finishing, road structures
and surfacing) in protected areas were evaluated under nine headings. The implementation
phases of these issues are important in reducing the adverse effects that will occur in pro-
tected areas. In this regard, during the construction phases of road networks, the issues to be
considered were evaluated together with the conceptual indicators in terms of management,
technique, economy, ecology, and aesthetics. Matters needing attention according to the sen-
sitivity of conceptual indicators during the construction phases of road networks in and around
protected areas that contain sensitive ecosystems have been identified and presented in a
framework to further the discussions on this issue. Accordingly, the use of the issues to be
considered in the planning and construction of road networks with conceptual indicators will
help evaluate the planning phase before and after construction. In particular, it can be ex-
pected to lead to the creation of a checklist after the planning phase. Thus, the continuity of
the issues to be considered during the maintenance, repair, and construction phases of the new
road networks or existing road networks planned to be built in a protected area and surround-
ing areas will provide significant contributions to the functions of the protected areas. The
main contributions may include increasing the number of visitors to the protected areas, re-
ducing impacts on wildlife in protected areas by implementing innovative technologies, and
developing alternative modes in tourism industry.
Keywords: protected areas, road networks, construction phases, conceptual indicators
1. Introduction structure, securing the balance between them (Sarsam
Rapid urbanization, population growth, and in- 2015). However, today, solutions to minimize ecologi-
creased environmental impacts as a result of the effects cal costs by maximizing socio-economic benefits in the
of climate change and socio-economic activities, force development of environmentally sustainable road net-
practitioners to develop new solutions in the develop- works are unlikely due to human demand for nature
ment and management of sustainable transport infra- (Riggs et al. 2020). This is why innovative approaches
structure (Umer et al. 2016). It is important to consider have been developed to reduce people’s demand for
environmental impacts, costs, and socio-economic fac- nature. These innovative approaches will constitute an
tors in the design of sustainable road network infra- important part of the good planning of the optimum
Croat. j. for. eng. 43(2022)1 219D. Şakar et al. Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237)
technical implementation of sustainable road network visitors coming to protected areas (Leung et al. 2018).
projects, which includes location selection, engineer- The most important of these, road networks, are es-
ing, construction, maintenance, and alternative materi- sential for increasing the access and satisfaction of
als (Ledec and Posas 2003, Mayer et al. 2012). visitors. In particular, road networks in protected ar-
Transport infrastructures, with a wide range of im- eas have crucial impacts not only on the access of in-
pacts on ecological processes, can have both positive coming visitors but also on the protection and control
and negative impacts on biodiversity (Karlson and of the protected areas and their environment (Eagles
Mörtberg 2015). For example, in the construction and et al. 2010). Therefore, before and after road network
use of road construction, it is easier to increase and construction works in these areas, eco-friendly sus-
maintain access to natural resources in terms of biodi- tainable approaches should be adopted, both econom-
versity. At the same time, long-term positive benefits ically and technologically (Tarimo et al. 2017).
can be seen, such as an increase in economic revenues In light of this information, the use of road net-
due to the rise in the number of visitors due to the works to provide transport and protection in and
formation of landscapes caused by land change (Findlay around protected areas is inevitable. Some potential
and Bourdages 2000). Protected areas are one of the impacts may emerge during the construction, mainte-
essential tools available for biodiversity conservation nance, and repair phases of road networks in sensitive
(Possingham et al. 2006). The protected areas are de- areas. This article aims to explain the considerations
fined as sensitive sites that are dedicated and managed for reducing potential impacts on protected areas.
to achieve the long-term conservation of nature with Practices related to these issues are presented within
associated ecosystem services and cultural values the conceptual framework. In addition, practices re-
(Borrini-Feyerabend 2013). According to the Interna- lated to the issues to be considered during the con-
tional Union for Conservation of Nature and Natural struction phases (i.e. road planning, tree felling and
Resources (IUCN) Protected Area Categories System, removing, excavation and embankment, subgrade
the protected areas are classified into six categories (i.e. finishing, road structures and surfacing) of road net-
nature reserve and wilderness areas, national parks, works in protected areas have been evaluated through
natural monument or feature, habitat/species manage- a wide-ranging literature review.
ment area, protected landscape/seascape, protected
area with sustainable use of natural resources) accord-
2. Issues to Consider During Construction
ing to their management objectives (Dudley et al. 2013).
Phases of Road Networks
The protected areas play an important role in pre-
vention of deforestation, while minimizing the impacts Within the scope of the study, considerations for
of logging operations, hunting, forest fires, and grazing reducing potential impacts during the construction
(Bruner et al. 2001). On the other hand, the impact of phases of protected areas and surrounding road net-
building road networks in protected areas is becoming works have been collected under 9 (nine) headings:
increasingly alarming. In particular, road construction ⇒ Determination of work machines used during
and use produce various direct or indirect impacts on the construction phases of road networks in an
ecosystem such as habitat loss and fragmentation, ecological manner
wildlife mortality, exhaust emissions, and noise pollu- ⇒ Necessity of geotextile materials used in road
tion (Arévalo and Blau 2017, Hoffmann et al. 2019). For networks construction
instance, according to Makki et al. (2013), the construc- ⇒ Importance of hydraulic structures in protected
tion phases and development of roads in protected areas
areas and ecologically sensitive areas have detrimental ⇒ Planting slopes for visual and ecological pur-
effects on wildlife populations. In addition, develop- poses during road construction in addition to
erosion prevention purpose
ment and improvement of roads can facilitate access to
⇒ Impacts of habitat fragmentation during road
poachers and uncontrolled tourism, which have a va-
construction in protected areas
riety of detrimental effects on protected areas.
