Rainforest conversion to smallholder cash crops leads to varying declines of beetles (Coleoptera) on Sumatra

Abstract

Southeast Asian arthropod biodiversity is in rapid decline, but the variability of responses within taxa has received little attention. Using canopy fogging, we collected ~50,000 beetles (Coleoptera) in (1) lowland rainforest, (2) jungle rubber (rubber agroforest), and smallholder monoculture plantations of (3) rubber and (4) oil palm in Sumatra, across two landscapes and seasons. On average, beetle abundance was more than 50%, and biomass over 75%, lower in rubber and oil palm plantations than in rainforest and jungle rubber. This pattern was influenced by landscape and season. Abundance and biomass declines were similar in Chrysomelidae, Elateridae, and Staphylinidae, but differed in Curculionidae, which were most abundant in oil palm due to the introduced oil palm pollinator Elaeidobius kamerunicus. Across beetle families, species richness in monocultures was reduced by at least 70% compared to rainforest, with beetle richness in jungle rubber being similar to rainforest. Community composition in oil palm plantations differed markedly from the other land‐use systems for Chrysomelidae and Curculionidae, but less for Elateridae and Staphylinidae. Turnover contributed more to overall beta diversity than nestedness for all families and land‐use systems. Likely undersampling of the beetle community in rainforest suggests that declines of beetle density and diversity are much more severe than reported here, especially for beetle families with many concealed species, such as Staphylinidae. This study provides first evidence that negative responses of beetles to tropical land‐use change vary among families, and is the first report of its kind from heavily understudied Sumatra. Abstract in Indonesia is available with online material.

Rainforest conversion to plantations fundamentally alters energy fluxes and functions in canopy arthropod food webs

“…On the other hand, abundance and biomass of some herbivorous taxa, such as Lepidoptera and Curculionidae, were not reduced in oil palm plantations. This is likely due to specialized herbivore species that thrive in oil palm plantations, such as red palm weevils, bagworms and nettle caterpillars, and to the introduced curculionid pollinatorElaeidobius kamerunicus , which is the dominating curculionid species in oil palm plantations in our study region (Greathead 1983;Kasmiatun et al 2022).…”

“…Studies on canopy arthropod groups such as ants, beetles, spiders and parasitoid wasps suggest substantial decline in species diversity, density and biomass if rainforest is converted into rubber and oil palm plantations (Nazarreta et al 2020;Azhar et al 2022;Kasmiatun et al 2022;Ramos et al 2022). Evaluating associated changes in energy fluxes may help to understand functional consequences of this decline (Barnes et al 2014;Zhou et al 2022).…”

Rainforest conversion to plantations fundamentally alters energy fluxes and functions in canopy arthropod food webs

“…Studies on canopy arthropod groups such as ants, beetles, spiders and parasitoid wasps suggest substantial decline in species diversity, density and biomass if rainforest is converted into rubber and oil palm plantations (Azhar et al, 2022;Kasmiatun et al, 2022;Nazarreta et al, 2020;Ramos et al, 2022). Evaluating associated changes in energy fluxes may help to understand functional consequences of this decline (Barnes et al, 2014;Zhou et al, 2022).…”

Response of arboreal Collembola communities to the conversion of lowland rainforest into rubber and oil palm plantations

“…The canopy of tropical rainforests represents one of the most complex habitats on earth and harbors exceptionally diverse communities of invertebrates, in particular insects [15][16][17]. However, most studies investigating these communities in detail have focused on arthropod taxa of rather large body size, such as cockroaches [18], beetles [19,20], ants [21][22][23], homopterans [24], spiders [25,26] and butterflies [27][28][29], but ignored less conspicuous taxa such as springtails (Collembola).…”

“…We used detailed (morpho)species level data to examine changes in the community composition of arboreal Collembola associated with the conversion of rainforest into plantation systems at the landscape scale and analyzed climatic variables to determine potential driving factors. Based on previous findings on other taxa in the same research framework [20,22,23,25,26,29,[53][54][55][56], we tested the following hypotheses: (1) Rainforest conversion to agroforestry systems and monocultures of rubber and oil palm are associated with a decline in abundance and diversity of arboreal Collembola. (2) The arboreal Collembola community in the jungle rubber agroforest is similar to that in the rainforest.…”