The development of butterfly indicators in the United Kingdom and assessments in 2010

The United Kingdom (UK) Government has national and international commitments to tackle the rate of biodiversity loss by 2010. Biodiversity indicators are used to measure and communicate progress in meeting these commitments. From 2005 onwards, butterflies have been adopted as Governmental biodiversity indicators in England, Scotland and for the UK as a whole. The indicators are compiled using butterfly abundance data collected through the UK Butterfly Monitoring Scheme, at a network of site established from 1976 onwards. The indicators show that butterfly numbers have fluctuated considerably from year-to-year, though analysis of the underlying smoothed multi-species trends for (habitat) ??specialist?? species show significant long-term declines in each country since the 1970s. Trends in wider countryside ??generalist?? species vary at the country-level from little or no overall change in Scotland and across the UK, to declines over selected years in England. Comparisons of changes in butterfly abundance before and after the 2010 target was set in 2002 suggest that the rate of decline at the UK-level is increasing for specialist species. In spite of large amounts of investment since 2000 to improve the habitat condition of protected areas, the trend for butterfly populations is no different in protected areas compared to elsewhere. Analysis by policy sector in England, shows that butterflies are declining rapidly in both forestry land and farmland, although in the latter habitat type, improvements are being seen on land entered into agri-environment schemes. We conclude by assessing the extent to which butterflies may represent broader biodiversity and help inform and evaluate conservation policy.     

Initial population trends from a 5-year butterfly monitoring scheme

The Irish Butterfly Monitoring Scheme started in 2007. The main objective of this study was to examine initial population trends from data gathered over 5 years (2008–2012) by approximately 150 volunteers across the Republic of Ireland. Nine of the 15 species analysed showed changes in population over the 5-year period; three species showed steep or moderate increases while six species showed moderate or steep declines in population. Some of these population changes are due to the highly variable weather conditions over the five years of monitoring, particularly the unusually cool, wet summer of 2012. However, factors affecting butterfly population trends are many and varied, so longer-term data are required to assess trends more reliably. A further six species had indeterminate trends over the 5-year period however, as the scheme develops, longer-term trends will have greater statistical reliability and give a clearer insight into Irish butterfly populations. The Irish Butterfly Monitoring Scheme is important in the national context, as there is little other countrywide systematic monitoring of insect populations. Furthermore, with a growing number of such standardised monitoring schemes internationally and development of bioindicators, it is now possible to monitor and track butterfly populations at larger spatial scales. We recommend that the Irish Butterfly Monitoring Scheme is continued over the long term and expanded to ensure that more Irish butterfly species are sufficiently monitored. However, in addition to monitoring population trends, basic research is still needed into the ecology and population dynamics of common butterfly species.     

Fluctuations in the abundance of butterflies, 1976–82

Abstract. 1. A scheme for monitoring the abundance of butterflies at about eighty sites in Britain is described.
2. Indices of abundance are presented for twenty-nine species for the years 1976–82.
3. There are marked differences between species in the scale of annual fluctuations.
4. Some species show correlations between successive index values; for example the summer generation index of Pieris brassicae is highly correlated with the spring generation index.
5. The annual changes in the index values of many species are highly Correlated. The index values themselves also show positive correlations, but these are less strong.
6. The drought of 1976 is believed to have severely depressed populations of many species in 1977.
7. The data do not indicate any general fall in butterfly numbers over the period at the sites in the scheme.
8. The sites are not representative of the countryside as a whole, but, for a number of species, it is considered that the index values reflect wider trends.     

A Hollywood drama of butterfly extirpation and persistence over a century of urbanization

Few long-term examples exist of wildlife population trends in urban environments despite the recent recognition of the importance of biodiversity in cities. Founded in 1896, Griffith Park’s over 1,700 ha in Los Angeles adjacent to Hollywood represent the largest municipal park in California. Through the 1920s, biologists studied the natural area with great interest but in the decades that followed, little fieldwork was conducted here as Los Angeles developed into a megacity surrounding the park. We combined thorough examination of Griffith Park historical field notes and specimen records (1900–1960) with recent field surveys (2011–2012) to determine (1) the extent of urbanization impacts on butterfly extirpation and persistence and (2) how butterfly traits and host plant relationships might be contributing to butterfly species status. Here we document multiple local butterfly extinctions in Griffith Park; 10 species or 18 % of the historically reconstructed community. Many of these species were lost early in the twentieth century, highlighting the importance of the historical record in understanding urban biodiversity patterns and trends. An analysis of larval host plant status and relationships suggests that a primary factor determining butterfly presence or extirpation is the abundance of the larval host plant in the park, in addition to host plant specificity. Despite these extirpations, we also found that the majority (over 80 %) of native butterfly species have persisted including species of conservation interest. While urban parks certainly suffer from surrounding anthropogenic pressure and impacts, this study also demonstrates the potentially high and underappreciated conservation and ecological value of urban parks.     

