Commercial Oil Palm Plantations Research Articles

Mapping oil palm expansion within the protected lowland rainforest of Nigeria using Google Earth engine

Increasing demand for Elaeis guineensis (African Oil Palm) products both for domestic and industrial use has led to its continuous expansion. The influence of oil palm plantation establishment on the economic well-being of communities and ecosystems cannot be over-emphasised. The study focuses on the rapid expansion of oil palm plantations within all protected areas and forest reserves in the lowland rainforests of Ondo State, Nigeria using. Object-Based Image Analysis (OBIA) was used to map oil palm expansion using 10-metre resolution Sentinel-2A images for 2015 and 2020 in Google Earth Engine (GEE). We found expansion of both smallholder and commercial oil palm plantations within eight of the thirteen protected areas with three protected areas (Ipele, Onisere and Akure Ofosu) showing a significant increase in oil palm plantation establishment. The use of object-based classification techniques, which combines contextual information within the image domain to discriminate landscape features such as oil palm canopy features, was effective in delineating oil palm from the forest canopy and other crops. While Google Earth Engine, a server-based remote sensing domain with petabytes of data, is effective for monitoring large-scale tropical forests.

UAV-based thermography reveals spatial and temporal variability of evapotranspiration from a tropical rainforest

Evapotranspiration (ET) from tropical forests plays a significant role in regulating the climate system. Forests are diverse ecosystems, encompass heterogeneous site conditions and experience seasonal fluctuations of rainfall. Our objectives were to quantify ET from a tropical rainforest using high-resolution thermal images and a simple modeling framework. In lowland Sumatra, thermal infrared (TIR) images were taken from an uncrewed aerial vehicle (UAV) of upland and riparian sites during both dry and wet seasons. We predicted ET from land surface temperature data retrieved from the TIR images by applying the DATTUTDUT energy balance model. We further compared the ET estimates to ground-based sap flux measurements for selected trees and assessed the plot-level spatial and temporal variability of ET across sites and seasons. Average ET across sites and seasons was 0.48 mm h–1, which is comparable to ET from a nearby commercial oil palm plantation where this method has been validated against eddy covariance measurements. For given trees, a positive correlation was found between UAV-based ET and tree transpiration derived from ground-based sap flux measurements, thereby corroborating the observed spatial patterns. Evapotranspiration at upland sites was 11% higher than at riparian sites across all seasons. The heterogeneity of ET was lower at upland sites than at riparian sites, and increased from the dry season to the wet season. This seasonally enhanced ET variability can be an effect of local site conditions including partial flooding and diverse responses of tree species to moisture conditions. These results improve our understanding of forest-water interactions in tropical forests and can aid the further development of vegetation-atmosphere models. Further, we found that UAV-based thermography using a simple, energy balance modeling scheme is a promising method for ET assessments of natural (forest) ecosystems, notably in data scarce regions of the world.

Wind regimes above and below a dense oil palm canopy: Detection of decoupling and its implications on CO2 flux estimates

In tall vegetation canopies, calm weather conditions may result in the formation of an isolated below-canopy air layer. Especially during night, below-canopy carbon dioxide (CO2) fluxes may be concealed from above-canopy eddy covariance (EC) measurements, masking the magnitude of CO2 net ecosystem exchange (NEE). Particular attention to this “nighttime problem” needs to be paid in oil palm (Elaeis guineensis Jacq.) plantations, which can form a dense top canopy and which are grown in tropical regions where wind speeds are often low. Here, we investigated EC-based NEE measurements, wind and micrometeorological patterns, and LiDAR-derived terrain and canopy structure in a mature commercial oil palm plantation in the tropical lowlands of Jambi province, Sumatra, Indonesia. Over 3 years, we assessed the strength of turbulent and thermal mixing and tested five different methods to determine decoupling: (i) single-level (above-canopy) and (ii) two-level (above- and below-canopy) friction velocity (u*), (iii) above- and below-canopy standard deviation of the vertical wind (σw), (iv) bulk Richardson number (Rib), and (v) vertical turbulence intensity (ITurb). Our results show that decoupling is a common phenomenon in this plantation, with the two-level filters of σw and u* being most sensitive in its determination, showing ∼93% nocturnal decoupling. Decoupling is driven by the oil palm canopy structure, which develops a marked blocking layer at ∼10 m above the ground, high frequency of calm weather conditions, inverse temperature gradients and a terrain slope of 3° which was enough to create a thermally-induced drainage flow. Filtering NEE data, especially the two-level filters of σw and u*, challenged estimations of the plantation's CO2 balance due to high uncertainties in nocturnal respiration rates which could not be reduced by adding storage components to the measured fluxes highlighting the importance of additional below-canopy CO2 flux measurements, especially in such a weak-wind and dense-canopy tropical environment.

