Small Water Bodies in Great Britain and Ireland: Ecosystem function, human-generated degradation, and options for restorative action

Abstract

Small, 1st and 2nd-order, headwater streams and ponds play essential roles in providing natural flood control, trapping sediments and contaminants, retaining nutrients, and maintaining biological diversity, which extend into downstream reaches, lakes and estuaries. However, the large geographic extent and high connectivity of these small water bodies with the surrounding terrestrial ecosystem makes them particularly vulnerable to growing land-use pressures and environmental change. The greatest pressure on the physical processes in these waters has been their extension and modification for agricultural and forestry drainage, resulting in highly modified discharge and temperature regimes that have implications for flood and drought control further downstream. The extensive length of the small stream network exposes rivers to a wide range of inputs, including nutrients, pesticides, heavy metals, sediment and emerging contaminants. Small water bodies have also been affected by invasions of non-native species, which along with the physical and chemical pressures, have affected most groups of organisms with consequent implications for the wider biodiversity within the catchment. Reducing the impacts and restoring the natural ecosystem function of these water bodies requires a three-tiered approach based on: restoration of channel hydromorphological dynamics; restoration and management of the riparian zone; and management of activities in the wider catchment that have both point-source and diffuse impacts. Such activities are expensive and so emphasis must be placed on integrated programmes that provide multiple benefits. Practical options need to be promoted through legislative regulation, financial incentives, markets for resource services and voluntary codes and actions.

Diffuse nitrogen pollution control: Moving from riparian zone to headwater catchment approach—A tribute to the influence of Professor Geoff Petts

“…The three drivers of denitrification (see above) are mostly found at the upslope wet area interfaces, which includes riparian zones, but also upslope seepages faces associated with hedges, ponds, and artificial ditches. Given the dendritic nature of drainage networks, the vast majority of these dry/wet interfaces occur in small headwater catchments, indeed typically “75%” of terrestrial land drains into these seepage channels, classified as the first‐ and second‐order streams (Bishop et al, ; Riley et al, ). A very small portion of the catchment land drains into the third‐ to fifth‐order streams directly.…”

Vegetation Response to Recent Trends in Climate and Landuse Dynamics in a Typical Humid and Dry Tropical Region under Global Change

“…In the short grass savanna, for instance, there has been much loss of shrubs and tree cover following drought periods and from cutting trees for firewood [36]. e rapid conversion of land for agriculture and plantation can alter discharge from headwaters and temperature regimes leading to further decline or loss of important functional species in some critical ecosystems such as riparian vegetation, streams, and lakes, with implications for drought and flood further downstream [36,59,60]. Alternatively, the ecosystem functions of present species might be replaced by other species with less functional redundancy or resilience to environmental perturbations [59,60].…”

“…e rapid conversion of land for agriculture and plantation can alter discharge from headwaters and temperature regimes leading to further decline or loss of important functional species in some critical ecosystems such as riparian vegetation, streams, and lakes, with implications for drought and flood further downstream [36,59,60]. Alternatively, the ecosystem functions of present species might be replaced by other species with less functional redundancy or resilience to environmental perturbations [59,60]. Flood regulation and control ecosystem services from riparian vegetation and gallery forest may come under attack from invasions by nonnative species, which along with the physical and chemical pressures may affect species richness and functional redundancy of important functional species with consequent implications for the wider biodiversity within the watershed.…”

Management pathways for the floodplain wetlands of the southern Murray–Darling Basin: Lessons from history

“…Clearly, there has been a long history of impacts other than regulation, diversion, and abstraction, so water recovery remains only one of the restorative measures required to recover the ecological assets and function of the past. As Ogden (: 497) observed, “attempts to rehabilitate rivers through environmental flows will fail unless steps are taken to remedy farm impacts.” A similar emphasis on managing headwater pressures has been recognized elsewhere (Riley et al, ).…”