From rainforest to plantation: conversion shapes food webs and biodiversity

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 (Image: Pixabay CC0)
(Image: Pixabay CC0)

Research team investigates effects of changing land use on ecosystems in Sumatra

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Every day, large areas of rainforest are converted into plantations. Biodiversity and the ecosystem are changing drastically as a result. However, knowledge about the consequences is patchy: previous studies have either focused on the diversity of species or the functioning of the ecosystem. Now an international research team led by the Universities of Göttingen and Bogor (Indonesia) has combined both aspects in one study. The researchers recorded animal communities ranging from microscopic mites in the soil to birds in the treetops and analyzed food webs in the rainforest and on rubber and oil palm plantations in Sumatra, Indonesia. Their study is the first to shed light on the transfer of energy between the animals of the soil and the tree canopy in tropical ecosystems, which are particularly species-rich. It shows that the conversion of rainforest into plantations fundamentally changes the food webs. The results were published in the scientific journal Nature.

The researchers compared 32 locations in the rainforest and on plantations with regard to the occurrence of animals and plants as well as the functioning of the food webs based on their trophic structure, biomass and energy flows. They used a variety of methods to collect data on the species with their respective numbers of individuals and their biomass: arthropods of the treetops such as insects and spiders were determined by fogging, birds by sound recordings and observation and arthropods of the soil and earthworms from soil cores. The researchers then analyzed the data using models that take into account characteristics such as the animals’ body size and diet. In this way, they reconstructed the food webs for each site and each animal community. The results served as a measure of the distribution of energy and the consumption of resources such as plants, animals, fungi and bacteria in food webs above and within the soil. This approach allows conclusions to be drawn about the contribution of animals to decomposition processes and their importance as predators of, for example, caterpillars and beetles.

According to the study, most of the energy in the animal communities in the rainforest flowed to the arthropods in the food web on the ground. On plantations, however, the energy was distributed differently: the food webs in the treetops were less rich and less complex. The food webs in the soil were also altered. Instead of a diverse community of arthropods, invasive earthworm species dominated, shaping the flow of energy through the entire food web. According to the researchers, this explains why there were only a few predators on the plantations studied, but relatively many herbivorous insects such as caterpillars and beetles.

-It’s fascinating how all these organisms are connected, from tiny arthropods to birds, from the ground to the treetops. These connections need to be explored across the different parts of the ecosystem. Especially the biodiversity in the soil beneath our feet requires more attention," says first author Dr. Anton Potapov, who was employed at the University of Göttingen during the data collection and subsequently at the German Centre for Integrative Biodiversity Research (iDiv).

-The progressive conversion of rainforest into plantations is not only leading to a massive decline in biodiversity. It also changes the way these ecosystems function," emphasizes Stefan Scheu, who heads the Department of Animal Ecology at the University of Göttingen and supervised the study. -For the sustainable management of converted ecosystems, we need to understand the effects on the interconnected components within them. Then a more holistic approach can be developed to promote the functioning of ecosystems above and below ground.

The research was funded by the German Research Foundation (DFG) as part of the Collaborative Research Center (990) -Ecological and socio-economic functions of tropical lowland rainforest transformation systems EFForTS. Researchers from the Universities of Hohenheim, Bern and Cambridge were also involved in the study.

Original publication: Potapov, A.M. et al.Rainforest transformation reallocates energy from green to brown food webs. Nature (2024). DOI: 10.1038/s41586’024 -07083-y