SUMMARY 1. Small-scale discontinuities, formed by accumulations of wood, are recognised as a key ... more SUMMARY 1. Small-scale discontinuities, formed by accumulations of wood, are recognised as a key feature of functionally intact forested streams because they promote organic matter retention, increase habitat complexity and provide flow refugia. Re-establishing such features in physically degraded streams is therefore a common priority for restoration schemes. Ecosystem engineering by beavers in the form of dam building might offer a natural mechanism for restoring degraded streams. Despite an increase in beaver reintroductions globally, the ecosystem engineering concept has rarely been applied to restoring biodiversity and ecosystem function, especially within degraded freshwater systems. 2. By comparing multiple beaver-modified and unmodified sites on headwater streams draining 13 ha of pastureland in eastern Scotland, U.K., we investigated if hydromorphological changes caused by reintroduced beavers (Castor fiber) translate into desirable biological responses when there is a long history of physical degradation and contraction of the regional species pool due to agricultural land use. 3. Beaver modified in-stream habitat by constructing 10 dams, thus creating a series of interconnected dam pools. Organic matter retention and aquatic plant biomass increased (7 and 20 fold higher respectively) in beaver ponds relative to unmodified channels, consistent with the lower fluctuation in stream stage observed below a series of dams. Growing season concentrations of extractable P and NO 3 were on average 49% and 43% lower respectively below a series of dams than above, although colour and suspended solids concentrations increased. 4. Macroinvertebrate samples from beaver-modified habitats were less taxon rich (alpha diversity on average 27% lower) than those from unmodified stream habitat. However, due to significant compositional differences between beaver versus unmodified habitats, a composite sample from all habitats indicated increased richness at the landscape scale; gamma diversity was 28% higher on average than in the absence of beaver-modified habitat. Feeding guild composition shifted from grazer/scraper and filter feeder dominance in unmodified habitats to shredder and collector-gatherer dominance in beaver-created habitats. 5. Dam building by beaver in degraded environments can improve physical and biological diversity when viewed at a scale encompassing both modified and unmodified habitats. By restoring ecosystem processes locally, it may also offer wider scale benefits, including greater nutrient retention and flood attenuation. These benefits should be evaluated against evidence of any negative effects on land use or fisheries.
• Ecological status of European surface waters is harmonised by intercalibration (IC). • IC ensur... more • Ecological status of European surface waters is harmonised by intercalibration (IC). • IC ensures greater parity in the funds invested to achieve good ecological status. • Less than half of the required IC is currently accomplished. • IC already yielded a unified vision of what constitutes good ecology across Europe. a b s t r a c t Ecological status boundary (Pseudo-)common metric Reference/alternative benchmarking Water Framework Directive Halting and reversing the deterioration of aquatic ecosystems requires concerted action across state boundaries and administrative barriers. However, the achievement of common management objectives is jeopardised by different national quality targets and ambitions. The European Water Framework Directive requires that quality classifications are harmonised via an intercalibration exercise, ensuring a consistent level of ambition in the protection and restoration of surface water bodies across the Member States of the European Union. We outline the key principles of the intercalibration methodology, review the achievements of intercalibration and discuss its benefits and drawbacks. Less than half of the required intercalibration has been completed, mostly due to a lack of national assessment methods. The process has fostered a scientific debate on ecological classification with important implications for environmental management. Despite a significant level of statistical abstraction, intercalibration yielded a fundamental and unified vision of what constitutes good ecology across Europe, in principle ensuring greater parity in the funds invested to achieve good ecological status.
The European Water Framework Directive adopted in 2000, despite being prescriptive, has stimulate... more The European Water Framework Directive adopted in 2000, despite being prescriptive, has stimulated the development of a diverse array of biological assessment methods in Europe. The multitude of indicators currently used in biomonitoring lacks consistency and thus constrains the comparability of assessments at an international scale. Therefore, there is an argument to define and validate metrics with more universal application that can be applied EU-wide. We explored two metrics based on macrophyte taxonomic composition, the empirically based Intercalibration Common Metric for lake macrophytes (ICM LM) and the expert-based Ellenberg Index (EI), for their ability to detect eutrophication in different types of European lowland lakes. Data from 1474 unique lake-years from 11 countries were used to explore relationships between these metrics and the seasonal mean concentration of total phosphorus (TP) using linear regression. ICM LM gave a linear and relatively strong (R = 0.72, p < 0.0001) response over the entire spectrum of TP concentrations, whereas EI performed best in lakes with the TP concentrations up to 250 g L −1 (R = 0.64, p < 0.0001) and was largely insensitive to higher phosphorus concentrations. Both metrics performed better in Nordic lakes than in the Central-Baltic ones. The responses of both metrics to TP were not modified or only very weakly modified by altitude, lake size and mean depth but were significantly affected by alkalinity. The ICM LM –TP relationship was stronger in lakes with water alkalinity > 0.2 meq L −1 and significantly weaker in less buffered lakes. EI performed better in lakes with alkalinity < 1.0 meq L −1 , whereas in high alkalinity lakes the response was significantly weaker. In all the lakes and in lakes from all the size, depth and alkalinity types, ICM LM was more strongly correlated with TP than EI and was proportionally less sensitive to alkalinity. We also tested the effect of including helophytes on the metric response to eutrophication pressure by comparing the strength of the relationships to TP of the Ellenberg Index calculated firstly using only hydrophyte taxa (EI HYDR) and secondly using all macrophyte taxa including both hydrophytes and emergent vegetation (EI TOT). The differences in metric performance in all the lakes and all the size, depth and alkalinity types, except for the Nordic lakes, were non-significant. Thus, including helophytes generally did not significantly improve the strength of the EI–TP relationships.