⇒ Importance of ecological road structures in pro-
The United Nations World Tourism Organization tected areas
reports that international tourist circulation (overnight ⇒ Fence applications that increase visual quality
visitors) has reached 1.5 billion in 2019 (URL1). Pro- of road construction in protected areas
tected areas constitute a large part of the global tour- ⇒ Effects of noise pollution during road construc-
ism industry. For this reason, the demand for basic tion in protected areas
infrastructure, employment, service, and protection ⇒ Determination of work schedule of road con-
requirements is increasing due to the large number of struction phases in protected areas.
220 Croat. j. for. eng. 43(2022)1Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237) D. Şakar et al.
Table 1 Conceptual indicators of issues to be considered during construction phases of road networks
Issues to Consider During Construction Phases of Road Networks Managerial Technical Economical Ecological Aesthetical
Determination of work machines used during construction phases of road networks in
X X X X X
an ecological manner
Necessity of geotextile materials used in road network construction X X X
Importance of hydraulic structures in protected areas X X X
Visual and ecological planting of slopes during road construction in protected areas X X X X
Impacts of habitat fragmentation during road construction in protected areas X X X X
Importance of ecological road structures in protected areas X X X X X
Fence applications that increase visual quality of road construction in protected areas X X X X X
Effects of noise pollution during road construction in protected areas X X X
Determination of work schedule of road construction phases in protected areas X X X
In the study, the issues that should be considered road networks constructions (Çalışkan and Çağlar
during the road construction phases are discussed 2010). Technologically selected road network con-
with a literature-based conceptual overview, with struction machines should be determined to best suit
managerial, technical, economical, ecological, and aes- economic and ecological conditions (Fannin and
thetical indicators. Conceptual indicators of these is- Lorbach 2007). In the literature, it is suggested to use
sues are reviewed and explained in a holistic way hydraulic excavators instead of dozer machines in
through a literature review. Table 1 shows the indica- terms of ecological damage in road constructions in
tors that were considered for each specified issue. The woodland areas (Özturk et al. 2010), because, during
results from the highway road construction related road construction, it offers the advantage of a con-
studies were also discussed in the literature review. struction technique that is more sensitive to ecological
Although there are differences in terms of road stan- impacts such as road width, landscape structure, wa-
dards and road construction methods, the fundamen- ter drainage and effective erosion control (Winkler
tal road location problem normally involves similar 1998). Comparisons of other characteristics of environ-
phases for both forest roads and highways. Thus, the mental impacts of work machines in road construction
suggestions provided by highway construction stud- practices are shown in Table 2 (Çalışkan and Çağlar
ies can be suitable to some extent for the construction 2010, Winkler 1999).
of forest road network in protected areas. Tunay and Melemez (2004) assessed the environ-
mental damage caused during the construction of for-
2.1 Determination of Work Machines Used est roads with dozers and excavators in steep slopes
During Construction Phases of Road Networks and difficult terrain conditions. In their study, both
in an Ecological Manner ecological and visual damages caused by road con-
Road network construction works in and around struction machinery in forest road construction were
protected areas have negative impacts on biodiversity revealed. Excavator was found to have less impact on
(Quintero 2002). Before starting road network projects the forest area during the road construction practice
in these areas, it is necessary to determine protection than on the area where the dozer was working. They
measures against ecological harm in terms of biodiver- determined that the construction of a forest road that
sity (Ledec and Posas 2003). Thus, in the planning is environmentally friendly and suitable for road plan-
phase of the road networks, the necessary protection ning techniques can be done by using an excavator.
inventory should be made and the area should be However, while using road construction technique,
evaluated before the road network construction begins the protection of landscape values in the forest areas
(Arıcak and Acar 2008). Unplanned road networks can should be considered with an environmentally sensi-
cause damages that are irreparable and sometimes tive approach (Winkler 1998). In particular, the visual
even impossible to compensate environmentally quality of the landscape of the forest area should be
(Winkler 1998). For this reason, it is very important to designed integrally in the planning of road construc-
use modern road network construction machines in tion and the necessary equipment should be preferred
Croat. j. for. eng. 43(2022)1 221D. Şakar et al. Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237)
Table 2 Environmental impact of excavator and bulldozer during road construction practices
Excavator Bulldozer
The excavator can be operated fixed or parallel to the road centerline,
Bulldozers can hardly be used in areas where minimum subgrade width is
keeping the subgrade width to the minimum determined by safety and
required for maneuvering
anticipated use
The excavated material is best placed as the excavator operates by Excess filling inside the bulldozer blade is insufficient to lay the material by
digging, swinging and depositing material with accuracy and care pushing or dragging into areas where it is needed
The excavated material can be separated and temporarily stacked by the
Excavation material cannot be placed in suitable layers in the filling
excavator taking account of its anticipated use in building up the fill
Construction width is minimized as subgrade width and length of fill slope The disturbance of the landscape and area that is dedicated to forest roads
is reduced is higher when compared to road construction by excavator
Since the excavation material joins the road, the erosion tendency
Unconsolidated side cast material increases the risk of erosion
decreases
The damage to the roadside forest is insignificant as excavators enable the During construction, excess material is thrown downhill, causing serious
operator to efficiently dig, swing and place material damage to the roadside forest
The fill slope can be shortened in length; the solid fill facilitates road Depending on the angle of the material thrown to the side on the slope
construction on the steep slope with a slope of more than 75%, the fill slope cannot be fully constructed
Culverts and retaining walls can be built up at any time during road Culverts and retaining structures can be placed after completion of
construction bulldozer work
during the implementation phase. The visual quality Geosynthetic is made of polymer materials (syn-
value of forest after the use of hydraulic excavators in thetic or natural) and is used together with other ma-
road construction is higher than after dozers (Tunay terials related to soil, rock or geotechnical engineering
and Melemez 2004). Thus, it is possible to avoid the (Burhan and Soyaslan 2016, Leão et al. 2012). There are
high costs that arise in subsequent improvement ef- several geosynthetic materials that have been devel-
forts to eliminate unwanted effects and scars in the oped according to design functions (Akhmetshin and
forest visual landscape (Winkler 1998). Kovalenko 2019). Geosynthetic material types can be
grouped according to areas of use such as geotextile,
The application times of construction machines
geogrid, geonet, geomembrane, geosynthetic clay
used during road construction can also have negative
liner, geopipe, geocomposite, geofoam, geotube, geo-
effects on wildlife from an ecological point of view. cell (Yılmaz and Eskişar 2006).
