Wild bees benefit from low urbanization levels and suffer from pesticides in a tropical megacity

Wenzel, Arne; Graß, Ingo; Nölke, Nils; Pannure, Arati; Tscharntke, Teja

doi:10.1016/j.agee.2022.108019

Cited by 7 publications

(10 citation statements)

References 62 publications

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“…Since we find that fertilizer, irrigation and pesticide use have negative effects on bee communities, it is reasonable to expect that they will also have negative effects on biodiversity and the ecosystem services such as pollination that are provided by bees. This negative relationship has been highlighted in the literature (Matson et al 1997;Tilman et al 2002;Winfree et al 2009) and is confirmed in a recent study by Wenzel et al (2022) for the crop Lablab (Lablab purpureus) in our study areas. However, since we did not measure direct pollination outcomes such as fruit or seed set, we cannot draw any conclusions about the effects of farm management practices on such outcomes; we can only conjecture based on other studies.…”

Section: Discussionsupporting

confidence: 91%

“…Physical infrastructure can impede biodiversity and ecosystem services due to changes in physical parameters (e.g., temperature), reduction of habitat size and connectivity (Faeth et al 2011;Pickett et al 2011;Turrini and Knop 2015), or light pollution (Altermatt and Ebert 2016). Furthermore, Banaszak-Cibicka and Zmihorski (2012) and Wenzel et al (2022), for example, show that ground-nesting pollinators have bigger problems with urbanization than cavity-nesting species. This could be a sign that bee richness is more affected by landscape configuration on large scale, whereas bee abundance is influenced by more local factors.…”

Section: Discussionmentioning

confidence: 99%

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Effects of local farm management on wild bees through temporal and spatial spillovers: evidence from Southern India

et al. 2022

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Context The agricultural landscape in many low- and middle-income countries is characterized by smallholder management systems, often dependent on ecosystem services, such as pollination by wild pollinator populations. Increased adoption of modern inputs (e.g., agrochemicals) may threaten pollinators and smallholder crop production. Objective We aimed to identify the link between the use of agrochemicals and wild bee populations in Southern India, while explicitly considering the effects of temporal and spatial scaling. Methods For our empirical analysis, we combined data from pan trap samples and a farm management survey of 127 agricultural plots around Bangalore, India. We implemented a Poisson generalized linear model to analyze factors that influence bee abundance and richness with a particular focus on the present, past, and neighboring management decisions of farmers with respect to chemical fertilizers, pesticides, and irrigation. Results Our results suggest that agricultural intensification is associated with a decrease in the abundance and richness of wild bees in our study areas. Both time and space play an important role in explaining farm-bee interactions. We find statistically significant negative spillovers from pesticide use. Smallholders’ use of chemical fertilizers and irrigation on their own plots significantly decreases the abundance of bees. Intensive past management reduces both bee abundance and richness. Conclusions Our results suggest that cooperative behavior among farmers and/or the regulation of agrochemical use is crucial to moderate spatial spillovers of farm management decisions. Furthermore, a rotation of extensive and intensive management could mitigate negative effects.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Effects of local farm management on wild bees through temporal and spatial spillovers: evidence from Southern India

et al. 2022

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“…Carpenter bees ( Xylocopa spp.) were particularly abundant in urban areas and have already been identified as one of the main pollinators of lablab ( Lablab purpureus ), a very popular pulse crop in South India (Wenzel et al, 2022). These large bees, which have greater foraging range (Greenleaf et al, 2007), could travel longer distances between foraging patches scattered within the urban matrix (Crowther et al, 2014; Kremen et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…However, these studies usually come from temperate regions, where bare soil is often replaced by sealed surfaces and intensively managed lawns, offering less suitable habitats for ground nesters in urban areas. By contrast, cities from the Global South have proportionally less impervious surfaces, and small areas of bare soil are still widely available due to unsealed surfaces besides the roads and around buildings and constructions, mostly in less developed neighborhoods (Guenat et al, 2019; Wenzel et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

“…During the cropping seasons, some species (e.g., Megachile spp., Xylocopa spp.) relied more on flowering crops, such as pulses (e.g., lablab or red gram; see Wenzel et al, 2022), than on natural vegetation. Nevertheless, natural weeds within and around cropping fields are essential to maintain bee communities throughout the year and to fill the food gap during the noncropping season (i.e., dry summer).…”

Section: Discussionmentioning

confidence: 99%

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Functional diversity of farmland bees across rural–urban landscapes in a tropical megacity

Marcacci

Graß

Rao

et al. 2022

Ecological Applications

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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.

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Field assessment of coconut-based activated carbon systems for the treatment of herbicide contamination

McGinley,

Healy,

Scannell

et al. 2024

Chemosphere

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Wild bees benefit from low urbanization levels and suffer from pesticides in a tropical megacity

Cited by 7 publications

References 62 publications

Effects of local farm management on wild bees through temporal and spatial spillovers: evidence from Southern India

Effects of local farm management on wild bees through temporal and spatial spillovers: evidence from Southern India

Functional diversity of farmland bees across rural–urban landscapes in a tropical megacity

Field assessment of coconut-based activated carbon systems for the treatment of herbicide contamination

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