The role of high conservation value areas to maintaining ecological balance in oil palm plantations PT. Waimusi Agroindah, South Sumatera

Currently, oil palm plantations must carry out environmentally friendly plantation activities, one of which is by maintaining the biodiversity in or around the plantation area. Biodiversity can also reduce pest attacks that can reduce oil palm productivity. The research activities were carried out at PT. Waimusi Agroindah by conducting an inventory of plant, mammal, and bird species in HCV areas and oil palm plantations (young, medium, and mature palms). The results of the research in the HCV area showed that there were 4 types of trees, 10 types of poles, 7 types of saplings, 4 understorey plants and seedlings, 4 types of mammals, and 34 species of birds. Within the HCV area, three species of mammals protected by the government were found, namely the silvery lutung (Trachypithecus cristatus) as many as 3 individuals, and three species of birds, namely Haliastur indus, Elanus caerulaus, and Anhinga melanogaster. In the oil palm plantation area, only understorey stands were found, but various types of mammals and birds were found. The number of species of mammals and birds found in HCV areas is higher than in oil palm plantations. The number of vegetation types in the HCV area is more diverse so that it can be used as a place for wildlife to live, both for forage plants and nests. This shows the need for HCV areas in biodiversity conservation and as an ecological balancer in oil palm plantation areas.


Introduction
The existence of oil palm plantations cannot be separated from the perception of the loss of biodiversity.Biodiversity and agriculture, in this case oil palm plantations, are things that support the economy in Indonesia.Land use for production is the biggest driver of biodiversity loss [1], with approximately 270 hectares of biodiversity hotspots in the tropics with potential for oil palm cultivation [2].In 2021, exportrevenues from oil palm plantations will be 35 billion dollars, 52% higher than in 2020 [3].This means that country income from exporting plantation products is increasing every year.However, although oilpalm contributes a large amount of income to the country, the opinion that biodiversity is declining dueto oil palm is still a matter of debate.The low biodiversity in oil palm plantations is caused by monocultures and the absence of the main components of forest vegetation which include forest trees, lianas and epiphytic orchids [4,5,6].
Oil palm plantations are currently required to implement the principles of environmental management, natural resources, and biodiversity as one of the requirements to obtain ISPO 1243 (2023) 012004 IOP Publishing doi:10.1088/1755-1315/1243/1/012004 2 (IndonesianSustainable Palm Oil) certification.As one of the countries with the largest exporters of palm oil plantation products, Indonesia is also a voluntary member of the Roundtable for Sustainable Palm Oil (RSPO).In other words, one of Indonesia's efforts to implement sustainable palm oil plantations is to implement the goals of ISPO and RSPO, namely conserving biodiversity and ensuring that no primary forest and high conservation value areas are used as oil palm plantations.One form of implementation of ISPO and RSPO carried out by oil palm plantations in Indonesia is to maintain areas with high conservation value.In 2018, the RSPO also made a policy for stakeholders to implement zero-deforestation activities [7].As of August 2022, the area that already has an RSPO certificate in Indonesiais 2,417,105 Ha [8].One of the efforts that can be made by oil palm plantations in increasing sustainableand environmentally friendly palm oil production is to apply RSPO principles.With the HCV area in oil palm plantations, it will make it easier for plantations to export oil palm production.Biodiversity management in HCV areas will also maintain the company's accreditation in implementing sustainable production.
High Conservation Area (HCV) is a basic component in the implementation of biodiversity conservation in oil palm plantations, which consists of HCV 1 to HCV 6. Areas that have HCV attributesor criteria carry out development activities by maintaining and enhancing HCVs [9].The current HCV criteria are still considered ineffective and have a strong basis, so it is necessary for various groups, bothgovernment and NGOs to create new criteria so that the implementation of HCV application in oil palmplantations can ensure the protection of biodiversity [10].With the HCV area, it is hoped that it can balance the sustainability of oil palm plantations in the ecological aspect.Therefore, there is a need for research on the role of HCVs in protecting biodiversity in oil palm plantations, the impacts that biodiversity have to enhance the economic and ecological values of the oil palm plantations.

