A decline in pollinator dependent vegetable crop productivity in India indicates pollination limitation and consequent agro-economic crises.

Approximately 70% of the tropical crop species depend on pollinators for optimum yields (Roubik, 1995, Klein 2007). The economic value of such pollinated crops to India is $726 million and India is the world's second largest vegetable producer (Sidhu, 2005). This status has been underpinned by large-scale changes in land-use and pesticide dependency (Fazal, 2000; Shaw & Satish, 2007). A method (c.f. Aizen et al. 2008) that partitions crops into categories depending on their relative pollinator dependence (Index of pollinator dependence, DI) was applied to analysis of vegetable yields for India over 45 years (1963-2008) using FAO data. This has revealed that since 1993, relative yields of crop production has either flattened or declined, while pollinator non dependent crops show no similar decline. This pattern of yield limitation may be due to several factors, among which pollinator limitation would be a major factor (Kearns et al. 1998) and this risk is discussed. Pollinator decline will have serious socio-economic consequences for countries like India, which host a large population of small and marginal farms for whom falling yield level would be critical for subsistence (Kearns et al. 1998; Kremen et al., 2002; Klein et al., 2007; Potts et al., 2010). We show here for the first time any indication of pollination limitation in India, an emerging economy that is still predominantly agrarian. Detailed land use and ecological surveys are urgently required to assess the ecology of pollinating insects within and around agricultural systems in India

Predicted thresholds for natural vegetation cover to safeguard pollinator services in agricultural landscapes

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

Selection of Non-Crop Plant Mixes Informed by Arthropod-Plant Network Analyses for Multiple Ecosystem Services Delivery towards Ecological Intensification of Agriculture

Ecological intensification (EI) of agriculture through the improvement of ecosystem service delivery has recently emerged as the alternative to the conventional intensification of agriculture that is widely considered unsustainable and has negative impacts on the environment. Although tropical agricultural landscapes are still heterogeneous, they are rapidly losing diversity due to agricultural intensification. Restoration of natural or semi-natural habitats, habitat diversity, and provision of multiple benefits have been identified as important targets for the transition to EI. Choosing the right plant mixes for the restoration of habitats that can offer multiple ecosystem service benefits is therefore crucial. The selection of candidate species for plant mixes is generally informed by studies focusing on a specific ecosystem service (e.g., pollination) and not based on the whole arthropod—non-crop plant interactions matrix. In this study, we try to identify non-crop plant mixes that would provide habitat for pollinators, act as refugia for natural pest predators, and also as a trap crop for potential crop pests by studying non-crop plants—arthropod interaction network. We have identified the non-crop plant species mixes by first identifying the connector species based on their centrality in the network and then by studying how their sequential exclusions affect the stability of the network

The last mile:Using local knowledge to identify barriers to sustainable grain legume production

Grain legumes (or pulses–annual leguminous crops that are harvested solely for their dried seeds such as lentils or chickpeas) are essential for sustainable cropping systems. They positively contribute to soil fertility and agricultural biodiversity and are a highly nutritious food source, yet they remain under-exploited across the world. In India–soon to be the world's most populous country and the world's largest importer, producer and consumer of pulses–they are substantially under-utilized and are the only major food group not to have increased in output since independence in 1947. Existing efforts to address low grain legume production have focused on the scientific and agronomic barriers, with little impact on productivity. In contrast, this project, using Tripura in India as a case study, recognizes the limits of imposing top-down solutions and instead focuses on the barriers to production as identified by the growers themselves. Working with 440 farmers from 19 non-tribal and 11 tribal villages in Tripura, NE India, we used facilitated discussion to identify their key barriers to pulse production, and facilitated pile sorting to identify the commonly consumed, grown and available pulses. Twenty-eight barriers to legume production were identified by farmers. The eight principal barriers were: insufficient water; lack of technical knowledge; unreliable seed supply; lack of processing units; soil fertility; financial constraints; limited fertilizer supply; and insufficient fencing material. These barriers are complex and overlapping and originate from system level failures to sufficiently prioritise grain legumes compared to cereals. However, recognizing the length of time it takes to address system level problems, in this paper we identify five immediately applicable mitigating strategies to help overcome the principle barriers identified here. Importantly, these will also create an improved environment to apply the technologically sophisticated grain legume R&D that has been carried out over the last 20 years but has yet to have a measurable impact on pulse production. Therefore understanding the wider socio-economic pathways to sustainable pulse production is essential to facilitate change on the ground. Our results, relevant to policy makers in India and around the world, demonstrate the value of listening to farmers when attempting to improve production, and emphasize the necessity of including the socio-economic systems surrounding pulse production, to complement the current emphasis on biological barriers

Collating and validating indigenous and local knowledge to apply multiple knowledge systems to an environmental challenge: A case-study of pollinators in India

