5 What are the five lessons learnt from the evaluation and what do these mean for the nature conservation policy ? a. Increasing the area of National Ecological Network further . In order to realise the National Ecological Network by 2018 and to enhance the coherence within the National Ecological Network great efforts have to be made towards realising the surface area of the National Ecological Network ( some 730,000 ha of land by 2018 ). In the years to come the strategy is aimed at further increasing the area of the National Ecological Network . b. Improving the quality of the National Ecological Network . The number of species is still declining , although the pace at which this is happening has slowed down . An impulse should be given with respect to the environmental conditions and the spatial coherence between the areas . Acidification and over-fertilisation in particular can be tackled more vigorously through instruments specifically designed for certain areas ( for example , expanding the nature areas and developing buffer zones around them ). The efforts against water depletion need to be intensified and require an a large-scale approach aimed at the entire water catchment , not just at individual sites . The benefits for the nature in the bordered National Ecological Network can be increased provided that specific measures are taken in each of the areas , while taking the entire water catchment into account . c. Maintaining pace of realisation . In addition to the government acquiring land for the organisations that manage large areas , the National Ecological Network can in part be realised by involving farmers and other private individuals ( for example country estate owners ) in the development and management of natural sites . The farmer remains owner of the land but in addition to being a farmer he would then be a manager of the natural site as well . The government provides the farmer with a subsidy for this management function . In addition , over the last few years the government has reserved extra financial resources for land acquisition because of the increased land prices . The present cabinet has also made more funds available in order to be able to complete the National Ecological Network by 2018 . These extra funds are intended for land acquisition , design , management , defragmentation measures and for measures to combat water depletion in the nature areas . d. Creating more connections as a solution for the problem of too little coherence . The construction of robust connections i.e. covering a large surface area ( often both in terms of width and length ) is receiving priority over the smaller connections . In 2000 the policy document " Nature for People , People for Nature " was issued in which the policy was modified according to the evaluation . The ambition of this policy document is to proceed more vigorously with the realisation of the National Ecological Network . The spatial coherence - and therefore the functioning - of the National Ecological Network is enhanced by constructing boundaries in a smarter way and by realising green connections between and within nature areas . That is why on the one hand extra efforts are being made to create " green-blue pathways " in the man-made landscape . This helps establish a coherent network of lines and flat elements in the landscape . On the other hand efforts are being made towards realising a number of robust connections between larger ecological core areas . The design phase is a very important stage in this process in order to convert the objectives ( and the wishes ) into the desired result . e. Creating robust connections has priority . Robust connections can either be green ( terrestrial ) or blue ( aquatic ). They connect nature areas that are spatially separated from one another and increase the spatial coherence at national level . This involves connections between comparable nature areas ( ecosystems such as marshes , woodland and heath ) or very dissimilar areas , for example transition areas from wet to dry or from oligotrophic to eutrophic . Examples of this are river valleys on sandy soil and the transition areas from dunes to peat marshes . Robust connections ensure that new nature areas are accessible and that areas where the species die out can be colonised once more . The connections also enable species to move to other regions ( for example , in the event of climate change or disasters ). The connections obtain their robustness through their area and form . As the robust connections have to accommodate a very wide range of species ( for example red deer , adders , otters and butterflies , but also birds ) they should consist of wide zones with a mosaic of various types of habitats . To an increasing extent they have to form more or less complete ecosystems in themselves . The robust connections will cover a total area of 27,000 ha ( see figure on the