Predicted thresholds for levels of natural vegetation that safeguard pollinator services

24 The conversion of natural vegetation into cultivated land can cause pollinator declines and 25 thereby degrade pollination services to crops and wildflowers. The effect of landscape 26 composition on pollinator abundance is well established, but its impact on pollination intensity 27 and crop yield is not fully resolved. We therefore studied pollination of two crops in India, 28 brinjal (Solanum melongena) and mustard (Brassica nigra), along a landscape-scale gradient 29 in habitat transformation from forest-dominated natural vegetation to intensive cultivation. 30 We quantified the pollination requirements (pollen receipt-seed set relationships) of the crops 31 and the levels of pollen delivery by their principal pollinators, bees. Combining these with 32 field surveys of pollinator abundance, we modelled the levels of pollination service to fields 33 along the landscape gradient. Projected pollination services declined as the area occupied by 34 natural vegetation decreased. We identified thresholds at which bee pollination no longer 35 supported maximum seed set, which were landscapes with approximately one quarter (27%) 36 of nearby natural vegetation for brinjal fields and one fifth (18%) for mustard. Our findings 37 indicate that preserving or restoring the cover of natural habitats above these minimum 38 thresholds could be a valuable strategy for maintaining pollinator abundance and safeguarding 39 yield in these bee-pollinated crops. 40