Crop diversification in Idaho's Magic Valley: the present and the imaginary

The simplification of agricultural landscapes, particularly in the United States (US), has contributed to alarming rates of environmental degradation. As such, increasing agrobiodiversity throughout the US agri-food system is a crucial goal toward mitigating these harmful impacts, and crop diversification is one short-term mechanism to begin this process. However, despite mounting evidence of its benefits, crop diversification strategies have yet to be widely adopted in the US. Thus, we explore barriers and bridges to crop diversification for current farmers, focused on the Magic Valley of southern Idaho-a region with higher crop diversity relative to the US norm. We address two main research questions: (1) how and why do farmers in this region enact temporal and/or spatial strategies to manage crop diversity (the present) and (2) what are the barriers and bridges to alternative diversification strategies (the imaginary)? Through a political agroecology and spatial imaginaries lens, we conducted and analyzed 15 farmer and 14 key informant interviews between 2019 and 2021 to gauge what farmers are doing to manage crop diversity (the present) and how they imagine alternative landscapes (the imaginary). We show that farmers in this region have established a regionally diversified landscape by relying primarily on temporal diversification strategies-crop rotations and cover cropping-but do not necessarily pair these with other spatial diversification strategies that align with an agroecological approach. Furthermore, experimenting with and imagining new landscapes is possible (and we found evidence of such), but daily challenges and structural constraints make these processes not only difficult but unlikely and even "dangerous" to dream of. Therein, we demonstrate the importance of centering who is farming and why they make certain decisions as much as how they farm to support agroecological transformation and reckoning with past and present land use paradigms to re-imagine what is possible.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13593-022-00833-0.

California Native Perennials Attract Greater Native Pollinator Abundance and Diversity Than Nonnative, Commercially Available Ornamentals in Southern California

While many factors have been implicated in global pollinator decline, habitat loss is a key driver of wild pollinator decline in both abundance and species richness. An increase in and diversification of pollinator habitat, even in urban settings, can assist in the conservation of pollinator populations. In Southern California, a highly fragmented and urbanized landscape with a rich yet threatened native pollinator fauna, the availability of food resources for native pollinators hinges largely upon the selection of ornamental plants grown in the urban landscape. To examine the pollinator attractiveness of ornamental plants in a Southern California context, we installed an experimental garden with common California native and nonnative ornamental perennials and observed floral visitation and visitor community composition for 3 yr. Our study demonstrates that while native pollinators visited common ornamental perennials native to California at a higher rate than they visited nonnative ornamentals, introduced honey bees showed no significant preference for either native or nonnative species. Native plants also received a greater diversity of visitor taxa, including a richer suite of native bees. Plant species differed dramatically in attractiveness, by as much as a factor of 12, even within the native status group. Our results suggest that including a data-driven selection of both native and non-native ornamental perennials in the urban landscape can diversify the assemblage of native pollinators, provide critical floral resources throughout the year, and reduce the impact of honey bee landscape foraging dominance by providing plants highly attractive to native pollinators and less so to honey bees.

Impact of the “Farming With Alternative Pollinators” Approach on Crop Pollinator Pollen Diet

Pollinators are facing declines at a global level. One of the main factors driving this decline is insufficient access to floral resources due to habitat loss and degradation that can affect both diet generalist species as well as those with more restricted floral preferences. Here we evaluated the effect of a novel mitigation strategy in agricultural ecosystems, Farming with Alternative Pollinators (FAP) on the pollen diet of crop pollinators. The approach dedicates 25% of the cropped area to Marketable Habitat Enhancement Plants (MHEP) that attract pollinators, natural enemies of the crops, and provide farmers with income. We assessed the effect of the approach on pollen diet of faba bean (Vicia faba) and pumpkin (Cucurbita maxima) flower visitors in four different regions in Morocco during 2018 and 2019 by comparing control fields (monoculture) and FAP fields in 13 trials and 101 sites. Results from 25 wild bee species show that almost two-thirds of the species carrying or collecting pollen when visiting pumpkin flowers and half of the species carrying or collecting pollen when visiting faba bean flowers gathered this pollen from two or more host plants (i.e., MHEP, main crop, and/or wild plants) and displayed a wide dietary breadth. Pollen grains from the main crops were poorly represented on the female scopae, indicating that crops were mainly visited for nectar. Hence, crop flower visitors may require alternative pollen sources to meet their nutritional needs. The number of pollen genera collected by flower visitors and the dietary breadth of crop flower visitors did not show a significant increase in response to FAP management. Among the selected MHEP, sunflower (Helianthus annuus) was the pollen resource for pumpkin flower visitors. In faba bean, flower visitors collected pollen from coriander (Coriandrum sativum) and canola (Brassica napus). Our study sheds light on the importance of characterizing the pollen diet and the foraging behavior of crop pollinators to identify appropriate plant species that complement their food, maintain and conserve their populations.

Critical links between biodiversity and health in wild bee conservation

Wild bee populations are declining due to human activities, such as land use change, which strongly affect the composition and diversity of available plants and food sources. The chemical composition of food (i.e., nutrition) in turn determines the health, resilience, and fitness of bees. For pollinators, however, the term 'health' is recent and is subject to debate, as is the interaction between nutrition and wild bee health. We define bee health as a multidimensional concept in a novel integrative framework linking bee biological traits (physiology, stoichiometry, and disease) and environmental factors (floral diversity and nutritional landscapes). Linking information on tolerated nutritional niches and health in different bee species will allow us to better predict their distribution and responses to environmental change, and thus support wild pollinator conservation.

