Ecosystem restoration strengthens pollinator network resilience and function

Human activities often have damaging effects on biodiversity and ecosystem functions, but whether the targeted manipulation of ecological communities can successfully mitigate and reverse these impacts is the subject of much debate. This new research assesses the effect of one form of restoration—the removal of all alien plant species—on the structure and function of plant–pollinator networks in mountain-top communities in the Seychelles.

Vegetation restoration leads to a marked increase in the number of pollinator species and pollinator visits to flowers. There is also an increase in the diversity of pollinator interactions and, importantly, the pollination of fruit crops and native plants. The findings suggest that the degradation of ecosystem functions, in this case pollination, is at least partly reversible.

Land degradation results in declining biodiversity and the disruption of ecosystem functioning worldwide, particularly in the tropics. Vegetation restoration is a common tool used to mitigate these impacts and increasingly aims to restore ecosystem functions rather than species diversity. However, evidence from community experiments on the effect of restoration practices on ecosystem functions is scarce.

Pollination is an important ecosystem function and the global decline in pollinators attenuates the resistance of natural areas and agro-environments to disturbances. Thus, the ability of pollination functions to resist or recover from disturbance (that is, the functional resilience) may be critical for ensuring a successful restoration process.

Here we report the use of a community field experiment to investigate the effects of vegetation restoration, specifically the removal of exotic shrubs, on pollination. We analyse 64 plant–pollinator networks and the reproductive performance of the ten most abundant plant species across four restored and four unrestored, disturbed mountaintop communities.

Ecosystem restoration resulted in a marked increase in pollinator species, visits to flowers and interaction diversity. Interactions in restored networks were more generalized than in unrestored networks, indicating a higher functional redundancy in restored communities. Shifts in interaction patterns had direct and positive effects on pollination, especially on the relative and total fruit production of native plants.

Pollinator limitation was prevalent at unrestored sites only, where the proportion of flowers producing fruit increased with pollinator visitation, approaching the higher levels seen in restored plant communities. Our results show that vegetation restoration can improve pollination, suggesting that the degradation of ecosystem functions is at least partially reversible.

The degree of recovery may depend on the state of degradation before restoration intervention and the proximity to pollinator source populations in the surrounding landscape. We demonstrate that network structure is a suitable indicator for pollination quality, highlighting the usefulness of interaction networks in environmental management

Download full paper from Nature.

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