Negative relationships between species richness and evenness render common diversity indices inadequate for assessing long-term trends in butterfly diversity

Species richness and evenness, the two principle components of species diversity, are frequently used to describe variation in species assemblages in space and time. Compound indices, including variations of both the Shannon–Wiener index and Simpson’s index, are assumed to intelligibly integrate species richness and evenness into all-encompassing measures. However, the efficacy of compound indices is disputed by the possibility of inverse relationships between species richness and evenness. Past studies have assessed relationships between various diversity measures across survey locations for a variety of taxa, often finding species richness and evenness to be inversely related. Butterflies are one of the most intensively monitored taxa worldwide, but have been largely neglected in such studies. Long-term butterfly monitoring programs provide a unique opportunity for analyzing how trends in species diversity relate to habitat and environmental conditions. However, analyzing trends in butterfly diversity first requires an assessment of the applicability of common diversity measures to butterfly assemblages. To accomplish this, we quantified relationships between butterfly diversity measures estimated from 10 years of butterfly population data collected in the North Saskatchewan River Valley in Edmonton, Alberta, Canada. Species richness and evenness were inversely related within the butterfly assemblage. We conclude that species evenness may be used in conjunction with richness to deepen our understandings of assemblage organization, but combining these two components within compound indices does not produce measures that consistently align with our intuitive sense of species diversity.     

欧洲蝴蝶监测的历史、现状与我国的发展对策

蝴蝶是进行生物多样性监测、评估及生态环境影响评价的重要指示生物.欧洲对蝴蝶的种类组成、种群动态与分布的长期监测已有数十年的历史,先后实施了许多具有国际性影响的长期监测计划.这些计划的目标是评估区域及国家范围的蝴蝶物种丰富度的变化趋势,分析其与栖境和气候变化等环境因素的相关性,为研究、保护和利用蝴蝶资源及预测环境变化提供基础数据,并在蝴蝶受威胁等级的划分、保护措施的制定、生态环境保护与管理等方面发挥了重要作用.本文在总结欧洲蝴蝶监测历史及现状的基础上,着重介绍英国蝴蝶监测计划(The UK Butterfly Monitoring Scheme, UKBMS)、德国及欧盟等重要的蝴蝶监测计划,同时提出了开展我国蝴蝶监测工作的具体建议.     

Power to detect trends in abundance of secretive marsh birds: Effects of species traits and sampling effort

Standardized protocols for surveying secretive marsh birds have been implemented across North America, but the efficacy of surveys to detect population trends has not been evaluated. We used survey data collected from populations of marsh birds across North America and simulations to explore how characteristics of bird populations (proportion of survey stations occupied, abundance at occupied stations, and detection probability) and aspects of sampling effort (numbers of survey routes, stations/route, and surveys/station/year) affect statistical power to detect trends in abundance of marsh bird populations. In general, the proportion of survey stations along a route occupied by a species had a greater relative effect on power to detect trends than did the number of birds detected per survey at occupied stations. Uncertainty introduced by imperfect detection during surveys reduced power to detect trends considerably, but across the range of detection probabilities for most species of marsh birds, variation in detection probability had only a minor influence on power. For species that occupy a relatively high proportion of survey stations (0.20), have relatively high abundances at occupied stations (2.0 birds/station), and have high detection probability (0.50), ≥40 routes with 10 survey stations per route surveyed 3 times per year would provide an 80% chance of detecting a 3% annual decrease in abundance after 20 years of surveys. Under the same assumptions but for species that are less common, ≥100 routes would be needed to achieve the same power. Our results can help inform the design of programs to monitor trends in abundance of marsh bird populations, especially with regards to the amount of sampling effort necessary to meet programmatic goals. © 2013 The Wildlife Society     