left ). The form and the size of the individual robust connections will vary from one another . Depending on the situation , a " corridor " or " stepping stone " may be required , or a combination of the two . In other words : the connections consist of smaller links and larger junctions ( living habitats ). For other species these links can also function as habitats . Robust connections are part of the National Ecological Network and function as part of nature . They form a condition for the preservation of the biodiversity at national , regional and local levels . But they can also provide space for recreation , water management or water extraction . In addition they improve the landscape and the cultural-historical identity of an area . In 2003 governmental agreements were made between the Ministry of Agriculture , Nature Management and Fisheries and the provinces regarding the general locations , the area required , the pace of the realisation and the ecological ambitions of the 12 robust connections . The setting of accurate boundaries and the delivery of robust connections is a task of the provinces . In 2018 the robust connections , along with the rest of the National Ecological Network , should be complete . The defragmentation of all state infrastructures within the robust connections would then also be accomplished . 6 Examples of the National Ecological Network , robust connections and nature development in the region . A great cultural feat . The aim is to realise the National Ecological Network by approximately 2018 . It is a lengthy process , as it involves a large part of the Netherlands . Results , however , have already been observed after a relatively short period of time , for example in the Oostvaardersplassen and in the nature development areas along the large rivers . Just as in the days of the reclamation of the peat bogs and/or the construction of the dikes in the battle against the water , this involves a great cultural feat . It will take time but will result in a sustainable , liveable and characteristic Netherlands . Nature restoration : not all past interventions are irreversible . After 10 years of National Ecological Network policy , the various efforts can already be seen to produce results . It even proves possible to change back interventions that initially seemed impossible to reverse to the original situation , for example the recent decision to demolish an industrial site in the Renkum river valley . This is the first step towards the realisation of the Renkumse Poort , an ecological corridor from the Veluwe to the Rhine . Reversing interventions of the past , such as the demolition of an industrial site that was built in a river valley , conveys the important message that it is indeed possible to create high-quality nature in a densely populated country such as the Netherlands . The same applies to returning straight running rivers to the meandering form they once had , nature development in the river valleys ( river forelands ) and peat bogs , stopping military activities on military exercise terrains and airfields , constructing ecoducts over motorways , etc . These all provide new opportunities to nature . Robust connection : the " Wet Axis ". The " Wet Axis " is a planned robust connection from the Lauwers Lake and the Dollard to the Zeeland Delta ( see figure , page 15 ). The purpose of this connection is to increase the coherence between important international peat bogs . With the " Wet Axis " some 11,000 ha of new natural wetland will be added to the ecological network as robust connections . The development of connected marshes , reed-lands and marsh woodlands creates opportunities for increasing the numbers of bitterns , otters and many other species . The bittern is a species of bird that lives in large marsh areas . The larger part of the Dutch population of bitterns is to be found in the planned " Wet Axis ". Although the Netherlands are internationally obliged to protect this species , the number of bitterns is dwindling . This is not because of a lack of suitable habitats . Rather , this is because the bittern can not make optimum use of the habitats as they are located too far from one another . In addition to increasing the natural value the " Wet Axis " contributes towards the solution of the water quality problems , improvement of the landscape and the cultural-historical quality but also pro-vides opportunities for recreational use . An example of an area that is currently being realised in the " Wet Axis " is the Strategisch Groenproject De Venen ( De Venen Strategic Green Project ), an area of 33,000 ha , situated in the triangle of Amsterdam , Utrecht and Gouda . De Venen has two core ecological areas ( Nieuwkoopse plassen en Vinkenveense plassen ) which are enlarged by nature restoration and the realisation of preservation areas . This provides a solution for sustainable agriculture , nature