Method
The research was conducted at PT. Waimusi Agroindah, South Sumatra.The data needed in this study is the diversity of plants, mammals, and birds in four locations, namely young growth oil palm plantations (YG), medium growth oil palm plantations (MG), and old growth oil palm plantations (OG),as well as in HCV areas.

Data retrieval methods
The collection of plant data in the HCV area consisted of data on trees, poles, saplings, seedlings and undergrowth.The plot size for trees (diameter above 19 cm) is 113.14 x 113.14 m², poles (diameter < 20 cm) is 60 x 60 m², saplings (diameter < 10 cm, height > 1.5 m) are 40x40 m², and seedling plots.andundergrowth (height < 1.5 m) of 10 x 10 m² [11].The method of collecting undergrowth data in the oil palm plantation area is in the form of 2 x 2 m² plots, each land cover consists of 15 plots.
Inventory of the diversity of mammal species was carried out using the line transect method, while the bird species inventory used the line transect method and observation points.The length of the path is 1 km with a width of 100 m.Observations were made in the morning (06:00-08:00 WIB) and afternoon(15:30-17:30 WIB) for 3 repetitions.The data recorded include the time of encounter and the number ofindividuals of each species.

Data analysis 2.2.1 Plant diversity Species diversity index (H')
The diversity of plant species is known using the Shannon-Wiener Diversity Index, with the formula: The richness of plant species is measured using the Margaleff Index.The Margaleff Index is a measureof diversity that is more responsive and sensitive to changes in species numbers [11].The Margaleff index uses the following equation: Information: Dmg = species richness index S = number of types N = total number of individuals of all species

Diversity of mammals and birds
Mammal and bird species diversity was analyzed by looking at the number of species and the number of individuals in each land area.Bird and mammal data were also analyzed for their rarity status to identify HCV criteria in PT Waimusi Agroindah.

Plant diversity
There were 17 plant species found in the HCV area of PT Waimusi, consisting of 4 species of trees, 10 species of poles, 7 species of saplings, and 4 species of seedlings and undergrowth.There were   [12].Although this species is not protected, if its presence is not noticed it will cause extinction at the local level and affect the existence of wildlife that use this plant as a food plant.
Inventory of oil palm plantations was carried out on 2 x 2 m² plots, with 15 plots each on each land cover.There were 19 understorey species found in old oil palm plantations and medium oil palm plantations, while in young oil palm plantations 17 species of understorey were found.understorey species were dominated by Clidemia hirta in old oil palm plantations, Ageratum conyzoides in mediumoil palm plantations, and Asystasia micrantha in young oil palm plantations.Table 2 shows the five dominant understorey species found in each oil palm land cover.As in HCV areas, none of the plant species found in oil palm plantations are included in the criteria for protected plants, either by the government, the CITES Appendix, and also the IUCN.
Although in the oil palm plantation area only understorey species are found, they can be used by wildlife such as butterflies.Most butterfly species were found in secondary forest and old oil palm areas.This is because butterfly species prefer more open land cover conditions with diverse understorey compositions as a place to find food and as host plants for butterfly larvae [13].Vegetation under stands shows a very important role in supporting sustainable oil palm cultivation.This role can be through the function of lower vegetation, both as a ground cover in soil and water conservation, and as a forage, which improvescarbon and nutrient cycles.Forage vegetation through the process of photosynthesis lowers CO2 emissions, while increasing carbon reserves in biomass and in soil [14].
The value of diversity and richness of plant species shows the balance of communities in a particulararea.Table 3 shows that the H' and Dmg values for each of their land cover and plant structures.In thiscase, the two locations cannot be compared with the values of H' and Dmg because they have different plant structures, where in oil palm plantations only undergrowth is found.H' value for each land cover in the low category, this indicates that the balance of the community is lessstable, so it is necessary to carry out species enrichment activities, especially in HCV areas.The higherthe value of species diversity in a habitat, the higher and more stable the balance of the community willbe.Although in oil palm plantation areas only undergrowth species are found, they can be useful as a source of vegetable insecticides in controlling pests such as caterpillars which sometimes become pests.Chromolaena odorata has a function as a source of vegetable insecticides and as a high-quality organicfertilizer material that is able to release nutrients in a relatively fast time because based on the results ofresearch this type has the potential to be a vegetable insecticide in controlling pests [15].In addition, thepresence of undergrowth vegetation is able to reduce CO2 emissions through photosynthesis activities.CO2 emissions in oil palm replanting lands are reduced by intercropping crops [16].

