Richard F. Pywell

Bio: Richard F. Pywell is an academic researcher from Natural Environment Research Council. The author has contributed to research in topics: Species richness & Biodiversity. The author has an hindex of 51, co-authored 221 publications receiving 9934 citations.

Restoration of ecosystem services and biodiversity: conflicts and opportunities

Abstract: Ecological restoration is becoming regarded as a major strategy for increasing the provision of ecosystem services as well as reversing biodiversity losses. Here, we show that restoration projects can be effective in enhancing both, but that conflicts can arise, especially if single services are targeted in isolation. Furthermore, recovery of biodiversity and services can be slow and incomplete. Despite this uncertainty, new methods of ecosystem service valuation are suggesting that the economic benefits of restoration can outweigh costs. Payment for Ecosystem Service schemes could therefore provide incentives for restoration, but require development to ensure biodiversity and multiple services are enhanced and the needs of different stakeholders are met. Such approaches must be implemented widely if new global restoration targets are to be achieved.

Country-specific effects of neonicotinoid pesticides on honey bees and wild bees.

Abstract: Neonicotinoid seed dressings have caused concern world-wide. We use large field experiments to assess the effects of neonicotinoid-treated crops on three bee species across three countries (Hungary, Germany, and the United Kingdom). Winter-sown oilseed rape was grown commercially with either seed coatings containing neonicotinoids (clothianidin or thiamethoxam) or no seed treatment (control). For honey bees, we found both negative (Hungary and United Kingdom) and positive (Germany) effects during crop flowering. In Hungary, negative effects on honey bees (associated with clothianidin) persisted over winter and resulted in smaller colonies in the following spring (24% declines). In wild bees (Bombus terrestris and Osmia bicornis), reproduction was negatively correlated with neonicotinoid residues. These findings point to neonicotinoids causing a reduced capacity of bee species to establish new populations in the year following exposure.

Plant traits as predictors of performance in ecological restoration

Abstract: Summary 1. There are few studies of the performance of species in restored vegetation communities. Here we report the results of a meta-analysis of 25 experiments concerned with species-rich grassland restoration on ex-arable land and agriculturally improved grasslands situated at a wide range of locations throughout lowland Britain. Differences in species’ performance were related to 38 physiological and morphological traits. 2. An experiment-adjusted performance index was calculated for each of the 58 species (13 grasses and 45 forbs). The performance index was calculated for the first 4 years after establishment together with a temporal trend. 3. Individual species showed large differences in performance indices. However, grasses consistently out-performed forbs. 4. We examined the linkage between species’ performance and traits according to four non-exclusive hypotheses. The ability to establish and persist in restored vegetation communities requires: (H1) good gap colonization ability; (H2) strong competitive capability; and (H3) ability to undergo vegetative regeneration. (H4) Successful species are generalists associated with fertile habitats. 5. Trait analyses supported all four hypotheses. Within the forbs, good establishment in the first year was linked to traits determining colonization ability: ruderality, percentage germination of seeds and autumn germination. However, traits linked to competitive ability, vegetative growth and seed bank persistence became increasingly important determinants of success with time. Species with generalist habitat requirements, and especially those associated with fertile soils, performed increasingly well with time. This reflects the development of a closed vegetation in which the ability to grow vigorously and out-compete other established plants is important. 6. Stress-tolerators, habitat specialists and species of infertile habitats performed badly. This may reflect high residual fertility in restored grasslands and particular niche requirements of these species. This may be a problem as grassland restoration often targets communities characterized by species with these traits and many are food plants of invertebrates of conservation value. 7. There were few significant correlations between the performance of the grasses and traits reflecting their overall good performance in comparison with the forbs. 8. This study has important implications for practical restoration programmes and policies. Efficiency might be increased by introducing only species with good performance, but this would lead to uniformity among restored grasslands and would diminish the benefits of habitat restoration for national and regional biodiversity. 9. Synthesis and applications. Future work should focus on practical methods to increase the successful establishment of the poor performing but desirable species, by (i) targeting restoration to low fertility soils, (ii) changing the abiotic environment or (iii) the ‘phased

