The potential role of herpetofauna species diversity on palm oil agro-ecosystems: a case study in the plantation of PT BSM South Sumatra

The palm oil industry is one of the national strategic industries that must gradually apply the concept of green economy where the use of biodiversity (to reduce the use of chemicals in increasing land fertility and controlling pests/diseases) should be optimized in various aspects of management. Therefore, the potential for species diversity and the role of biodiversity in palm oil agro-ecosystems needs to be investigated, one of which is herpetofauna diversity. Data collection on the diversity of herpetofauna species was carried out simultaneously on seven types of land cover for PT BSM’s palm oil plantations using the Visual Encounter Survey (VES) method. The results showed that the number of herpetofauna species varied according to land cover type with a total of 26 species. The highest number of species and individuals was found in shrubs (12 species and 18 individuals). While the lowest number of species and individuals was found in smallholder palm oil plantations 1 (5 species and 9 individuals). Based on the list of herpetofauna species in the study area, nine of these species have potential roles for the oil palm agro-ecosystem. These roles as biological control (predators, parasitoids, pathogens) include Takydromus sexlineatus, Eutropis multifasciata, Chalcorana chalconota, Occydoziga sumtrana, Malayopython reticulatus, Bungarus candidus, and Naja sumatrana, as well as decomposition controllers, Varanus salvator. The Shrubs land cover has a complete composisition of the roles of herpetofauna, while in the others land cover, have one individuals that play a role in the oil palm agroecosystem.