A five year trial reintroduction of the European beaver in Knapdale, Argyll, began in spring 2009... more A five year trial reintroduction of the European beaver in Knapdale, Argyll, began in spring 2009. An independent monitoring programme was established to investigate the effects beavers might have upon particular aspects of the natural heritage were they to be released more widely in Scotland. The aspects studied included: semi-aquatic and aquatic macrophytes; damselflies and dragonflies; fish; water chemistry; hydrology; and fluvial geomorphology and river habitat. In addition to extensive surveys at the beginning and end of the trial period, interim monitoring was undertaken to establish the rate of any changes related to beaver activity. This report describes the extensive final survey and analysis of the data on fluvial geomorphology and river habitat collected during the trial period. Beavers appear to have explored much of the stream network, but have largely chosen not to exploit the river and riparian resources available and have therefore had limited influence on the fluv...
The Science of the total environment, Jan 13, 2015
Floodplains are key ecosystems of riverine landscapes and provide a multitude of ecosystem servic... more Floodplains are key ecosystems of riverine landscapes and provide a multitude of ecosystem services. In most of the large river systems worldwide, a tremendous reduction of floodplain area has occurred in the last 100years and this loss continues due to pressures such as land use change, river regulation, and dam construction. In the Danube River Basin, the extent of floodplains has been reduced by 68% compared to their pre-regulation area, with the highest losses occurring in the Upper Danube and the lowest in the Danube Delta. In this paper, we illustrate the restoration potential of floodplains along the Danube and its major tributaries. Via two case studies in the Upper and Lower Danube, we demonstrate the effects of restoration measures on the river ecosystem, addressing different drivers, pressures, and opportunities in these regions. The potential area for floodplain restoration based on land use and hydromorphological characteristics amounts to 8102 km(2) for the whole Danub...
Although the Water Framework Directive specifies that macrophytes and phytobenthos should be used... more Although the Water Framework Directive specifies that macrophytes and phytobenthos should be used for the ecological assessment of lakes and rivers, practice varies widely throughout the EU. Most countries have separate methods for macrophytes and phytobenthos in rivers; however, the situation is very different for lakes. Here, 16 countries do not have dedicated phytobenthos methods, some include filamentous algae within macrophyte survey methods whilst others use diatoms as proxies for phytobenthos. The most widely-cited justification for not having a dedicated phytobenthos method is redundancy, i.e. that macrophyte and phytoplankton assessments alone are sufficient to detect nutrient impacts. Evidence from those European Union Member States that have dedicated phytobenthos methods supports this for high level overviews of lake condition and classification; however, there are a number of situations where phytobenthos may contribute valuable information for the management of lakes.
... some time that defining assemblages of plants in terms of functional plant characteristics, r... more ... some time that defining assemblages of plants in terms of functional plant characteristics, rather ... display such extreme phenotypic plasticity and wide ecological amplitude that classifications are pointless ... Woodward &amp;amp; Cramer,z 1996) to classify hydrophytes into groups of plants ...
Recovery of plants from disturbance is frequently associated with the presence of an extensive se... more Recovery of plants from disturbance is frequently associated with the presence of an extensive seed bank. In a cut-off channel of the Rhone River subjected to fluctuating water levels and scouring forces during flash floods, regenerative strategies of aquatic plants were investigated through the study of the sediment propagule bank and its comparison with the established vegetation. Within this channel, the zone disturbed only by scouring floods (zone F) had a small propagule bank (as assessed by greenhouse germination trials), whereas more propagules regrew in zone FE which was subjected to both scouring floods and episodic sediment emersion. There, regrowth was mostly from sexual propagules, with the stonewort Chara vulgaris being the dominant component. In zone F, no relationship between propagule bank composition and established vegetation was demonstrated. In zone FE, a strong positive relationship between vegetative propagules (buds + rhizomes + fragments) and the established ...