Direct and indirect responses of tallgrass prairie butterflies to prescribed burning

Fire is an important tool in the conservation and restoration of tallgrass prairie ecosystems. We investigated how both the vegetation composition and butterfly community of tallgrass prairie remnants changed in relation to the elapsed time (in months) since prescribed fire. Butterfly richness and butterfly abundance were positively correlated with the time since burn. Habitat-specialist butterfly richness recovery time was greater than 70 months post-fire and habitat-specialist butterfly abundance recovery time was approximately 50 months post-fire. Thus, recovery times for butterfly populations after prescribed fires in our study were potentially longer than those previously reported. We used Path Analysis to evaluate the relative contributions of the direct effect of time since fire and the indirect effects of time since fire through changes in vegetation composition on butterfly abundance. Path models highlighted the importance of the indirect effects of fire on habitat features, such as increases in the cover of bare ground. Because fire return intervals on managed prairie remnants are often less than 5 years, information on recovery times for habitat-specialist insect species are of great importance.     

Butterfly abundance in a warming climate: patterns in space and time are not congruent

We present a model of butterfly abundance on transects in England. The model indicates a significant role for climate, but the direction of association is counter to expectation: butterfly population density is higher on sites with a cooler climate. However, the effect is highly heterogeneous, with one in five species displaying a net positive association. We use this model to project the population-level effects of climate warming for the year 2080, using a medium emissions scenario. The results suggest that most populations and species will decline markedly, but that the total number of butterflies will increase as communities become dominated by a few common species. In particular, Maniola jurtina is predicted to make up nearly half of all butterflies on UK Butterfly Monitoring Scheme (UKBMS) transects by 2080. These results contradict the accepted wisdom that most insect populations will grow as the climate becomes warmer. Indeed, our predictions contrast strongly with those derived from inter-annual variation in abundance, emphasizing that we lack a mechanistic understanding about the factors driving butterfly population dynamics over large spatial and temporal scales. Our study underscores the difficulty of predicting future population trends and reveals the naivety of simple space-for-time substitutions, which our projections share with species distribution modelling.     

Species richness and trait composition of butterfly assemblages change along an altitudinal gradient

Species richness patterns along altitudinal gradients are well-documented ecological phenomena, yet very little data are available on how environmental filtering processes influence the composition and traits of butterfly assemblages at high altitudes. We have studied the diversity patterns of butterfly species at 34 sites along an altitudinal gradient ranging from 600 to 2,000 m a.s.l. in the National Park Berchtesgaden (Germany) and analysed traits of butterfly assemblages associated with dispersal capacity, reproductive strategies and developmental time from lowlands to highlands, including phylogenetic analyses. We found a linear decline in butterfly species richness along the altitudinal gradient, but the phylogenetic relatedness of the butterfly assemblages did not increase with altitude. Compared to butterfly assemblages at lower altitudes, those at higher altitudes were composed of species with larger wings (on average 9 %) which laid an average of 68 % more eggs. In contrast, egg maturation time in butterfly assemblages decreased by about 22 % along the altitudinal gradient. Further, butterfly assemblages at higher altitudes were increasingly dominated by less widespread species. Based on our abundance data, but not on data in the literature, population density increased with altitude, suggesting a reversed density–distribution relationship, with higher population densities of habitat specialists in harsh environments. In conclusion, our data provide evidence for significant shifts in the composition of butterfly assemblages and for the dominance of different traits along the altitudinal gradient. In our study, these changes were mainly driven by environmental factors, whereas phylogenetic filtering played a minor role along the studied altitudinal range.     

Forces driving the composition of butterfly assemblages in Andorra

Despite the impact that human presence has on the area, Andorra in the eastern Pyrenees still harbours a rich butterfly fauna and is a potentially excellent area for studying the effects of global change on biodiversity. The aim of this study was to identify and understand the factors that are inducing observed patterns of butterfly richness in Andorra. We used data collected between 2006 and 2010 from six transects of the Andorran Butterfly Monitoring Scheme that lie at heights from 1,000 to 2,400 m a.s.l. These transects are divided into 44 discrete sections and during the study period 18,603 individuals belonging to 126 butterfly species were recorded. The effects of elevation and habitat composition on species richness and abundance were analyzed, as was the presence of spatial structure in the butterfly assemblages. We found a clear tendency for species richness to decrease as elevation increased and also identified a major faunal turnover. Habitat composition seems to have little effect on species richness and butterfly abundance. A spatial structure was observed in the dataset, with a positive spatial autocorrelation at section scale that reflects a clear effect of altitudinal gradient on species assemblages. Finally, a cluster analysis enabled us to define two main faunistic groups, corresponding to lower (generally in closed habitats) and higher sites (generally in subalpine meadows and grasslands). We thus conclude that the elevation gradient is the principal factor driving butterfly distribution and abundance in Andorra.     

