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Action for Scotland's Biodiversity

4 LOCHS, RIVERS AND MARSHES

Introduction

Freshwater eystems represent a major group of habitats in Scotland. Not only are the habitats themselves important for biodiversity, but the medium itself - fresh water - is of fundamental significance to human welfare everywhere. It is essential to humans for drinking water, transport, irrigation, energy, removing waste material and for recreation and sport. Some species of freshwater habitats, such as fish, provide important food resources; other species provide useful materials such as reeds for thatching. All fresh waters are dynamic systems. Their organisms are affected by physico-chemical conditions (and thus by human activities), but the species of plants and animals interact, influencing both the habitat and one another in a variety of different ways.

Because of the relatively small size of many wetland habitats, they are very vulnerable to human activities and cannot be protected completely without control of the whole catchment (all of the land draining into the river or loch). Fortunately, the corollary of this is that, providing the man-induced changes are not irreversible, most freshwater habitats and their flora and fauna will respond positively to sensible management procedures aimed at restoration. However, for some wetland habitats (e.g. exploited peatlands) recovery may be extremely slow, or impossible, depending on the extent of the damage.

Freshwater habitats are very variable in character, ranging from running to standing waters, alkaline marshlands to acid peat bogs, mountain trickles to major rivers, and small puddles to lochs over 300 m deep. This chapter considers running waters (rivers and burns), standing waters (lochs and ponds) and other freshwater habitats (fens). Peat bogs are highly dependent on freshwater but are dealt with in chapter 7.

Integrated catchment management is vital for Scotland's rivers and lochs

Description of the Freshwater Resource

More than 2 per cent of the Scottish land surface is covered by over 27,000 lochs and more than 50,000 km of rivers and burns. Fresh waters represent a more significant landscape feature in Scotland than in any other part of Britain. In fact, 91 per cent of the volume of standing fresh water in Great Britain is within Scotland. Management of water is of crucial importance to our daily lives and to Scotland's biodiversity. A number of priority species are associated with freshwater habitats. Some, like the reed beetle, have very specific habitat requirements. Others, like the otter, are highly mobile, moving between different types of aquatic habitat.

Running Waters: Rivers and Streams

Running waters are characterised by having an obvious direction of flow. They change gradually in character (size, substrate, plants and animals) from source to mouth. Erosion is a characteristic effect of running water, and materials so removed may be transported considerable distances. As a further consequence of erosion and deposition, most running waters increase the length of their channels with age, as both cutting back to the source and meandering on the flood plain proceed.

Scotland has about two-thirds (950) of the main river systems in Great Britain. The character of these rivers is mainly determined by climate and topography. Scotland's high rainfall, low evaporation and lack of extreme temperatures create rivers with a large flow relative to the size of the catchment, a dense network of rivers and burns, and moderate water temperature fluctuations. Scotland's largely mountainous topography results in energetic, steeply flowing, rivers with beds of coarse material - gravels and boulders (e.g. the River Dee in the Eastern Cairngorms). Scotland also has slower flowing, more silty, river stretches in the lowlands (e.g. the lower River Endrick), but these are not typical of the majority of rivers in Scotland. As a general rule, the main east/west watershed is close to the west coast. Hence most of the rivers flowing to the west are short and have steep gradients compared to the longer, more gently graded east flowing rivers.

Water Vole Species Action Plan

box 4.3

The water vole is the most rapidly declining species of mammal in Britain. Sensitive river bank management is vital for its survival, as is the control of the American mink The water vole is recognised as the most rapidly declining species of mammal in Britain. Once common along the waterways of the British mainland, a survey of the species' distribution in 1989-90 confirmed that, although still present over the whole of mainland Britain, it had been lost from three quarters of the sites occupied before 1939. It was predicted that, if such a rate of loss continued, 94 per cent of all former sites would be lost by the year 2000. The primary objectives of the plan are to arrest the decline and maintain the current distribution and status of the water vole, to restore water voles to their pre-1970 range by the year 2000, and to ensure management of watercourses and wetland habitats which will maintain the restored population. Action has already been successful in adding the water vole to Schedule 5 of the Wildlife & Countryside Act 1981; this provides legal protection for the species and its place of shelter. However, other work is required to ensure that the species is taken into account in policies and practices affecting river management, e.g. agri-environment schemes, so as to consolidate this protection. Fundamental to the success of the Species Action Plan is knowing where the remaining populations are. Hence actions also aim to identify large, viable breeding populations which can provide an initial focus for conservation action. Work to identify areas suitable for re-establishing lost populations is also included. Underpinning all of this work is the need to protect large populations from predators, specifically American mink. Practical advice to landowners and managers on the best ways to manage riparian habitats to encourage water vole survival has been made available. The plan therefore relies on action by a wide range of statutory and voluntary organisations in association with landowners and managers.