During the construction practices in protected areas
Geosynthetic materials are widely used in low-
and their surroundings, depending on the noise, as the
volume, unpaved and forest road network construc-
working distance of the work machines increases, the
tion (Powell et al. 1999). These materials increase the
working time also increases (Kantová and Motyčka
strength of road structures and provide high resis-
2014). It is necessary to encourage the use of innova- tance to environmental conditions (Akhmetshin and
tive technologies to reduce ecological impacts. For Kovalenko 2019). Geotextile materials are also avail-
example, using new intelligent compaction technolo- able for use during road construction. Geotextiles ba-
gy and equipment during road construction, it is pos- sically perform six identical functions: separation, fil-
sible to ensure rapid compaction of the roller machine tration, drainage, reinforcement, sealing and
in the optimum vibration mode and to measure the protection, and also can execute one or more than one
compaction level continuously (Quintero 2002). This task at a time. (Annu and Verma 2018). Thus, geotex-
leads to a decrease in behavioral changes, such as tile material has the potential to serve as a filter fabric
stress and the need to relocate wildlife in the region and a fabric supplement to stabilize and maintain
(Boston 2016). weak lower echelons in road construction (URL2). For
example, as the effect of surface drainage is signifi-
2.2 Necessity of Geotextile Materials Used cantly reduced as a result of heavy rains on unpaved
in Road Network Construction roads, an increase in groundwater level occurs, and
222 Croat. j. for. eng. 43(2022)1Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237) D. Şakar et al.
geotextiles with high transmissivity provide a con- Clevenger et al. (2001) investigated the use of box
tinuous drainage between the basic layers (URL3). In culverts in the road corridors in Banff National Park
addition, geotextile material can be effectively applied in Canada intended for small and medium-sized
in necessary road infrastructure practices such as soft mammals to increase fragmentated habitat connectiv-
landfilling, landfilling with vertical drainage on very ity. The culvert performance of groups of wildlife spe-
soft soil, strengthening infrastructure layers and cies has been evaluated according to environmental
causeway filling (URL4). impacts. To maximize connectivity across roads for
Geotextile material also plays a critical role in the the wildlife, Clevenger et al. (2001) have stated that
performance of road networks (Khan et al. 2014), be- future road construction schemes should include fre-
ing versatile, easily available and environmentally quently spaced culverts of mixed size classes and that
friendly. While these materials reduce the cost, espe- there should be plenty of vegetal cover near the culvert
cially in road network construction and maintenance- entrances.
repair works, they also provide a long-lasting use of Engineering structures are needed in order to
the road and have the ability to be easily assembled maintain the functions of water resources encountered
(Akhmetshin and Kovalenko 2019, Powell et al. 1999). in protected areas, their surroundings and in forest
road networks. For this reason, Çalışkan and Acar
2.3 Importance of Hydraulic Structures
(2003) stated the reasons why hydraulic structures
in Protected Areas
should be used in forest roads. These reasons are list-
Inland water ecosystems (streams, groundwater, ed as follows:
other brackish and freshwater habitats, etc.) have an ⇒ in areas with abundant rainfall, precipitation
important place in protected areas (Worboys et al.
waters cannot leave the road platform quickly,
2015). These areas holistically maintain hydrological
leading to disruption and destruction on the
and biophysical functions such as water volume, flow
platform
quality, water habitat, and sustainability in their natu-
ral environment (ICEM 2003). Therefore, internal wa- ⇒ sediment deposition on road networks at the
ter ecosystems must be well defined in the planning river crossing points
process. The ecological effects of these sensitive areas ⇒ at river crossing points, the water disrupts the
should be well determined, especially in road network road platform and creates deep crevices
planning. Otherwise, inland water ecosystems can ⇒ surface destruction on the road platform caused
have many ecological negative effects, such as the dis- by material detachments and landslides in
integration of natural flows such as surface water and slopes
groundwater flow, alterations in water flow directions ⇒ slippage over time on the damaged and moving
with the increase of floods caused by the rise of peak road platform during road construction.
flows in streams and rivers and they may also cause
Wetlands have an important place in the hydro-
the pollution of streams and rivers caused by sediment
logical system in protected areas. Practices in these
flow, as well as a decrease in water habitat types and
areas have a sensitive impact on terrestrial and aquat-
populations (Eker et al. 2010, Trombulak and Frissell
ic ecosystems. Especially during road construction,
2000). Therefore, it is important to use hydraulic struc-
engineering structures should be designed consider-
tures to reduce these effects in the road network plan-
ing the land conditions suitable for hydrological and
ning process.