Improving the methodology for root biomass estimation in monocotyledonous tree plantations: case of oil palm (Elaeis guineensis. Jacq) in West Africa

Root biomass is one of the most widely used parameters to characterise root growth and belowground carbon stock. Our aim was to define a standard method to estimate the root biomass of young and adult oil palm trees in commercial plantations. Three methods based on the sampling excavation volume were compared using the same sampled tree. Work time and the number of workers required for each operation were recorded. We compared two large excavation volumes based on Voronoi tessellation and the standard root auger coring method in one 2-year-old and one 16-year-old commercial oil-palm plantation in Benin, West Africa. Oil palm total root biomass was estimated at 0.84 and 22.23 Mg ha−1 in the 2-year-old and 16-year-old plantation, respectively. Compared to the reference method, the simplified Voronoi trench method estimated slightly higher (+5%) and lower (−17%) total root biomass with no significant differences but required 2 and 3 times more labour time, respectively, while the auger method estimated significantly lower (−23% and − 53%) total root biomass in the 2-year-old and 16-year-old plantation, respectively. Coarse and fine root biomass were significantly higher under the windrow than under the footpath zones. The simplified Voronoi trench method required twice as much labour time as the auger method but was most efficient way to estimate oil palm total root biomass, irrespective of the age of the plantation.

Selection of Entomopathogenic Fungi for the Biological Control of Demotispa neivai (Coleoptera: Chrysomelidae) in Oil Palm Plantations in Colombia

AbstractDemotispa neivai (Bondar) is an economically important pest of oil palm, Elaeis guineensis Jacq., plantations in Colombia. During our search for alternatives to conventional chemical insecticides for controlling D. neivai, we initially screened 50 isolates of various entomopathogenic fungi against adults and larvae. At a concentration of 1 × 107 conidia/ml, 28 of the isolates caused fungal-induced mortality. Isolates of Metarhizium anisopliae (Metchnikoff) Sorokin, designated CPMa1502 and CeMa9236, caused the greatest mortality in adults and larvae. These isolates were further evaluated for efficacy against natural infestations of D. neivai in oil palm fruit bunches by applying each isolate at a rate of 1 × 1013 conidia/ha. The CPMa1502 isolate caused a significantly (F = 39.22; df = 6, 8; P < 0.0001) higher larval mortality (87.7%) than that of the CeMa9236 isolate. Three concentrations (5 × 1012, 7.5 × 1012, and 1 × 1013 conidia/ha) of the CPMa1502 isolate were then compared in a field efficacy test, and no significant differences were observed among the treatments. CPMa1502 also was applied to commercial oil palm plantations in two tests at a rate of 1 × 1013 on a large plot with 23 palms and a rate of 5 × 1012 conidia/ha on a 511-palm plot. Larval mortality in these field tests was greater than 62%.