Habitats which are associated with rivers are important, not only for their contribution to riverine biodiversity, but also as significant systems in their own right. They include riparian trees (especially alder and willow species) and river gravels and shingles; many rare and lesser known species occur in the latter habitat. Bankside and riverbed vegetation has a vital role in maintaining the health of river systems by stabilising the bank and river bed and preventing erosion. These associated riverine habitats are also of importance to many birds (e.g. dipper) and mammals (e.g. water shrew and otter), providing food and cover. Riverside trees can provide the basis of an important food chain in the form of falling leaves in autumn; these provide food for river invertebrates and therefore assist production of salmon and trout.

River Jelly Lichen Species Action Plan

box 4.4

Scotland may now be the world stronghold for the river jelly lichen, which depends heavily on water quality The river jelly lichen grows on submerged rocks in partial shade in fast-flowing intermediate and upland streams. It has been declining for several decades and is now considered rare in the UK and listed as vulnerable in both the international and GB Red Lists. Scotland is now believed to be the world stronghold for this species and those involved in the Species Action Plan are determined to maintain and improve its status here. It is protected under Schedule 8 of the Wildlife & Countryside Act 1981. The factors causing decline are believed to be eutrophication, increased silting, acidification and lower water levels. All Scottish sites for this species were surveyed in 1994 in fulfilment of two of the Species Action Plan's objectives to establish the current status of the species and to safeguard known populations. Research will be required to ensure effective conservation management and to re-establish populations at five former sites by 2005. Land management and its effects on river quality will be tackled through advice which encourages best practice in minimising nutrients and silt entering rivers. Water level management may be an issue where water abstraction takes place for irrigation. Catchment management plans will provide an opportunity to address such factors affecting the river jelly lichen.

Standing Waters: Lochs and Lochans

Because standing waters are characterised by a lack of water flow, conditions in them are normally much more homogeneous than in running waters. They may reach great depths, but most have simple, often broad, basins. Whilst erosion does occur in standing waters, it is only severe on exposed shores and eroded materials usually remain within the same basin. In addition, materials from inflowing streams are constantly being deposited, tending to fill in the basin and eventually obliterate it completely.

Standing waters are classified as shown in Box 4.2. The great majority of Scotland's lochs are oligotrophic; a typical example is the deep, clear Loch Morar. Eutrophic lochs are relatively uncommon in Scotland and occur mainly in the Lowlands. They are naturally rich in nutrients, which can lead to them having lush shore vegetation and blooms of algae which can use up most of the available oxygen in the summer months and hence affect fish and other aquatic life. Mesotrophic lochs contain enough nutrients to support rich and diverse plant growth while usually remaining clear; they are not dominated by algae. They are typically very rich in plant and animal life, a good example being Loch Ussie, near Dingwall. Mesotrophic and eutrophic waters are artificially increasing in number due to agricultural eutrophication, as explained later.

The majority of Scotland's lochs are naturally low in nutrients, or oligotrophic, like Loch Morar	Mesotrophic lochs, such as the Lake of Menteith, have higher nutrient levels and occur mainly in the lowlands

Mesotrophic Lakes Habitat Action Plan

box 4.5

The vendance is found in a few mesotrophic lochs and is rare enough to be one of the few fish species to have its own Species Action Plan Mesotrophic lochs do not have sufficient nutrients for thick algal blooms to occur. They are, therefore, productive and typically support a diverse mixture of submerged water plants and their associated animal life. These assemblages are increasingly rare, under threat around the World, and are in need of conservation. In Scotland, natural mesotrophic standing waters are typically found in the borders of upland areas and in the Lowlands. Their mesotrophic condition is determined by the nature of the catchment, in particular the leaching rate of mineral nutrients. The Mesotrophic Lochs Habitat Action Plan recognises their great conservation value; several sites across Scotland are Sites of Special Scientific Interest (SSSI) and candidate Special Areas of Conservation (SAC). Additionally some mesotrophic lochs have been designated as Special Protection Areas for their bird assemblages. The Lake of Menteith and the Dunkeld-Blairgowrie Lochs in Perthshire, designated for the conservation of the slender naiad, are two of the best examples of mesotrophic waters. Mesotrophic lakes support some rare plant species including slender naiad and Shetland pondweed, both of which have Species Action Plans. The vendace, a rare species of fish, also has a Species Action Plan and is typically found in mesotrophic lochs.

