Freshwaters : openwaters, wetlands and floodplains [chapter 9]

Key Findings*Rivers, lakes, ponds, groundwaters and wetlands provide major services, but their benefits are inadequately identified and valued 1 .This has resulted in habitat losses that are among the fastest in the UK.When managed appropriately, Freshwaters should transport water, matter, energy or organisms within and between terrestrial systems, riparian zones, estuaries and near-coastal waters.They provide: consumptive and nonconsumptive uses of water; organisms for food, recreation and conservation; and energy.They can regulate flooding, erosion, sedimentation, local climates and water quality, while facilitating the dilution and disposal of pollutants.They support dispersal through, and resilience in, adjacent ecosystems (for example, though water or nutrient supply), and act as a medium for key biogeochemical cycles.They have large cultural value for recreation, tourism, education, heritage and as inspiration for arts and religion.Costs for people include their role in waterborne diseases and their propensity to flood low-lying infrastructure.1 well established Rivers, lakes and wetlands are present throughout UK landscapes.Historically, they were highly connected to each other and to their catchments, but are now fragmented and disconnected 1 .There are more than 389,000 km of rivers in the UK, almost 6,000 permanent large lakes covering around 200,000 ha and nearly half a million ponds (covering less than 2 ha); but the true extent of the UK's wetlands is less well defined.Distribution is also uneven, with Scotland holding more than 90% of the volume and 70% of the total surface area of Freshwater in the UK-it has over 30,000 openwater bodies, as well as some 40% of active raised bog.The llynnau of North and mid-Wales and the tarns of Cumbria form distinctive clusters of natural lake systems on the west coast.In central and southern England, where natural lakes are rare, artificial reservoirs provide important standing water habitats.Natural, small water bodies are also widespread, such as the pingo ponds of the Norfolk and Suffolk Breckland and the smaller Cheshire and Shropshire meres and pools.There are at least 392,000 ha of fen, reedbed, lowland raised bog and grazing marsh, but the true extent is uncertain.Floodplains are the most widespread (963,700 ha) and productive Freshwater systems and are shaped by the natural dynamics of river flows.However, they have been extensively impacted by engineering, including flood embankments and channel modifications, so that over two-fifths (42% by area) of all floodplains in England and Wales (defined by the 100-year flood envelope) have been separated from their rivers. well establishedNo completely pristine Freshwater ecosystems remain in the UK; almost all have been affected by human activity, including drainage, changes in land cover and atmospheric deposition, and most are now managed to a lesser or greater extent 1 .Habitat fragmentation and degradation have reduced their service value 2 .However, while the least damaged are expected to provide the most natural service profile 2 , some managed Freshwaters and artificial habitats can be locally important, such as chalk rivers, reservoirs, fenlands, water meadows and ponds 2 .More information is still required about ecosystem services provided by Freshwaters under various levels of management or condition. well established 2 established but incomplete evidenceThere is considerable uncertainty about how ecosystem services are related to ecosystem structure, functioning, habitat type, size, spatial extent and fragmentation 1 .The functions Freshwater ecosystems provide depend on their type, size, condition and position within a catchment 2 .Water connects diverse habitat types along gradients through catchments (with interaction in both directions) via exchanges between the atmosphere, uplands and lowlands, terrestrial and aquatic systems, fresh and saline waters, and between surface and groundwater.We lack precise knowledge of the importance of connectivity, and, in particular, the role of the many small wetlands or water bodies whose number remains poorly estimated and location often unrecorded 1 .1 well established 2 established but incomplete evidence * Each Key Finding has been assigned a level of scientific certainty, based on a 4-box model and complemented, where possible, with a likelihood scale.Superscript numbers indicate the uncertainty term assigned to each finding.Full details of each term and how they were assigned are presented in Appendix 9.5.Broad Habitats | Chapter 9: Freshwaters -Openwaters, Wetlands and Floodplains Table 9.1 Ecosystem services provided by the Freshwater Broad Habitat.Component and sub-component habitats potentially delivering ecosystem services are river (R), lake (L), pond (P), grazing marsh (GM), reedbed (RB), fen (F), and lowland raised bog (LRB).Final services of Freshwater habitat Habitats potentially delivering services Conditions or characteristics of habitats required R L P GM RB F LRB Provisioning Fish • • • • Commercially significant fisheries (crayfish, salmon, trout) based on rivers, lakes and ponds in suitable conditions.Dairy and beef • • Wetland grasses provide grazing, silage and hay.Nutrition level depends upon management.Reeds, osiers and watercress • • • • • • Reeds grow in saturated soils and slow flowing or still water up to 0.3 m deep.Osiers produce withies for basket making; requiring saturated soil conditions.Cress-beds need swiftly flowing high pH clean water.Water • • • • • Open water habitats provide a water source for public supply, irrigated crops, power station cooling, industrial processing and fish farming, but high evaporation rates may suppress total water availability.Peat • • • • • • Peat provides the basis of some composts for horticulture.Peat needs to be >0.5 m deep to be commercially exploitable due to recent planning guidance.Navigation • • Navigable waterways need sufficient water depth and low velocity.Health products • • • • Mineral spas, medicinal plants (e.g.bogbean), medical leeches.Regulating Carbon regulation • • • • • • Carbon accumulates where production of plant litter exceeds decomposition and generally under waterlogged, predominantly anaerobic conditions.Deposition of organic sediments within lakes, ponds and reservoirs is an important component of the carbon budget.Flood regulation • • • • • • Flood reduction relies on available water storage.Permanently saturated habitats with no storage may generate or augment floods.Flow regulation • • • • • • • River flow, groundwater recharge influenced by landscape location, water storage characteristics and connection with other water bodies.Water quality regulation • • • • • • Freshwater systems can dilute, store and detoxify waste products and pollutants, however there are threshold levels and some systems may accumulate substances to toxic levels.Local climate regulation • • • • • • • Temperature and humidity may be different within the habitat and without; degree depends on size.Important moist microclimates can develop.Fire regulation • • • • • Open water bodies can act as natural fire breaks.Human health regulation • • • • • • • Natural freshwater systems can increase well-being and quality of life if visually attractive and supportive of physical recreation.Mismanaged freshwaters can be sources of water borne diseases and disease vectors (e.g.mosquitoes), but also sources of biocontrol agents.Cultural Science and education • • • • • • • Lake, floodplain and mire sediment sequences contain palaeo-environmental archives and human (pre)history, artefacts that may be lost if disturbed or desiccated.Freshwater