geological functions (Gülci 2014). Otherwise, bridges,
Hydraulic structures planned in protected areas pits, culverts, ditches and all impermeable surfaces as-
should be designed in harmony with the natural en- sociated with road construction can change water flow
vironment. In particular, these engineering structures patterns and destroy wetlands through silts (Eagles
should be sized according to their technical functions
and McCool 2002). Accordingly, the necessary mea-
(Çalışkan and Acar 2003). For this reason, the hydrau-
sures to protect water resources during road con
lic structures (culverts, pipes, bridges and tunnels, etc.)
struction in wetlands are as follows (Quintero 2002,
used in surface waters, groundwater and stream cross-
Lindström-Jönsson et al. 2014, Partington et al. 2016):
ings on road networks should also be designed to be
used for the transition of wild animals between frag- ⇒ a crossing over water should be located where
mented habitats (Çalışkan and Acar 2003, Quintero the foundation can be set in bedrock or in soil
2002). This is why hydraulic structures have an impor- type of frictional qualities
tant place not only in the inland water ecosystem but ⇒ avoiding the passage of roads through steep
also in the wildlife habitat that benefits from it. slopes as much as possible
Croat. j. for. eng. 43(2022)1 223D. Şakar et al. Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237)
⇒ minimizing the number of water crossings more ecologically appropriate for protected areas
wherever possible (Akbar et al. 2003). During the construction of road
⇒ using only clean fill materials around water- networks, on the other hand, topsoil extracted from
courses the cut slopes is compacted towards the fill slope.
⇒ avoiding to protection zoning of existing planta- Therefore, due to the compression in this area, the
tions in areas between road sites and bodies of physical properties of the soil (depth, density, infiltra-
water tion capacity, water holding capacity, etc.) may change
⇒ reducing the amount of sediment transport dur- and difficulties may occur in the re-vegetation process
ing the paving process of dirt and gravel road (Eker et al. 2010). It should be remembered that the soil
platforms close to water bodies must be processed sensitively when doing plant work
⇒ s oil and granular materials should be used for in such areas.
roads constructed across wetlands Slope stabilization in protected areas and the sur-
⇒g eosynthetic materials (i.e. s geotextiles, rounding road network construction practices should
geogrids, and geocells) should be used to reduce be included in the planning in a natural and visually
any impacts of roads on wetland hydrology aesthetic way. Especially during the construction of
⇒ placing appropriate size of culverts (transverse the road, the application of slopes in accordance with
hydraulic structures) that will drain the flow the topographic structure and as flat as possible causes
that may come from the basin in river crossings the road to look better visually and planting work to
⇒ not disturbing the stability of slopes that may be be easy and maintenance costs less (Türk 2006). In ad-
sources of sediment around the water resources dition, applications of technical and biotechnical mea-
during road construction sures that can be taken in terms of landscape restora-
⇒ keeping openings wide in bridge construction tion of road slopes that are in danger of landslides or
and limiting their impact on water resources situated in landslide areas should be made from a
⇒ designing bridges and culverts with hydraulic perspective that will prioritize drainage and mainte-
properties that ensure safe passage to the habi- nance work (Öztürk et al. 2016).
tat areas of aquatic creatures. Akbar et al. (2003) surveyed 183 road users for their
views on their perception of the natural beauty and
2.4 Planting Slopes for Visual and Ecological natural value of Northern England’s roadside vegeta-
Purposes During Road Construction in Protected tion. 83 percent of the participants described the scenic
Areas quality of roadside vegetation as an important feature
It is important to ensure biodiversity and protect of the roadside environment. They showed a positive
plant species in protected areas. Planning road net- attitude towards establishing a variety of vegetation
works to these areas can have direct effects on biodi- types rather than one type. According to their natural
versity in terms of landscape and ecology (Ledec and and aesthetic demands, they have raised awareness of
Posas 2003). Therefore, the most affected part of the the landscape aspects for the choice of different com-
planned road networks occurs in the plant diversity binations of plant species on the side of the road. They
in and around the roadside construction site. In par- found that especially the flowering plant species near
ticular, these areas and most plant species around the road is more preferred than the trees and grass on
them may be under threat from a landscape and eco- the far side of the road.
logical point of view (Heywood 2019). Roadside veg- Since the measures that can be taken regarding the
etation is often an important part of the natural vegeta- slopes in road construction practices in protected areas
tion that remains in an area. It, therefore, provides a are very effective on the visual quality, this issue
valuable habitat and connection between vegetation should be handled with sensitivity. While planning
blocks (Lamont et al. 2005). For this reason, it is impor- roads in these areas, the following should be taken into
tant to preserve the ecological, biological and aesthet- consideration in protecting the visual aesthetic values
ic values contained in roadside habitat (Jackson 2002). of endemic natural vegetation, wildlife habitat and
Before starting the planned road network construc- slopes (Lamont et al. 2005):
tion practices in protected areas, the vegetation in the ⇒ trees to be removed from the site and protected
area should be moved. Especially after construction, for road construction must be marked in ad-
these original plant species should be re-evaluated on vance
both cut and fill slopes of road network (Ledec and ⇒ habitat of sensitive species to be protected must
Posas 2003). For this reason, the preference of native be identified, (e.g. endemic plants found in the
species found in the area for re-planting roadsides is area, threatened wild animals, etc.)
