No abstract

Urbanization has been identified as one of the main drivers of biodiversity decline and biotic homogenization worldwide (Faeth et al., 2011;McKinney, 2006). The accelerating expansion of urban areas leads to severe land-use changes and can affect biodiversity and ecosystem functions in persistent ways through habitat degradation or destruction, urban warming and pollution (Grimm et al., 2008;McKinney, 2008). Moreover, cities are growing at an exponential rate with already half of the world population considered as urban dwellers (United Nations, 2018). On top of that, current projections estimate that this number will further increase to reach 68% by 2050

Urbanization poses a major threat to biodiversity and food security, as expanding cities, especially in the Global South, increasingly compete with natural and agricultural lands. However, the impact of urban expansion on agricultural biodiversity in tropical regions is overlooked. Here we assess how urbanization affects the functional response of farmland bees, the most important pollinators for crop production. We sampled bees across three seasons in 36 conventional vegetable‐producing farms spread along an urbanization gradient in Bengaluru, an Indian megacity. We investigated how landscape and local environmental drivers affected different functional traits (sociality, nesting behavior, body size, and specialization) and functional diversity (functional dispersion) of bee communities. We found that the functional responses to urbanization were trait specific with more positive than negative effects of gray area (sealed surfaces and buildings) on species richness, functional diversity, and abundance of most functional groups. As expected, larger, solitary, cavity‐nesting, and, surprisingly, specialist bees benefited from urbanization. In contrast to temperate cities, the abundance of ground nesters increased in urban areas, presumably because larger patches of bare soil were still available beside roads and buildings. However, overall bee abundance and the abundance of social bees (85% of all bees) decreased with urbanization, threatening crop pollination. Crop diversity promotes taxonomic and functional diversity of bee communities. Locally, flower resources promote the abundance of all functional groups, and natural vegetation can maintain diverse pollinator communities throughout the year, especially during the noncropping season. However, exotic plants decrease functional diversity and bee specialization. To safeguard bees and their pollination services in urban farms, we recommend (1) preserving seminatural vegetation (hedges) around cropping fields to provide nesting opportunities for aboveground nesters, (2) promoting farm‐level crop diversification of beneficial crops (e.g., pulses, vegetables, and spices), (3) maintaining native natural vegetation along field margins, and (4) controlling and removing invasive exotic plants that disrupt native plant–pollinator interactions. Overall, our results suggest that urban agriculture can maintain functionally diverse bee communities and, if managed in a sustainable manner, be used to develop win–win solutions for biodiversity conservation of pollinators and food security in and around cities.

Agricultural intensification and land‐use changes are major factors impacting farmland biodiversity. The Ortolan Bunting Emberiza hortulana is the long‐distance trans‐Saharan migratory passerine that has undergone the most dramatic decline among all European farmland birds. The factors responsible for this decline may originate from the breeding grounds, migration stopovers and/or overwintering quarters. Very little is known about conditions on the species' wintering grounds, but a recent study has highlighted the utmost importance of the traditionally managed agroecosystems in the Ethiopian Highlands as a key wintering area, apparently harbouring as much as 90% of the world's Ortolan Bunting population. Using radiotracking and line transect surveys, this study aimed to provide fine‐grained information about species–habitat relationships in the Ortolan Bunting overwintering quarters. Our results showed the importance, at the landscape scale, of small‐scale agriculture, notably of traditionally managed, cereal‐dominated fields interspersed with semi‐natural structures. At a foraging‐site scale, on the other hand, patches of bare ground in combination with large areas of post‐harvesting stubble represented key habitat features. Stubbles provide an essential food resource and bare ground promotes ground foraging by enhancing food accessibility. The maintenance of a traditional agricultural economy will be essential to maintain the habitat potential for the Ortolan Buntings overwintering in the Ethiopian Highlands and will be instrumental in preserving its world population from further decline.