## 3 Soil and Water Conservation and Its Impacts on Biodiversity  
Indonesia is one of the seventeen global megadiverse countries, with two out of the twenty-five biodiversity hotspots in the world [40]. However, the rate of primary forest loss in Indonesia is double that of the Democratic Republic of the Congo and triple that of Brazil [41]. The drivers of forest loss in Indonesia range vastly from the industrial-scale logging of montane rainforests to the small-scale destruction of coastal peatlands. The loss of forest cover that human-induced factors have caused impacts Indonesia's biodiversity at various levels. Although the type of forest loss varies widely across the landscape, the continued exploitation of primary tropical rainforests remains the most prevalent type of forest loss in Indonesia [41].  
In order to address long-term concerns in biodiversity conservation, Indonesia must strike a balance between protection and sustainable utilization to its national biodiversity. Thus, SWC becomes a crucial component of the environmental sustainability of forestry systems [42]. SWC's favourable impact on vegetation cover, plant diversity, richness, and restoration is logical [43]. On the other hand, vegetation has been an essential component in the watershed ecosystem, providing a buffer element for soil erosion and drought [44] and increasing soil's capacity to hold water [45]. The diversity of tree species in upstream watersheds, such as _Alstonia scholaris_, _Arenga pinnata_, _Artocarpus heterophyllus_, and the commonly dominant species _Pinus merkusii_, has essential roles in maintaining soil conservation and forest ecosystems in general [46]. Likewise, _Coffea arabica_, an important crop and vital product in several highland countries, contributes significantly to water conservation [47]. Other species that can be cultivated for vegetative SWC are _Tectona grandis_, _Delonix regia_, _Switenia nahogoni_, _Cassia sianem_, and _Samanea suman_[48]. Tree-level vegetation has various characteristics that can affect surrounding environmental conditions.  
Additionally, the establishment of understorey plants that have the potential to maintain SWC in the upstream area is urgently needed. A previous study proved that _Mimosa pudica_, _Ageratum cynzooides_, and various other understorey plants possess a high potential for conserving soil in watershed areas [44]. The functions of ecosystems' soil conservation can be improved through vegetation restoration, which can also successfully lessen soil erosion [49]. Grassy vegetation covers can hold the surface runoff and increase water infiltration into the soil [50]. The presence of vegetation will positively impact the ecosystem's balance on a broader scale in a complex landscape system (Figure 1) [51].  
In other words, the presence of forest vegetation and its litter layers may reduce the amount of surface runoff and convert rainwater into groundwater supply [52]. Such a condition is vital in maintaining soil stability and reducing soil loss in steep slopes [53]. Knowing that each vegetation type has its respective role and understanding the potential of runoff suppression plants and their role in supporting SWC are crucial. As important resources, soil and water can be preserved by utilizing native plants adapted to local  
Figure 1: Key components related to SWC in the ecosystem management.  
rainfall and soil conditions. Local communities believe that native plant species have the ability to maintain the existence of natural springs and preserve the soil. To ensure better management and utilization of natural resources, local communities are expected to be able to collaborate with local and national governments [54].