224 Croat. j. for. eng. 43(2022)1Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237) D. Şakar et al.
⇒ materials brought for road construction should ⇒ destruction of habitat during road building
be placed in unused places or away from the ⇒ modification of the environment next to roads
water sources as much as possible ⇒ increased road traffic resulting in animal mor-
⇒ dead trees and snags in the area that do not pose talities
a problem in terms of safety should be stored in ⇒ increased road speed resulting in animal mor-
places that can create visual aesthetic value talities
⇒ materials released during road construction ⇒ greater frequency of fires
must be quickly removed from the area by se-
⇒ litter dumped on the road and its immediate
lecting suitable areas outside the site
surroundings
⇒ as a part of road construction and maintenance-
⇒ impediment of wildlife movement between two
repair activities, cleared areas should be re-
sides of the road and, outside of reserves
stored to their natural state
⇒ increased accessibility of natural resources lead-
⇒ along with existing road networks, areas where
ing to increased exploitation
natural vegetation is bare or badly degraded, as
well as areas used to obtain road construction ⇒ increased settlement of people into areas tra-
materials, should be re-planted with species versed by roads (Caro 2015).
suitable for the region Although planning of road network construction
⇒ to reduce roadside plant species loss, stabiliza- in protected areas has harmful consequences such as
tion should be minimized in terms of soil and habitat loss and fragmentation, it may also lead to the
nutrients loss in the area protection of habitat types indirectly depending on the
⇒ i n order to reduce noise and disturbance, espe- area in geographical conditions (Haddad et al. 2015,
cially along wetland crossings, and to provide Quintero 2002). For example, Brun et al. (2015) used
replacement habitat for wildlife, it is important spatial modelling with remote sensing maps of land-
to increase the plantings that will reduce the use change from 2000 to 2010 to analyze deforestation
negativities by growing later on the roadsides patterns in Indonesia and the effectiveness of protect-
(NEIWPCC 2010). ed areas. The existence of road networks, the type of
lands (roads, rivers, agricultural land and forest) and
2.5 Impacts of Habitat Fragmentation During the slope of the lands were taken into account in the
Road Construction in Protected Areas development of the modeling. They have explained
Protected areas, which are one of the most effective the spatial pattern of deforestation by transport cost,
tools for the protection of biodiversity, are important agricultural rent and history of nearby illegal logging.
for landscape and wildlife. In particular, they contrib- As a result, they found that protected areas managed
ute to the prevention of habitat loss and disintegration for scientific or wildlife conservation have an effect on
of landscape and wildlife species (Çağlayan 2011). All slowing down deforestation. They also determined
kinds of large and small-scale man-made construc- that monitoring and prevention of road construction
tions (irrigation projects, roads and highways, sports depending on the geographical prioritization in pro-
and tourism facilities, communication and energy tected areas will be suitable for conservation. On the
transmission lines, urban expansion, etc.) have the po- other hand, in different parts of the same habitat in the
tential to create serious pressures on ecosystems and protected area, wildlife species exhibit different be-
species (Worboys et al. 2015). It can be said that pro- haviors according to the types of road networks. For
tected areas and road networks planned to be built example, Blake et al. (2008) examined the wildlife ac-
around, which is also one of these pressures, will cre- tivity of forest elephants in the Congo Basin in relation
ate negative ecological impacts on biodiversity (Ledec to roads and roadless wilderness. Especially by moni-
and Posas 2003). Habitat fragmentation and habitat toring forest elephants in the protected area with GPS,
loss, which are the leading ecological effects of road they determined that they exhibit different behavior
network construction and use, can affect the mobility on the unprotected road, that is outside protected ar-
and distribution of wild animals and cause their death eas compared to within protected areas, and they re-
(Arévalo and Blau 2017, Wemple et al. 2018). However, corded a 14-fold increase in their speed of movement.
UNESCO has identified 9 (nine) main reasons that They also determined that monitoring and preventing
may be grounds for removing road networks from road construction in protected areas and planning ac-
protected areas due to increasing human activity. cording to the geographical prioritization in the area
These are: would be appropriate for conservation.
Croat. j. for. eng. 43(2022)1 225D. Şakar et al. Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237)
Solutions to reduce the impact of road networks on In recent years, the use of ecological road structures
wildlife also have a positive impact on protected areas has become widespread in reducing ecological im-
(Lesbarrères and Fahrig 2012). Caro (2015) planned to pacts in road network practices in protected areas.
upgrade a Murram road in Western Tanzania Katavi Especially in studies on minimizing wildlife losses and
National Park, which connects regional capitals to pre- fragmentation in protected areas, ecological road
serve the sanctity of the protected area. Despite em- structures come to the fore as an important solution.