Medicinal Leech Species Action Plan

box 4.6

Once widely used for medical purposes, the medicinal leech was thought to be extinct in Britain but has been re-discovered in Argyll and on Islay The medicinal leech was formerly much more widespread in Great Britain and the rest of Europe and was once important in medicine for blood-letting. It has come to prominence again in medical circles because of its value in plastic and micro-surgery and in the production of some pharmaceutical products. Thought originally to be extinct in the British Isles, and apparently extinct in Ireland, the present status of the medicinal leech in Great Britain is unclear, but it is certainly threatened. It is now known from several sites in Wales and England and its current status in Scotland has recently been reviewed. It was definitively known from only one site, but during 1995 nine sites with old records were visited and sampled, as well as all other standing waters within 3 km of them. A further 21 sites in Scotland were selected at random and also sampled. The medicinal leech was found at only three of the previously recorded sites and none of the others. Recommendations have been made for the future management of the three proven sites, one on Islay and the other two in mainland Argyll. Recent surveys have identified suitable sites for translocation to establish safeguard populations.

Wetlands

Wetland habitats are intermediate in character between terrestrial habitats and truly aquatic habitats. They may be either permanently wet, as most peatlands, or only seasonally wet, such as many marshlands and swamps. They may be transitional areas between open water and the land, as are the fringes of emergent vegetation found along the shores of many lochs. All are dynamic, evolving in time towards a different kind of habitat. This evolution may be imperceptibly slow in many peat bogs or relatively rapid in marshes where there is annual accumulation of organic and inorganic material, leading to terrestrial conditions.

Fens are peatlands which receive water and nutrients from the soil, rock and ground water as well as rainfall. Two types of fens are distinguished - topogenous, where water movements in the peat are vertical (basin fens and floodplain fens) and soligenous, where water movements are lateral (mires in the uplands; valley mires, springs and flushes in the lowlands). Fens may also be described as poor fens (characterised by short vegetation, much Sphagnum moss and acid water) and rich fens (typically with taller vegetation, little Sphagnum and calcareous water). Fen habitats support a diverse community of plants and animals - some individual fens are known to contain more than 33 per cent of our native plant species and more than 50 per cent of the native dragonfly species.

Trends and Objectives

As well as the natural successional changes which affect many freshwater habitats, there are several major trends due to human activities which require action if the full value of Scotland's freshwater resource is to be saved for future generations.

Running waters in Scotland have changed significantly in many places over the last two hundred years or so. Some have had their courses altered (usually by dredging and straightening) for drainage or flood defence schemes or to make way for developments such as roads. Domestic and industrial pollution, formerly a major threat to many rivers, is gradually being controlled. However, diffuse pollution from various types of land use is still responsible for over-enriching and silting many rivers. Bank erosion and loss of riparian vegetation due to overgrazing by cattle and sheep and, in some cases, management for angling, has damaged many running waters and their associated species of plants and animals. Abstraction of water for domestic supply or irrigation reduces the flow in many rivers, whereas dams may block the channel for migrating fish and create massive reservoirs upstream with consequent large fluctuations in water levels downstream. Introduced species of plants and animals are causing problems both along river banks (e.g. giant hogweed and American mink) and in the rivers themselves (e.g. Canadian pondweed and signal crayfish).

Standing waters are also subject to a number of pressures. Though few have been subject to direct pollution, many are affected by diffuse pollution from land use and other activities in the catchment. This causes increased enrichment and silting. The shorelines of many of Scotland's lochs have been altered by engineering developments, usually for roads, which means that the natural shores have been replaced by concrete or stone riprap. Demands for water, mostly for public supply or power generation, have resulted in many of Scotland's largest lochs being dammed and the water levels subsequently controlled by users. There is increasing use of the water surface for recreational purposes and jet-skis and other noisy craft are causing problems on previously quiet lochs. As in rivers, non-native species of plants (e.g. New Zealand stonewort) and animals (e.g. ruffe and other alien fish in Loch Lomond) are establishing in many lochs and causing major changes in aquatic ecology.