Introduction
Palm oil (Elaeis guineensis) plays an important role in both the industrial sector and economic sector.Having the status as the highest vegetable oil producing plant, this commodity has an important role in Indonesian economy as the country's main source of foreign exchange, reaching a value of US$ 25.60 billion in 2020 [1].In relation to the sustainable production of Indonesian palm oil which is very promising, the Government of Indonesia in its development planning has included aspects of environmental considerations in policies related to the palm oil industry through Presidential Regulation (Perpres) No. 44 of 2020 concerning the Indonesian Sustainable Palm oil Plantation Certification System.The policy prioritizes contributing to the responsible use of natural capital, preventing and reducing pollution, and creating opportunities to improve overall social welfare by building a green economy, and ultimately enabling the achievement of sustainable development goals [2].
In the responsible use of natural sources, the use of chemical fertilizers and pesticides as an effort to 1243 (2023) 012012 IOP Publishing doi:10.1088/1755-1315/1243/1/012012 2 increase production has become entrenched in plantation activities.The monoculture system used in palm oil plantations combined with the continuous use of chemical fertilizers can result in a drastic reduction in biodiversity.According to [3], the use of chemical fertilizers leaves residues on the soil so it is not environmentally friendly.In the long term, monoculture farming is vulnerable to decrease soil fertility due to the intensive use of chemical fertilizers and pesticides.One alternative in overcoming the problem of using chemical fertilizers and pesticides is to optimize the role of biodiversity as pest/disease control.One of the natural pest control is herpetofauna.
The existence of herpetofauna is very important for the balance and sustainability of ecosystems in an area [4].The diversity of herpetofauna is one of the balance parameters for the sustainability of ecosystems in the area and the quality of the environment in which they live.Herpetofauna also plays an important role in food webs in ecosystems as predators and prey, as evidenced by the presence of several types of herpetofauna that can act as pest controllers (types that eat rats and insects) [5].The diversity of herpetofauna is a parameter of the balance and sustainability of ecosystems in an area and the quality of the surrounding environment.The disappearance or decrease in populations of herpetofauna species in their habitats is a sign of a change in the quality of the environment in that area.
By knowing the diversity of herpetofauna species at PT. BSM, we can know the quality of the environment and also as a recommendation for natural pest control which can be a solution in reducing the use of chemicals in oil palm plantations.Based on this, it is necessary to study the potential and distribution of herpetofauna diversity in palm oil agro-ecosystems in South Sumatra.
In young palm oil plantations (YP), the understory plants that were commonly found were Mucuna bracteata, Ludwigia perennis L. and Tibouchina urvilleana.There is a canal surrounding this block and will be filled with water if rains.This area is borders with old palm oil plantation in the south and east, and also with palm oil year of planting 2000 in north part, and there is a causeway on the west side.The ambient temperature in the area is around 29°C with a relative humidity of 91%.
The canopy cover in medium palm oil plantations (MP) is quite tight, but there are some places that are not too tight so that sunlight can penetrate to the palm oil plantations floor.The relative humidity in this area is 91% with an average temperature of 26°C.There are canals on each side of the block.The palm oil plantations floor is overgrown with undergrowth but not too tightly.The most common species found in this area are Asystasia gangetica and Adiantum sp..There is a small reservoir between the medium and old palm oil areas.The type of soil in this area is mineral soil.The northern and eastern boundaries of this plantation are palm oil with the planting year 1996.Meanwhile, the western and southern parts are bordered by palm oil with planting year 1997.
Old palm oil plantations (OP) have a mineral soil type.There is a partition in the form of a small canal along the side of the block.The the palm oil plantations floor is dominated by undergrowth such as Asystasia sp., Spigelia athelmia, Ageratum conyzoides, Melastoma affine and grass.When compared to the MP area, the canopy cover in this area tends to be more open.The relative humidity in this area is also lower than the MP area, which is 64% with an average temperature of 29°C.This area is surrounded by palm oil plantations with the same planting year (1996).
High Conservation Value (HCV) area at PT. BSM is in the form of a watershed and borders with other palm oil companies, meanwhile on the left and right with palm oil plantations year 1996.The canopy cover is quite tight.The vegetation that dominates this area is Bambusoae, Paspalum conjugatum and Asystasia gangetica.In addition, there are also Terminalia catappa and solep trees with stake habitus.The condition of the river tends to be shallow with less water, but there are some places that are filled with quite a lots of water.The average temperature in this area is 29°C with a relative humidity level of 77%.Shurbs (S) area at PT. BSM is borders with other palm oil companies in eastern part.Meanwhile there is a swamp in the south.This location is dominated by gelam, bongkol and Lygodium microphyllum.The condition of the floor in this area is watery with red soil type.At some points the canopy cover is very tight and causes light cannot penetrate to the forest floor, but there are some areas that are quite large with canopy cover that tends to be open.The relative humidity in this area is quite high at 83% with an average temperature of 28°C.
The smallholder oil palm plantations I (SH1) and 2 (SH2) are adjacent and bordered by the HCV river area, having the same planting year in 1996.The soil types are sandy and mineral soil, respectively.Tight canopy cover but sunlight can still penetrate to the smallholder plantations floor.In SH 1 have a small canal and in the middle of the plantation area there is a ditch filled with water.The ground floor is covered with several undergrowth such as Ageratum conyzoides, Tibouchina urvilleana, Ottochloa nodosa, Asystasia gangertica, Chromolaena odorata and Spigelia athelmia.The relative humidity level is 87% with an average temperature of 27°C.

Research methods
Herpetofauna data retrieval was carried out using the Visual Encounter Survey (VES) method combined with a 1 km line transect, with three repetitions then turning 150 meters and walking again for 1 km.Observation time was carried out at 19.00 -21.00 WIB.According to [6], the use of the VES method through the following assumptions: 1) every individual of all species has the same opportunity to be observed; 2) each species likes the same place or habitat; 3) all individuals are only counted once in the observation; and 4) survey results are the results of observations of more than one person.Data collection is carried out by capturing and collecting samples as well as recording species, position, substrate and activity.The data obtained then recorded in the tally sheet.After data on the diversity of herpetofauna species on various types of land cover in palm oil plantations was obtained, then it was analyzed quantitatively descriptively.

Data analysis
Data analysis includes quantitative and descriptive qualitative analysis.Quantitative analysis used species diversity indices, while descriptive qualitative analysis described the condition of land cover species and the role of butterfly species.To determine the variation of species diversity in various types of land cover used calculations consist of species shannon index (1), species richness index (2), and evenness index (3) (Table 1).

