Insects are a functionally diverse group, with economically relevant roles on key ecosystem services, such as pollination. The current trend of biodiversity loss and consequent degradation of ecosystem services delivered by insects is leading to additional pressure on modern agriculture, particularly in crops that depend on insects for pollination. Understanding how insect pollinator diversity varies at local and landscape scales is very important to recognize trends in pollinator populations. The present work quantified the effect of in-field management practices and different landscape types on insect pollinator communities in kiwifruit, a pollinator-dependent crop. Twenty-two orchards were selected and characterized for in-field practices, landscape structure, plant-pollinator interactions, and productivity. We observed that orchards with practices that are less harmful to insect pollinators are related to a higher pollinator diversity and higher abundances of certain wild pollinator groups, although this was not related with increased productivity. Additionally, in the studied production region, agricultural dominated landscapes harbor lower pollinator diversity, lower wild pollinators abundance and higher managed honeybee abundance than forest and herbaceous dominated landscapes, but no differences were detected in productivity among landscape types. In turn, abundance of Bombus spp. and the use of pollination support practices were significantly and positively correlated with orchard productivity. Despite the differences in pollinator communities, comparable yields were observed across different landscape types. Additionally, simple changes towards less harmful agricultural practices and the presence of forest and herbaceous habitats can promote wild pollinators and respective pollination services.

Biodiversity loss during the Anthropocene is a serious ecological challenge. Pollinators are important vectors that provide multiple essential ecosystem services but are declining rapidly in this changing world. However, several studies have argued that a high abundance of managed bee pollinators, such as honeybees (Apis mellifera), may be sufficient to provide pollination services for crop productivity, and sociological studies indicate that the majority of farmers worldwide do not recognize the contribution of wild pollinator diversity to agricultural yield. Here, we review the importance of pollinator diversity in natural and agricultural ecosystems that may be thwarted by the increase in abundance of managed pollinators such as honeybees. We also emphasize the additional roles diverse pollinator communities play in environmental safety, culture, and aesthetics. Research indicates that in natural ecosystems, pollinator diversity enhances pollination during environmental and climatic perturbations, thus alleviating pollen limitation. In agricultural ecosystems, pollinator diversity increases the quality and quantity of crop yield. Furthermore, studies indicate that many pollinator groups are useful in monitoring environmental pollution, aid in pest and disease control, and provide cultural and aesthetic value. During the uncertainties that may accompany rapid environmental changes in the Anthropocene, the conservation of pollinator diversity must expand beyond bee conservation. Similarly, the value of pollinator diversity maintenance extends beyond the provision of pollination services. Accordingly, conservation of pollinator diversity requires an interdisciplinary approach with contributions from environmentalists, taxonomists, and social scientists, including artists, who can shape opinions and behavior.

Insect pollinator biodiversity and occurrence is on global decline, threatening human food supply and ecosystem functions. Extensive, pasture monoculture cattle production systems in tropical Latin America are among the principal drivers of this decline. This, in combination with other environmental problems caused by the conventional cattle sector, such as deforestation or greenhouse gas emissions, puts emphasis on the development of alternative, more sustainable production systems. One solution is the inclusion of forage legumes (fabaceae) in cattle production systems, for example as forage banks or within silvo-pastoral systems (SPS), which are mostly pollinated by insects, in particular bees. Such systems have been widely promoted to improve livestock production and soil fertility, but not to enhance ecosystem services from pollinators. Shortages of seed for the establishment of legumes as forage banks or within pastures or SPS remain a bottleneck for the improvement of ecosystem services brought about by pollinators within these systems and beyond. Against this background and based on literature review, we provide an overview of forage legumes, their interplay with pollinators, and the ecological and socio-economic benefits of pollinator–forage legume interactions, at different scales (farm and landscape level). We also discuss the challenges and opportunities of scaling these sustainably intensified cattle production systems that integrate legume forage-seed production with principles of pollinator ecology and native beekeeping. Our analysis shows that the main benefits include the provision of habitats for pollinators on decline and the promotion of legume seed required for the wider adoption of sustainable, forage-based cattle systems. This comes along with livelihood benefits for the producers, who can diversify (cattle production, legume seed production, honey making) and increase their incomes. At the landscape level, the interplay of pollinators and forage legumes can positively affect the yield of nearby pollinator-dependent crops. Finally, we provide interested stakeholders, policy- and decision-makers with a perspective on how such agroecosystems may be designed and scaled into multifunctional landscapes. This includes the improvement of enabling conditions, such as policies, knowledge transfer, payment schemes for ecosystem services, incentives, and new value chains.

