Restoring wetland biodiversity using research: Whole‐community facilitation by beaver as framework

• 1. Wetlands are declining worldwide, and there is a great need for their restoration and creation. One natural agent of wetland engineering is beavers, Castor spp., which have returned or are returning to many parts of their former range.
• 2. We initially studied the facilitative effect of the beaver Castor canadensis on a waterbird community consisting of three waders and four ducks in boreal wetlands in southern Finland. Both waterbird species diversity and abundance increased when beavers impounded a pond. Common teal Anas crecca and green sandpiper Tringa ochropus were the species showing the most positive numerical response, but the other five species also increased upon flooding.
• 3. This article evaluates how the results of the study have been used in management, both in theory and practice. The whole‐community facilitation concept has been taken up in numerous articles considering the restorative effects of beavers. It has also been used as ecological background when planning and executing man‐made wetland projects in Finland within both the public and the private sectors.
• 4. Our study and its publication in Aquatic Conservation: Marine and Freshwater Ecosystems have set a foundation for further evidence‐based management of waterbird communities. As the results show, having beavers as wetland managers is a feasible tool for creating and restoring wetlands for waterbirds and other biota. Moreover, wetland restoration projects are becoming more popular endeavours, owing to an understanding of the diverse benefits of wetlands. Flooding by beavers is used as a model for managers when creating man‐made wetlands; for example, in urban areas where it is difficult to maintain beavers.

     

Relationships between breeding waterbird abundance,diversity, and clear water status after the restoration of two shallow nutrient‐rich Danish lakes

1. Breeding waterbird communities have suffered globally from the effects of anthropogenic changes in water quality (especially nutrient enrichment) in recent decades, but few studies have demonstrated the positive effects of restorative actions.
2. Annual breeding waterbird surveys in the period 1977–2005 at two restored southern Danish lake basins (combining nutrient load reduction and biomanipulation) showed an up to five‐fold increase in abundance, and considerable changes in species richness and diversity, following restoration to clear water status in both lakes.
3. Parallel surveys at a third lake, which retained clear water quality throughout, offering a form of natural ‘control', showed no such changes over the same time period.
4. Consistent relationships between breeding waterbird abundance, species richness, and diversity with measures of water clarity (Secchi disc depth, chlorophyll a, and suspended matter) suggest that water clarity mainly drives the relationship; inverse relationships between these measures and total nitrogen and phosphorus were less consistent than for water clarity.
5. The results suggest that an improvement in water clarity plays a key role in restoring breeding waterbird communities and suggest that breeding waterbirds can be indicators of the success of lake restoration projects, but more studies are needed to confirm their wider utility under a variety of conditions.

     

Declines in the tuber‐feeding waterbird guild at Shengjin Lake National Nature Reserve,China – a barometer of submerged macrophyte collapse

• 1. The Yangtze floodplain is globally unique for its extensive ephemeral wetlands, recharged by summer monsoon precipitation. The annual cycle of inundation and water table recession favours submerged macrophytes, including Vallisneria that overwinters in desiccated substrates as tubers, which provide high‐energy winter food for tuber‐feeding waterbirds that were formerly abundant in the region.
• 2. Large declines among the tuber‐feeding waterbirds swan goose Anser cygnoides (L.), tundra swan Cygnus columbianus (Ord) and hooded crane Grus monacha Temminck between 2004/2005 and 2009/2010 at Shengjin Lake, Anhui Province, suggest that major changes in food availability have occurred there.
• 3. Based on observations of feeding behaviour and energy budgets of these species, it was calculated that at least 5.0 and 8.9 km² of Vallisneria beds in 2004 and 2005, respectively, would be needed to support observed numbers of these species, compared with less than 1.5 km² found in 2009 and 2010.
• 4. An incomplete macrophyte survey in summer 2000 located at least 7.7 km² of Vallisneria beds in the Upper Lake, where none was present during resurveys in 2008 and 2009. Declines in tuber‐feeding waterbirds at Shengjin Lake coincide with the disappearance of their submerged macrophyte food plants, possibly as a result of eutrophication since the mid‐2000s.
• 5. Widespread declines and concentration of tuber‐eating wintering waterbirds at other sites elsewhere in the Yangtze floodplain may also reflect the local collapse of submerged macrophytes and of ecosystem services that these wetlands provide to the human communities. Copyright © 2010 John Wiley & Sons, Ltd.