pirical evidence suggesting upgrading would damage For this reason, research and practices on ecological
trees, increase traffic, adversely affect large mammals, road structures and wildlife overpasses are evaluated
and result in more litter, the ecological data was not within the concept of road ecology. Generally, in ad-
taken into account. In order to preserve the sanctity of dition to highways, ecological road structures can be
the protected area, it has been decided not to make constructed in order to provide passage over railways,
upgrades for environmental and socio-political rea- rivers and dams (Gülci et al. 2014). Therefore, research
sons. Caro has shown that it is necessary to work with on wildlife crossing practices used for wild animals is
politicians to achieve environmentally friendly results increasing every day (Gülci 2014). For example, eco-
on the roads in these areas. logical overpasses are used as an ecological road struc-
Biodiversity varies by species in studies on habitat ture in the road network practices in Turkey. These are
loss and fragmentation caused by road network in 2 (two) in total: Northern Marmara Motorway and the
wetlands from aquatic ecosystems of protected areas. Pozantı-Mersin Gülek Pass Motorway. On the other
For example, Findlay and Bourdages (2000) examined hand, there are also different practices related to eco-
the lag in biodiversity loss in different taxa related to logical passages in different countries around the
road construction in existing lands around wetland world (Tercan 2017):
biodiversity in Canada. They found that the full effects ⇒ Banff National Park in Canada, which is one of
of road construction on wetland biodiversity have the best practice examples in protected areas
been undetectable in some taxa for decades. Rainfall and divided by the Trans-Canada Highway, has
et al. (1982), on the other hand, examined the physical 24 wildlife crossing points built along the road,
and chemical effects of an existing bridge highway 2 (two) above, 22 (twenty-two) below, for 10
construction on water quality in the Louisiana wet- (ten) mammal species living in the area
land. They determined that the impact on the site ⇒ the Netherlands has 66 (six-year) underpasses
tended to be temporary, and that the increase in tur- and overpasses providing wildlife crossings for
bidity and color during construction gradually re- other wildlife species in the region along with
turned to pre-construction conditions when construc- European badgers. 9 (nine) of these crossings,
tion was completed. For this reason, differences can with an average width of 50 m, are located on
occur depending on the degree of impact and duration roads that intersect Veluwe Park, the largest
of habitat loss and fragmentation. Therefore, they plain in North-Western Europe
noted that the long-term degradation and recovery ef- ⇒ there are wildlife crossings built on the Inter-
fects on biodiversity and the function of the species state (I-90) highway, which connects through
could not be fully determined (Haddad et al. 2015). the northern part of the United States. Especial-
ly pronghorns use Highway 191 as a wildlife
2.6 Importance of Ecological Road Structures crossing point on their 273 km migration jour-
in Protected Areas ney from Grand Teton National Park to the
Protected areas play an active role in the conserva- south
tion of biodiversity, which has many ecological and ⇒ there is a 62-meter wide ecological passage that
biological criteria (Asaad et al. 2017). Any intervention connects Singapore’s Bukit Timah Natural
in these areas has an ecological impact on biodiversity. Reserve habitat with the habitat in the Central
Of these impacts, it is not possible to ignore the eco- Catchment Nature Reserve
logical impact of road networks (Gülci and Akay ⇒ there is an ecological road structure built to en-
2014). The main threats to the preservation of biodi- sure that the red crabs living in Australia’s
versity in particular are habitat loss and fragmentation Christmas Island, who travel from the rainforest
(Ćurčić and Đurđić 2013). This is often associated with to the sea to breed every year, reach the sea by
habitat areas of wildlife in and around the protected ecological passages (URL5).
area (Hansen and DeFries 2007). For this reason, hab- Ecological road structures are classified in 2 (two)
itat areas should be protected for wild animals to feed, main groups as ecological underpasses and over
breed and to have shelter (Gülci and Akay 2014). passes according to the characteristics of wild animal
226 Croat. j. for. eng. 43(2022)1Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237) D. Şakar et al.
s pecies. While ecological underpasses are determined construction. Especially in road network practices, a
as small size underpasses, medium size underpasses, safe working area should be provided with fences
large size underpasses, and viaducts, ecological over- (Worboys L. et al. 2015). For this reason, fencing prac-
passes are determined as wildlife overpasses and tices must be determined to minimize the risk of dete-
bridge overpasses (Gülci and Akay 2014, Kintsch and rioration of the area during road network construction
Cramer 2011). Therefore, when planning road net- (URL6). For example, the fences used during the con-
works in protected areas, it is necessary to determine struction of the road network provide a safe working
which group of ecological road structures will be used area and can be used to improve visual quality for
(Clevenger et al. 2001). That is, the ecological road visitors to the area, as well as make an important con-
structures to be applied in these areas are important tribution to wildlife.
for the continuity and protection of the habitats of wild Visual screen walls can be used as an effective tool
animals. to prevent noise and air pollution as well as visual
pollution during road construction (Fig. 1). Especially
2.7 Fence Applications that Increase Visual in screening works, using fences that are compatible
Quality of Road Construction in Protected Areas with nature, easy to install, reusable, low cost, cost-
Road networks are often one of the most difficult effective can be a solution to this issue. Therefore, in
parts in managing transport infrastructures in pro- terms of economy and continuity, it is important to
tected areas (Eagles et al. 2010). As well as road net- screen the constructed parts of the road during the
work planning and designing of these areas, necessary construction and to shift the screening fences in the
measures must be taken and managed during road finished part to the ongoing parts of the construction.
Fig. 1 Screening of road construction in protected areas with fences for visual quality
Croat. j. for. eng. 43(2022)1 227D. Şakar et al. Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237)
Fig. 2 Tarpaulin fence curtain containing field information in order to guide and inform visitors
On the other hand, fences used for safety for pedes- purpose, tarpaulin, artificial ivy or jute fence can be
trians and drivers should be designed within the limits used in order to hide the unwanted image and reduce
of visibility at protected area entrances and crossings noise and air pollution in road construction in pro-
(Da Andalucia 2009). For this, screening fences for vi- tected areas (Fig. 2, Fig. 3 and Fig. 4).