Moths count: recording moths for conservation in the UK

Insects are under-represented in current assessments of biodiversity loss at global and national scales. Butterflies, and a few other insect taxa, have been used as indicators of biodiversity change and as flagships for conservation, especially in temperate zones, but these groups are typically species-poor and may not be representative of insects as a whole. Macro-moths, on the other hand, are an important component of UK biodiversity, in terms of both species richness and ecosystem function. Moth abundance has decreased significantly in the UK and there is rapidly growing interest in the surveillance and monitoring of macro-moths among amateur and professional scientists. The Moths Count project was instigated to raise awareness of moths, increase moth recording and set up a long-term National Moth Recording Scheme for c.900 species of macro-moth in the UK. Since 2006, Moths Count has promoted moths to millions of people, trained and engaged thousands in recording and collated over eight million species distribution records into the National Moth Recording Scheme. These data, though incomplete at present, are already contributing to assessments of biodiversity loss and to conservation initiatives. We present initial results which show that substantial changes are already evident for macro-moths in the UK. The northern range margins of a sample of 12 species have shifted northwards by 194.8 km on average between 1982 and 2009 (7.8 km year^?1 over the 25 years between survey mid-points). Provisional distribution trends (not corrected for variation in recording effort) were calculated for 43 species and the results corroborated both positive and negative population-level changes assessed previously.     

Bounded random walks as a null model for evaluating population trends

Management of wildlife and protection of endangered species depend on determination of population trends. Because population changes are stochastic and autoregressive, there is reason to believe that population trends might not be properly determined by simple regression over short time periods. A bounded random walk (BRW) model is introduced as a null model for evaluating population trends. The BRW model shows long-term stability but rising and falling sequences of up to many decades. For a given variability and survey length, there will be an expected probability of finding a greater than X% slope simply by chance. This false positive probability needs to be considered when evaluating trends. Breeding Bird Survey data for 128 species over 46 years for two states were analyzed for trends for different series lengths. Trends estimated from short series were likely to not agree with the 46-year trends. Very short series (e.g., 5 years) tended to indicate no trend due to loss of statistical power. A 101-year series for sandwich term (Sterna sandvicensis) revealed that even for 40 year-long series, 33% of subset series had a negative trend compared to the strong 101 year full series positive trend. The BRW model simulations and both data sets pointed to 20 years as a minimum time period for estimating trends reliably, though this can be longer for species that tend to cycle. Proper inference should thus consider the implications of inherent time series variability.     

Butterfly community recovery in degraded rainforest habitats in the Upper Guinean Forest Zone (Kakum forest, Ghana)

Successful regeneration of secondary tropical forest might be crucial in the conservation of rainforests, since large areas of primary forest have been destroyed or degraded. Animal communities might play an important role in restoration of biological diversity in these secondary habitats, since some groups have high mobility and capacity for dispersal. Fruit-feeding butterflies were trapped to measure differences between butterfly communities in primary rainforest and disturbed forest habitats of different stage of regeneration including clear-cut, abandoned farmland, newly planted forest and middle-aged secondary growth. 3465 specimens representing 114 species were identified from 56 traps operated for 36 days. Extremely high values of rarefied species richness were estimated in the clear-cut habitat, due to the high number of singletons and doubletons. This was caused by a gap-effect that allowed penetration of canopy and open area species after disturbance. The differences between butterfly communities were best demonstrated through ecological composition, richness and abundance of indicator groups and habitat similarity based on Jaccard’s similarity index. The results show a clear ability of butterfly communities in degraded forest habitats to regenerate in 50–60 years after clearance.     