Comparing the efficacy of agri-environment schemes to enhance bumble bee abundance and diversity on arable field margins

Abstract: 1. Declines in abundance and diversity of bumble bees (Bombus spp.) in Europe have been linked to agricultural intensification and the resulting loss of suitable foraging and nesting habitats. Environmental Stewardship (ES) is a new scheme in England offering the opportunity to restore habitats of value for these important pollinators to agricultural land. Scientific evaluation of the options prescribed within the scheme is essential to ensure that their objectives are met and that the benefits can be realized by the full bumble bee species assemblage. 2. We compared the efficacy of different ES options for field margins on arable land in enhancing the abundance and diversity of flowering resources and foraging bumble bees. Our study was conducted over 3 years using a multisite experiment. 3. Overall, uncropped margins sown with mixtures containing nectar and pollen-producing plants were more effective in providing bumble bee forage than margins sown with a grass mix, allowed to regenerate naturally or managed as conservation headlands. 4. A mixture of agricultural legumes established quickly and attracted on average the highest total abundance and diversity of bumble bees, including the rare long-tongued species Bombus ruderatus and Bombus muscorum. However, marked differences were observed between species and sexes in their responses to field margin management over time. 5. A diverse mixture of native wildflowers attracted more of the shorter-tongued Bombus spp. and provided greater continuity of forage resources, especially early in the season. Allowing Cirsium spp. to flower on such margins also increased their attractiveness to male bumble bees. 6. Synthesis and applications. Our results suggest that the legume-based 'pollen and nectar flower mix', as prescribed under Entry Level Stewardship in England, can quickly provide a highly attractive forage resource for bumble bees, but that issues of seasonal flowering phenology and longevity of the mixture need to be addressed. Establishment of 'floristically enhanced margins' under Higher Level Stewardship will be important to provide diverse perennial communities of forage plants and to support a greater range of Bombus spp. and other pollinators. The population-level responses of bumble bees to introduced seed mixtures and other agri-environment options require further study in order to maximize the benefits of such schemes in intensively farmed landscapes. © 2006 The Authors.

Importance of pollinators in changing landscapes for world crops

Abstract: The extent of our reliance on animal pollination for world crop production for human food has not previously been evaluated and the previous estimates for countries or continents have seldom used primary data. In this review, we expand the previous estimates using novel primary data from 200 countries and found that fruit, vegetable or seed production from 87 of the leading global food crops is dependent upon animal pollination, while 28 crops do not rely upon animal pollination. However, global production volumes give a contrasting perspective, since 60% of global production comes from crops that do not depend on animal pollination, 35% from crops that depend on pollinators, and 5% are unevaluated. Using all crops traded on the world market and setting aside crops that are solely passively self-pollinated, wind-pollinated or parthenocarpic, we then evaluated the level of dependence on animal-mediated pollination for crops that are directly consumed by humans. We found that pollinators are essential for 13 crops, production is highly pollinator dependent for 30, moderately for 27, slightly for 21, unimportant for 7, and is of unknown significance for the remaining 9. We further evaluated whether local and landscape-wide management for natural pollination services could help to sustain crop diversity and production. Case studies for nine crops on four continents revealed that agricultural intensification jeopardizes wild bee communities and their stabilizing effect on pollination services at the landscape scale.

Global pollinator declines: trends, impacts and drivers.

Abstract: 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 the maintenance of wild plant diversity, wider ecosystem stability, crop production, food security and human welfare.