sual quality can be made using animate and inanimate In addition to road construction in and around pro-
materials. However, given the negative effects caused tected areas, fence curtains that increase visual quality
by road construction and the fact that it will increase are used in bridge sections as well. Especially in the
the cost, it is not recommended to implement animate practices planned at crossing points important for
materials in the fence construction that increase visual wildlife, fences with escape ramps that increase visual
quality. Especially in applications, baseless carriers quality should be applied. For this purpose, during
(lugs, pontoons, etc.) or movable (lockable wheeled) road construction phases, these fences can be placed
systems should be preferred to keep the fence stable on the edges of the bridges without gaps and in ap-
without being fixed to the ground in order for the fence propriate size according to the conditions of the re-
to be easily installed-uninstalled and reusable. For this gion. With this application, by using fences on one
228 Croat. j. for. eng. 43(2022)1Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237) D. Şakar et al.
Fig. 3 Fence curtain made using artificial planting (artificial ivy) to create a background that increases visual quality in harmony with nature
or both sides of the bridge, the passage of wildlife wildlife. On the other hand, noise pollution caused by
species will not be prevented (Arizona Game and Fish road network construction has a short-term negative
Department 2008). impact. In literature studies on the impact of the use
of work machines on wildlife, especially during con-
2.8 Effects of Noise Pollution During Road struction in protected areas and their surroundings, it
Construction in Protected Areas has been reported that the duration of work and dis-
Increases in road networks in protected areas can tance between the machines and the nests of wild
lead to habitat loss and fragmentation in terms of bio- animals are two important parameters (Kantová and
diversity, as well as negative effects such as habitat Motyčka 2014). These parameters can prevent com-
change (Bennett 2017). Noise, in particular, due to the munication disruption by masking acoustic signals that
construction and use of road networks, has negative affect wild animal behavior (Cardoso 2014, Iglesias-
effects on wildlife in protected areas (Arévalo and Blau -Merchan et al. 2015). As a result, it has been empha-
2017). Of these, traffic noise pollution was found to sized that it can cause temporary or permanent hear-
have an impact on wildlife according to 242 articles ing loss and stress of wild animals (Parris 2015).
published between 1990 and 2013, and terrestrial wild- Noise pollution also has physical, physiological
life responded to a noise level of 40 dB (Madadi et al. and psychological effects on human health (Yılmaz
2017). For this reason, an increase of this level can have and Özer 1997). For this reason, while providing ac-
chronic effects for wild animals, including high-stress cess to the protected areas and its surroundings with-
levels and associated physiological responses (Blickley in the field, security is also of great importance. There-
and Patricelli 2010). As a result, traffic noise pollution fore, within the scope of visitor management, visitors
has a permanent and long-term negative impact on who go to see the protected areas should be informed
Croat. j. for. eng. 43(2022)1 229D. Şakar et al. Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237)
Fig. 4 Fence curtain made using jute to create a background with colors that are in harmony with nature and to gain spatial depth
before road construction begins. At the same time, ⇒ suitable and well-maintained equipment should
technical measures such as placing video screens in be used
the field, placing guiding signs and warning signs that ⇒ materials leaving the construction site shall be
ensures a safe transportation network, and closing the transported during non-peak hours in order to
work area by placing sound-resistant panel fences minimize traffic noise due to the increase in traf-
should be taken by the relevant institutions. On the
fic volumes
other hand, measures to minimize noise pollution dur-
ing the construction of protected areas and surrounding ⇒ applicable electrically powered equipment
road construction can be listed as follows (Integrated should be used instead of fuel-powered equip-
Environments Ltd. 2010, Kantová and Motyčka 2014, ment. In addition, by reducing vibration with
Parris 2015, Quintero 2002): air-powered equipment, smooth transport for
⇒ during the construction phases of the road net- tools and materials should be provided
work, the working schedule should be planned ⇒ noise pollution reduction should be planned to
and the speed limit should be placed on the ser- protect wild animals and their acoustic environ-
vice roads ment before road construction
230 Croat. j. for. eng. 43(2022)1Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237) D. Şakar et al.
⇒ mobile noise-canceling barriers or natural noise presented in the study are determined within the
barriers should also be arranged according to framework of conceptual indicators. In particular, the
the site layout plan conceptual indicators determined in the study and the
⇒ during the road construction phases, renewable, issues that need to be considered are presented within
natural, quiet and recycled road products the scope of implementation and planning studies
should be used at low temperatures, because the based on literature. In addition, the planning and im-
surface coatings of these products, which have plementation phase of road networks has been evalu-
a noise-reducing effect, can provide a 9 dB re- ated with an interdisciplinary approach to determine
duction in traffic noise compared to traditional the difference of conceptual indicators from research
mixtures. in the literature. For this reason, the issues that should
be considered during the construction of road net-
2.9 Determination of Work Schedule of Road works have been addressed in a holistic way with con-
Construction Phases in Protected Areas ceptual indicators and efforts have been made to con-
Planned road networks in protected areas should tribute to the development of these issues.
be done in an environmentally sensitive and secure Issues to be considered during the planning and
manner (Eagles et al. 2010). During the planning construction of road networks in protected areas have
phase, it is very important that it is programmed and been evaluated together with the conceptual indica-
completed on time as part of an effective protection of tors in terms of management, technique, economy,
the area. Therefore, a working schedule should be pre- ecology, and aesthetic. Technical and ecological assess-
pared in accordance with the flowcharts of the plan- ments, in particular, seem to contain more elements in
ning phase (Worboys L. et al. 2015). Especially when terms of innovative technologies and sensitive protec-
planning a work schedule for the road construction in tion in applications than other indicators. The reasons
and around the protected areas, in addition to ensur- for this may be mainly due to the difficulties faced in
ing visitor safety, measures should also be taken to practice against environmental sensitivity in the con-
ensure that endemic plant species are protected and struction of road networks in protected areas, as well
that the wild animals in the area are least affected by as confusion as a result of unplanned processes, be-
the activities performed. cause the importance of environmental sensitivity in
Before starting planning, the necessary information road network practices is increasing day by day as
about the protected area should be collected. Feeding, part of sustainability in protected areas. Accordingly,
sheltering and breeding periods of the endemic spe- when the development and improvement of road net-
cies or wildlife species in the area and the visitor in- works is not well planned in terms of sustainability, it
formation should be known, and the working sched- can create difficulties in practice (Tarimo et al. 2017).