Recent trends in butterfly populations from north-east Spain and Andorra in the light of habitat and climate change

Although butterfly declines have been reported across Europe, no assessment based on detailed quantitative data has ever been made for any extensive area in the Mediterranean Basin. In 1994, a Butterfly Monitoring Scheme was launched in Catalonia (NE Spain), and in 2005 a similar, albeit much smaller, scheme started in the neighbouring Pyrenean country of Andorra. Here we provide a first thorough assessment of butterfly trends in both areas for the last 15 years. Several patterns emerged, above all a worrying decline of a substantial part of the fauna. It was also evident that habitat specialists are experiencing greater declines than habitat generalists, thereby butterfly communities becoming progressively dominated by common species. However, habitat indicators based on characteristic species also revealed that trends are actually associated with habitat types, grassland and scrub specialists declining strongly but woodland specialists showing a marginal increase. These differences are certainly related to profound landscape changes, mainly a dramatic reduction of semi-natural grasslands and open Mediterranean scrub, and a major increase in woodlands. The general effect of climatic warming on butterfly populations was investigated by using the temperature community index (CTI) approach. The thermal structure of butterfly communities remained very stable over time, except in one case where, contrary to the expectations, a significant negative trend in the CTI was noted. However, this surprising result can be explained by taking into account the above-reported pattern of butterfly communities becoming dominated by common species, characterized by low thermal indices in comparison with declining Mediterranean specialists.     

Climate conditions and resource availability drive return elevational migrations in a single-brooded insect

Seasonal elevational migrations have important implications for life-history evolution and ecological responses to environmental change. However, for most species, particularly invertebrates, evidence is still scarce for the existence of such migrations, as well as for the potential causes. We tested the extent to which seasonal abundance patterns in central Spain for overwintering (breeding) and summer (non-breeding) individuals of the butterfly Gonepteryx rhamni were consistent with three hypotheses explaining elevational migration: resource limitation (host plant and flower availability), physiological constraints of weather (maximum temperatures) and habitat limitation (forest cover for overwintering). For overwintering adults, abundance was positively associated with host plant density during two intensive survey seasons (2007–2008), and the elevational distribution was relatively stable over a 7-year period (2006–2012). The elevational distribution of summer adults was highly variable, apparently related both to temperature and habitat type. Sites occupied by adults in the summer were on average 3 °C cooler than their breeding sites, and abundance showed negative associations with summer temperature, and positive associations with forest cover and host plant density in 2007 and 2008. The results suggest that the extent of uphill migration in summer could be driven by different factors, depending on the year, and are mostly consistent with the physiological constraint and habitat limitation hypotheses. In contrast, the patterns for overwintering adults suggest that downhill migration can be explained by resource availability. Climate change could generate bottlenecks in the populations of elevational migrant species by constraining the area of specific seasonal habitat networks or by reducing the proximity of environments used at different times of year.     

Is the Natura 2000 network sufficient for conservation of butterfly diversity? A case study in Slovenia

Slovenia has one of the most extensive Natura 2000 networks in Europe with 259 SAC’s covering 31.4% of the country. To determine how well does the current network cover the areas of high butterfly diversity and/or aggregation of the butterfly species of conservation concern, the data from the recent survey for a distribution atlas were used. Altogether 99,423 records of 173 species collated after 1979 were used. The data distribution is slightly biased towards SAC’s, with 44.8% of localities within them, most likely due to sparsely sampled urban areas and intensive farmland areas which are found only outside SAC’s. The diversity and distribution of red listed species was evaluated at a 5 × 5 km grid square level. Additionally the importance of the size of the SAC’s was compared to their butterfly species diversity. In general the high diversity areas also hold the largest aggregation of red listed species with core areas concentrated in SW Slovenia. The SAC’s cover majority of areas with high diversity and the distribution of all but one threatened butterfly species. That species is Colias myrmidone, which is now considered extinct in Slovenia with no records after 1993. The most prominent areas with high conservation value in Slovenia not included in the SAC’s network are the Koro?ka region, Gori?ka Brda region, lower Sava River valley and Slovenske Gorice region. The butterfly diversity in small SAC’s is relatively high with increases in size only gradually increasing the species numbers, thus emphasizing the importance and conservation value of small SAC’s for sustaining high butterfly diversity in Slovenia.     