Through the passage of time, standing waters naturally tend to become silted up and successional changes accelerate through the availability of nutrients locked up in the deposits and released when shallowness permits their utilisation, predominantly by macrophytes. This process has been greatly accelerated by eutrophication due to human activities. In lowland areas with fertile soils, intensive arable farming with heavy applications of fertilisers, particularly nitrates, leads to enrichment of ground water and runoff. Eutrophication occurs even in some water bodies in nutrient-poor areas due to mineral release during ground preparation for afforestation, run off from fertiliser applications from agriculture and domestic sewage or other nutrient-rich effluents. Nutrients are derived from fish farming (from fish urine and faeces and from waste feed as it drops to the bottom). Principal among the nutrients concerned are compounds of nitrogen and phosphorus. Anthropogenic eutrophication is likely to be the main cause of the extinction of fish in many lochs, as for example the extinction of the vendace in Castle and Mill Lochs at Lochmaben. These two lochs were the only locations previously for the species in Scotland, but a re-introduction programme has aimed to establish the vendace in further lochs where it will not be threatened by 'cultural eutrophication'.

Wetlands have suffered primarily from drainage and transformation to agricultural ground or forest. There has also been some impact by eutrophication, from agricultural runoff, which changes the nature of the wetland vegetation. The major overall change has thus been one of direct loss of habitat, with the consequent decline of associated plant and animal species.

Summary of Main Objectives and Actions

Pollution has caused many problems for Scotland's fresh waters, including the elimination of the entire fish populations from some rivers. However, action by the River Purification Boards in the past, and currently by the Scottish Environment Protection Agency, has shown that it is possible to control direct pollution. Many rivers have now shown major recovery as is indicated by the natural return of fish to them (e.g. Atlantic salmon to the Rivers Clyde and Carron). Whilst constant vigilance and co-operation will always be necessary, the positive results of proper pollution control have been demonstrated. For example, following improvements in water quality, there has been an economic revitalisation of the lower reaches of the Water of Leith in Edinburgh. Aesthetically pleasant walks have been created along the River Kelvin in Glasgow, and many other rivers, enabling the public to enjoy the associated wildlife such as kingfishers and herons.

Land use, however, still poses a threat to many fresh waters through diffuse pollution and silting of lochs and rivers caused by runoff from agricultural fields and afforested areas. The development of good practice, promoted by the Scottish Executive, Scottish Environment Protection Agency, Scottish Natural Heritage, Scottish Agricultural College, Forestry Commission, World Wide Fund for Nature and other organisations has shown, through demonstration sites and advisory literature, that diffuse pollution can be avoided in a variety of ways. These include the use of riparian strips, more appropriate drainage systems, less intensive use of fertilisers, etc. As well as improving water quality, such measures can also have economic benefits such as improved fisheries and the avoidance of soil loss. A good example of an initiative in this field was the production by the Forestry Commission of its Forests and Water Guidelines; these have substantially lessened the negative impact of forestry operations on fresh waters in many areas.

Clean water underpins the commercial success of several of Scotland's most distinctive products

Water use can have a major impact on biodiversity through affecting water levels in rivers, lochs and other wetlands. The abstraction of water from rivers in Scotland has led to rivers drying up downstream. The water resources of Scotland are subject to a wide range of uses such as hydro-power generation, public water supply, industrial processing and agricultural irrigation. Action is needed to ensure that rivers and wetlands have adequate flows to allow them to function effectively.

Introduced species of plants and animals from southern Britain or abroad are an increasing threat to the ecology of Scotland's waters. Whereas only a few are released intentionally, the majority of introductions are the results of escapes from captivity (e.g. Atlantic salmon of non-local origin from fish farms, American mink from mink farms), thoughtless releases for livebaiting (e.g. ruffe, gudgeon), or the dumping of unwanted plants or pets (e.g. Japanese knotweed, Canadian pondweed, goldfish). Most of these introductions could have been avoided with improved legislation and better education among the groups concerned (e.g. anglers, aquarium owners, fish farmers, gardeners).

Just as these non-native species can threaten Scotland's biodiversity, action is needed to restore some species that have been lost. The vendace has already been re-introduced to at least one loch in Scotland in the last few years, and discussions are progressing concerning the re-introduction of the European beaver. This 'engineer' of the riparian environment occurred naturally in Scotland until it was exterminated by hunting some 450 years ago. Should this part of Scotland's biodiversity now be re-introduced?

Many other issues remain to be resolved and campaigns in Scotland such as 'Operation Brightwater' by the Scottish Conservation Projects Trust and 'Wild Rivers' by the World Wide Fund for Nature may be necessary from time to time to highlight current problems and required action. There is a common objective shared by government, industry, land users and the public - high quality water in a natural environment, inhabited by healthy communities of native plant and animal species. Far from holding development and employment back, this clean image has numerous economic benefits for tourism and many other industries, including food production and processing, in Scotland.

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