and recreation . Robust connections as gradient : expanding habitat of red deer as guide species . The red deer is the largest wild mammal in the Netherlands . Its natural habitat includes woodlands of both the poorer , higher sandy areas , and the lower wet and nutrient richer grasslands of the river valleys , where more food is available . At present , however , the parts of its natural habitat that are rich in food are hardly accessible to the red deer . By realising robust connections between the Veluwe and the river valleys , the Oostvaardersplassen and the nature areas in Germany , various parts of the natural habitat would become interconnected and the gradient differences reinforced . There would then be sufficient food throughout the year , which would increase the survival rates of the present populations and the viability of these populations . Other species in the wake of the red deer would be able to benefit by this connection , species such as wild boar , roe deer and pine martens . Migrating species would be able to carry all sorts of seeds and eggs in their fur or feathers or on their hooves . In this way less mobile plant and animal species can benefit by a coherent ecological network as well . Intermezzo : nature development - from random processes to purposeful interventions . Nature development aims at creating new nature . It is not possible to protect nature merely by conservation and management , nature should also be given the opportunity to develop . This insight has been reinforced by a surprising event that started to take place in the Flevo polder during the eighties . In this polder , within a short period of time , the Oostvaardersplassen have developed into a wonderful natural site with an unprecedented wealth of bird life , although initially it was intended as an industrial area . The area now enjoys international recognition . It is quite remarkable how nature can create such wonderful new valuable ecological areas in just a short period of time . Nature development in the Netherlands has already proven to be a successful instrument in the battle against the decline of nature . In theory this can be applied anywhere : in ( former ) agricultural areas , along rivers and in city parks . Opportunities There are all sorts of new opportunities as well , such as co-operation with private managers , for example farmers . An example , although still in its infancy , is the creation of new country estates as steppingstones in the National Ecological Network . Another example is the co-operation with the Ministry of Transport , Public Works and Water Management . Better protection against high waters can be achieved by solutions such as providing the rivers with more space . This can very well be combined with nature development , for example the creation of ancillary channels that flow along with the river . In this way both the budget for river safety and the budget for the realisation of the National Ecological Network can be used for connectivity . 12. General overview of the site : The Humber Estuary is the largest macro-tidal estuary on the British North Sea coast . It drains a catchment of some 24,240 square kilometres and is the site of the largest single input of freshwater from Britain into the North Sea . It has the second-highest tidal range in Britain ( max 7.4 m ) and approximately one-third of the estuary is exposed as mud or sand flats at low tide . The inner estuary supports extensive areas of reedbed with areas of mature and developing saltmarsh backed in places by limited areas of grazing marsh in the middle and outer estuary . On the north Lincolnshire coast the saltmarsh is backed by low sand dunes with marshy slacks and brackish pools . The Estuary regularly supports internationally important numbers of waterfowl in winter and nationally important breeding populations in summer . 14. Justification for the application of each Criterion listed in 13 above : Ramsar criterion 1 . The site is a representative example of a near-natural estuary with the following component habitats : dune systems and humid dune slacks , estuarine waters , intertidal mud and sand flats , saltmarshes , and coastal brackish / saline lagoons . It is a large macro-tidal coastal plain estuary with high suspended sediment loads , which feed a dynamic and rapidly changing system of accreting and eroding intertidal and subtidal mudflats , sandflats , saltmarsh and reedbeds . Examples of both strandline , foredune , mobile , semi-fixed dunes , fixed dunes and dune grassland occur on both banks of the estuary and along the coast . The estuary supports a full range of saline conditions from the open coast to the limit of saline intrusion on the tidal rivers of the Ouse and Trent . Wave exposed sandy shores are found in the outer / open coast areas of the estuary . These change to the more moderately exposed sandy shores and then to sheltered