Mapping the global distribution of pollinator-dependence in wild and cultivated plants

Plant-pollinator interactions represent a mutualistic relationship of global importance, contributing to the reproduction of most of the world's vascular plants. However, a range of drivers such as climate change and increased land-use intensity are contributing to observed declines in global pollinator numbers. The risk of this decline to both ecosystems and human-wellbeing remains unclear, despite observed cases of pollen limitation in ecosystems and crop systems. Pollen-limited natural vegetation can lead to habitat degradation, impacting biodiversity and regulatory ecosystem services, whilst pollen-limited crops can result in crop shortages, threatening food security. Global, spatial models of pollinator-dependence in plants are required to identify where vegetation is most vulnerable to becoming pollen-limited if pollinators decline.

We take a dataset of measured pollinator-dependence values and use it to phylogenetically model the pollinator-dependence of 159,366 wild plant species, using and testing an assumption that pollinator-dependence can be inferred from species relatedness. We pair this with species distribution maps and pollinator-dependence data for 98 crops to generate a global, spatially explicit, dataset of pollinator-dependence in both wild and cultivated plants at a 20 km resolution.

We find that natural vegetation has a global average pollinator-dependence of 0.51 (0 = pollinator-independent, 1 = complete pollinator-dependence). This rises to approach 0.70 in the tropics, and tropical forests specifically. The Amazon Basin and the Indonesian Archipelago emerge as geographical hotspots of high pollinator-dependence in natural vegetation. We show that areas that have higher numbers of plant species, tend to have a higher average pollinator-dependence. Additionally, we see many pollinator-dependent crops, such as coffee and cocoa, being grown in areas where adjacent ecosystems are highly pollinator-dependent. We also find that approximately half of the global human population lives close to pollinator-dependent natural vegetation.

This study offers an insight into global trends of pollinator-dependence in wild and cultivated plants, and explores how the risk of a global pollinator decline to biodiversity and human well-being may be spatially uneven. Our dataset allows for pollinator-dependence to be incorporated into spatially explicit ecosystem models, allowing for further work aimed at understanding the relative importance of pollinators in limiting the growth of plant populations at a global scale.