The Asean Way and Haze Mitigation Efforts

Transboundary haze pollution is an almost annual occurrence in Southeast Asia. Haze originates from peat and forest fires mostly in Indonesia, with Malaysia and Singapore suffering the worst of its effects. Most of these fires are manmade, and linked to land clearing activities of local and foreign commercial oil palm plantations. The regional nature of haze has concentrated mitigation activities at the ASEAN level. However these initiatives continually fail to effectively mitigate haze. This article argues that haze mitigation has been problematic due to the ASEAN style of regional engagement, which prioritizes the maintenance of national sovereignty. States are compelled to act in their national interests, as opposed to the collective regional interests. The economic importance of the oil palm sector to the states involved, coupled with traditionally close relationships between key economic actors and political elites, meant that the maintenance of the status quo, where major plantation companies could continue to clear land using the cost-effective method of burning, was of crucial national interest. Therefore, the ASEAN style of regional engagement has enabled member states to shape ASEAN initiatives to preserve the interests of these political and economic elite, while the public continue to suffer the haze.

El Niño–Southern Oscillation (ENSO) event reduces CO<sub>2</sub> uptake of an Indonesian oil palm plantation

Abstract. The El Niño–Southern Oscillation (ENSO) in 2015 was one of the strongest observed in almost 20 years and set the stage for a severe drought and the emergence of widespread fires and related smoke emission over large parts of Southeast Asia. In the tropical lowlands of Sumatra, which were heavily affected by the drought and haze, large areas of tropical rainforest have been converted into oil palm (Elaeis guineensis Jacq.) plantations during the past decades. In this study, we investigate the impact of drought and smoke haze on the net ecosystem CO2 exchange, evapotranspiration, yield and surface energy budget in a commercial oil palm plantation in Jambi province (Sumatra, Indonesia) by using micrometeorological measurements, the eddy covariance method, yield data and a multiple linear regression model (MLRM). With the MLRM we identify the contribution of meteorological and environmental parameters to the net ecosystem CO2 exchange. During the initial part of the drought, when incoming shortwave radiation was elevated, net CO2 uptake increased by 50 % despite a decrease in upper-layer soil moisture by 35 %, an increase in air temperature by 10 % and a tripling of atmospheric vapour pressure deficit. Emerging smoke haze decreased incoming solar radiation by 35 % compared to non-drought conditions and diffuse radiation almost became the sole shortwave radiation flux for 2 months, resulting in a strong decrease in net CO2 uptake by 86 %. Haze conditions resulted in a complete pause of oil palm net carbon accumulation for about 1.5 months and contributed to a decline in oil palm yield by 35 %. With respect to a projected pronounced drying trend over the western Pacific during a future El Niño, our model showed that an increase in drought may stimulate net CO2 uptake, while more severe smoke haze, in combination with drought, can lead to pronounced losses in productivity and net CO2 uptake, highlighting the importance of fire prevention.

Comparación in vitro de la capacidad invasiva de dos formulaciones a base de beauveria bassiana como control biológico de opsiphanes cassina

Opsiphanes cassina is the most common defoliating pest in the country’s commercial oil palm plantations, being responsible for low yields and the disappearance of large numbers of hectares of cultivation. The objective of this work was to evaluate in laboratory the invasive capacity of two formulations (powder and liquid presentation) based on Beauveria bassiana on the insect Opsiphanes cassina.Microbiological quality control tests showed germination percentages of B. bassiana spores for the solid formulation of 90% while in the liquid they were 97.7%. 100% purity was achieved for both formulations and the concentration of spores was 4.9x1010 spores/ml in the solid formulation and 8.6x1010 spores/ml in the liquid formulation. Concluding that the liquid formulation causes greater mortality in a smaller time (6 days) on the larvae of the III instar, being feasible its production and commercialization.

