**4.1 Impact on the forest peripheries and forest interiors**

Figure 6 shows the temperature differences between the forest peripheries and the forest interiors, while Fig. 7 shows the differences in relative humidity in the same locations.

The 1990s saw the rapid development of the residential areas and Fig. 5 shows the numbers of such development, all within a 2km radius, which may be considered a walking distance from the forest. Residential development in such close proximity invariably lures the city dwellers and the natural environment of the forest is always a point of attraction, much advertised by the developers. From one condominium in 1984 with 157 residents near this forest, 2009 saw 24 condominiums and more than 21,000 residents, all within a short walking distance away from the forest boundaries (Fig.5) and the number is increasing with two very big developments launched in 2011 barely 300

The forest boundaries also have urban infrastructural set-ups such as major roads, a railway line, a rifle range and even a golf course around it. 1985 saw the opening of a six-lane highway connecting the northern parts of the island with the rest, running through the dense forested areas of the Central Water Catchment, literally severing all forested connections between the bigger forests of the catchment with the now truncated BTNR (Fig. 4). So while the urban infrastructural growth connected the island's north and south, the island's most significant forest reserve got fragmented. BTNR now resides as a truncated urban forest, full of original wilderness properties that attract large numbers of newly-aware

Figure 6 shows the temperature differences between the forest peripheries and the forest interiors, while Fig. 7 shows the differences in relative humidity in the same locations.

visitors to the interiors but is ill-placed to handle such large degree of impact.

meters away from the forest.

Fig. 5. Residential development within 2km of BTNR

**4. Effects of high density residential development 4.1 Impact on the forest peripheries and forest interiors** 

Fig. 6. Isotherms showing distribution of temperature in and around BTNR

Fig. 7. Isohumes showing distribution of Relative Humidity in and around BTNR

From the data obtained from 162 locations reveal that there is a sharp increase in temperature by 8 deg C in the outer boundaries and that the gradients are very steep in some locations, such as the areas skirting the Bukit Timah Expressway (BKE) as well as along the Dairy Farm Road, another dual-carriageway. Gradient is particularly steep all along the BKE –BTNR interface, with temperature increase of 8 deg C within 50m at the edge of the forest from 25 deg C to 33 deg C. Similar effects are felt for relative humidity. Along the boundaries there has been a recorded drop of 40% in the humidity levels along the BKE-BTNR interface within a horizontal distance of 70m. Along the Dairy Farm Road

Sustainability of an Urban Forest: Bukit Timah Nature Reserve, Singapore 151

figure of > 915 visitors per day. This amounts to >86 persons trampling for around 2 hours per km of the trails, which is alarmingly high. While in 2004, 46% percent had visited most of the trails, the 2006 survey revealed that at least 92% had ventured into at least one or more of the walking trails; 78% said they stay for two or more hours at each visit in 2004

**2004 2006 Comments** 

visits

19% 11% Solitary activities have seen a decline

increase in the frequency of

trails might have gone up

>10 times 31% 64% There has been a drastic

>2 hours 17% 16% Many people are staying in 2 hours 61% 42% the forest for a shorter time

Main Road 24% 17% Percentage of people visiting

Jogging, exercise, Exercise activities on the rise

81% 89%

The more revealing information relating to altered usage of the forest comes from the 2006 data which show that 89% of the visitors visit the forest for exercise, trail walk, jogging, and biking, with only 11% of the visitors having nature and bird watching in their mind. It is quite obvious that over the years BTNR is seen more as an exercise spot than as an area for

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

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

while in 2006 surveys revealed that 83% of the visitors spend 1-2 hours in the forest..

3 – 10 times 39% 25% 1 – 2 times 30% 11%

1 hour 22% 42%

Trails 68% 60% No Preference 8% 23%

**Categories surveyed** 

Nature Watch (bird watching)

Table 1. Results of surveys done for visitors to BTNR (n=850)

walking

quite appreciation of Nature.

**4.2.1 Impact of high visitor arrivals** 

increased movement of people within the forest.

**Type of observation** 

visit

Frequency of visit in a year

Length of each

Destinations within the forest

Favourite activities while in the forest

average relative humidity drop was recorded to be about 30% all along the outside boundary. The slightly lower value recorded along the Dairy Farm Road is thought to be because of the presence of more trees along the outer boundaries of the forest and also because of some planted trees along the roadside. This is not the case along BKE, where the forest ends abruptly at the expressway. All data show clearly that the boundary environment is very different from the inner forest and the outer peripheries of this small forest are subjected to much harsher environment than the forest interior, creating a steep edge: interior difference. This is obviously detrimental to the well-being of the forest vegetation in particular and the entire forest ecosystem in general.