ules should be determined accordingly. For example, This situation may create an interdisciplinary effect
when creating a work schedule, planning should be among the conceptual indicators in road network
made for the times other than the days and hours practices (Caro et al. 2014). Therefore, it is stated that
when the area is most crowded (URL7). On the other technical and ecological indicators belonging to the
hand, planning should be carried out based on infor- issues that should be considered in the development
mation such as nutrition, shelter and breeding periods and improvement of the road network in protected
for wild animals habitats in the area. Thus, when cre- areas should be included in the design and implemen-
ating the work schedule for the protected areas and tation of road projects. Therefore, these indicators can
the road construction around it, the most appropriate support the importance of how the goal of environ-
periods and the factors affecting these periods should mentally sustainable development can be translated
also be included in the analysis of the process. into a concrete reality (Ledec and Posas 2003). On the
other hand, the volume of traffic used in road net-
works in protected areas was not addressed in deter-
3. Discussion mining the issues that should be considered in road
Planning and implementation processes must be network projects. The reason is that there are many
handled delicately when constructing sustainable evaluations in the literature regarding road networks
road networks in and around protected areas. In this and traffic volume. The ecological effects of road net-
context, issues that should be considered in the devel- work traffic, particularly in protected areas, on natural
opment and improvement of road networks were resources, habitats and species have been identified in
evaluated. Accordingly, the points to be considered the short and long term (Spellerberg 1998). It has also
during the construction phases of the road networks been noted that, while there are few studies within the
Croat. j. for. eng. 43(2022)1 231D. Şakar et al. Essential Issues Related to Construction Phases of Road Networks in Protected Areas: A Review (219–237)
scope of these ecological impacts, there are many stud- In the light of the information obtained from the
ies in terms of mitigation measures (Cheng et al. 2015). literature, the planning phase can be implemented
Regarding the necessity of the geotextile material with a checklist in line with the conceptual indicators
used in the construction phases of road networks, the of the issues to be considered during the construction
importance of hydraulic structures and the visual and phases of road networks. The issues that should be
ecological vegetation applications of the slopes, the evaluated during the construction and maintenance of
managerial indicator is insufficient. The reason for this road networks in and around these protected areas
is that road network planners may be exposed to re- increase the protection functionality.
strictive factors in design in protected areas during the
implementation phase (Ledec and Posas 2003). How-
4. Conclusions
ever, the managerial indicator was considered to be
not developed politically, as the road networks in ar- In the study, the issues to be considered during the
eas protected by social-economic pressures remain construction phases of protected areas and surround-
naturally (Caro et al. 2014). On the other hand, it can ing road networks were evaluated within the scope of
be revealed that the managerial indicator has its literature-based studies and integrated within the
strengths and weaknesses compared to other indica- framework of the relevant conceptual indicators. The
tors in road network construction and maintenance. It considerations determined in this context have been
can help develop solutions, especially in the measures supported by including the literature practices.
that need to be taken for road networks after imple- Ecological and technical indicators, which are the
mentation (Tarimo et al. 2017). However, these solu- main considerations that should be considered during
tions may not be applicable in all areas depending on the construction phases of road networks in protected
the topographical conditions in protected areas. areas, seem to have the most important place in the
When the aesthetic indicator of the road networks implementation practices. Especially when planning
in protected areas is evaluated during the construction new road networks, ecological value and conservation
phases, it is seen that it is preferred less than other priority should be taken into account depending on
indicators in terms of priority in practice. This may be the nature of habitats in protected areas. For this pur-
due to factors such as planning, time and cost, which pose, before construction begins, road networks in
are included in the managerial and economic indica- protected areas should be planned according to the
tors. However, when considering these factors in ecological value index of the area within the frame-
terms of ecotourism in protected areas, it can be said work of sustainable infrastructure services (Hoffmann
that they will make a significant contribution to the et al. 2019). Thus, areas in sensitive ecosystems should
development and use of road networks. In particular, be designed with innovative approaches and with eco-
in order to provide access to these areas, the develop- logical indicators (noise pollution prevention, habitat
ment of road networks with visual views compatible improvement, etc.) during the planning phase. It is
with nature and the environment should be encour- necessary to reduce the ecological impact with the un-
aged. However, it has been stated that it is necessary derstanding of the managerial indicator along with the
to construct a road network design that meets the aes- ecological indicator and pay attention at the planning
thetic expectations, prevents ecological disruption and phase in terms of the technical indicator. In particular,
ensures traffic safety (Cheng et al. 2015). more research is needed on the various effects of noise
The economic indicator is less important than oth- pollution on wildlife and their ecological communi-
er indicators in determining the effects of noise pollu- ties. As far as wildlife habitats are concerned, it is quite
tion and the work schedule during the construction important to protect natural acoustic environments
phases of road practices in protected areas. This may from high noise levels caused by road constructions.
be due to the increase in construction items in provid- Therefore, appropriate noise reduction strategies
ing safety measures in the area of road network con- should be considered at the beginning of the road
struction and maintenance. Therefore, this can affect planning process. If necessary, the construction phas-
the increase in construction cost and related working es of road networks should be followed within the
time. In addition, it can be determined how this eco- scope of managerial and technical indicators, and in
nomic increase in road network construction and unusual cases such as an increase in noise levels, con-
maintenance work can affect other indicators, espe- struction activities should be terminated and a new
cially the ecological indicator, in the short and long working schedule should be prepared (Environmental
term (Caro et al. 2014). Services Group 2004).
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