Selection of Entomopathogenic Nematodes to Control Nymphs of <i>Haplaxius crudus</i> (Van Duzee) (Hemiptera: Cixiidae)

<i>Haplaxius crudus</i> transmits the pathogen that causes Lethal wilt (ML for its name in Spanish), one of the main diseases that affects oil palms in Colombia. In its nymphal stage it feeds from grasses present at the plantations, and adults feed on oil palm leaves. With the objective of controlling the nymphal stage of <i>H. crudus</i>, the effectiveness of the following entomopathogenic nematodes was assessed: <i>Steinernema colombiense</i>, <i>S. websteri</i>, <i>Steinernema</i> sp. 1, <i>Steinernema</i> sp. 2, <i>Heterorhabditis bacteriophora</i>, <i>Heterorhabditis</i> sp. (Gua 31), <i>Heterorhabditis</i> sp. (Gua 236), <i>Heterorhabditis</i> sp. (CPHsp1301) and <i>Heterorhabditis</i> sp. (CPHsp1302). Pathogenicity was assessed under laboratory conditions using Petri dishes with roots of <i>Paspalum virgatum</i>. Virulence was assessed using mesh houses with PVC tubes and plastic trays with <i>P. virgatum</i>. Once the most virulent nematode was selected, three dosage levels were assessed under simulated field conditions, in order to select the most effective dosage. All assessed nematode species were pathogenic to nymphs of <i>H. crudus</i>, and nymph stage IV was the most susceptible stage, with death rates of over 80%. Regarding virulence, there were statistically significant differences among treatments (P≤0.05), producing nematode death rates between 28.3 and 88.2%. <i>Heterorhabditis</i> sp. (CPHsp1301), obtained from the soil of palm plantations, was selected because it caused a mortality rate of 78.4% with at a dosage of 1300 IJ/cm² in the sprayed area. The results are promising and further research should be performed under commercial oil palm plantation conditions.

Oil palm plantations vs. shifting cultivation for indigenous peoples: Analyzing Mizoram's New Land Use Policy

Mizoram state of Northeast India is referred to as ‘Bamboo Queen’ for its largest bamboo forest. It is becoming famous for country's first commercial oil palm plantations. The state's 90% of the population are diverse ethnic minority tribes otherwise identified as indigenous peoples, traditionally practicing jhum or shifting cultivation. In 2011, Mizoram implemented New Land Use Policy (NLUP) to formalize forestland titles that has been till date decentralized and managed by traditional laws. How the centralized NLUP brings change by replacing shifting cultivation through settled farming i.e. mainly palm oil plantation is examined here. The paper analyzes the NLUP using empirical data collected from focus group discussions and interviews of diverse stakeholders, including indigenous peoples of two districts: Kolasib, and Lai Autonomous District Council of Lawngtlai. The study result indicates even after the NLUP the bamboo forests are allocated for shifting cultivation. These abandoned lands are then promoted by the Agriculture Department for palm oil plantations. Gender dynamics is observed wherein women's roles become ‘submissive’ in settled cultivation of oil palm as compared to their contribution in shifting cultivation. Private palm oil companies do not collect fruits from farmers living away from motorable roads, which pushes men to do daily-wage labour work, and women to do artisanal palm oil extraction at home. The key recommendations for implementing the NLUP are (a) introduce the RSPO sustainable certificate for palm oil, (b) acknowledges indigenous system of land-use for conservation and gender equity, and (c) prioritizing household land titling as well community land tenure.

Textural measures for estimating oil palm age

ABSTRACTIn oil palm management, age is one of the yield determinant factors. The conventional field investigations are often exhaustive and costly methods when implemented on a large scale. Despite much attention to classify individual oil palm ages by using various remote sensing images, none of the studies depicted satisfying overall accuracies. The overall aim of this study was to optimize window size and number of texture measurements for oil palm ages classification. The study was conducted in a commercial oil palm plantation comprised of palms of multiple ages planted from 1991 to 2008. Three Satellite Pour l’Observation de la Terre (SPOT)-5 multispectral images, acquired on 12 April 2012, 4 April 2013, and 14 April 2014, were evaluated. The individual ages were successfully classified with accuracy ranging from 59% to 97%, with an average overall accuracy of 84%. The results illustrated that the largest window size related to the smallest oil palm planting block in the study area, 390 m × 390 m on-the-ground window size, and seven combination of texture measurements, resulted in the highest classification overall accuracy. The utilization of texture measurements produced synergistic effects able to discriminate the oil palm age, with mean, entropy, homogeneity, and angular second moment as among the significant textures.