Assessing the accuracy of species distribution models: prevalence, kappa and the true skill statistic (TSS)

Abstract: Summary 1In recent years the use of species distribution models by ecologists and conservation managers has increased considerably, along with an awareness of the need to provide accuracy assessment for predictions of such models. The kappa statistic is the most widely used measure for the performance of models generating presence–absence predictions, but several studies have criticized it for being inherently dependent on prevalence, and argued that this dependency introduces statistical artefacts to estimates of predictive accuracy. This criticism has been supported recently by computer simulations showing that kappa responds to the prevalence of the modelled species in a unimodal fashion. 2In this paper we provide a theoretical explanation for the observed dependence of kappa on prevalence, and introduce into ecology an alternative measure of accuracy, the true skill statistic (TSS), which corrects for this dependence while still keeping all the advantages of kappa. We also compare the responses of kappa and TSS to prevalence using empirical data, by modelling distribution patterns of 128 species of woody plant in Israel. 3The theoretical analysis shows that kappa responds in a unimodal fashion to variation in prevalence and that the level of prevalence that maximizes kappa depends on the ratio between sensitivity (the proportion of correctly predicted presences) and specificity (the proportion of correctly predicted absences). In contrast, TSS is independent of prevalence. 4When the two measures of accuracy were compared using empirical data, kappa showed a unimodal response to prevalence, in agreement with the theoretical analysis. TSS showed a decreasing linear response to prevalence, a result we interpret as reflecting true ecological phenomena rather than a statistical artefact. This interpretation is supported by the fact that a similar pattern was found for the area under the ROC curve, a measure known to be independent of prevalence. 5Synthesis and applications. Our results provide theoretical and empirical evidence that kappa, one of the most widely used measures of model performance in ecology, has serious limitations that make it unsuitable for such applications. The alternative we suggest, TSS, compensates for the shortcomings of kappa while keeping all of its advantages. We therefore recommend the TSS as a simple and intuitive measure for the performance of species distribution models when predictions are expressed as presence–absence maps.

Landscape perspectives on agricultural intensification and biodiversity – ecosystem service management

Abstract: Understanding the negative and positive effects of agricultural land use for the conservation of biodiversity, and its relation to ecosystem services, needs a landscape perspective. Agriculture can contribute to the conservation of high-diversity systems, which may provide important ecosystem services such as pollination and biological control via complementarity and sampling effects. Land-use management is often focused on few species and local processes, but in dynamic, agricultural landscapes, only a diversity of insurance species may guarantee resilience (the capacity to reorganize after disturbance). Interacting species experience their surrounding landscape at different spatial scales, which influences trophic interactions. Structurally complex landscapes enhance local diversity in agroecosystems, which may compensate for local high-intensity management. Organisms with high-dispersal abilities appear to drive these biodiversity patterns and ecosystem services, because of their recolonization ability and larger resources experienced. Agri-environment schemes (incentives for farmers to benefit the environment) need to broaden their perspective and to take the different responses to schemes in simple (high impact) and complex (low impact) agricultural landscapes into account. In simple landscapes, local allocation of habitat is more important than in complex landscapes, which are in total at risk. However, little knowledge of the relative importance of local and landscape management for biodiversity and its relation to ecosystem services make reliable recommendations difficult.

REVIEWS AND SYNTHESES Landscape perspectives on agricultural intensification and biodiversity - ecosystem service management

Abstract: Understanding the negative and positive effects of agricultural land use for the conservation of biodiversity, and its relation to ecosystem services, needs a landscape perspective. Agriculture can contribute to the conservation of high-diversity systems, which may provide important ecosystem services such as pollination and biological control via complementarity and sampling effects. Land-use management is often focused on few species and local processes, but in dynamic, agricultural landscapes, only a diversity of insurance species may guarantee resilience (the capacity to reorganize after disturbance). Interacting species experience their surrounding landscape at different spatial scales, which influences trophic interactions. Structurally complex landscapes enhance local diversity in agroecosystems, which may compensate for local highintensity management. Organisms with high-dispersal abilities appear to drive these biodiversity patterns and ecosystem services, because of their recolonization ability and larger resources experienced. Agri-environment schemes (incentives for farmers to benefit the environment) need to broaden their perspective and to take the different responses to schemes in simple (high impact) and complex (low impact) agricultural landscapes into account. In simple landscapes, local allocation of habitat is more important than in complex landscapes, which are in total at risk. However, little knowledge of the relative importance of local and landscape management for biodiversity and its relation to ecosystem services make reliable recommendations difficult.