     

Ecology and conservation of grassy wetlands dominated by spiny mud grass Pseudoraphis spinescens in the southern Murray–Darling Basin,Australia

相似文献   

Willow (Salix spp.) and aspen (Populus tremula) regrowth after felling by the Eurasian beaver (Castor fiber): implications for riparian woodland conservation in Scotland

• 1. A proposed trial reintroduction of the Eurasian beaver (Castor fiber L.) to Scotland has recently been approved (May 2008). A previous proposal was turned down by the licensing authority, partly over the perceived risks to woodland within a Special Area of Conservation.
• 2. This paper presents data on two years of willow (Salix spp.) and aspen (Populus tremula L.) regrowth following tree felling by captive beavers within two large semi‐natural enclosures in eastern Scotland. Both willow and aspen are highly preferred by beavers.
• 3. Regrowth of willow stems was quantified from cut stumps, felled logs and partially severed (‘incompletely felled’) trees, and compared with growth of stems in the canopies of untouched willows.
• 4. Maximum annual regrowth was observed in incompletely felled trees, followed by cut stumps and then unfelled control trees. Mean regrowth rates were ca 18 m regrowth per metre of measured tree section per year in incompletely felled trees. This was approximately 12 times more annual regrowth than that observed in unfelled trees, despite apparently selective browsing of the regrowth of incompletely felled trees by roe deer.
• 5. Although incompletely felled willows represent a relatively small component of felling activity (9% of all felled willow), they contribute disproportionately to the biomass of beaver‐engineered riparian woodlands, creating a more multi‐layered habitat structure.
• 6. Willow regrowth in inundated areas was avoided by deer, and harvesting of regrowth by beavers was rare.
• 7. Significant regrowth from 11 stumps of aspen in 2 years post‐felling occurred by suckering, with 85 suckers of mean height 2.1 m being recorded, all of which were subsequently avoided by browsing deer and beavers.
• 8. These data suggest that rapid regeneration of willow and aspen will occur in riparian woodlands in the event of major felling activity by Eurasian beaver, even in the presence of low to moderate levels of roe deer browsing, and that the conservation status of both these trees or the wider habitats that they form would not be threatened by a well planned and managed reintroduction of beavers to Scotland.

Copyright © 2008 John Wiley & Sons, Ltd.     

Complementary use of natural and artificial wetlands by waterbirds wintering in Doñana,south‐west Spain

• 1. The Doñana wetland complex (SW Spain) holds more wintering waterfowl than any other wetland in Europe.
• 2. This study focused on the use made by 12 common waterbirds (eight ducks and four waders) of the natural seasonal marshes in Doñana National Park (DNP) and the adjacent Veta la Palma (VLP) fish ponds created in the early 1990s. Data used were from aerial and terrestrial surveys collected between October and February during six consecutive winters from 1998/99 to 2003/04. Changes in distribution of each bird taxon were related to changes in the extent of flooded marshes within DNP. Up to 295 000 ducks were counted in VLP during dry periods, and up to 770 000 in DNP when it was flooded.
• 3. The timing and extent of flooding in DNP was highly variable, but there was a consistent pattern in which ducks concentrated in VLP during dry months and winters but redistributed to DNP as more of it was flooded. This refuge effect was also strong for black‐tailed godwits Limosa limosa, but much less so for other waders. Waders feed mainly on invertebrates, and invertebrate biomass in VLP was found to be higher than in DNP. Ducks feed mainly on seeds and plant material, which are more abundant in DNP when flooded.
• 4. When water levels in DNP were stable over the course of a winter, or controlled for in multivariate models, the numbers of ducks at VLP declined over time, probably due to reduced availability of plant foods. In contrast, numbers of waders at VLP were more stable, and their invertebrate prey became more abundant over time, at least in the winter 2003/4.
• 5. In this extremely important wetland complex, the value of natural and artificial wetlands for wintering waterbirds are complementary, providing suitable habitat for different species and for different conditions in a highly variable Mediterranean environment.

Copyright © 2009 John Wiley & Sons, Ltd.     

Invasion of artificial ponds in Doñana Natural Park,southwest Spain,by an exotic estuarine copepod

• 1. During a study of five artificial brackish ponds situated in Doñana Natural Park and the Guadalquivir delta between July 2001 and June 2002, a total of six copepod species (two calanoids, three cyclopoids and one harpacticoid) were recorded. All of them are typical of brackish or estuarine habitats.
• 2. The estuarine calanoid copepod Acartia tonsa (originally from North America) was present in all the ponds studied. This exotic species has been found previously in European estuaries, but has not previously been recorded from artificial wetlands.
• 3. Both the relative and absolute abundance of the species varied significantly among months and ponds. A. tonsa was most abundant during autumn and spring, while Calanipeda aquae‐dulcis was most abundant in summer. This seasonal pattern of the copepod community composition was different from that reported in studies from other European estuaries or wetlands.
• 4. The invasion by and dominance of A. tonsa in the area of Doñana Natural Park has important implications for the conservation of the diverse native zooplankton fauna in the natural marshes of the adjacent Doñana National Park, which includes endemic species.

Copyright © 2005 John Wiley & Sons, Ltd.     