Termite Associated to Oil Palm Stands in Three Types of Soils in Ladang Endau Rompin, Pahang, Malaysia

Termites are found in various habitats, particularly diverse communities occurring in tropical forest and peatlands. Termites are beneficial insects, which function as soil engineers, improving the soil quality. However, in peatlands converted to commercial oil palm plantations, they are considered as pests. There is lack of studies on termite communities in converted peatlands in Peninsular Malaysia. Thus, this study investigated termite species associated with oil palm stands in three soil types (clay, shallow peat and deep peat) in Endau Rompin Plantation. The stand scouting method was used to record the numbers and types of termites associated with palm trees in the individual stands on different soil types. A total of 29 termite species associated with the palm stands were identified morphologically. All the species belonged to the families Rhinotermitidae and Termitidae. Twenty-three of the 29 species were found in the shallow peat, 16 in clay soil and 15 in deep peat. The community structure was synthesized by two-way cluster analysis with Sorensen (Bray Curtis) distance measure. Five termite groups associated with two soil types (clay soil and shallow/deep peat) were generated. Moisture levels and organic content were likely to determine the presence of soil feeders identified in the presence study. This study provides information on the status of termite species in oil palm plantation areas. Such information may be useful in future planning strategies by the plantation management.

Using Bayesian networks to predict future yield functions with data from commercial oil palm plantations: A proof of concept analysis

Bayesian networks were used to predict yield functions from three commercial oil palm estates. The networks were trained using a range of environmental, agronomic and management data routinely collected during plantation management. The Bayesian networks predicted fruit yield (FFB), average weight of fruit bunches (ABW) and average bunch number per hectare (BUNCH_HA). Comparing the predictions of most probable yield against observed data showed the Bayesian networks were highly accurate, with r2 values between 0.6 and 0.9. Predictions for attaining specific yield targets exceeded 75% accuracy for the FFB, 85% for the BUNCH_HA, and 90% for the ABW function. Supplementary analysis compared the precision of the Bayesian networks with artificial neural networks (ANNs), and demonstrated that the Bayesian networks gave equivalent or superior accuracy for every test. The utility of the networks were demonstrated by predicting the probability of achieving above average yield functions for each block across the three estates using a set of hypothetical rainfall and fertiliser input scenarios during the year prior to harvest. For the majority of blocks, the probability of exceeding the yield target depended on the level of fertiliser and rainfall inputs received, indicating that production from these blocks is greatly influenced by prior rainfall and fertilizer. However, some blocks in favourable areas showed a very high probability of exceeding the mean yields at all rainfall and fertiliser inputs, while a number of other blocks showed a consistently low probability of achieving the same productivity; production from these blocks will be resistant to the effects of historic rainfall and fertiliser inputs. The ability of Bayesian networks to represent future yield expectations will greatly assist managers under pressure to improve the economic and environmental sustainability of plantations. The demonstration that machine learning can extract important insight from complex datasets will have broad application in the analysis of big data collected from oil palm as well as other agricultural industries.

DIFFERENTIAL PROTEOMIC STUDY OF OIL PALM LEAVES IN RESPONSE TO IN VITRO INOCULATION WITH PATHOGENIC AND NON-PATHOGENIC GANODERMA spp.

Basal stem rot is an aggressive disease in oil palm caused by Ganoderma species. The disease threatens the commercial oil palm plantations of South East Asia, especially in Malaysia. In order to understand the mechanism involved in the early stage of interaction between Ganoderma spp. and its host at systemic level, proteomic analysis of oil palm leaves was conducted on protein samples collected over 72 hours during inoculation with pathogenic Ganoderma boninense and non-pathogenic Ganoderma tornatum. A total of 82 proteins resolved during two-dimensional gel electrophoresis with significant differences in the spot abundance. However, only 24 differentially expressed proteins in response to Ganoderma spp. inoculations were successfully identified by mass spectrophotometry as compared to the non-inoculated control. These proteins are mainly involved in photosynthesis, signalling, stress/defense, energy and metabolism regulation. Changes in relative abundance of these proteins suggest an important role in disease susceptibility. Most proteins showed altered abundance in response to both G. boninense and G. tornatum, while some proteins were only affected by either G. boninense or G. tornatum. The putative role of the identified proteins in oil palm leaves during the interaction with both Ganoderma spp. is discussed.