The value of non‐commodity ecosystem services provided by forests is widely recognized, but intensive forest management practices are increasing, with uncertain consequences for a multitude of these services. Quantitative relationships among biodiversity conservation, timber production and other ecosystem services remain poorly understood, especially during the early‐successional period of intensively managed forestlands. We manipulated management intensity in regenerating forest plantations to test the prediction that treatments aimed at maximizing timber production decrease biodiversity conservation and non‐timber services. We measured species richness of 3 taxonomic groups and 13 proxies for provisioning, cultural and regulating services within stands randomly assigned to one of the three herbicide application intensities or an untreated control. Herbicides increased allocation of net primary production to crop trees, increasing projected timber volume and revenues at 40‐ and 60‐year harvest ages. Commonly used herbicide prescriptions reduced culturally valued plants by 71%, wild‐ungulate forage by 41%, avian richness by 20% and pollinator floral resources by 42%, the latter being associated with 38% fewer pollinator species. However, agriculturally valued bumblebees, pollination of blueberries, avian‐mediated arthropod control, wild ungulate observations and regulation services tied to forest productivity appeared unaffected by increasing management intensity and timber production. Species richness and flora‐provided services in young forest plantations exhibited strong trade‐offs with projected timber production, whereas post‐treatment vegetation regeneration and site‐level variation likely maintained a range of other services. Although vegetation recovery is important for supporting wildlife and some ecosystem services on industrial forestlands, it is unlikely that any single prescription can optimize both timber and non‐timber benefits to society across managed forest landscapes. Instead, producing different services in discrete portions of the landscape may be necessary. Synthesis and applications. We tested the effects of intensive forest management via herbicides on ecosystem services and found that biodiversity responses and services from early‐successional vegetation trade‐off against timber production. A number of services appeared to be compatible with timber production, although no single prescription optimized the full range of services. Stand‐level biodiversity conservation and a variety of services could potentially be provided by treatment skips and less‐intensive management on productive sites, although it is unlikely that all services can be optimized without landscape‐level planning.

Common air pollutants, such as nitrogen oxides (NOx), emitted in diesel exhaust, and ozone (O3), have been implicated in the decline of pollinating insects. Reductionist laboratory assays, focused upon interactions between a narrow range of flowering plant and pollinator species, in combination with atmospheric chemistry models, indicate that such pollutants can chemically alter floral odors, disrupting the cues that foraging insects use to find and pollinate flowers. However, odor environments in nature are highly complex and pollination services are commonly provided by suites of insect species, each exhibiting different sensitivities to different floral odors. Therefore, the potential impacts of pollution-induced foraging disruption on both insect ecology, and the pollination services that insects provide, are currently unknown. We conducted in-situ field studies to investigate whether such pollutants could reduce pollinator foraging and as a result the pollination ecosystem service that those insects provide. Using free-air fumigation, we show that elevating diesel exhaust and O3, individually and in combination, to levels lower than is considered safe under current air quality standards, significantly reduced counts of locally-occurring wild and managed insect pollinators by 62 to 70% and their flower visits by 83 to 90%. These reductions were driven by changes in specific pollinator groups, including bees, flies, moths and butterflies, and coincided with significant reductions (14-31%) in three different metrics of pollination and yield of a self-fertile test plant. Quantifying such effects provides new insights into the impacts of human-induced air pollution on the natural ecosystem services upon which we depend.

Common air pollutants, such as nitrogen oxides (NOₓ), emitted in diesel exhaust, and ozone (O₃), have been implicated in the decline of pollinating insects. Reductionist laboratory assays, focused upon interactions between a narrow range of flowering plant and pollinator species, in combination with atmospheric chemistry models, indicate that such pollutants can chemically alter floral odors, disrupting the cues that foraging insects use to find and pollinate flowers. However, odor environments in nature are highly complex and pollination services are commonly provided by suites of insect species, each exhibiting different sensitivities to different floral odors. Therefore, the potential impacts of pollution-induced foraging disruption on both insect ecology, and the pollination services that insects provide, are currently unknown. We conducted in-situ field studies to investigate whether such pollutants could reduce pollinator foraging and as a result the pollination ecosystem service that those insects provide. Using free-air fumigation, we show that elevating diesel exhaust and O₃, individually and in combination, to levels lower than is considered safe under current air quality standards, significantly reduced counts of locally-occurring wild and managed insect pollinators by 62–70% and their flower visits by 83–90%. These reductions were driven by changes in specific pollinator groups, including bees, flies, moths and butterflies, and coincided with significant reductions (14–31%) in three different metrics of pollination and yield of a self-fertile test plant. Quantifying such effects provides new insights into the impacts of human-induced air pollution on the natural ecosystem services upon which we depend.

There is a global concern of pollinator declines and linked ecosystem service losses. However, although land-use changes are a primary threat to biodiversity, how land-use change affects pollinator communities, pollination networks and fruit-set of food crops is poorly understood. The impact of land-use changes is especially understudied in tropical systems, even though most tropical crops are highly dependent on animal pollination. Using 40 sites to investigate diurnal and nocturnal flower visitors in small-scale agroecosystems across land-use gradients in Thailand and tropical South-western China, we show that habitat structure shapes pollinator communities at local (floral species richness) and landscape level (percentage of tree plantation in a 500 m radius and percentage forest in a 5 km radius), influencing both the species richness of pollinators and their visitation rates. These, in turn, alter plant-pollinator network structure: community-level specialization increases with floral species richness and percentage of forest cover. However, the specialization decreases with percentage of tree plantation, illustrating that natural habitat better supports specialized species. Furthermore, fruit-sets of several crops were affected by land-use. Notably, fruit-set of mango was positively associated with the percentage of forest cover in the surrounding landscape. These findings reveal how land-use influence pollinator communities and highlight how natural habitats may safeguard ecosystem services.