SUMMARY 1. Small-scale discontinuities, formed by accumulations of wood, are recognised as a key ... more SUMMARY 1. Small-scale discontinuities, formed by accumulations of wood, are recognised as a key feature of functionally intact forested streams because they promote organic matter retention, increase habitat complexity and provide flow refugia. Re-establishing such features in physically degraded streams is therefore a common priority for restoration schemes. Ecosystem engineering by beavers in the form of dam building might offer a natural mechanism for restoring degraded streams. Despite an increase in beaver reintroductions globally, the ecosystem engineering concept has rarely been applied to restoring biodiversity and ecosystem function, especially within degraded freshwater systems. 2. By comparing multiple beaver-modified and unmodified sites on headwater streams draining 13 ha of pastureland in eastern Scotland, U.K., we investigated if hydromorphological changes caused by reintroduced beavers (Castor fiber) translate into desirable biological responses when there is a long history of physical degradation and contraction of the regional species pool due to agricultural land use. 3. Beaver modified in-stream habitat by constructing 10 dams, thus creating a series of interconnected dam pools. Organic matter retention and aquatic plant biomass increased (7 and 20 fold higher respectively) in beaver ponds relative to unmodified channels, consistent with the lower fluctuation in stream stage observed below a series of dams. Growing season concentrations of extractable P and NO 3 were on average 49% and 43% lower respectively below a series of dams than above, although colour and suspended solids concentrations increased. 4. Macroinvertebrate samples from beaver-modified habitats were less taxon rich (alpha diversity on average 27% lower) than those from unmodified stream habitat. However, due to significant compositional differences between beaver versus unmodified habitats, a composite sample from all habitats indicated increased richness at the landscape scale; gamma diversity was 28% higher on average than in the absence of beaver-modified habitat. Feeding guild composition shifted from grazer/scraper and filter feeder dominance in unmodified habitats to shredder and collector-gatherer dominance in beaver-created habitats. 5. Dam building by beaver in degraded environments can improve physical and biological diversity when viewed at a scale encompassing both modified and unmodified habitats. By restoring ecosystem processes locally, it may also offer wider scale benefits, including greater nutrient retention and flood attenuation. These benefits should be evaluated against evidence of any negative effects on land use or fisheries.
• Ecological status of European surface waters is harmonised by intercalibration (IC). • IC ensur... more • Ecological status of European surface waters is harmonised by intercalibration (IC). • IC ensures greater parity in the funds invested to achieve good ecological status. • Less than half of the required IC is currently accomplished. • IC already yielded a unified vision of what constitutes good ecology across Europe. a b s t r a c t Ecological status boundary (Pseudo-)common metric Reference/alternative benchmarking Water Framework Directive Halting and reversing the deterioration of aquatic ecosystems requires concerted action across state boundaries and administrative barriers. However, the achievement of common management objectives is jeopardised by different national quality targets and ambitions. The European Water Framework Directive requires that quality classifications are harmonised via an intercalibration exercise, ensuring a consistent level of ambition in the protection and restoration of surface water bodies across the Member States of the European Union. We outline the key principles of the intercalibration methodology, review the achievements of intercalibration and discuss its benefits and drawbacks. Less than half of the required intercalibration has been completed, mostly due to a lack of national assessment methods. The process has fostered a scientific debate on ecological classification with important implications for environmental management. Despite a significant level of statistical abstraction, intercalibration yielded a fundamental and unified vision of what constitutes good ecology across Europe, in principle ensuring greater parity in the funds invested to achieve good ecological status.
The European Water Framework Directive adopted in 2000, despite being prescriptive, has stimulate... more The European Water Framework Directive adopted in 2000, despite being prescriptive, has stimulated the development of a diverse array of biological assessment methods in Europe. The multitude of indicators currently used in biomonitoring lacks consistency and thus constrains the comparability of assessments at an international scale. Therefore, there is an argument to define and validate metrics with more universal application that can be applied EU-wide. We explored two metrics based on macrophyte taxonomic composition, the empirically based Intercalibration Common Metric for lake macrophytes (ICM LM) and the expert-based Ellenberg Index (EI), for their ability to detect eutrophication in different types of European lowland lakes. Data from 1474 unique lake-years from 11 countries were used to explore relationships between these metrics and the seasonal mean concentration of total phosphorus (TP) using linear regression. ICM LM gave a linear and relatively strong (R = 0.72, p < 0.0001) response over the entire spectrum of TP concentrations, whereas EI performed best in lakes with the TP concentrations up to 250 g L −1 (R = 0.64, p < 0.0001) and was largely insensitive to higher phosphorus concentrations. Both metrics performed better in Nordic lakes than in the Central-Baltic ones. The responses of both metrics to TP were not modified or only very weakly modified by altitude, lake size and mean depth but were significantly affected by alkalinity. The ICM LM –TP relationship was stronger in lakes with water alkalinity > 0.2 meq L −1 and significantly weaker in less buffered lakes. EI performed better in lakes with alkalinity < 1.0 meq L −1 , whereas in high alkalinity lakes the response was significantly weaker. In all the lakes and in lakes from all the size, depth and alkalinity types, ICM LM was more strongly correlated with TP than EI and was proportionally less sensitive to alkalinity. We also tested the effect of including helophytes on the metric response to eutrophication pressure by comparing the strength of the relationships to TP of the Ellenberg Index calculated firstly using only hydrophyte taxa (EI HYDR) and secondly using all macrophyte taxa including both hydrophytes and emergent vegetation (EI TOT). The differences in metric performance in all the lakes and all the size, depth and alkalinity types, except for the Nordic lakes, were non-significant. Thus, including helophytes generally did not significantly improve the strength of the EI–TP relationships.