Mammals and birds diversity
Observations showed that the mammal species found in HCV were more diverse and more numerous than those in oil palm plantations (Table 4).The Malaysian Field Rat (Rattus tiomaticus) species was found in every location, this is because this species is very adaptable to new places.In addition, there are many types of feed, both in oil palm plantations and in HCV areas.Although the oil palm plantationarea is not a forested area, it can be inhabited by certain types of mammals.A number of forest animal species (especially mammals) are able to take advantage of the environment.One of the reasons habitatheterogeneity can increase species diversity is that the more diverse the habitat, the more capable it is to support populations of different species [17].The cause of the low biodiversity in oil palm plantationsis thought to be due to the nature of the monoculture cropping pattern and the absence of the main component of forest vegetation which includes forest trees, lianas and epiphytic orchids [4], so that the diversity of mammal species in oil palm plantations is lower than that of oil palm plantations.forested areas such as HCV and secondary forest planted with oil palm as their habitat, although not as the mainhabitat [18].

Table 4. Diversity of mammals
The only mammal species found in the HCV area are the Silvery Lutung (Trachypithecus cristatus) and the Long Tailed Macaque (Macaca fascicularis).This is because the plant species in the HCV areaare more diverse and there are many tall trees for these two species for activities such as playing and foraging.Lutung is a species that requires trees for foraging activities, as a place to sleep, and also as a place to move from one tree to another.The population density of langurs and other primates in a placedepends on the presence of trees and the carrying capacity of their habitat [19,20,21].
Bird species found varied in each land cover, dominated by Eurystomus orientalis, Elanus  1, it is known that the HCV area has more diverse bird species than the oil palm plantation area.The diversity of bird species in the HCV area indicates that some birdspecies prefer forested areas that have a diversity of plant species, as well as the presence of tall trees.Increases in bird diversity and bird abundance depend on increasing tree numbers [22].Like the eagle species, they need tall trees for perching and nesting [23].

Figure 1. Diversity of birds and mammals
Mammals and birds play a role in pest control, seed dispersers, predators, and pollinators for plants.The existence of mammals and birds plays an important role in the balance of natural ecosystems.Although the number of mammal and bird species in oil palm plantations is lower, the presence of HCVareas is expected to increase biodiversity of both plants, mammals and birds, so that the existence of HCV areas can increase the ecological value of oil palm plantations.The presence of birds is very important in oil palm plantations, especially species of insectivores that can act as natural pest control inoil palm plantation areas [24].

The role of HCV areas in oil palm plantations
PT Waimusi Agroindah was established in 1990 and has an HCV area of 21.51 Ha.Based on the resultsof the research, it shows that the HCV area of PT Waimusi Agroindah is HCV 1, which is an area that has important biodiversity, and HCV 5, which is an area that has a role in providing natural environmental services.The determination of HCV 1 at PT Waimusi is in accordance with the species of birds and mammals that fall into the IUCN VU (Vulnerable) and EN (Endangered) criteria, App II CITES, and is protected under Indonesian regulations, while the determination of HCV 5 because the HCV area is also a river border .The implementation of HCVs is linked to the RSPO on principle 7 andISPO on principle 3, namely environmental responsibility and conservation of natural resources and biodiversity [9].This shows that PT Waimusi Agroindah has implemented principle 7 of the RSPO in supporting biodiversity.
Based on the results of the inventory in the HCV area, there are plant species that are only found 1 and 2 individuals in one family, this requires more attention when monitoring and evaluating the HCV area so that these species remain sustainable, because if these species are lost, the biodiversity in the areaHCV will also be disturbed.In addition, in the HCV area, two primate species were found as factorsin the criteria for HCV 1, namely Trachypithecus cristatus and Macaca fascicularis.Although the M.fascicularis species is not protected under Indonesian regulations, the global population of this species continues to decline, this has resulted in an increase in its status to Endangered in 2022, from previouslyVulnerable in 2020, and LC (Least Consern) in 2008.The decline in the global M. fascicularis populationis due to the large number of hunting carried out by humans, because its existence is considered a nuisance.M. fascicularis species will enter land and residential areas becausethere is little food in the forest, so they will go to look for food in human territory [25].Conflict betweenhumans and the species M. fascicularis will lead to hunting for this species, so that its population decreases [26].
The determination of the criteria for the HCV area is also based on the biodiversity in it, as with mammals, protected bird species also determine the criteria for determining the HCV.One of the HCV criteria required is the presence of species that are protected under government regulations, included in the IUCN (Vulnerable and Endangered) list, as well as CITES Appendix I and II [27].Table 5 shows the bird species found and included in the HCV criteria.