A massive spoonbill stopover episode: identifying emergency sites for the conservation of migratory waterbird populations

相似文献   

Fishless shallow lakes of Southern Patagonia as habitat for waterbirds at the onset of trout aquaculture

• 1. The Strobel Meseta, a basaltic plateau of Patagonia (Santa Cruz Province, Argentina), holds thousands of shallow fishless lakes that are prime habitat for many species of waterbirds, including some considered ‘near threatened’. In recent years, several lakes have been stocked with trout which has created uncertainty about the potential effects on the recipient ecosystem.
• 2. Limnological and topographical analyses were performed in a group of 32 lakes of the Strobel Meseta in order to characterize and classify individual lakes of the meseta based on their limnological and topographic features, analyze the association between lake type and use by aquatic birds in general and by the endemic hooded grebe (Podiceps gallardoi) in particular, and evaluate the overlap between trout aquaculture and critical habitat for waterbirds.
• 3. The lakes were classified by multivariate analyses into four characteristic types: turbid, high conductivity lakes (T), small vegetated lakes (SV) and larger lakes which were subdivided into either vegetated (LV) or unvegetated (LU). In general, macrophyte cover was the main classificatory variable, whereas conductivity, pH, surface, and depth contributed moderately. Large vegetated lakes were generally found to be important for waterbirds and provided critical habitat for the hooded grebe, whereas trout farmers largely favoured large unvegetated lakes. However, since some large vegetated lakes have already been stocked, there is some level of geographical overlap between waterbird habitat and trout farming.
• 4. The existence of some level of spatial segregation between production and critical waterbird habitat affords opportunities for designing a spatially‐based management system for trout aquaculture.

Copyright © 2008 John Wiley & Sons Ltd.     

Managed and natural inundation: benefits for conservation of native fish in a semi‐arid wetland system

相似文献   

Change of fish fauna in ponds after eradication of invasive piscivorous largemouth bass,Micropterus salmoides,in north‐eastern Japan

• 1. The change in fish fauna was monitored in ponds within irrigation systems in Iwate prefecture, north‐eastern Japan to evaluate the effectiveness of eradicating the invasive piscivorous largemouth bass, Micropterus salmoides.
• 2. Eleven study ponds were categorized into three pond groups: bass‐dwelling (n=3), bass‐eradicated (n=3) and non‐invaded ponds (n=5).
• 3. Species richness and diversity, which temporally decreased in bass‐dwelling ponds, increased in bass‐eradicated ponds. Furthermore, in bass‐eradicated ponds, the mean numbers of topmouth minnow and freshwater goby were gradually restored, but in bass‐dwelling ponds the numbers decreased and both species eventually disappeared.
• 4. Although the eradication of piscivorous invaders is helpful for restoring fish species diversity in ponds, its effectiveness varies among species, and other alien fish such as the rose bitterling (Rhodeus ocellatus ocellatus) often invade and proliferate in the bass‐eradicated ponds.
• 5. To ensure successful restoration of native biota and avoid undesirable results, it is necessary to plan and implement continuous monitoring and adaptive management after eradication of alien predators. Copyright © 2010 John Wiley & Sons, Ltd.

     

Beaver dams shift desert fish assemblages toward dominance by non‐native species (Verde River,Arizona, USA)

The reintroduction of beaver (Castor canadensis) into arid and semi‐arid rivers is receiving increasing management and conservation attention in recent years, yet very little is known about native versus non‐native fish occupancy in beaver pond habitats. Streams of the American Southwest support a highly endemic, highly endangered native fish fauna and abundant non‐native fishes, and here we investigated the hypothesis that beaver ponds in this region may lead to fish assemblages dominated by non‐native species that favour slower‐water habitat. We sampled fish assemblages within beaver ponds and within unimpounded lotic stream reaches in the mainstem and in tributaries of the free‐flowing upper Verde River, Arizona, USA. Non‐native fishes consistently outnumbered native species, and this dominance was greater in pond than in lotic assemblages. Few native species were recorded within ponds. Multivariate analysis indicated that fish assemblages in beaver ponds were distinct from those in lotic reaches, in both mainstem and tributary locations. Individual species driving this distinction included abundant non‐native green sunfish (Lepomis cyanellus) and western mosquitofish (Gambusia affinis) in pond sites, and native desert sucker (Catostomus clarkii) in lotic sites. Overall, this study provides the first evidence that, relative to unimpounded lotic habitat, beaver ponds in arid and semi‐arid rivers support abundant non‐native fishes; these ponds could thus serve as important non‐native source areas and negatively impact co‐occurring native fish populations.     

