Oil palm plantations have expanded rapidly in recent decades. This large-scale land-use change has had great ecological, economic, and social impacts on both the areas converted to oil palm and their surroundings. However, research on the impacts of oil palm cultivation is scattered and patchy, and no clear overview exists. We address this gap through a systematic and comprehensive literature review of all ecosystem functions in oil palm plantations, including several (genetic, medicinal and ornamental resources, information functions) not included in previous systematic reviews. We compare ecosystem functions in oil palm plantations to those in forests, as the conversion of forest to oil palm is prevalent in the tropics. We find that oil palm plantations generally have reduced ecosystem functioning compared to forests: 11 out of 14 ecosystem functions show a net decrease in level of function. Some functions show decreases with potentially irreversible global impacts (e.g. reductions in gas and climate regulation, habitat and nursery functions, genetic resources, medicinal resources, and information functions). The most serious impacts occur when forest is cleared to establish new plantations, and immediately afterwards, especially on peat soils. To variable degrees, specific plantation management measures can prevent or reduce losses of some ecosystem functions (e.g. avoid illegal land clearing via fire, avoid draining of peat, use of integrated pest management, use of cover crops, mulch, and compost) and we highlight synergistic mitigation measures that can improve multiple ecosystem functions simultaneously. The only ecosystem function which increases in oil palm plantations is, unsurprisingly, the production of marketable goods. Our review highlights numerous research gaps. In particular, there are significant gaps with respect to socio-cultural information functions. Further, there is a need for more empirical data on the importance of spatial and temporal scales, such as differences among plantations in different environments, of different sizes, and of different ages, as our review has identified examples where ecosystem functions vary spatially and temporally. Finally, more research is needed on developing management practices that can offset the losses of ecosystem functions. Our findings should stimulate research to address the identified gaps, and provide a foundation for more systematic research and discussion on ways to minimize the negative impacts and maximize the positive impacts of oil palm cultivation.
ABSTRACT. Conversions of natural ecosystems, e.g., from rain forests to managed plantations, result in significant changes in the hydrological cycle including periodic water scarcity. In Indonesia, large areas of forest were lost and extensive oil palm plantations were established over the last decades. We conducted a combined social and environmental study in a region of recent land-use change, the Jambi Province on Sumatra. The objective was to derive complementary lines of arguments to provide balanced insights into environmental perceptions and eco-hydrological processes accompanying land-use change. Interviews with villagers highlighted concerns regarding decreasing water levels in wells during dry periods and increasing fluctuations in stream flow between rainy and dry periods. Periodic water scarcity was found to severely impact livelihoods, which increased social polarization. Sap flux measurements on forest trees and oil palms indicate that oil palm plantations use as much water as forests for transpiration. Eddy covariance analyses of evapotranspiration over oil palm point to substantial additional sources of evaporation in oil palm plantations such as the soil and epiphytes. Stream base flow from a catchment dominated by oil palms was lower than from a catchment dominated by rubber plantations; both showed high peaks after rainfall. An estimate of erosion indicated approximately 30 cm of topsoil loss after forest conversion to both oil palm and rubber plantations. Analyses of climatic variables over the last 20 years and of a standardized precipitation evapotranspiration index for the last century suggested that droughts are recurrent in the area, but have not increased in frequency or intensity. Consequently, we assume that conversions of rain forest ecosystems to oil palm plantations lead to a redistribution of precipitated water by runoff, which leads to the reported periodic water scarcity. Our combined social and environmental approach points to significant and thus far neglected eco-hydrological consequences of oil palm expansion.