Palm Weevil Pheromones - Discovery and Use.

Male-produced aggregation pheromones of seven major pest species of weevils in the subfamily Rhynchophorinae have been identified as a closely related set of methyl-branched secondary alcohols. Although the weevils produce only one stereoisomer of these alcohols, no instances of isomeric inhibition have been observed, enabling stereoisomeric mixtures to be used in traps. Addition of fermenting plant material to traps synergizes attraction of weevils to the pheromones. The weevils are large, have long life cycles, and are strong fliers. These characteristics make mass trapping a suitable tactic to add to existing management strategies. When coupled with good phytosanitary practices, mass trapping of Rhynchophorus palmarum at 1 trap/5-ha significantly lowered the incidence of red ring nematode infection vectored by the weevil in commercial oil palm plantations in the Americas. Similarly, trap densities of 1-10 traps/ha have significantly lowered R. ferrugineus infestation of date palm throughout the Middle East. Although management of R. ferrugineus in urban areas is more problematic, trapping is an integral part of most programs aimed at protection of ornamental Canary palms in Europe. Overall, semiochemically-based management of these large weevils is now a mature and usually economically feasible control technology.

Patronage politics, plantation fires and transboundary haze

Since 1982, haze pollution has become an almost annual occurrence in Southeast Asia, with the worst episodes being in the period of 1997–1998 and in 2006–2007. Haze originates from peat and forest fires, mostly in Indonesia. The negative effects of haze can be observed at the global level, with increased carbon emissions exacerbating climate change, and more importantly at the regional level, with serious environmental and socioeconomic effects in Indonesia and its neighbouring countries. Most of these fires are manmade, and can be traced back to land-clearing activities of commercial oil palm plantations. This article questions why these companies have been able to burn with such impunity, even though using fire for land clearing is against Indonesian law. It argues that local and foreign plantation companies have cultivated strong patronage linkages with key patrons among the ruling elite. Hence, patrons are encouraged to protect their clients from the repercussions of their actions. This weakens the power of the state in terms of law enforcement, where national laws against the use of fire are thus rendered useless in the face of powerful economic interests. Well-connected companies therefore continue to use fire as a cost-efficient way to clear land while disregarding its serious environmental and socioeconomic implications.

Regional cooperation, patronage and the ASEAN Agreement on transboundary haze pollution

Transboundary haze pollution is an almost annual occurrence in Southeast Asia. Haze originates from peat and forest fires mostly in Indonesia, with Malaysia and Singapore suffering the worst of its effects. Most of these fires are man-made and linked to land-clearing activities of local and foreign commercial oil palm plantations. The regional nature of the haze has resulted in a concentration of haze mitigation activities at the Association of Southeast Asian Nations (ASEAN) level. However, these initiatives continually fail to effectively mitigate haze. This article argues that this failure is due to the influence of patronage politics in the sector, which is linked to the ASEAN style of regional engagement that prioritises the maintenance of national sovereignty. States are compelled to act in their national interests, as opposed to the collective regional interests. The economic importance of the oil palm sector to the states involved, coupled with the political importance of the clients populating this sector to elite patrons in the governments, meant that the maintenance of the status quo, where clients could continue to clear land using fire, was of crucial national interest. Therefore, the ASEAN style of regional engagement has enabled political elites to shape ASEAN initiatives to preserve the interests of their clients, while the public continue to suffer the haze. This article demonstrates this through a close analysis of the negotiations, outcomes and the implementation of the ASEAN Agreement on transboundary haze pollution, with a special focus on Indonesia’s decision to withhold ratification of the treaty.