The role of pond management for biodiversity conservation in an agricultural landscape

相似文献   

Characterizing seasonal dynamics of Amazonian wetlands for conservation and decision making

1. In many wetlands the timing and duration of inundation determine ecological characteristics and the provision of ecosystem services; however, wetland conservation decisions often rely on static maps of wetland boundaries that do not capture their dynamic hydrological variability and connectivity.
2. The Amazon River basin contains some of the world's most extensive wetlands, many of which are floodplains where seasonal flood pulses result in a temporally varying inundation area and hydrological connectivity with river systems.
3. This study classified Amazon wetlands according to the timing and duration (months per year) of inundation detected by remote sensing, and also investigated the contribution of precipitation regimes in affecting wetland distribution and hydrological dynamics.
4. Permanently inundated wetlands account for the largest area and are mainly floodplains located in the lowlands of the catchment. Seasonally inundated wetlands varied greatly in the duration of inundation over the course of the year, ranging from 1 to 9 months. Distinct seasonal timing was detected among the large wetland complexes, reflecting rainfall regimes as well as time lags for drainage and drying. For example, inundation in the extensive Llanos de Moxos region of the southern Amazon was protracted and lasted well after the rainy season, compared with the Roraima region of the northern Amazon, where inundation was shorter and tracked the rainy season.
5. The integration of inundation dynamics into wetland classification captures regional differences in timing and duration of inundation in the major wetlands of the basin that should be considered for conservation planning and other ecological applications. This information can aid regional wetland management and planning, especially with regards to minimizing the effects of dam and waterway construction that can directly affect the natural wetland dynamics. The use of global remotely sensed inundation data makes this approach easily transferable to other large tropical wetlands.

     

Distribution and reproduction of Procambarus clarkii in relation to water management,salinity and habitat type in the Camargue

相似文献   

Contrasting influences of inundation and land use on the rate of floodplain restoration

1. This study examined the assisted natural restoration of native vegetation in an Australian floodplain wetland where flows were reinstated and the river was reconnected to the floodplain, following cessation of agricultural cultivation.
2. Extant vegetation was surveyed three times during an inundation event at plots with different land‐use histories.
3. Restoration rate was more influenced by past land use than long‐term inundation frequency and success decreased with antecedent land‐use intensity. Prolonged land‐use history (>3 years cultivation) restricted restoration success. Sites with longer cultivation histories tended to have fewer aquatic species, more terrestrial species and exotic species. For example, amphibious responders with floating leaves were found only in reference plots and less frequently in farmed treatment plots. In this scenario, increased persistence of exotics and dryland species suggested alternative trajectories. Fields with a short land‐use history (1–3 years of clearing and cultivation) resembled undisturbed floodplain communities, consistent with a ‘field of dreams’ hypothesis.
4. Although river–floodplain reconnections can restore wetlands, legacy effects of past land use may limit the pace and outcomes of restoration.

     

The relevance of preserving temporary ponds during drought: hydrological and vegetation changes over a 16-year period in the Doñana National Park (south-west Spain)

• 1. Although the Doñana National Park is given the highest degree of environmental protection in Spain, it is likely that groundwater discharge to several ponds within the Biological Reserve has been damaged by abstraction to a tourist resort located less than 1 km away.
• 2. Hydrological changes were monitored over 16 years (1 October 1989 to 30 September 2005) by recording the shallow water table of six temporary ponds at 1–8-week intervals, and the duration of pond wet phase (or hydroperiod) during each hydrological cycle.
• 3. The average rainfall for the study period was 563.2 mm, and included 6 wet, 5 moderate, and 5 dry years in a seemingly random sequence. The average rainy season extended from October until the end of March, while the dry season occupied the rest of the year.
• 4. The water table generally oscillated following this alternation of rainy and dry seasons, but this fluctuation was minimal during dry years, and even failed to occur at some ponds.
• 5. Since 1998/99, the average hydroperiod has shortened by 3 months at Charco del Toro pond, and by almost 2 months at Brezo pond, while the rest of the ponds exhibited a reduction of less than 1 month.
• 6. Vegetation changed in the ponds between May 1990 and 2005. Total plant cover increased (range of increase: 16–65%), and species richness decreased in all ponds (range of species loss: 4–18).
• 7. The reduction in the hydroperiod probably enhanced the growth of a few woody plants to the detriment of flooding-dependent species as the cover of Pinus pinea increased nearly fourfold at Brezo pond, while that of Scirpus lacustris was halved at Charco del Toro pond.
• 8. The pumping area for the nearby tourist resort should be relocated, and a specific management strategy should be developed in order to prevent further damage to the ponds.

Copyright © 2007 John Wiley & Sons, Ltd.     

Stable isotope ratios of egg albumen of three waterbird species nesting in the Colorado River Delta indicate differences in foraging ground and isotopic niche breadth

相似文献   

Assessing the extent to which temporal changes in waterbird community composition are driven by either local,regional or global factors

相似文献   

The response of otters to environmental changes imposed by the construction of large dams

相似文献