Pollinators are a key component of global biodiversity, providing vital ecosystem services to crops and wild plants. There is clear evidence of recent declines in both wild and domesticated pollinators, and parallel declines in the plants that rely upon them. Here we describe the nature and extent of reported declines, and review the potential drivers of pollinator loss, including habitat loss and fragmentation, agrochemicals, pathogens, alien species, climate change and the interactions between them. Pollinator declines can result in loss of pollination services which have important negative ecological and economic impacts that could significantly affect themaintenance of wild plant diversity, wider ecosystemstability, crop production, food security and human welfare.

1. New incentives at the national and international level frequently lead to substantial structural changes in agricultural landscapes. Subsidizing energy crops, for example, recently fostered a strong increase in the area cultivated with oilseed rape Brassica napus across the EU. These changes in landscape structure affect biodiversity and associated ecosystem services. 2. Mass-flowering oilseed rape has been shown to positively affect colony growth and densities of bumblebees, which may enhance pollination services in agroecosystems. Not considered, however, have been species-specific traits of pollinators resulting in disproportionate benefits from these recurrent resource pulses. A subsequent community shift towards the subsidized species potentially distorts plant-pollinator interactions in the surrounding landscape. 3. We analysed the effects of mass-flowering crops on the abundance of legitimate long-tongued bumblebee pollinators, nectar robbing by illegitimate short-tongued bumblebees and seed set in the long-tubed flowers of red clover Trifolium pratense in 12 landscape sectors with differing amounts of oilseed rape. 4. Densities of long-tongued bumblebees visiting long-tubed plants decreased with increasing amounts of oilseed rape. The simultaneous increase of nectar robbing suggests that resource depletion is a likely explanation for this decline which may lead to a distortion in plant-pollinator interactions. The decline in long-tongued bumblebees, however, did not result in an immediate effect on seed set. In contrast, seed set increased with increasing amounts of semi-natural habitats, indicating the positive effects of these habitats on the legitimate long-tongued pollinators. 5.Synthesis and applications. Accounting for species-specific traits is essential in evaluating the ecological impacts of land-use change. The disproportional trait-specific benefits of increasing oilseed rape to short-tongued bumblebees may abet an increasingly pollinator-dependent agriculture but simultaneously threaten the more specialized and rare long-tongued species and their functions. Semi-natural habitats were found to positively affect seed set in long-tubed plants indicating that they can counteract the potentially distorting effects of transient mass-flowering crops on plant-pollinator interactions in agroecosystems. Future agri-environmental schemes should aim to provide diverse and continuous resources matching trait-specific requirements of various pollinators in order to avoid resource competition. Thereby they harmonize the economic interest in abundant pollinators and the conservation interest in protecting rare species.

Conservation practitioners often lack tools to monitor functioning of communities because time and monetary constraints create a gap between the optimal monitoring methods and the practical needs in conservation. Interaction networks provide a framework that has proven useful in ecological research. However, they are considered time consuming and too expensive for conservation purposes. We investigate whether it is possible to sample interaction networks cost-efficiently and whether a compromise exists between data quality and amount of resources required to sample the data by using a highly resolved mutualistic plant-pollinator network sampled over two years in Norway. The dataset was resampled with decreasing sampling intensity to simulate decreasing monitoring costs and we investigated the cost-efficiency of these monitoring regimes. The success in monitoring community structure varied largely with sampling intensity and the descriptor investigated. One major result was that a large proportion of the functionally most important species in the community, both plants and insects, could be identified with relatively little sampling. For example, monitoring only in “peak-season”, which costs ca. 20% relative to full monitoring, resulted in recording of 70% (in 2003) or 85% (in 2004) of the top 20 most functionally important pollinator species. Also, peak-season monitoring resulted in relatively precise estimates of several network descriptors. We present a first estimation of the full cost (travel time, sampling time and taxonomic services) of constructing pollination networks with different sampling effort. We recommend monitoring plant-pollinator networks in temperate regions during peak-season to cost-efficiently collect data for practical habitat management of ecosystem functioning.

Rapid biodiversity assessment (RBA) is proposed as an affordable indicator for monitoring local species richness of arthropods and sustainability of related ecosystem services. The indicator is based on strictly standardised sampling procedures and the identification of parataxonomic units (morphospecies) instead of species identification. The collection of arthropods was optimized with regard to trap types, time and length of collecting period, selection of four out of seven weekly samples, and choice of counted taxa and trophic guilds. By measuring arthropod activity, RBA is an indicator for functional diversity. Over a period of 8 years, average yearly numbers of morphospecies were assessed in Switzerland in 15 agricultural habitats, 15 managed forests, and in 12 unmanaged habitats ranging from protected lowland wetlands to Alpine meadows. The yearly RBA-trend in unmanaged habitats is used for assessing the influence of climate and weather on biodiversity, and as a reference for measuring the relative influences of recent management changes in agriculture and forestry. The average number of morphospecies per sampling station per year depends on temperature, and was only marginally significantly increasing over time in agriculture, but not in forestry or unmanaged areas. Three RBA indices considered to be relevant for maintaining ecosystem services were calculated from the average number of morphospecies per location per year: (1) indicator for ecological resilience and sustainability (all morphospecies); (2) indicator for pollinator diversity (taxa with a majority of pollinators) and (3) indicator for biocontrol diversity (ratio between carnivore and herbivore guilds).