muddy shores within the main body of the estuary and up into the tidal rivers . The lower saltmarsh of the Humber is dominated by common cordgrass Spartina anglica and annual glasswort Salicornia communities . Low to mid marsh communities are mostly represented by sea aster Aster tripolium , common saltmarsh grass Puccinellia maritima and sea purslane Atriplex portulacoides communities . The upper portion of the saltmarsh community is atypical , dominated by sea couch Elytrigia atherica ( Elymus pycnanthus ) saltmarsh community . In the upper reaches of the estuary , the tidal marsh community is dominated by the common reed Phragmites australis fen and sea club rush Bolboschoenus maritimus swamp with the couch grass Elytrigia repens ( Elymus repens ) saltmarsh community . Within the Humber Estuary Ramsar site there are good examples of four of the five physiographic types of saline lagoon . Ramsar criterion 3 . The Humber Estuary Ramsar site supports a breeding colony of grey seals Halichoerus grypus at Donna Nook . It is the second largest grey seal colony in England and the furthest south regular breeding site on the east coast . The dune slacks at Saltfleetby-Theddlethorpe on the southern extremity of the Ramsar site are the most north-easterly breeding site in Great Britain of the natterjack toad Bufo calamita . 16. Physical features of the site : General description of the Physical Features : The Humber estuary is approximately 70 km long from the limit of saline intrusion on the River Ouse at Boothferry to the estuary mouth at Spurn Head , where it enters the North Sea . The area of the estuary is approx. 365 km2 , and it has a width of 6.6 km at the mouth . The Humber is a macro-tidal estuary with a tidal range of 7.4 m , the second-largest range in the UK and comparable to other macro-tidal estuaries worldwide . It is a shallow and well mixed estuary , with an average depth of 6.5m rising to 13.2 m at the mouth . The Humber is the second-largest coastal plain estuary in the UK , and the largest coastal plain estuary on the east coast of Britain . Suspended sediment concentrations are high , and are derived from a variety of sources , including marine sediments and eroding boulder clay along the Holderness coast . This is the northernmost of the English east coast estuaries whose structure and function is intimately linked with soft eroding shorelines . Upstream from the Humber Bridge , the navigation channel undergoes major shifts from north to south banks . This section of the estuary is noteworthy for extensive mud and sand bars , which in places form semi-permanent islands . The estuary covers the full salinity range from fully marine at the mouth of the estuary ( Spurn Head ) to the limit of saline intrusion on the Rivers Ouse and Trent . A salinity gradient from north to south bank is observed in the outer estuary , due to the incoming tide flowing along the north bank , while the fresh water keeps to the south bank as it discharges to the sea . As salinity declines upstream , reedbeds and brackish saltmarsh communities fringe the estuary . 17. Physical features of the catchment area : The Humber catchment covers an area of ca . 24,240 km2 , more than 20% of the land area of England . Average annual precipitation in the upland areas of the catchment is as much as 1000 mm . Average freshwater flow into the Humber estuary from the rivers is 250 m3s-1 , ranging from 60 m3s-1 in drier periods to 450 m3s-1 in wet periods . Peak flows of up to 1500 m3s-1 have been recorded during floods . The rivers Trent and Ouse , which provide the main fresh water flow into the Humber , drain large industrial and urban areas to the south and west ( River Trent ), and less densely populated agricultural areas to the north and west ( River Ouse ). The Trent / Ouse confluence is known as Trent Falls . On the north bank of the Humber estuary the principal river is the river Hull , which flows through the city of Kingston-upon-Hull , and has a tidal length of 32 km , up to the Hempholme Weir . The Hull provides only about 1% of the freshwater input to the estuary . On the south bank , the River Ancholme enters the Humber at South Ferriby , but the tide is excluded by a sluice and a tidal lock . Altogether , the total tidal length of rivers and estuary is 313 km . There are several major urban centres within the river catchments . Nottingham , Leicester , and the West Midlands / Birmingham conurbation are drained by the Trent , the Leeds-Bradford area in West Yorkshire is drained by the Aire / Calder and the Sheffield / Rotherham / Doncaster area in South Yorkshire is drained by the Don . There are also large rural regions , whose populations are currently experiencing high population growth , while the urban areas are showing a small decline . The 1992 population for the Ouse catchment was 4.1 million , and for the Trent catchment was 7.1 million . The population