Building effective policies to conserve pollinators: translating knowledge into policy

Pollination management recommendations are becoming increasingly precise, context-specific and knowledge-intensive. Pollination is a service delivered across landscapes, entailing policy constructs across agricultural landscapes. Diversified farming practices effectively promote pollination services. Yet it remains difficult to secure large-scale uptake by farming communities. A strong foundation upon which to base policy formulation stems from respecting the perspective of farmers and local communities on the need to conserve pollinators, alongside scientific understanding. Ecological intensification resonates with both indigenous knowledge, local communities and scientific understanding. It emphasizes that the regulating functions of nature require both landscape-level agroecosystem design and recognition of the complexity of agricultural systems. Facilitating ecological intensification across landscapes requires collective decision-making, with institutional innovation in local structures and food system governance.

Specialist Bee Species Are Larger and Less Phylogenetically Distinct Than Generalists in Tropical Plant–Bee Interaction Networks

Bee pollinators are key components of terrestrial ecosystems. Evidence is mounting that bees are globally in decline, and species with a higher degree of specialization are the most vulnerable to local extinction. However, ecological features that could explain bee specialization remain poorly tested, especially in tropical species. Here, we aim to determine the most specialized bee species and their associated ecological traits in tropical plant–bee interaction networks, answering three questions: (1) Which bees in the interaction networks are specialists? (2) Is body size related to their role as specialists in interaction networks? (3) Are there phylogenetic relationships between the bee species identified as specialists? We used fifteen quantitative plant–bee interaction networks from different Brazilian biomes covering 1,702 interactions (386 bee and 717 plant species). We used the normalized degree (standardized number of partners) as a metric to determine trophic specialization of bee species. Body size was estimated by measuring intertegular distance (ITD), i.e., the distance between the bases of the wings on the thorax. Evolutionary distinctiveness (ED) was used to quantify species uniqueness, i.e., the singularity of species in the phylogenetic tree. Relationships between dietary specialism, ITD and ED were assessed using generalized linear models. We detected 34 specialist bee species (9% of total species), distributed in 13 genera, and four families. ITD and ED were important variables explaining the specialization of tropical bee species. Specialists were larger and less phylogenetically distinct than expected by chance. Based on a large data set covering some of the main tropical biomes, our results suggest that loss of specialist bees from Brazilian plant–bee networks could have deleterious consequences for native plant species preferentially pollinated by large-bodied bees. Moreover, by affecting more evolutionarily distinct species, i.e., those with fewer extant relatives, the loss of specialist bees will likely affect few clades but can result on considerable loss of evolutionary history and phylogenetic diversity in the Brazilian bee communities. The results are important for decision-making concerning conservation measures for these species and may also encourage the development of sustainable management techniques for bees.

Distribution of wild bee (Hymenoptera: Anthophila) and hoverfly (Diptera: Syrphidae) communities within farms undergoing ecological transition

Background

In Havelange (Belgium), two farms are experiencing an ecological transition. We aimed to evaluate the impact of their agricultural activities on insect pollinator communities. This article depicts the situation at the very early stage of the farm transition. This study supports the fact that the maintenance of farm-level natural habitats provides environmental benefits, such as the conservation of two important pollinator communities: wild bees and hoverflies.

New information

Over two years (2018-2019), by using nets and coloured pan-traps, we collected 6301 bee and hoverfly specimens amongst contrasting habitats within two farmsteads undergoing ecological transition in Havelange (Belgium). We reported 101 bee species and morphospecies from 15 genera within six families and 31 hoverfly species and morphospecies from 18 genera. This list reinforces the national pollinator database by providing new distribution data for extinction-threatened species, such as Andrenaschencki Morawitz 1866, Bombuscampestris (Panzer 1801), Euceralongicornis (L.) and Halictusmaculatus Smith 1848 or for data deficient species, such as A.semilaevis Pérez 1903, A.fulvata (Müller 1766), A.trimmerana (Kirby 1802) and Hylaeusbrevicornis Nylander 1852.

Lethal and Sublethal Effects of Pyriproxyfen on Apis and Non-Apis Bees

Pyriproxyfen is a juvenile hormone mimic used extensively worldwide to fight pests in agriculture and horticulture. It also has numerous applications as larvicide in vector control. The molecule disrupts metamorphosis and adult emergence in the target insects. The same types of adverse effects are expected on non-target insects. In this context, the objective of this study was to evaluate the existing information on the toxicity of pyriproxyfen on the honey bee (Apis mellifera) and non-Apis bees (bumble bees, solitary bees, and stingless bees). The goal was also to identify the gaps necessary to fill. Thus, whereas the acute and sublethal toxicity of pyriproxyfen against A. mellifera is well-documented, the information is almost lacking for the non-Apis bees. The direct and indirect routes of exposure of the non-Apis bees to pyriproxyfen also need to be identified and quantified. More generally, the impacts of pyriproxyfen on the reproductive success of the different bee species have to be evaluated as well as the potential adverse effects of its metabolites.