**4.2.1 Impact of high visitor arrivals**

In response to this rising demand for nearness to Nature, Forest managers usually respond with more inroads into the forest and more alluring facilities, which unfortunately, not only take more number of visitors to the interiors, but also allow them to stay longer in the forest. Research shows that the fastest growing recreational activities are associated with forest trail use (Lynn & Brown, 2003) as visitors use these inroads to venture into the remote wild, which may otherwise be non-passable. In BTNR, 84% of the visitors stay for 1-2 hours and all that time are spent on the trails. Trail degradation is established as one of the most evident consequences of expanding visitor numbers in nature parks. While trails are intended to confine visitors to predetermined paths and, thereby, minimize the negative impacts of human visits, additions to the trail network are an inevitable response to the increased movement of people within the forest.

Trampling on trails by increasing number of visitors alters the soil surface characteristics, mechanical properties and hydrophysical behavior. Severe compaction of the top surface leads to greater trail-surface erosion and changes in the forest floor environment, with top

Sustainability of an Urban Forest: Bukit Timah Nature Reserve, Singapore 153

Seraya Loop: Site1 689.4 1323.7 1613.2 861.75 In this section, there is

Steps

Site1 322.0 1623.5 1814.2 761.8 This section of the trail

Trailside

Comments

trail

The trail has many bike tread marks and deep grooves

The mean width of this section of the trail is 3.4m

> is very steep – in places > 35 deg

exposed rocks, tree roots, and pot holes

sideways extension

The trail has many

The trail has very limited room on the side for

room for straying on the side of the

Location Forest Trail Root

Seraya Loop: Site2 103.4 1116.8 1654.6 689.4

Seraya Loop: Site3 386.1 2171.6 2668.0 930.7

Seraya Loop: Site4 344.7 1034.1 1964.8 758.3

Seraya Loop: Site5 344.7 1447.7 1778.7 896.2

Seraya Loop: Site6 137.8 792.8 1916.5 654.9

Seraya Loop: Site7 193.0 2344.0 1379.0 978.9

Site2 104.4 2116.8 2655.0 859.4

Site3 295.1 1971.6 2668.0 980.0

Site4 231.7 1641.1 2660.3 758.8

Site5 244.4 2400.7 2195.7 996.0

Site6 136.8 1752.8 2016.5 723.9

Site7 153.0 2405.0 1878.0 1578.9

Table 3. Mean Penetration resistance values (kPa) of surface soils on forest, trail, trail-side

Due to excessive compaction, as shown in the surface penetration data, such trails go beyond repair, disallowing any root penetration, even after being left unused for some length of time. What is alarming is not just the degradation of the demarcated trails, but the increasing penetration data obtained from the trail-sides. These tracts running along the designated trails are initially covered often with indigenous ground vegetation, young saplings and fresh leaf litter, a major source of nutrients to the forest vegetation. With very high human traffic on the trails, visitors tend to go beyond the designated trails and this problem is exaggerated during heavy rains when the trails, with their compacted surfaces

Dairy Farm Loop:

Dairy Farm Loop:

Dairy Farm Loop:

Dairy Farm Loop:

Dairy Farm Loop:

Dairy Farm Loop:

Dairy Farm Loop:

and root steps in Bukit Timah Nature Reserve

soil washed out, tree roots exposed, litter protection removed, and very importantly, compacting the soil beyond root penetration. Over time, the concentration of such activities on pre-defined trails result in extensive surface degradation and wildlife habitat disruption. This reduces the quality of wilderness experience of the visitors, in addition to degradation of the forest environment. As the recreational value of nature trails grows with public engagement in outdoor activities (Bhuju & Ohsawa, 1998), park managers are faced with the dilemma of satisfying demands for opportunities of experiencing Nature from the growing number of visitors and the progressively deteriorating trails. Extensions of trail lengths have been the usual response to reduce impact per length of the trail. However, with the increasing number of visitors, this does not seem to ameliorate the problem but further impact the forest by taking visitors more and more into the forest interiors. Research has also established that trails are not only heavily used, but also widened through overuse, thus degrading the immediate peripheries of the trails as well (Chatterjea, 2007). With mainly recreational use of the forest, as Sutherland et al. (2001) suggest, it is important to examine the impact of recreational hiking on soil hydro-physical characteristics as well as to identify indicators of trail degradation so that the data can be used by land managers to assess the degree of stress imposed by recreational impacts.

