State of Nature report - RSPB

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FRESHWATER AND WETLANDS verall, slightly more freshwater species have declined than increased over recent decades. Some river birds, such as dippers and kingfishers, show declines, but 74% of freshwater and wetland birds are increasing. These include widespread species such as the mallard, recent colonists such as little egrets, and species such as ospreys which are recovering from earlier declines, thanks to conservation efforts. Index (1975 = 100) 200 150 100 An indicator based on trends in 26 freshwater and wetland birds (see Figure 19) is used as a measure of freshwater biodiversity 10 . There are marked differences in the trends of birds in different habitats, although some are based on only a few species. All (1008) Invertebrates (502) Plants (458) Vertebrates (48) 0 25 50 75 100 Percentage of species Strong decrease Slight decrease Strong increase Slight increase 50 0 1975 1977 1979 1981 1983 1985 1987 1989 The wetland plants included in this report were split almost equally between those declining (54%) and increasing (46%) in range (see Figure 17), although aquatic plants may be faring worse. Many declining species, such as frogbit, are associated with small pools on farmland, which are prone to eutrophication and in-filling. A recent assessment of our native fish suggested that 40% were declining, with nearly all of those increasing (40%) doing so at least partly due Numbers of fish 600000 500000 400000 300000 200000 100000 0 1971 1974 1977 1980 1983 1986 All water and wetland birds (26) Reedbed birds (4) Wet grassland birds (8) Fast-flowing water birds (4) Birds of slow-flowing and standing water (6) 1991 Year 1989 Year 1992 1995 1998 2001 2004 2007 2010 1993 1995 1997 1999 2001 2003 2005 2007 2009 to stocking – the process of releasing fish, often captive-reared, into water courses 11 . Losses of European eel have been so great that it is considered Critically Endangered globally 7,12 , and although Atlantic salmon have returned to some rivers (including the Tyne and Mersey, but not the Thames), they remain at an all-time low (see Figure 18) 4 . Many freshwater invertebrates are also struggling: 64% of wetland moths have declined in the last 40 years, and 44% have declined strongly. 2011 Of the 849 freshwater and wetland plant species assessed in recent national Red Lists, 86 are threatened with extinction in the UK. Some groups uniquely associated with wetland habitats, such as stoneworts, dragonflies and water beetles have also been assessed recently. Stoneworts are a unique group of algae with hard mineral walls around their cells, which can be up to 20cm long – the largest cells known to science. Sadly, almost 40% of UK stonewort species are considered threatened 13 . 48 STATE OF NATURE 2013
Why is freshwater and wetland wildlife changing? It could be argued that freshwaters are affected by more threats than any other part of the natural environment. The few exceptions tend to be in well-protected catchments, such as more remote upland areas or small, non-intensively managed catchments that are isolated from the influences of farming and urban areas. The main causes of change in freshwater habitats are summarised below. Substantial efforts to control these impacts have been in progress for around 100 years, but mitigation has often proved difficult and in some cases has shown little benefit. Problems such as diffuse nutrient pollution from farmland run-off are particularly difficult to tackle. Many freshwaters face more than one problem, and this probably underlies the loss of most wildlife. In addition, habitat fragmentation caused by the absence of clean water from large parts of the landscape makes many scarcer species very vulnerable to extinction locally or nationally. Example Many rivers have lost their natural banks and meanders, and ancient wetlands have been drained. 227,000 ponds were lost on farms between 1945 and 1998 15 . Example The glutinous snail was found in clean unpolluted lakes, ponds and ditches. It now survives in just one site in Wales and was declared extinct in England in 2010 16 . Water pollution Example Without active management, such as grazing and cutting, fens, reedbeds and other early successional habitats will turn to scrub and woodland. Physical modification and drainage Lack of active management Example The range of the Arctic char is contracting in the UK as a result of increasing water temperatures 17 . Dragonflies are expanding northwards and colonising from the continent 18 . Climate change What factors affect freshwater and wetland wildlife? Water abstraction Example This is implicated in the decline of fen and chalk stream quality: 15% of river catchments are over-abstracted 20 . This may also be responsible for the extinction of the pool frog from its last UK site. Non-native species and introduced diseases Creation of new wetland habitat Example White-clawed crayfish have been eliminated from large parts of southern Britain by crayfish plague 19 . Example New habitat has been created following mineral extraction, as well as through direct reedbed and wetland restoration. Many freshwater birds, including tufted ducks, bitterns and marsh harriers have benefited. STATE OF NATURE 2013 49
Page 3 and 4: STATE OF NATURE Foreword by Sir Dav
Page 5 and 6: UPLAND STATE OF NATURE 2013 29
Page 7 and 8: Although robust data are in short s
Page 9 and 10: ought species back from the brink o
Page 11 and 12: Wasps (175) All (5%) Moths (676) La
Page 13 and 14: MEASURING THE STATE OF NATURE Measu
Page 15 and 16: Although the evidence for the wides
Page 17 and 18: FARMLAND Farmland makes up around 7
Page 19 and 20: Why is farmland wildlife changing?
Page 21 and 22: Brown hares have benefited from hab
Page 23 and 24: lowland semi-natural grassland and
Page 25 and 26: Why is lowland semi-natural grassla
Page 27 and 28: 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: FRESHWATER AND WETLANDS Freshwater
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 and 80: A: In some datasets, both total cha
Page 81 and 82: Watchlist indicator Between 1995 an
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

State of Nature report - RSPB

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