Pollination is an essential ecosystem service, increasing reproductive success of many crops, which can be provided by managed pollinators, wild bees (including honeybees) and other insect pollinators. However, the pollination services and the economic value of wild pollinators are often underestimated. Better understanding of the factors that influence honeybee foraging behaviour and pollination efficiency can contribute to the improvement of management practices that aim to enhance crop pollination and ecosystem services. The objectives of this study were to investigate the importance of managed honeybees and wild honeybees to sunflower pollination as well as to evaluate the response of honeybees to different levels of floral rewards and to behavioural interactions with wild flower visitors. The study was conducted in 16 commercial sunflower farms and one experimental farm of South Africa during the 2009 sunflower flowering season. The results showed that insects, particularly honeybees, were efficient pollinators, improving sunflower production in all self-fertile sunflower cultivars used in this study. Furthermore, wild honeybee colonies were found to be as efficient as managed honeybee colonies in sunflower pollination near to natural habitat. Both sunflower yield and the abundance of pollinators decreased with distance from natural habitat, suggesting that sunflower yield is directly correlated with the abundance of pollinators. The amount of nectar present in the florets of sunflower significantly affected pollinator behaviour, influencing honeybee visitation length and foraging rate which prefer to exploit floral rewards from the same source if they find the higher amount per foraging trip, possibly having a negative impact on cross-pollination. Moreover, the concentration of nectar collected from honeybees was significantly lower than the nectar concentration from florets, suggesting that honeybees diluted highly concentrated sunflower nectar with their saliva to their optimum concentration level. Interspecific exploitative competition between honeybees and wild pollinators (wild bees, butterflies and moths) significantly increased the movement of honeybees among sunflower heads, which enhances cross-pollination. Furthermore, behavioural interactions influenced the length of foraging time spent by individual honeybees per sunflower head. Butterflies were the most influential in enhancing honeybee foraging movement, followed by wild bees and then moths. The importance of a given flower visitor species to honeybee movement is likely related to the size of the visitor, as the bigger size of butterflies and movement of their wings increases the chance of disturbing a neighbouring honeybee. Conservation of natural habitat is important to maintain the diversity of flower visitors which indirectly contribute to crop production by enhancing honeybee foraging activity and consequent direct pollination service. Furthermore, the pollination effectiveness of wild pollinators, density of wild honeybees surrounding sunflower fields and effects of human activities on pollination disruption are suggested as topics for future research.

It is now widely accepted that agricultural intensification drives the decline of biodiversity and related ecosystem services like pollination. Conservation management, such as agri-environment schemes (AES), has been introduced to counteract these declines, but in Western European countries these tend to produce mixed biodiversity benefits. Not much is known about the effects of AES in Central and Eastern European countries. We evaluated the effect of reduced stocking rates (0.5cow/ha vs. >1cow/ha) on bees and insect-pollinated plants in semi-natural pastures in Hungary. We sampled bees using sweep net and transect surveys in the edge and interior of the fields three times in 2003. On the same transects, we also estimated the cover of all plant species. We found no management effect on species richness and abundance with respect to cover of bees and insect-pollinated plants, but grazing intensity resulted in differences in species composition of insect-pollinated plants. Furthermore, we compared our results with those of a similar study carried out in Switzerland, and the Netherlands, but with different management regimes. There were positive effects of management in Switzerland, but conservation effects were lacking in the Netherlands. Species richness of both bees and insect-pollinated plants was highest in Hungary, intermediate in Switzerland and lowest in the Netherlands. Across all countries, the richness of insect-pollinated plants was a good predictor of bee species richness. Grassland extensification schemes were effective for bees and insect-pollinated plants in the country with intermediate land-use intensity and biodiversity only (Switzerland). The absence of effects in the Netherlands may have been caused by the management being highly intensive on both field types. In Hungarian grasslands biodiversity levels were high regardless of management and both investigated stocking rates may be qualified as conservation management. Therefore, agricultural policy in Hungary should encourage the maintenance of a variety of traditional grazing practices for conserving this still highly diverse pollinator fauna.