of Humberside , which comprises North and North-east Lincolnshire , the East Riding of Yorkshire , and Kingston-upon-Hull ( Hull ), was just under 0.9 million . Land use around the estuary itself is 50-98% agricultural , within only two areas of high population / industry - the major conurbation around Kingston-upon-Hull ( Hull ) on the north bank , and several large industrial areas around Grimsby / Immingham / Cleesthorpes on the south bank . The area around the Humber estuary is low-lying , and much land-claim of wetlands and supratidal zones , as well as parts of the intertidal zone , was carried out in the past two centuries . The mid to outer estuary ( Humber Bridge to Spurn Point ) changed from a region of low water erosion in the 19th century to one of accretion in the 20th century , nonetheless a net loss of intertidal zone of some 3000 ha has taken place since the mid-19th century . Around the estuary some 894 km2 of land are below the 5 m contour , protected by extensive coastal defences . Most of the sediment entering the estuary comes from the North Sea , and a large part of it is believed to come from the continuing erosion of the Holderness Cliffs , which form the coastline to the north of the estuary mouth at Spurn Head . The estuary currently has approximately 1,775 ha of saltmarsh . 20. General ecological features : Description . Much of the intertidal area of the Humber Estuary consists of mudflats with fringing saltmarsh . There are smaller areas of intertidal sand flats , and sand dunes . The saltmarsh is both eroding and accreting ; although coastal squeeze is resulting in net losses , and cord grass Spartina anglica is a major colonising species . In areas of reduced salinity such as the Upper Humber there are extensive areas of common reed Phragmites australis with some sea club-rush Bolboschoenus maritimus . Mid-level saltmarsh tends to be much more floristically diverse , and in the higher level marsh with its dendritic network of drainage channels , salt pans and borrow pits grasses dominate with thrift Armeria maritima where the marsh is grazed by cattle and sheep . Extensive areas of eel grass Zostera marina and Z. nolti have been known to occur at Spurn Bight , although in recent years records are limited . Behind the sandflats of the Cleethorpes coast the mature sand-dune vegetation contains some locally and nationally rare species including chestnut flat sedge Blysmus rufus , bulbous meadow grass Poa bulbosa and dense silky-bent Apera interrupta . The sand dunes , which cap the shingle spit that forms Spurn Peninsula are dominated by marram grass Ammophila arenaria and patches of dense sea buckthorn Hippophae rhamnoides . 30. Current communications , education and public awareness ( CEPA ) activities related to or benefiting the site : There are a four National Nature Reserves with associated facilities within the Ramsar site ( Spurn , Far Ings , Donna Nook and Saltfleetby â Theddlethorpe Dunes ) and a number of other visitor , information and / or education centres including the Spurn Bird Observatory , the Cleethorpes Discovery Centre , Waterâs Edge and Far Ings . A wide range of Humber wide and area-specific information is available through a range of media ( eg leaflets , displays , internet etc ) including ' Humber Estuary European Marine Site Codes of Conduct ' developed with a range of stakeholders to cover a range of recreational and educational activities and ' Coastal Futures ' - a partnership project working with local communities affected by flood risk and associated issues including managed realignment includes proactive education work within schools . LIVING PLANET INDEX . The Living Planet Index is a measure of the state of the world 's biodiversity based on trends from 1970 to 2003 in over 3 600 populations of more than 1 300 vertebrate species from around the world . It is calculated as the average of three separate indices that measure trends in populations of 695 terrestrial species , 274 marine species , and 344 freshwater species . The index shows an overall decline of around 30 per cent over the 33-year period , as do each of the terrestrial , marine , and freshwater indices individually . The decline in the indices , and in particular the freshwater index , is less than in previous reports , because the indices have been aggregated in a different way , designed to reduce the degree of uncertainty around them ( see technical notes , page 37 ). No attempt is made to select species on the basis of geography , ecology , or taxonomy , so the index dataset contains more population trends from wellresearched groups , especially birds , and well-studied regions , particularly Europe and North America . In compensation , temperate and tropical regions are given equal weight ( with equal weight to each species in each region ) within the terrestrial and freshwater indices , and to ocean basins within the