Abstract. In many tropical regions, the rapid expansion of monoculture plantations has led to a sharp decline in forest cover, potentially degrading the ability of watersheds to regulate water flow. Therefore, regional planners need to determine the minimum proportion of forest cover that is required to support adequate ecosystem services in these watersheds. However, to date, there has been little research on this issue, particularly in tropical areas where monoculture plantations are expanding at an alarming rate. Therefore, in this study, we investigated the influence of forest cover and oil palm (Elaeis guineensis) and rubber (Hevea brasiliensis) plantations on the partitioning of rainfall into direct runoff and subsurface flow in a humid, tropical watershed in Jambi Province, Indonesia. To do this, we simulated streamflow with a calibrated Soil and Water Assessment Tool (SWAT) model and observed several watersheds to derive the direct runoff coefficient (C) and baseflow index (BFI). The model had a strong performance, with Nash-Sutcliffe efficiency values of 0.80-0.88 (calibration) and 0.80-0.85 (validation) and percent bias values of −2.9-1.2 (calibration) and 7.0-11.9 (validation). We found that the percentage of forest cover in a watershed was significantly negatively correlated with C and significantly positively correlated with BFI, whereas the rubber and oil palm plantation cover showed the opposite pattern. Our findings also suggested that at least 30 % of the forest cover was required in the study area for sustainable ecosystem services. This study provides new adjusted crop parameter values for monoculture plantations, particularly those that control surface runoff and baseflow processes, and it also describes the quantitative association between forest cover and flow indicators in a watershed, which will help regional planners in determining the minimum proportion of forest and the maximum proportion of plantation to ensure that a watershed can provide adequate ecosystem services.
ABSTRAKAnalisis mengenai daya dukung lahan pertanian tanaman pangan sangat penting dilakukan untuk mengetahui sejauh mana kemampuan lahan pertanian dalam mendukung pemenuhan kebutuhan pangan penduduk di suatu daerah. Salah satu permasalahan di Daerah Aliran Sungai (DAS) Cibaliung adalah rendahnya kemampuan lahan dalam memenuhi kebutuhan pangan sehingga penduduk tidak bisa memenuhi kebutuhannya secara mandiri. Penelitian ini bertujuan untuk mengetahui tingkat daya dukung lahan pertanian tanaman pangan dalam mencukupi kebutuhan pangan masyarakat di DAS Cibaliung, Provinsi Banten. Secara spasial penelitian ini meliputi 2 kabupaten yang terdiri atas 15 kecamatan dalam lingkup DAS Cibaliung. Data yang digunakan adalah data sekunder yang diambil dari Badan Pusat Statistik dan Dinas Pertanian dan Peternakan Kabupaten Pandeglang dan Kabupaten Lebak. Hasil penelitian menunjukkan bahwa secara keseluruhan berdasarkan data 4 tahun (periode tahun 20132016) daya dukung lahan pertanian pangan DAS Cibaliung secara keseluruhan masih rendah. Selain itu, jumlah penduduk optimal yang mampu didukung kebutuhan pangannya oleh lahan yang tersedia masih lebih kecil dibandingkan dengan jumlah penduduk yang tercatat di masing-masing kecamatan di DAS Cibaliung. Hal ini menunjukkan bahwa wilayah DAS Cibaliung belum mampu berswasembada pangan dan belum mampu memberikan kehidupan yang layak bagi penduduknya. Oleh karena itu, perlu dilakukan upaya-upaya tertentu untuk meningkatkan daya dukung lahan pertanian pangan di daerah ini, misalnya dengan menekan jumlah penduduk dan memperbaiki kualitas sumber daya lahan pertanian melalui upaya pertanian konservasi dan diversifikasi jenis tanaman pangan. Kata kunci: daya dukung, DAS Cibaliung, lahan pertanian ABSTRACT Analysis of carrying capacity of agricultural land for food crops is very important to do to determine the extent of the ability of agricultural land in supporting the fulfillment of the food needs of the population in an area. One problem in the Cibaliung watershed is the low ability of land to meet food needs so that residents cannot meet their needs independently. This study aims to determine the level of carrying capacity of agricultural food crops in meeting the food needs of the community in the Cibaliung River Basin (DAS) of Banten Province. Spatially, this study covered 2 regencies consisting of 15 districts within the scope of the Cibaliung watershed. The data used were secondary data taken from the Central Statistics Agency and the Agriculture and Animal Husbandry Office of Pandeglang and Lebak Regencies. The results showed that overall based on 4-year data (for the period of 2013-2016) the carrying capacity of the Cibaliung watershed agricultural land as a whole was still low. In addition, the optimal number of populations that is able to be supported by the available food needs is still smaller than the total population recorded in each district in the Cibaliung watershed. This shows that the Cibaliung watershed area has not been able to be selfsufficient in food and has not be...
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