The role of plant and wildlife diversity in HCV in improving the ecological and economicfunction of oil palm plantations
Waimusi Agroindah has an HCV area that has a variety of plant and satwaliar species, so that the existence of HCV can increase the ecological of oil palm plantations.The results of the plant inventory show that the diversity of plant species in HCV is higher than that of oil palm plantations.Thisshows that one of the roles of HCV in increasing ecological value in oil palm plantations is by preservingHCV areas.Likewise, the diversity of mammal and bird species shows that the HCV area ishigher thanthat of oil palm plantations.HCVs that are still forested have a role in preserving the diversityof mammalspecies as evidenced by a higher level of diversity when compared to non-forested HCV areas, especiallywith oil palm plantations [28].
One of the objectives of maintaining HCV areas is as a commitment to follow RSPO and ISPO regulations, as well as ISCC (International Sustainability and Carbon Sertification).In addition, HCV has an economic role where in the implementation of HCV area monitoring can involve the surroundingcommunity, so that PT Waimusi can create jobs for the surrounding community.The role of HCV in maintaining a sustainable plantation system can be judged by certification or recertification activities carried out by the company in collaboration with authorized institutions in accreditation activities.Goodassessment results in terms of ecology can be a reference for the continued operation of production activities in oil palm plantations, so that it indirectly also has an impact on economic aspects.The resultsof the assessment carried out by the certification body depend on the monitoring activities of the HCV area, whether plants, birds or mammals.
Wildlife, especially birds and mammals, are animals that actively move, either in foraging or for other activities such as breeding.Mammals and birds found in HCV areas will also move to oil palm plantations because the areas are adjoined, even if they are not found at the time of observation.Mammals also play an important role in the ecological process in oil palm plantations.Mammals include seed-feeding animals that help maintain ecosystem stability [29].By maintaining the condition of the HCV area ecosystem, the survival of mammals and birds will continue to be maintained.This is becausebird and mammal feed sources are more abundant in the HCV area as evidenced by the variety of plantspecies found in the HCV area.

Conclusion
The existence of HCV areas in oil palm plantations is essential in maintaining the diversity of plant andanimal species in and around them.This is also one of the ways to support the government's efforts to protect protected species based on the Regulation of the Minister of Environment and

Table 1 .
Plant species diversity in the IUCN least concern category 12 families found in the HCV area, and dominated by 162 individuals of Nypa fruticans, 59 individuals of Nauclea officinalis, and 44 individuals of Barringtonia acutangula.Of the 17 plant species found in theHCV area, none are included in the protected list according to the Regulation of the Minister of Environment and Forestry of the Republic of Indonesia No. P.106/MENLHK/SETJEN/KUM.1/12/2018concerning Protected Types of Plants and Animals and CITES Appendix, but there are five plant speciesthat are included in the IUCN LC (Least Consern), but the LC category is not included in the HCV criteria.More in Table 1.N : number of individuals

Table 1
No other plant species were found in the Hypericaceae family.The species Cratoxylum formosum is a plantspecies that has many uses, such as building materials, clothing dyes, and edible young leaves shows that there is only one individual in one family, namely Cratoxylum formosum.

Table 2 .
Dominant understorey species in oil palm plantations

Table 3 .
The value of plant diversity and richness