Measured values of penetration resistance and shear strength, infiltration rate (Gardner and Chong, 1990) of the top surface soil can be analysed to show how increase in trail use leads to increased surface soil compaction and thus alters the original forest surface hydrological characteristics. Chatterjea (2007) gives details of the trail degradation and provides spatial information on hazardous trail segments which can be used by the forest management to target their repair works to affected sites as well as to plan future repairs, depending on requirements. Data regarding trail degradation along the well-used forest paths in BTNR are compared with the original undisturbed forest surfaces (Table 2). Impact of the heavy use is most obvious in the altered surface compaction. Readings of surface penetration resistance at 406 locations on all trails show alarming rise, as seen in Table 2 below.


Table 2. Average Surface Penetration Resistance values, indicating surface compaction on trails in BTNR (From 406 locations)

Some trails such as Seraya Loop, being closer to one of the accessible boundary paths, has been widened beyond 3.5m and illustrates how the trails develop severely compacted surfaces, give rise to ready surface wash during frequent rainstorms, wash off the top soil on the trail as well as from the surrounding slopes, become extremely slippery and hence highly hazardous. Surface compactions from two severely degraded trail segments are shown in Fig. 9 and Table 3. They show the differences in surface compaction on trails and undisturbed forest slopes, to illustrate the changes brought about by excessive use of the trails by visitors.

soil washed out, tree roots exposed, litter protection removed, and very importantly, compacting the soil beyond root penetration. Over time, the concentration of such activities on pre-defined trails result in extensive surface degradation and wildlife habitat disruption. This reduces the quality of wilderness experience of the visitors, in addition to degradation of the forest environment. As the recreational value of nature trails grows with public engagement in outdoor activities (Bhuju & Ohsawa, 1998), park managers are faced with the dilemma of satisfying demands for opportunities of experiencing Nature from the growing number of visitors and the progressively deteriorating trails. Extensions of trail lengths have been the usual response to reduce impact per length of the trail. However, with the increasing number of visitors, this does not seem to ameliorate the problem but further impact the forest by taking visitors more and more into the forest interiors. Research has also established that trails are not only heavily used, but also widened through overuse, thus degrading the immediate peripheries of the trails as well (Chatterjea, 2007). With mainly recreational use of the forest, as Sutherland et al. (2001) suggest, it is important to examine the impact of recreational hiking on soil hydro-physical characteristics as well as to identify indicators of trail degradation so that the data can be used by land managers to

Measured values of penetration resistance and shear strength, infiltration rate (Gardner and Chong, 1990) of the top surface soil can be analysed to show how increase in trail use leads to increased surface soil compaction and thus alters the original forest surface hydrological characteristics. Chatterjea (2007) gives details of the trail degradation and provides spatial information on hazardous trail segments which can be used by the forest management to target their repair works to affected sites as well as to plan future repairs, depending on requirements. Data regarding trail degradation along the well-used forest paths in BTNR are compared with the original undisturbed forest surfaces (Table 2). Impact of the heavy use is most obvious in the altered surface compaction. Readings of surface penetration resistance

**Surface Resistance Forest Trail Trail-side** 

Maximum Resistance (kPa) 965 .3 2068.4 2137.4

Minimum Resistance (kPa) 68.9 137.9 68.9

Mean Resistance (kPa) 419.2 1238.8 912.0 Table 2. Average Surface Penetration Resistance values, indicating surface compaction on

Some trails such as Seraya Loop, being closer to one of the accessible boundary paths, has been widened beyond 3.5m and illustrates how the trails develop severely compacted surfaces, give rise to ready surface wash during frequent rainstorms, wash off the top soil on the trail as well as from the surrounding slopes, become extremely slippery and hence highly hazardous. Surface compactions from two severely degraded trail segments are shown in Fig. 9 and Table 3. They show the differences in surface compaction on trails and undisturbed forest slopes, to illustrate the changes brought about by excessive use of the

assess the degree of stress imposed by recreational impacts.

trails in BTNR (From 406 locations)

trails by visitors.

at 406 locations on all trails show alarming rise, as seen in Table 2 below.