A five year trial reintroduction of the European beaver in Knapdale, Argyll, began in spring 2009... more A five year trial reintroduction of the European beaver in Knapdale, Argyll, began in spring 2009. An independent monitoring programme was established to investigate the effects beavers might have upon particular aspects of the natural heritage were they to be released more widely in Scotland. The aspects studied included: semi-aquatic and aquatic macrophytes; damselflies and dragonflies; fish; water chemistry; hydrology; and fluvial geomorphology and river habitat. In addition to extensive surveys at the beginning and end of the trial period, interim monitoring was undertaken to establish the rate of any changes related to beaver activity. This report describes the extensive final survey and analysis of the data on fluvial geomorphology and river habitat collected during the trial period. Beavers appear to have explored much of the stream network, but have largely chosen not to exploit the river and riparian resources available and have therefore had limited influence on the fluv...
The Science of the total environment, Jan 13, 2015
Floodplains are key ecosystems of riverine landscapes and provide a multitude of ecosystem servic... more Floodplains are key ecosystems of riverine landscapes and provide a multitude of ecosystem services. In most of the large river systems worldwide, a tremendous reduction of floodplain area has occurred in the last 100years and this loss continues due to pressures such as land use change, river regulation, and dam construction. In the Danube River Basin, the extent of floodplains has been reduced by 68% compared to their pre-regulation area, with the highest losses occurring in the Upper Danube and the lowest in the Danube Delta. In this paper, we illustrate the restoration potential of floodplains along the Danube and its major tributaries. Via two case studies in the Upper and Lower Danube, we demonstrate the effects of restoration measures on the river ecosystem, addressing different drivers, pressures, and opportunities in these regions. The potential area for floodplain restoration based on land use and hydromorphological characteristics amounts to 8102 km(2) for the whole Danub...
Although the Water Framework Directive specifies that macrophytes and phytobenthos should be used... more Although the Water Framework Directive specifies that macrophytes and phytobenthos should be used for the ecological assessment of lakes and rivers, practice varies widely throughout the EU. Most countries have separate methods for macrophytes and phytobenthos in rivers; however, the situation is very different for lakes. Here, 16 countries do not have dedicated phytobenthos methods, some include filamentous algae within macrophyte survey methods whilst others use diatoms as proxies for phytobenthos. The most widely-cited justification for not having a dedicated phytobenthos method is redundancy, i.e. that macrophyte and phytoplankton assessments alone are sufficient to detect nutrient impacts. Evidence from those European Union Member States that have dedicated phytobenthos methods supports this for high level overviews of lake condition and classification; however, there are a number of situations where phytobenthos may contribute valuable information for the management of lakes.
... some time that defining assemblages of plants in terms of functional plant characteristics, r... more ... some time that defining assemblages of plants in terms of functional plant characteristics, rather ... display such extreme phenotypic plasticity and wide ecological amplitude that classifications are pointless ... Woodward &amp;amp; Cramer,z 1996) to classify hydrophytes into groups of plants ...
Recovery of plants from disturbance is frequently associated with the presence of an extensive se... more Recovery of plants from disturbance is frequently associated with the presence of an extensive seed bank. In a cut-off channel of the Rhone River subjected to fluctuating water levels and scouring forces during flash floods, regenerative strategies of aquatic plants were investigated through the study of the sediment propagule bank and its comparison with the established vegetation. Within this channel, the zone disturbed only by scouring floods (zone F) had a small propagule bank (as assessed by greenhouse germination trials), whereas more propagules regrew in zone FE which was subjected to both scouring floods and episodic sediment emersion. There, regrowth was mostly from sexual propagules, with the stonewort Chara vulgaris being the dominant component. In zone F, no relationship between propagule bank composition and established vegetation was demonstrated. In zone FE, a strong positive relationship between vegetative propagules (buds + rhizomes + fragments) and the established ...
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Papers by Nigel Willby