The spesies diversity
Observation of herpetofauna on 7 types of land cover in palm oil plantations at PT. BSM South Sumatra found as many as 26 species of herpetofauna from 14 different families (10 species of reptiles and 4 species of amphibians), as presented in Table 2.The most common herpetofauna species were found in shrubs land cover, namely, 12 species with 18 individuals, followed by area with high conservation value, namely 10 species with 14 individuals.Meanwhile, the least herpetofauna species were found on the land cover of the smallholder palm oil plantations 1 with the acquisition of 9 individuals and 5 species.The presence of individuals and the highest number of herpetofauna species were found in shrubs land cover.The shrubs area in PT BSM is dominated by gelam, bongkol and Lygodium microphyllum plants with the floor condition in this area being watery and having a red soil type.In the Southern part of this area there is a swamp.At some points the canopy cover is very tight and causes light cannot penetrate to the forest floor, but there are some areas that are quite large with canopy cover that tends to be open.
The results of this study indicate that there are differences with [7] who conducted research on one of the large palm oil plantations in Ogan Komering Ilir Regency, South Sumatra.Where shrubs are the type of land cover with the lowest number of herpetofauna species, with 6 species and the most types are in palm oil land cover types with 10 species.This difference is due to habitat conditions in a type of land cover that support herpetofauna species to breed.This is corroborated by [8] which states that the change in habitat from forest vegetated areas to palm oil plantations is thought to still be able to provide suitable environmental conditions for herpetofauna species because vegetation and water sources can still be found in the vicinity.
Takydromus sexlineatus is a reptile with the highest number of individuals in the shrubs cover, with 5 individuals.[9] said that the reptile species Takydromus sexlineatus was not affected by large canopy cover because it had to take direct environmental heat from sunlight to bask during the day.Correspondingly, in the shrubs cover, there are areas with canopy cover that tend to be open, allowing Takydromus sexlineatus to bask in the sun during the day.
Diversity is associated with the number of species found in a particular community [10].The diversity index of herpetofauna in 7 land cover types at PT BSM showed that the highest diversity was in the shrubs cover type (H'= 2.35), followed by the high conservation value land cover type (H'= 2.21).Meanwhile, the lowest diversity was in smallholder palm oil plantation cover 1 (H'= 1.43) (Figure 2).The high value of diversity in shrubs is due to the availability of environmental factors that affect the presence of herpetofauna such as water canals and undergrowth plants that covering the soil surface.This is in accordance with [11] where dense undergrowth is favored because it provides shelter, breeding, playing, and foraging for wildlife.The types of understorey that dominate the shrubs are gelam, bongkol, and Lygodium microphyllum.
The highest species richness index was found in the shrubs land cover type (Dmg = 3.81), followed by the high conservation value land cover type (Dmg = 3.41), and the lowest was in the community garden 1 (Dmg = 1.82).(Figure 2).The value of species richness index for each type of land cover is different due to variations in the number of individual species in each type of land cover.The most individuals were in the shurbs land cover type as many as 18 individuals, high conservation value land cover as many as 14 individuals, land cover in young palm oil and medium age palm oil, also in smallholder oil plantation 2 had the same number of individuals as many as 13 individuals, while old palm oil as many as 12 individuals, and smallholder oil plantation 1 as many as 9 individuals.According to [12], the richness of herpetofauna species can increase along with the increasingly diverse habitats, thus it can be said that the shrubs land cover has diverse habitats because it has a high species richness index among other land cover types.
The evenness index value for all types of land cover is high, ranging from 0.87-0.96.The evenness index has a value ranging from 0 to 1, if the value is close to 1 then the distribution of individuals is relatively even, whereas if the value is close to 0 then the distribution of individuals between species is uneven and dominates by certain individuals [13].Land cover with high conservation value has the highest evenness index (E= 0.96), while the lowest evenness value (E= 0.87) is in smallholder palm oil plantations 2. This shows that all types of land cover at PT BSM have an equally distribution of each species and not dominates by spesific species.