Table 3. Mean Penetration resistance values (kPa) of surface soils on forest, trail, trail-side and root steps in Bukit Timah Nature Reserve

Due to excessive compaction, as shown in the surface penetration data, such trails go beyond repair, disallowing any root penetration, even after being left unused for some length of time. What is alarming is not just the degradation of the demarcated trails, but the increasing penetration data obtained from the trail-sides. These tracts running along the designated trails are initially covered often with indigenous ground vegetation, young saplings and fresh leaf litter, a major source of nutrients to the forest vegetation. With very high human traffic on the trails, visitors tend to go beyond the designated trails and this problem is exaggerated during heavy rains when the trails, with their compacted surfaces

Sustainability of an Urban Forest: Bukit Timah Nature Reserve, Singapore 155

heavily used every day, leaving little time for natural regeneration or management intervention. Figure above shows the spatial extent of one of the damaged trail sections in BTNR and even newer trails such as Kampong Trail are not spared with rapid degradation subsequent to the opening up for public use. As these trails run through much of the forest interiors, trail degradation can be seen as a cause for concern as far as the health and

**5. BTNR in the eyes of the visitors: Perceptions and views of stakeholders**  As the forest became increasingly popular to the local visitors, it became increasingly clear that the views, perspectives of the visitors drive the way this forest is managed. With initiatives from the National Parks Board which manages the forest, the forest has gone through some major facelift in terms of facilities aimed at attracting visitors and it sees large numbers of visitors, mostly locals from the neighbourhood and organized groups from schools and other organizations. It also provides opportunities for local schools, universities and other research bodies to conduct forest ecology related research. The forest has therefore moved from an unknown forest to one that provides services such as recreation,

sustainability of the forest is concerned.

Fig. 11. Surface degradation along trails

education, and research opportunities.

Fig. 9. Comparative Shear Strength of surface materials on different surfaces, indicating compaction: higher shear strength indicates greater compaction

are sites of heavy surfacewash. Top surfaces get muddy and subsequently the slippery surfaces are avoided by the joggers. This leads to widening of the existing trails. Fig.10 shows the width of one of the trails in BTNR, as measured and there is a marked increase in the width in all of the trails from the original layout of 0.5m.

Fig. 10. Width of trail along Kampong Trail, a newly laid out trail at BTNR: x6 increase in some sections

With prolonged impact on the trails, many of the trail segments are ridden with rills, pot holes, exposed tree roots, exposed and lose rock fragments, and smoothened soil surfaces (Fig. 11). Trails with such severe surface degradation and high surface compaction lead to permanent damage to the forest floors, inhibiting further root generation and extension. Plant saplings along the trail-sides often get smothered as trails are extended beyond the original layout. This impact, therefore, is extended to the immediate forest interiors.

Many trails get entrenched with bike tire treads and thus assist in channelizing the developed surface wash (Fig.11). Such damages cannot be easily repaired as trails are

**Comparative Shear Strength of Surface Materials on Forest and Trail Section**

> Trail Forest

Average for trail = 78.06 kPa

Average for forest = 32.45 kPa

Fig. 9. Comparative Shear Strength of surface materials on different surfaces, indicating

0 200 400 600 800 1000 1200 1400 1600 1800 2000 **Distance (m)**

are sites of heavy surfacewash. Top surfaces get muddy and subsequently the slippery surfaces are avoided by the joggers. This leads to widening of the existing trails. Fig.10 shows the width of one of the trails in BTNR, as measured and there is a marked increase in

Fig. 10. Width of trail along Kampong Trail, a newly laid out trail at BTNR: x6 increase in

original layout. This impact, therefore, is extended to the immediate forest interiors.

With prolonged impact on the trails, many of the trail segments are ridden with rills, pot holes, exposed tree roots, exposed and lose rock fragments, and smoothened soil surfaces (Fig. 11). Trails with such severe surface degradation and high surface compaction lead to permanent damage to the forest floors, inhibiting further root generation and extension. Plant saplings along the trail-sides often get smothered as trails are extended beyond the

Many trails get entrenched with bike tire treads and thus assist in channelizing the developed surface wash (Fig.11). Such damages cannot be easily repaired as trails are

compaction: higher shear strength indicates greater compaction

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 110.00 120.00 130.00

**Shear Strength(kPa)**

the width in all of the trails from the original layout of 0.5m.

some sections

heavily used every day, leaving little time for natural regeneration or management intervention. Figure above shows the spatial extent of one of the damaged trail sections in BTNR and even newer trails such as Kampong Trail are not spared with rapid degradation subsequent to the opening up for public use. As these trails run through much of the forest interiors, trail degradation can be seen as a cause for concern as far as the health and sustainability of the forest is concerned.

Fig. 11. Surface degradation along trails