Turnover and trends in butterfly communities on two British tidal islands: stochastic influences and deterministic factors

Aim Community trends were investigated for two small islands and two local mainland butterfly communities within the UK over a period of 20–30 years. Location Hilbre Island off the Wirral Peninsula at 53.33° N, 3.10° W; Lindisfarne, an island off the Northumberland coast at 56.41° N, 1.48° W; Leighton Moss at 54.08° N, 2.26° W; Wyre Forest at 52.23° N, 2.14° W, UK. Methods Butterfly species data were collected on Hilbre and two mainland sites (Leighton Moss and Wyre Forest) from 1983 to 2006, and on Lindisfarne from 1977 to 2006, as part of the National Habitat Survey, the UK Butterfly Monitoring Scheme and ‘Butterflies for the New Millennium Atlas’ recording. Matrices of associations (Sokal and Michener’s matching coefficient S_SM; resemblance coefficient) were computed between years and subject to non‐metric multidimensional scaling (NMDS) and Mantel tests. The pattern of extinctions and colonizations at sites were examined, their heterogeneity tested by applying a Friedman test to fractional incidences for the same years. Regression analysis (multiple regression and logit regression) was used to relate butterfly numbers and incidences to climate variables, time and previous records. Results Significant community trends based on population counts and species’ incidences were found for all four sites. There was a significant climatic signal for Hilbre; although this was not apparent for the remaining sites, significant associations occurred between records for a number of species and climatic variables at all sites. Substantial turnover of species on the islands was inversely related to numbers of records for species but not to their conspicuousness to recorders. Main conclusions We argue that time trends are widespread in butterfly communities, even for relatively short periods; they are largely generated by stochastic influences rather than by more substantive factors such as climate change. Potential biases in surveying and recording history are shown to be unlikely. A clear climate signal was found only for the small Hilbre Island, for which there was also evidence for the significant influence of colonization capability of individual source species. We conclude that for many species, small islands will be sinks or pseudosinks and their ‘populations’ vulnerable to small changes in source–sink dynamics.     

Butterfly monitoring in Europe: methods,applications and perspectives

Since the first Butterfly Monitoring Scheme in the UK started in the mid-1970s, butterfly monitoring in Europe has developed in more than ten European countries. These schemes are aimed to assess regional and national trends in butterfly abundance per species. We discuss strengths and weaknesses of methods used in these schemes and give examples of applications of the data. A new development is to establish supra-national trends per species and multispecies indicators. Such indicators enable to report against the target to halt biodiversity loss by 2010. Our preliminary European Grassland Butterfly Indicator shows a decline of 50% between 1990 and 2005. We expect to develop a Grassland Butterfly Indicator with an improved coverage across European countries. We see also good perspectives to develop a supra-national indicator for climate change as well as an indicator for woodland butterflies.     

Signals of Climate Change in Butterfly Communities in a Mediterranean Protected Area

The European protected-area network will cease to be efficient for biodiversity conservation, particularly in the Mediterranean region, if species are driven out of protected areas by climate warming. Yet, no empirical evidence of how climate change influences ecological communities in Mediterranean nature reserves really exists. Here, we examine long-term (1998–2011/2012) and short-term (2011–2012) changes in the butterfly fauna of Dadia National Park (Greece) by revisiting 21 and 18 transects in 2011 and 2012 respectively, that were initially surveyed in 1998. We evaluate the temperature trend for the study area for a 22-year-period (1990–2012) in which all three butterfly surveys are included. We also assess changes in community composition and species richness in butterfly communities using information on (a) species’ elevational distributions in Greece and (b) Community Temperature Index (calculated from the average temperature of species'' geographical ranges in Europe, weighted by species'' abundance per transect and year). Despite the protected status of Dadia NP and the subsequent stability of land use regimes, we found a marked change in butterfly community composition over a 13 year period, concomitant with an increase of annual average temperature of 0.95°C. Our analysis gave no evidence of significant year-to-year (2011–2012) variability in butterfly community composition, suggesting that the community composition change we recorded is likely the consequence of long-term environmental change, such as climate warming. We observe an increased abundance of low-elevation species whereas species mainly occurring at higher elevations in the region declined. The Community Temperature Index was found to increase in all habitats except agricultural areas. If equivalent changes occur in other protected areas and taxonomic groups across Mediterranean Europe, new conservation options and approaches for increasing species’ resilience may have to be devised.