A recent study, led by Michelle Larkin and Dara Stanley and published in Basic and Applied Ecology, has shed new light on the intricate relationship between local grassland management and biodiversity. The researchers specifically investigated the impact of results-based agri-environmental payment schemes (RBAPSs) on plant-pollinator interaction networks.
RBAPSs are incentivising programs that financially reward farmers for managing their land in a way that enhances biodiversity. While these schemes have been observed to improve plant diversity, their influence on plant-pollinator interactions – crucial relationships that drive plant reproduction and ecosystem stability – was previously unclear.
The team sampled networks across 23 grasslands in the West of Ireland, analysing parameters such as network size, connectance, nestedness, and linkage density. These are measures of the structure, complexity, and stability of interaction networks.
Their results indicate that grasslands under RBAPSs hosted larger and more complex interaction networks, suggesting a healthier and more resilient ecosystem. Notably, these beneficial effects were amplified when the grasslands were embedded in landscapes with a higher proportion of semi-natural grassland.
Perhaps most strikingly, they found that different pollinator groups, such as bumblebees, solitary bees, hoverflies, and butterflies, favoured different key plant species. In their article Larkin and Stanley write:
There were several key plant species identified for each pollinator group. Centaurea nigra was an important forage source for bumblebees and butterflies while members of the Ranunculaceae and Asteraceae were popular among solitary bees and hoverflies. While each pollinator group did differ in what plant species they found attractive, many of the plant species had open floral structures with shallow corollas making it easier to access pollen and nectar for solitary bees, short-tongued bumblebees and hoverflies with a short proboscis (Rotheray & Gilbert, 2011; Wood, Holland, & Goulson, 2017). However, even bumblebees with long tongues that are closely associated with members of the Fabaceae (Goulson, Hanley, Darvill, Ellis, & Knight, 2005) also commonly visited C. nigra. Warzecha et al. (2018) found that the presence of certain key plant species was more attractive to bumblebees and hoverflies than the overall species richness of wildflower seed mixes commonly used to establish wildflower strips for pollinating insects in agri-environmental schemes.Larkin & Stanley 2023.
These findings highlight the value of managing grasslands to promote plant diversity at local and landscape scales. It is a valuable insight for conservation strategies aiming to preserve biodiversity and maintain ecological stability, particularly given the rising threats posed by habitat fragmentation and agricultural intensification. The ecologists conclude:
Based on these findings, it is recommended that future RBAPS developments should aim to provide diverse and abundant key plant species at local scale and adopt metrics to promote semi-natural grassland restoration and conservation within the wider landscape like measuring the area of semi-natural grassland across farmland (Öckinger et al., 2007). These approaches will help to ensure that the structure and stability of networks and the vital ecosystem services they provide will be preserved throughout the agricultural landscape.Larkin & Stanley 2023.
READ THE ARTICLE
Larkin, M. and Stanley, D.A. (2023) “Impacts of local and landscape grassland management on the structure of plant-pollinator networks,” Basic and Applied Ecology, 70, pp. 50–59. Available at: https://doi.org/10.1016/j.baae.2023.04.003.