Anthropogenic habitat change is a major driver of species extinctions and altered species communities worldwide. These changes are particularly rapid in the tropics, where logging of rainforests and conversion to agricultural habitats is widespread. Because species have varying effects on their abiotic 2 environment, we expect shifts in species composition to drive changes in ecosystem processes. One important ecosystem process is animal-driven bioturbation: the turnover of soil material by soil-dwelling organisms. We developed a protocol for measuring aboveground bioturbation, and assessed how bioturbation rates and standing amounts of aboveground bioturbated soil change as primary tropical rainforests are logged and converted to oil palm plantation. By identifying the animals that created soil structures, we assigned bioturbation activity to different soil-dwelling groups. Across all habitats, most standing bioturbated soil was generated by termites (97.0%), while short-term, small-scale bioturbation was mainly generated by earthworms (87.3%). The species diversity of social insects (ants and termites) involved in bioturbation was higher in primary forest than in either logged forest or oil palm plantation. However, neither standing bioturbated soil, nor short-term bioturbation rate differed among habitats. Unexpectedly, in primary forest, high levels of bioturbation were associated with low bioturbator diversity. This was because two termite species, where present, conducted nearly all bioturbation. There was no relationship between levels of bioturbation and diversity in the other habitats. Our results emphasize the importance, across all habitats, of termites for generating standing aboveground soil structures, and earthworms for short-term soil turnover. In oil palm plantation, bioturbation relies on a smaller number of species, raising concerns about future environmental change and consequent species loss.

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Context Intact tropical rainforests are considered robust to plant invasions. However, land-use change alters the structure and species composition of native forest, opening up tropical landscapes to invasion. Yet, the relative roles of key drivers on tropical forest invasions remain little investigated. Objectives We examine factors affecting plant invasion of rainforest remnants in oil-palm dominated landscapes in Sabah, Malaysian Borneo. We hypothesized that invasion is greater in highly fragmented landscapes, and in disturbed forests with lower native plant diversity (cf. old-growth rainforests). Methods Native and exotic plants were surveyed in 47 plots at 17 forest sites, spanning gradients in landscape-scale fragmentation and local forest disturbance. Using partial least squares path-modelling, we examined correlations between invasion, fragmentation, forest disturbance, propagule pressure, soil characteristics and native plant community. Results We recorded 6999 individuals from 329 genera in total, including eight exotic species (0-51% of individuals/plot, median = 1.4%) representing shrubs, forbs, graminoids and climbers. The best model (R 2 = 0.343) revealed that invasion was correlated with disturbance and propagule pressure (high prevalence of exotic species in plantation matrix), the Electronic supplementary material The online version of this article (

Many companies have made zero-deforestation commitments (ZDCs) to reduce carbon emissions and biodiversity losses linked to tropical commodities. However, ZDCs conserve areas primarily based on tree cover and aboveground carbon, potentially leading to the unintended consequence that agricultural expansion could be encouraged in biomes outside tropical rainforest, which also support important biodiversity. We examine locations suitable for zero-deforestation expansion of commercial oil palm, which is increasingly expanding outside the tropical rainforest biome, by generating empirical models of global suitability for rainfed and irrigated oil palm. We find that tropical grassy and dry forest biomes contain >50% of the total area of land climatically-suitable for rainfed oil palm expansion in compliance with ZDCs (following the High Carbon Stock Approach; in locations outside urban areas and cropland), and that irrigation could double the area suitable for expansion in these biomes. Within these biomes, ZDCs fail to protect areas of high vertebrate richness from oil palm expansion. To prevent unintended consequences of ZDCs and minimise the environmental impacts of oil palm expansion, policies and governance for sustainable development and conservation must expand focus from rainforests to all tropical biomes.

Background Oil palm is a key driver of deforestation, but increasing yields in existing plantations could help meet rising global demands, while avoiding further conversion of natural habitat. Current oil palm plantations present substantial opportunities for sustainable intensification, but the potential for local yield improvements depends partly on the role of climate in determining yield. Methods We determine the importance of local climatic conditions for oil palm yields in 12 commercial plantations in Peninsular and East Malaysia (Borneo), during 2006–2017. We quantify relationships between climatic conditions (raw and anomalised monthly temperature and rainfall data) and yield for lag times up to 36 months prior to harvest, corresponding to key stages in oil palm fruit development. Results Overall, climatic conditions explained < 1% of the total variation in yield. In contrast, variation in yield among plantations accounted for > 50% of the explained variation in yield (of total R2 = 0.38; median annual fresh fruit bunch yield 16.4–31.6 t/ha). The main climatic driver of yield was a positive effect of maximum monthly temperature during inflorescence development (Spearman’s Rho = 0.30), suggesting that insufficient solar radiation is the main climatic constraint to yield in our study sites. We also found positive impacts of rainfall during key stages of fruit development (infloresence abortion and sex determination: Spearman’s Rho 0.06 and 0.08 respectively, for rainfall anomalies), suggesting minor effects of water-limitation on yield; and a negative impact of maximum temperature during the month of harvest (Spearman’s Rho – 0.14 for temperature anomalies), suggesting possible heat stress impacts on plantation workers. Conclusions Our findings imply a relatively minor role of climate in determining yield, and potentially substantial yield gaps in some commercial plantations in Malaysia (possibly up to ~ 50%). Thus, there appear to be substantial opportunities for improving oil palm yield in existing plantations in Malaysia, with further research needed to identify the drivers of such yield gaps.