There is an important role for indigenous and local knowledge in a Multiple Evidence Base to make decisions about the use of biodiversity and its management. This is important both to ensure that the knowledge base is complete (comprising both scientific and local knowledge) and to facilitate participation in the decision making process. We present a novel method to gather evidence in which we used a peer-to-peer validation process among farmers that we suggest is analogous to scientific peer review. We used a case-study approach to trial the process focussing on pollinator decline in India. Pollinator decline is a critical challenge for which there is a growing evidence base, however, this is not the case world–wide. In the state of Orissa, India, there are no validated scientific studies that record historical pollinator abundance, therefore local knowledge can contribute substantially and may indeed be the principle component of the available knowledge base. Our aim was to collate and validate local knowledge in preparation for integration with scientific knowledge from other regions, for the purpose of producing a Multiple Evidence Base to develop conservation strategies for pollinators. Farmers reported that vegetable crop yields were declining in many areas of Orissa and that the abundance of important insect crop pollinators has declined sharply across the study area in the last 10–25 years, particularly Apis cerana, Amegilla sp. and Xylocopa sp. Key pollinators for commonly grown crops were identified; both Apris cerana and Xylocopa sp. were ranked highly as pollinators by farmer participants. Crop yield declines were attributed to soil quality, water management, pests, climate change, overuse of chemical inputs and lack of agronomic expertise. Pollinator declines were attributed to the quantity and number of pesticides used. Farmers suggested that fewer pesticides, more natural habitat and the introduction of hives would support pollinator populations. This process of knowledge creation was supported by participants, which led to this paper being co-authored by both scientists and farmers

A global-scale expert assessment of drivers and risks associated with pollinator decline.

Pollinator decline has attracted global attention and substantial efforts are underway to respond through national pollinator strategies and action plans. These policy responses require clarity on what is driving pollinator decline and what risks it generates for society in different parts of the world. Using a formal expert elicitation process, we evaluated the relative regional and global importance of eight drivers of pollinator decline and ten consequent risks to human well-being. Our results indicate that global policy responses should focus on reducing pressure from changes in land cover and configuration, land management and pesticides, as these were considered very important drivers in most regions. We quantify how the importance of drivers and risks from pollinator decline, differ among regions. For example, losing access to managed pollinators was considered a serious risk only for people in North America, whereas yield instability in pollinator-dependent crops was classed as a serious or high risk in four regions but only a moderate risk in Europe and North America. Overall, perceived risks were substantially higher in the Global South. Despite extensive research on pollinator decline, our analysis reveals considerable scientific uncertainty about what this means for human society.University of Reading’s Building Outstanding Impact Support Programm

Wild insect diversity increases inter-annual stability in global crop pollinator communities.

While an increasing number of studies indicate that range, diversity and abundance of many wild pollinators has declined, the global area of pollinator-dependent crops has significantly increased over the last few decades. Crop pollination studies to date, have mainly focused on either identifying different guilds pollinating various crops, or on factors driving spatial changes and turnover observed in these communities. The mechanisms driving temporal stability for ecosystem functioning and services, however, remain poorly understood. Our study quantifies temporal variability observed in crop pollinators in 21 different crops across multiple years at a global scale. Using data from 43 studies from six continents, we show that (i) higher pollinator diversity confers greater inter-annual stability in pollinator communities, (ii) temporal variation observed in pollinator abundance is primarily driven by the three most dominant species, and (iii) crops in tropical regions demonstrate higher inter-annual variability in pollinator species richness than crops in temperate regions. We highlight the importance of recognising wild pollinator diversity in agricultural landscapes to stabilize pollinator persistence across years to protect both biodiversity and crop pollination services. Short-term agricultural management practices aimed at dominant species for stabilising pollination services need to be considered alongside longer-term conservation goals focussed on maintaining and facilitating biodiversity to confer ecological stability

Does agricultural intensification impact pest regulation service by frogs in a natural multi-trophic system?

Agricultural intensification is a major driver of biodiversity loss. However, the exact impacts of such loss of key ecosystem service (ES) provisions in agriculture require more scrutiny. We assessed the population loss impacts of a key ES-providing species in an agricultural landscape. We tested the hypothesis that intensive agriculture causes density reduction of frogs known as pest regulators and that negatively affects pest regulation. Different frog densities (high and low) observed in a previous study in low and high agricultural intensification areas were used as treatments in a semi-controlled field experiment. Functional response of the frog species was also studied. Neither high nor low frog density had any significant effect on respective pest populations. Limited feeding rate of the frog species might have contributed to reduced predation pressure on pests. Surprisingly, at low density, frogs significantly reduced the arthropod natural enemies, probably their preferred prey due to the latter’s agility. Unlike in low frog density treatment, increased intraspecific competition at high frog density made them seek out pests as alternative prey to the preferred arthropod pest enemies, whose populations were not affected by frog density. This study for the first time links the population loss of frogs, a potential bio-control agent to ES provision in a multi-trophic system