Insect pollination is an economically important ecosystem service that depends heavily on wild pollinators. Landscape transformation caused by conversion to agriculture threatens habitats of wild pollinators, reducing their potential to provide ecosystem services. The landscape in Jambi Province, Sumatra, Indonesia, is an example of a region undergoing landscape transformation, from biodiverse natural forests, to intermediate land uses such as fallow shrubland and jungle rubber, to monospecific oil palm plantations. My dissertation explores how transitions between these land uses impact pollinator biodiversity and ecosystem functions and services. I consider different facets of this interface: the impacts of adjacent forest on pollination services to oil palm; mechanisms driving ecosystem functions and services following agroforestry enrichment within oil palm; and landscape-scale comparisons quantifying interacting local and landscape effects on a native pollinator species. My first chapter reviews the state of the knowledge of oil palm pollination by insects. I conducted a systematic review of biotic and abiotic drivers of oil palm pollination and pollinator populations. I present the current understanding of the globally introduced West African Weevil (Elaeidobius kamerunicus), whose regional population fluctuations have negatively impacted yield and resilience, as well as other potential pollinator species endemic to particular growing regions. Based on my review, I describe specific issues concerning biotic, management, and climate drivers of pollination that should be the focus of future oil palm pollination research. In my second chapter, I examine the role that natural habitat can play as a source of pollination ecosystem services and ecological spillover effects in an oil palm field experiment. I compared treatments controlling visitors and pollination of female oil palm inflorescences over a distance gradient from an adjacent forest border. I found that exclusion of all visitors significantly decreased fruit set compared to other treatments, confirming insect pollination is necessary for adequate yield. Forest proximity had a significant positive effect on fruit set when large visitors were excluded. This effect was not significant for treatments that minimized pollinator contributions, suggesting this trend was not due to abiotic factors. However, insect abundances associated with oil palm inflorescences were not strongly related to distance from forest, and only E. kamerunicus had a significant relationship with fruit set. These results could suggest that non-consumptive ecological spillover from forests may influence oil palm pollination, though more experimental work is needed to identify these interactions. In my third chapter, I explore how enriching the oil palm agricultural matrix with up to six tree species played a role in driving insect-mediated ecosystem functions. Within a plantation-scale, long-term oil palm biodiversity enrichment project, I disentangled the direct and indirect effects of enrichment on services (pollination, biocontrol) and disservices (herbivory) using random partition analysis and structural equation models. These models indicate that changes in canopy openness, driven by enrichment treatments, played an important role in ecological patterns at multiple levels of interaction. These had effects on herbivorous insects and pollinators, the latter of which had a positive effect on the fruit production of phytometer plants (Capsicum annuum) placed in the plots. Our results show that, even in early stages of ecological restoration of oil palm, ecosystem functions and services can be affected. These effects are mediated by decreasing canopy openness; however, these relationships may change as enrichment communities continue to develop. In my fourth chapter, I examine the counterbalancing roles of local land use and amount of landscape habitat in pollinator survival and growth, using the native stingless bee Tetragonula laeviceps as a focal species. I established three colonies in 40 plots within Jambi’s transformation landscape, selecting from four predominant habitat types (degraded primary forest, shrubland, rubber plantation, and oil palm plantation) and controlling for a gradient of natural habitat (i.e., forest and shrubland) composition in a 500 m radius. I found that hives with higher local flower species richness had more pollen stores, which in turn was associated with increased bee and colony size. Colonies in structurally complex habitats such as forest and rubber plantations had lower mortality and greater gains in hive size than colonies in open habitats such as oil palm and shrubland; however, open habitats had higher flower species richness and abundance. Open habitats, which are increasing with rainforest conversion, reduce suitable nesting habitat but may increase floral resources in the landscape. Considering the key pollinating function of stingless bees, understanding how this trade-off translates to landscape and population scales will be critical in light of the continued deforestation crisis in the tropics. In summary, understanding and protecting the resources supporting pollination are critical to improving the sustainability of oil palm and can support the livelihoods of people living in the landscape. The impact of habitat loss from agriculture conversion can adversely impact wild pollinator populations through the loss of suitable habitats, as I observed with T. laeviceps, but also changes the flowering resource landscape. In my review of oil palm pollination, I show that a better understanding of biodiversity and landscape drivers of pollination of oil palm itself is needed. My own oil palm field experiment demonstrates how natural habitat and biodiversity may interact positively with oil palm production. I show in my experiments within the oil palm biodiversity enrichment project that tree biodiversity enrichment can indirectly influence pollination services and ecosystem functions, even at an early stage. However, the ecosystem services and disservices affected by ecological restoration will continue to change as the ecological community develops. Our task in future research will be to continue to disentangle these relationships with the aim of recovering or preserving biodiversity and ecosystem function while informing sustainable ecological strategies for farmers and land managers. | 2022-10-04