State of Nature report - RSPB

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METHODS Methods (cont.) Biological recording data National recording schemes collect data on a vast array of taxonomic groups, from slime moulds to spiders. However, it can be difficult to use these datasets from opportunistic records to assess changes over time, as recording effort varies across the UK and over time. Several statistical techniques are now available to help control for these biases, and three of these, Frescalo 18 , list length 19 and mixed model 20 were used here to measure change in distribution at a 1 km grid scale for selected groups. An average of the three z-scores obtained from the three methods was used to place each species into the four trend categories as follows: Strongly increasing: Species with a statistically significant positive z-score Slightly increasing: Species with a non-significant positive z-score Strongly decreasing: Species with a statistically significant negative z-score Slightly decreasing: Species with a non-significant negative z-score Habitat associations Since most species use more than one habitat, they were assigned to more than one in our analyses. As a result, the habitat-specific information does not add up to the overall information. We defined the habitat associations of the following taxonomic groups: Flowering plants 2 Bryophytes 21 Birds 22 Butterflies Bats 23 Moths 24 Bees, wasps and ants 25 Lichens 26 Mammals 27 Carabids Ladybirds National Red Lists At a global level, the IUCN co-ordinates the process of assessing which species are threatened with extinction and have developed assessment criteria to make the process as transparent and consistent as possible 28 . These criteria are based on a variety of parameters, including the rate of change in species abundance or distribution, total population size and the number of populations. How threatened a species is may vary across its range and often regional or national Red Lists are produced, documenting which species are threatened at different spatial scales. In the “Facts behind the headlines” section, we have brought together all the national Red Lists, for either the UK or Great Britain, that have been produced using the latest guidelines from the IUCN, as well as those produced using older “Red Data Book” type assessments that were done before the more recent IUCN guidelines were available, or non-IUCN criteria. Red Lists for the following taxonomic groups were included: Flowering plants 29 Mosses, liverworts and hornworts 30 Stoneworts 31 Lichens 32 Dragonflies 33 Butterflies 34 Flies (families Nematocera, Aschiza and Empidoidea) 35 Water beetles 36 Birds 37 Crustaceans 38 Molluscs 38 Various insect groups 39 Spiders 40 In the habitat chapters, we report only on flowering plants and bryophytes as these have up-to-date Red Lists and published accounts of habitat associations. 80 STATE OF NATURE 2013
Watchlist indicator Between 1995 and 1999, 577 species were identified as priorities for conservation, under the UK BAP. The list was reviewed in 2007, and doubled in length to 1,150 species. This list has been superseded by priority species lists for the UK’s four nations individually, but remains a good indication of species that have been conservation priorities in the UK since the 1990s and remain so now. We have developed a new Watchlist Indicator, showing the overall trend in population of 155 conservation priority species – about 13% of those listed as UK BAP priorities. The species included were all those where information was available on changes in population abundance over time, and do not represent a random sample of those on the UK BAP list. Annual estimates of relative abundance were available for 51 birds 4–9 , 77 moths 16 , 19 butterflies 15 and eight mammals 7,10,11,12 . For many of these species, data were available from the 1970s to the present day. However, for some species, the time series available was substantially shorter. In order to combine the species into a composite indicator, we first scaled the data for each species so that the estimate for each year was expressed as a proportion of the estimate in the first year. The composite index shown in the report is the geometric mean of the scaled species-level data. The index has been adjusted to take into account the different starting years for different species, with “new” species entering the index scaled to the overall index value for the year of entry. The 95% confidence intervals around the composite index were generated by bootstrapping the species-level trend data. CaveaTS The datasets presented in this report are a summary of the information available: this is the first time that these data have been brought together and assessed as a whole. However, the datasets have not been selected to reflect a representative sample of UK species, either within or between taxonomic groups or habitats. This means that we should be cautious about extrapolating findings beyond the species assessed. Additionally, although there are numerous studies investigating the underlying reasons for these changes in abundance or distribution, it is difficult to interpret the observed patterns for many species. Here we have put together datasets collected using different methods, measuring different aspects of species status on a variety of spatial scales and analysed using different statistical techniques. There are two points to note about this. Firstly, how a species has been monitored – the method, effort and extent of surveying – can influence whether the results were suitable for our analyses, and indeed the species’ trend itself. Whether trends in abundance or range are reported can be influential. For example, when a widespread species begins to decline, changes in abundance may be detected before changes in distribution. Conversely, increases in distribution in an already widespread species may be difficult to detect. The scale at which trends in range are measured can also be influential, with range loss at a fine spatial scale not detected if mapping is done at a coarser resolution. Many of the monitoring schemes that produce the datasets included in this report have a wide range geographically, but may not have sufficient sampling density locally to pick up changes in localised or particularly rare species. As a result, trends for relatively few of these species are reported. Our measures of the balance of increasing and decreasing species may therefore be biased towards the more common, widespread and generalist species. Secondly, although official guidelines are used to produce national Red Lists, there is room for variation in interpretation of these guidelines and so there are small differences in the way different authors have compiled the national Red Lists summarised here. This is particularly true in defining which species are not threatened (of Least Concern). STATE OF NATURE 2013 81
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STATE OF NATURE Foreword by Sir Dav
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UPLAND STATE OF NATURE 2013 29
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Although robust data are in short s
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ought species back from the brink o
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Wasps (175) All (5%) Moths (676) La
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MEASURING THE STATE OF NATURE Measu
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Although the evidence for the wides
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FARMLAND Farmland makes up around 7
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Why is farmland wildlife changing?
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Brown hares have benefited from hab
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lowland semi-natural grassland and
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Why is lowland semi-natural grassla
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Common lizard Steve Knell All six o
Page 29 and 30: UPLAND The UK’s uplands are the h
Page 31 and 32: o single factor is responsible for
Page 33 and 34: Golden eagles and other animals are
Page 35 and 36: WOODLAND Much of Britain was once c
Page 37 and 38: Why is woodland wildlife changing?
Page 39 and 40: Increased grazing pressure from dee
Page 41 and 42: COASTAL Wrapped in a narrow ribbon
Page 43 and 44: Why is coastal wildlife changing? T
Page 45 and 46: Genevieve Leaper Sea thrift on a cl
Page 47 and 48: FRESHWATER AND WETLANDS Freshwater
Page 49 and 50: Why is freshwater and wetland wildl
Page 51 and 52: Common frog Mark Sisson Freshwater
Page 53 and 54: URBAN There are many different ways
Page 55 and 56: Why is urban wildlife changing? A s
Page 57 and 58: The renovation or demolition of old
Page 59 and 60: URBAN Derelict, disused and unloved
Page 61 and 62: MARINE he UK is truly a maritime na
Page 63 and 64: hanges in the temperature, circulat
Page 65 and 66: Harbour seals have declined by near
Page 67 and 68: UK OVERSEAS TERRITORIES The UK has
Page 69 and 70: Just one individual of St Helena’
Page 71 and 72: EXTINCTIONS AND COLONISATIONS You w
Page 73 and 74: Little egret Ernie Janes The little
Page 75 and 76: CONSERVATION HEROES Picture the sce
Page 77 and 78: Climate change Climate change is al
Page 79: A: In some datasets, both total cha
Page 83 and 84: 11: Fuller RM (1987) Biological Con
Page 85 and 86: in urban area: implications for nat
Page 87 and 88: ACKNOWLEDGEMENTS Acknowledgements T
Page 89 and 90: Conchological Society of Great Brit
Page 92: The State of Nature report is a col
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