Stakeholders' incentives for land-use change and REDD +: The case of Indonesia

The opportunity costs of Reducing Emissions from Deforestation and Forest Degradation (REDD+) accruing to different stakeholders in Indonesia, including companies and the national, provincial and district level governments, are estimated, with particular emphasis on the influence of alternative discount rates. A cost–benefit analysis of the opportunity costs of avoided deforestation is conducted. The three major land-use activities considered are commercial logging, timber and oil palm plantation. The opportunity cost of oil palm plantations on mineral soil preceded by logging of degraded forest is prohibitively high. REDD+ measures that impose restrictions on the development of those land-use activities would lead to a substantial loss of public revenues at the various government levels. The results of this study reveal that land-use management in Indonesia is rather centralistic, where the national government retains most of the revenues from land-use alternatives to REDD+. To influence their behaviour towards land-use change, REDD+ schemes need to create a direct link between the distribution of public revenues and district governments' decisions on land-use activities in their localities.

Patronage politics as a driver of economic regionalisation: The Indonesian oil palm sector and transboundary haze

Abstract: Recent evidence has linked illegal peat and forest fires in Indonesia to commercial oil palm plantations. Fire is the most cost‐efficient way to clear land for planting, but these fires release smoke causing transboundary haze pollution. The countries worst affected by the haze are neighbouring Malaysia and Singapore. Malaysian and Singaporean investors control more than two‐thirds of the Indonesian oil palm plantation sector and they have been implicated in the fires alongside local plantations. Using information obtained from interviews with individuals linked to the sector, this paper aims to explain why these companies continue to burn despite the dire consequences of the haze. It identifies patronage politics as a common business culture in Southeast Asia, and argues that because these Malaysian and Singaporean investors are already familiar with patronage practices at home, they have easily inserted themselves into existing patronage networks in Indonesia. Hence, these companies enjoy the protection of their Indonesian patrons during their operations. Furthermore, in a business atmosphere defined by patronage politics, clients are largely motivated by material gain. This explains why Malaysian and Singaporean investors continue to clear land by fire in the interests of cost‐efficiency, despite their home countries suffering the worst effects of haze.

Scale-Dependent Effects of a Heterogeneous Landscape on Genetic Differentiation in the Central American Squirrel Monkey (Saimiri oerstedii)

Landscape genetic studies offer a fine-scale understanding of how habitat heterogeneity influences population genetic structure. We examined population genetic structure and conducted a landscape genetic analysis for the endangered Central American Squirrel Monkey (Saimiri oerstedii) that lives in the fragmented, human-modified habitats of the Central Pacific region of Costa Rica. We analyzed non-invasively collected fecal samples from 244 individuals from 14 groups for 16 microsatellite markers. We found two geographically separate genetic clusters in the Central Pacific region with evidence of recent gene flow among them. We also found significant differentiation among groups of S. o. citrinellus using pairwise FST comparisons. These groups are in fragments of secondary forest separated by unsuitable “matrix” habitats such as cattle pasture, commercial African oil palm plantations, and human residential areas. We used an individual-based landscape genetic approach to measure spatial patterns of genetic variance while taking into account landscape heterogeneity. We found that large, commercial oil palm plantations represent moderate barriers to gene flow between populations, but cattle pastures, rivers, and residential areas do not. However, the influence of oil palm plantations on genetic variance was diminished when we restricted analyses to within population pairs, suggesting that their effect is scale-dependent and manifests during longer dispersal events among populations. We show that when landscape genetic methods are applied rigorously and at the right scale, they are sensitive enough to track population processes even in species with long, overlapping generations such as primates. Thus landscape genetic approaches are extremely valuable for the conservation management of a diverse array of endangered species in heterogeneous, human-modified habitats. Our results also stress the importance of explicitly considering the heterogeneity of matrix habitats in landscape genetic studies, instead of assuming that all matrix habitats have a uniform effect on population genetic processes.