Tree biodiversity in Bornean lowland forest: What are the key species for forest city development in the new capital city of Indonesia?

PLOS ONE | https://doi.org/10.1371/journal.pone.0320489 April 8, 2025 14 / 19 PLOS ONE Tropical urban tree selection city park, sub-district park, village park, green belt, burial ground); conservation area; and mangrove ecosystems. The Urban Forest covers an area of 64,618 ha, most of which will be developed from the former concession area of plantations of Eucalyptus spp. Not all parts of the site will be used to build infrastructure facilities; however, most will be rehabilitated to restore the Eucalyptus plantation to the original tropical rain forest using the native and endemic species of the low- land tropical forest of Borneo. The urban forest also includes two wildlife corridors that will be built in the IKN area, namely the northern corridor connecting Bukit Suharto Grand Forest Park (GFP) with the Production Forest and the southern corridor connecting Bukit Suharto GFP with Sungai Wain Protection Forest. Bukit Suharto GFP is the only conservation area in IKN that covers lowland forest areas to the coast, including the unique heath forest ecosystem. The area of 64,255 ha is not entirely forest; forest fires have damaged part of it, and some of it has been converted into agricultural fields and is occupied by the local community. This area will be maintained and restored to become a key part of the identity of the forest city. Hajjar et al. [68] stated that community participation will improve their responsibility and commitment to preserve the forest. This involvement should start from the project plan and design to the program’s implementation,

including the methods used in forest management and species selection for rehabilitation activities. In Indonesia, Safe’i et al. [69] demonstrated that a social forestry program with a community forest scheme in Tanggamus Regency, Lampung (Sumatra), contributed to the economic improvement of the forest farmer group by about 15%. Another community’s forest scheme also contributed to the recovery of the forest area of about 29.3% from 40 ha of the project area in Gunung Kidul Regency, Yogyakarta [70]. Several factors that contribute to social forestry programs’ success include technical and financial assistance for forest farmers in forest management and product processing [71], and their capacity building [72]. Land rehabilitation, forest reclamation, and social forestry could all use species as food source trees to meet 10% of the targeted green cover in IKN. Nevertheless, the choice of food source trees needs to be considered with the involvement of local communities who have knowledge of the species’ attributes in terms of economic benefits, medicinal use, and social/ cultural values [73]. The introduction of poorly-known species in community participation projects is possible as long as this is followed by supporting activities in the appropriate plant- ing techniques, maintenance, harvesting, post-harvest production, and marketing strategies. As 10% of the green cover is allocated for food security, the zoning of species planted in land rehabilitation activities is important to avoid animal-human conflict. Planting animal

food source species should be done in forest edge areas or restored forest areas. The species selected for planting in these areas are those with potential for animals but low preference for humans. Meanwhile, human food source species should be planted away from forest boundaries or around settlements. To mitigate the risk of conflict, we propose a spatial zoning approach in the city forest design where trees that serve as animal food sources are planted in areas further from human settlements and city centers, creating natural buffers and wildlife corridors. This would encourage wildlife to remain in designated forest areas while mini- mizing direct interactions with the urban population. Additionally, as part of the forest city planning, monitoring and management strategies should be developed to address potential human-wildlife interactions proactively. Forest rehabilitation in the IKN area also could be conducted via natural regeneration [74] or secondary forest succession. In particular, for the Eucalyptus plantations, the canopy cover could be opened to facilitate the climax species seed germination and initiate appropriate microclimate conditions as shown by Brancallion et al. [75] in Brazil. Removal of Eucalyp- tus close to the natural forest border is also essential to facilitate the natural regeneration