Smallholder palm oil plantations 1 is a land cover with a low number of species, diversity index, richness, and even distribution of species (S= 5 species; H'= 1.43; Dmg= 1.82, E= 0.89).With sandy soil type, dense canopy cover, and overgrown with several types of undergrowth plants, and there is a small canal on the side of the area.Having a dense canopy can affect the growth of understorey that animals use to hide from predators and also prevent animals from getting sunlight.[14] vegetation can affect the existence of herpetofauna because it can be used as a place to shelter (cover) and also a place to live for animals, especially herpetofauna.Herpetofauna, especially amphibians, need moisture to maintain their skin, so the role of undergrowth is very influential on the type of amphibians.While reptiles need sunlight to bask, the less light that can enter the reptile will move to another place with sufficient light intensity for sunbathing.
The microhabitat conditions will affect the hydration process and the resistance of the herpetofauna species, especially amphibians [15].So that habitat conditions, habitat diversity and different microhabitats can affect the diversity of herpetofauna species [16].In line with [17] Kampar Regency, Riau shows that the highest index of species diversity and herpetofauna species richness is found in young palm oil land cover with the planting year 2004.
Families Colubridae and Ranidae are reptile and amphibian families with at most 5 individuals and 4 individuals, respectively.This is influenced by the high adaptability of species from the two families, so they can live in various habitats and even disturbed habitats [18].
The most common reptile and amphibian species found in this study were 5 individuals each of Takydromus sexlineatus and 16 species of Fejervarya limnocharis.In addition, the next largest number of individuals from the Ranidae family is Fejervarya cancrivora with 14 individuals.Fajervarya cancrivora is a frog with a wide distribution area.The species found in this study are mostly tolerant species that have high adaptability to environmental changes such as Amnirana nicobariensis, Fejervarya cancrivora, Hylarana erythreae, Fejervarya limnocharis, Limnonectes sp.B, Polypedates sp., Polypedates leucomystax and varanus salvator.These results are in line with the research results of [19] and [20], who found species tolerant of environmental disturbances.[21] stated that palm oil plantations appear to attract nuisance tolerant species.
Shrubs areas and areas with high conservation value had the highest number of species, namely 12 species and 10 species, respectively, while Smallholder palm oil plantations 1 was the land cover type with the least herpetofauna found, about 5 species.Research from [18] in one of the landscapes of large palm oil plantations in Central Kalimantan, the highest number of species was found in land cover areas with high conservation value and secondary forest with 12 species each.Meanwhile, shrubs were the land cover type with the least herpetofauna found, namely 6 species.This is influenced by the fact that the canopy cover of the shrubs in the area is relatively open due to the lack of canopies from trees and stakes.On the other hand, the shrubs in PT BSM's palm oil plantations have high canopy density in some areas, but there are some areas that are quite large with a canopy cover that tends to be open, allowing sunlight to enter.In line with [22] an open canopy can affect changes in intensity, light, conductivity and pH of water flow, air temperature, humidity and leaf litter distribution.According to [23] the lack of structural complexity of vegetation and canopy cover can reduce humidity and increase temperature fluctuations between day and night.*Based on [24], The food preferences of V. salvator are flexible, allowing them to "clean up" the environment by scavenging dead or decaying organic matter, thereby helping to reduce the spread of disease and also to recycle essential nutrients -an integral ecosystem service.
Table 2 shows that the shrubs (S) land cover type has a complete composition of potential herpetofauna compared to other land covers, although the potential distribution of species can be said to exist in the seven land cover types.The most potential species found in the shrubs land cover type, caused because S has suitable conditions for herpetofauna to live.The number of species and the number of individual herpetofauna in this shrubs land cover is also influenced by the availability of food.[25] stated that the availability of food will affect the number of herpetofauna species and individuals found in an ecosystem.
The existence of herpetofauna species is also influenced by the similarity of the habitat, [26] states that the similarity of the community can be formed by several environmental factors such as the distance between adjacent habitats and the same composition of vegetation.The types of herpetofauna that can be found in medium-aged palms, old palms, areas with high conservation value, shrubs, smallholder palm oil plantations 1, and smallholder palm oil plantations 2 is Naja sumatrana.
