1 General introduction
1.5. The overview of the Bornean forest
The island of Borneo is the largest island in South-East Asia and is shared between 3 countries Indonesia, Malaysia, and Brunei. In 2010, forest area including degraded, managed and intact forests represented about 53% of the total areas of the island (Gaveau et al. 2014) (Figure 1-3). Forests of Borneo as in the entire Malesia region, are dominated by the
35 Dipterocarpaceae family. The Dipterocarpaceae is a family amongst the tallest trees found in the Bornean lowland forests (Appanah and Turnbull 1998; Ashton 1983; Banin et al. 2012;
Whitmore 1984). The family gathers about 695 species (Christenhusz and Byng 2016) and approx. 267 species are found in Bornean forests (Ashton 1983; Brearley, Banin, and Saner 2016;
Whitmore 1984). This taxon is the most dominant family in the island followed by Euphorbiaceae with 22% and 12% of all trees (DBH ≥9.8 cm), respectively (Slik et al. 2003). Due to its dominance both in terms of stems (up to 25% of the total tree density) and basal area (often 50% of the total basal area), forests dominated by Dipterocarpaceae are called mixed Dipterocarp forests (Whitmore 1984). Shorea and Dipterocarpus are the most abundant genera of the family Dipterocarp forests (Slik et al. 2003) and are the common Dipterocarpaceae tree species harvested in the island as it produces long, straight, and knot free logs which are ideal for the timber industry (FAO 2016).
Figure 1-3 Forest status in Borneo based on Gaveau et al. (2014). Study sites of this thesis are in Malinau (white box) and Berau (blue boxes).
Most of the forests in Borneo are under intense pressure and threatened by anthropogenic activities such as logging, and conversion to monoculture plantation and mining industry (Gaveau et al. 2014; Nasi and Frost 2009; Sodhi et al. 2009; Wilcove et al. 2013). Those activities result in a detrimental impact on SE Asia’s biodiversity (Sodhi et al. 2009) and the shrinkage of intact forests (Gaveau et al. 2014) that are essential for biodiversity conservation (e.g. Barlow et al. 2007; Gibson et al. 2011; Hughes, Daily, and Ehrlich 2002). During 1973-2010, forests in Indonesian Borneo have lost about 30% or equivalent to 12.4 million ha (Table 1-3).
36 Gaveau et al. (2014) identified around 21 million ha of intact forests of which 8.8 million ha (approx. 42% of the intact forests) fall within the production forests land-use class and prone to be logged in the near future and 3.4 million ha (approx. 16% of the intact forests) to be converted to other land-uses. Assuming that all production forests are logged, and areas designated for conversion are converted, logged forests will be the main land-use class in the islands with 26.8 million ha (approx. 36% of the total land area) followed by intact forests with 8.8 million ha (approx. 16% of the total area). Therefore, logged forests will play crucial roles in the trade-off between the provision of goods (timber, rattan, food, etc.) and maintenance of C stocks, biodiversity, and other ecosystem services (Meijaard and Sheil 2007; Sist et al. 2015). Although protected areas in the island cover about 6.6 million ha (Proctor, McClean, and Hill 2011), these areas still impacted by deforestation through forest conversion or forest degradation (Curran et al. 2004).
Table 1-3 Summary of forest area in Borneo in the year 1973 and 2010 (in million ha). Data were extracted from Gaveau et al. (2014).
Borneo Kalimantan Brunei Sabah Sarawak
Total land area 73.7 53.3 0.6 7.4 12.4
Mixed Dipterocarp forests in Borneo have long been exploited for timber production in SE Asia (Nasi and Frost 2009; Nicholson 1979), unfortunately with a poor implementation of sustainable forest management practices. In the 1990s, three innovative logging guidelines, one published by International Tropical Timber Organization (ITTO) namely the ITTO Guidelines for Sustainable Management of Natural Tropical Forests Management (1992) and the two others published by Food and Agricultural Organization (FAO) namely the FAO Model Code of Forest Harvesting Practice (Dykstra and Heinrich 1996) and the FAO Code of Practice for Harvesting in Asia-Pacific (1999), were released in order to support sustainable forest management. At the same time, with increasing awareness for tropical forests, Indonesia and Malaysia went further developed their own guidelines to complement the ITTO guideline. Particularly in Indonesia, extensive research on how to reduce forest damage and minimizing the effect of logging through reduced-impact logging (RIL) was carried out in Berau (East Kalimantan) and followed in Malinau (North Kalimantan, formerly East Kalimantan) (Sist, Sheil, et al. 2003; Sist et al. 1998; Sist and Nguyen-Thé 2002). The studies demonstrated that RIL techniques under moderate logging intensities (8 trees harvested ha-1) could reduce forest damage significantly. Sist et al. (1998) reported that RIL reduced damage by 50% compared with conventional logging (CVL) in Berau but the damage was dependent on logging intensity. Further, in the case of Malaysian
37 production forests, Pinard and Putz (1996) reported that one year after logging, forests harvested by RIL have 67% of the biomass of pre-logging levels compared with 44% of biomass when CVL was applied. With regards to C stocks, Putz et al. (2008) reported that using an improved timber harvesting (RIL) practices would retain at least 0.16 Gt C year-1, and predicted to be at least 30 Mg ha-1 higher than those conventionally logged due to reduced collateral damage after 30 years of logging (Pinard and Cropper 2000; Pinard and Putz 1997). Based on carbon dynamic models in Dipterocarp forests, Pinard and Cropper (2000) reported that over 60 years following RIL, the average of total C stored in the forest was 36 Mg C ha-1 higher than that CVL. Therefore, RIL is recommended as an appropriate technique for selective logging in the tropics (Elias et al. 2001; Sist, Garcia-Fernandez, and Fredericksen 2008).
Logging in Bornean lowland forests will always be a routine activity due to at least two reasons. The first reason is that forestry industry sectors will always continue in order to fulfill timber demand that is increasing over time (ITTO 2015). As an example, timber consumption has increased from 271 million m3 (2012) to 275 million m3 (2014) worldwide. The second reason is that forestry industry sectors are a significant source of income to the developing countries (Berry et al. 2010; Miles and Kapos 2008) such as Indonesia (approx. 2.6 billion USD) and Malaysia (3.7 billion USD) that produce approx. 41% of roundwood of the world timber market (FAO 2016). However, the contribution benefits to the income of the countries grew slower (Lebedys and Li 2014) and logged forests are under pressure for conversion to other more profitable land uses such as palm oil plantation and agricultural use (Sodhi et al. 2004).