marine index ( see pages 6-11 ). The map opposite shows the Earth 's surface divided into 14 terrestrial biomes , or habitat types , and eight biogeographic realms . The biomes are based on habitat cover ( agricultural and urban land is classified according to potential vegetation type ) and realms are defined according to biological evolutionary history . Although ecosystems within a single biome share the same ecological processes and vegetation types , their exact species composition varies depending on the realm in which they are found . Patterns in freshwater biodiversity follow similar distinctions based on biogeographic realms , but marine realms are less well defined , partly because marine species tend to be distributed more widely across the world 's oceans . Figure 4 : Terrestrial Living Planet Index . The terrestrial species index shows a 31 per cent decline on average from 1970 to 2003 . Figure 5 : Marine Living Planet Index . The marine species index shows an average decline of 27 per cent between 1970 and 2003 . Figure 6 : Freshwater Living Planet Index . The freshwater species index declined by approximately 28 per cent between 1970 and 2003 . TERRESTRIAL SPECIES . Populations of terrestrial species declined by about 30 per cent on average between 1970 and 2003 . This decline hides a marked difference in trends between temperate and tropical species . Tropical species populations declined by around 55 per cent on average from 1970 to 2003 , while temperate species populations , which would have shown marked declines prior to 1970 , have shown little overall change since . Figure 7 shows average trends in populations of 695 temperate and tropical terrestrial species ( of which 562 occur in temperate zones and 150 in tropical zones ), indexed to a value of one in 1970 . The rapid rate of population decline in tropical species is mirrored by the loss of natural habitat to cropland or pasture in the tropics between 1950 and 1990 ( Figure 9 ), agricultural conversion being the main driver . The tropical forests of Southeast Asia , part of the Indomalayan biogeographic realm , have seen the fastest conversion in the last two decades . In temperate ecosystems , the conversion of natural habitat to farmland largely took place before 1950 , when populations of temperate species are likely to have declined , before stabilizing . The biomes (see Map 1) with the fastest rate of conversion in the last half of the 20th century were tropical grasslands , flooded grasslands , and tropical dry forests ( Figure 8 ). Temperate , tropical , and flooded grasslands , Mediterranean woodlands , temperate broadleaf forests , and tropical dry forests have all lost more than half of their estimated original habitat cover . The biomes least transformed by agricultural conversion are boreal forests and tundra . Figure 7 : Temperate and tropical terrestrial Living Planet Indices . Tropical terrestrial species populations declined by 55 per cent on average from 1970 to 2003; temperate species populations remained fairly stable . Figure 8 : Loss of natural habitat , by biome . With the exceptions of Mediterranean and temperate mixed forests , where extensive habitat loss stabilized after 1950 because most land suitable for agriculture had already been converted , the biomes which lost most habitat prior to 1950 continued to lose it rapidly between 1950 and 1990 ( Millennium Ecosystem Assessment , 2005 ). Figure 9 : Loss of natural habitat to agriculture , by realm . The rate of natural habitat loss over this period was greatest in the tropics . Agriculture expanded in Australasia at a rate similar to the Neotropics , but there was a relatively low level of cultivation in 1950 ( Millennium Ecosystem Assessment , 2005 ). See Map 1 for the boundaries of the realms . Map 2 : Trends in selected terrestrial species populations . These are not necessarily indicative of general species trends in each region , but illustrative of the kinds of data used in the terrestrial index . MARINE SPECIES . The marine environment , which covers almost 70 per cent of the Earth 's surface , includes some of the world 's most diverse and productive ecosystems , but these were adversely affected by human action over the last half of the 20th century . The marine index is split by ocean basin . The Pacific Ocean , the largest , covers more than a third of the planet 's surface . The Atlantic Ocean includes the Arctic basin . The Indian Ocean includes the coastal seas of Southeast Asia for the purposes of the index . The Southern Ocean comprises the seas around Antarctica , its northern limit defined as the line of latitude 60 . The marine index includes trends in 1 112 populations of 274 species between 1970 and 2003 , and shows a greater than 25 per cent decline on average across the four ocean basins . Relatively stable trends are evident in the Pacific and in the Arctic / Atlantic Oceans , in comparison with dramatic declines in the Indian / Southeast Asian and Southern Oceans . Overall increases in the populations of sea birds and some mammal species in the Atlantic and Pacific Oceans since 1970 , however , mask a decline in many fish species , especially those of economic importance such as cod and tuna , which are decreasing as a result of overfishing , as well as turtles and other species that are caught as by-catch . There are comparatively few data from the Southern and Indian Oceans , so those indices end in 1997 and 2000 . Mangroves - saltwater-tolerant , inter-tidal forests growing along tropical shorelines are among the most productive ecosystems on Earth and critical to the health of tropical marine ecosystems . Mangroves provide nurseries for 85 per cent of commercial fish species in the tropics and are essential in maintaining fish stocks and hence food resources . Mangroves are being degraded or destroyed at about twice the rate of tropical forests . It is estimated that more than a third of the global area of mangrove forest was lost between 1990 and 2000 ( Figure 12 ). Figure 10 : Arctic / Atlantic and Southern Ocean Living Planet Indices . Populations of Southern Ocean species declined by about 30 per cent between 1970 and 1998 , while trends in the Arctic / Atlantic Ocean increased overall . Figure 11 : Indian / Southeast Asian and Pacific Ocean Living Planet Indices . The Indian Ocean and Southeast Asian seas saw average declines of more than half between 1970 and 2000 , while trends in Pacific Ocean species remained stable overall . Figure 12 : Mangrove area , by region . More than a quarter of Asia 's mangrove cover was lost in the ten-year period preceding 2000 . In South America , almost half was lost over the same period ( Mayaux et al ., 2005 ). Map 3 : Trends in selected marine species populations . These are not necessarily indicative of general species trends in each region , but illustrative of the kinds of data used in the Living Planet Index . FRESH WATER SPECIES . An estimated 45 000 vertebrate species live in or around lakes, rivers, streams, and wetlands. Their population trends are indicative of the health of the world 's freshwater ecosystems . The freshwater index ( Figure 13 ) shows average trends in 344 species ( of which 287 occur in temperate zones and 51 in tropical zones ). Species populations in both declined by about 30 per cent between 1970 and 2003 . There is a difference in trends between freshwater birds , which appear to have been relatively stable , and other freshwater species , which have declined on average by about 50 per cent over the same period . The main drivers are habitat destruction , overfishing , invasive species , pollution , and the disruption of river systems for water supplies . The decline in the freshwater index is less than previously , as it has been aggregated differently to bring it in line with the terrestrial index ( see technical notes , page 37 ). It also contains a number of new species . The alteration and damming of river systems for industrial and domestic use , irrigation , and hydroelectric power have fragmented more than half of the world 's large river systems . Some 83 per cent of their total annual flow is affected - 52 per cent moderately ; 31 per cent severely - with Europe 's river flow being the most regulated and Australasia 's the least ( Figure 15 ). Worldwide , the amount of water stored in reservoirs behind dams is three to six times the quantity contained in rivers . Fragmentation and alteration of natural river flows affects the productivity of wetlands , flood plains , and deltas , disrupts the migration and dispersal of fish , and causes declines in freshwater species . Mediterranean woodlands , deserts and xeric shrublands , temperate broadleaved forests , and temperate , flooded , and montane grassland biomes all have more than 70 per cent ( by catchment area ) of their large river systems severely disrupted , primarily for irrigation ( Figure 14 ). Tundra is the only biome where they are mainly unaffected . Figure 13 : Temperate and tropical freshwater Living Planet Indices . Temperate and tropical species populations declined by around 30 per cent overall from 1970 to 2003 . Figure 14 : Fragmentation and flow regulation of large river systems , by biome . Percentage of the total area within catchments of 14 terrestrial biomes severely or moderately impacted by dams ( Nilsson et al ., 2005 ). See Table 6 , page 37 . Figure 15 : Fragmentation and flow regulation of large river systems , by region . Percentage of total annual discharge severely or moderately impacted by dams ( Nilsson et al ., 2005 ). See Table 6 , page 37 . Map 4 : Trends in selected freshwater species populations . These are not necessarily indicative of general species trends in each region , but illustrative of the kinds of data used in the Living Planet Index .