In most ecosystems, snake density can be related to prey abundance.In naturally forested areas, prey abundance is limited by forest productivity, and by competition with other animals for limited resources.However, in palm oil plantations, a monoculture system can provide a food source for several types of rodent species [27].This particular species can sometimes reach very high population densities in palm oil plantations (> 400 individuals/ha) [28].With increasing population density of rodent species, the population of snakes as predators increases.
Actions to reduce pest attacks on palm oil plantations through the use of natural enemies are needed to maintain environmental conditions.In addition, the density of herpetofauna species share several biological characteristics: many of them are habitat generalists (does not require complex primary forests to survive) which can enable them to respond rapidly to food surpluses.
In several studies on palm oil plantations, freshwater monitor lizards (Varanus salvator) were found in many types of palm oil land cover [17].Meanwhile, in this study, freshwater monitor lizards were found in shrubs land land cover types.This is possible due to the condition of shrubs that support the habitat of V. salvator.Supported by the generalist diet of freshwater monitor lizards (eating almost everything) enables it to tolerate the ecological conditions of its habitat.The food preferences of V. salvator are flexible, allowing them to "clean up" the environment by scavenging dead or decaying organic matter, thereby helping to reduce the spread of disease and also to recycle essential nutrientsan integral ecosystem service [24].
This is what plays an important role in the process of the food chain.Agro-ecosystem holds a key factor in meeting the food needs of a nation.Palm oil plantations are built on sustainability principles that emphasize the importance of biological resources as a driver of ecological processes in a landscape.Ecological processes that include pollination, biological control (predators, parasitoids, pathogens), and decomposition take place through a very complex system.Palm oil plantations support a variety of pests including rodents such as rats and squirrels as well as insects due to the continuous availability of food at all times and in all places.These organisms may have several local influences including attracting other predatory species (such as snakes, owls, leopards and pigs) which may impact surrounding habitats if the balance of the food chain is not maintained.
The increase in pest attacks is also caused by the unwise use of pesticides which have an impact on the disruption of functions and natural control factors in the palm oil plantation ecosystem, allegedly due to the death of natural enemies (parasitoids and predators).In fact, many potential natural enemies have been found and can be bred in the laboratory and even traded, but they do not seem attractive for use by plantation players.This is thought to be due to the killing power of pathogenic (entomopathogenic) microorganisms that work indirectly to kill target pests such as pesticides but take several days [27].
To realize sustainable agriculture, it is necessary to reduce pest attacks through the use of natural enemies and increase plant diversity such as the application of intercropping, crop rotation and planting open lands because it increases ecosystem stability and reduces the risk of pest disturbances [29].Natural mechanisms such as predatism, parasitism, pathogenicity, intraspecies and interspecies competition, succession, productivity, stability and biodiversity can be utilized to achieve sustainable agriculture.Thus the vision of Indonesia's green economy can be achieved, one of which is to realize sustainable economic growth with a more integrated and comprehensive approach to utilize natural capital in a more environmentally responsible in the economic process, in order to achieve sustainable development.

Conclusion
Herpetofauna diversity in PT BSM consists of 92 individuals from 26 species belonging to 14 families.Variations in land cover types provide different responses to the level of herpetofauna species diversity in palm oil plantations.Types of land cover shrubs have the highest number of species, diversity index, the eveness, and has a complete ecological role compared to other types of land cover.Meanwhile the type of land cover with the the lowest number of species is in the type of smallholder palm oil plantations 1.
The average herpetofauna species found are generalist species that can adapt quickly to environmental changes.There are two ecological roles for herpetofauna that found in the seven land cover types, as biological controls (predators, parasitoids, pathogens) and as a decomposition control.
) with ܲ݅ = ୬୧ H'= Shannon index ni = Number of individuals of type-i N = Number of individuals of all species Notes: YP=young age palm, MP=medium age palm, OP=old age palm, S=shrubs, HCV=highconservation value, SH=smallholder palm

Figure 2 .
Figure 2. Comparison number of species, species diversity, species evenness, and species richness of herpetofauna in various types of land cover

Table 2 .
List of herpetofauna species found in various types of land cover PT.BSM

Table 3 .
The potential of herpetofauna and their distribution by land cover type's