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Aquatic ecosystem functions of an isolated floodplain and their implications for flood retention and management

Reckendorfer, W., A. Funk, C. Gschöpf, T. Hein, and F. Schiemer,2013: “Aquatic ecosystem functions of an isolated floodplain and their implications for flood retention and management.” Journal of Applied Ecology, v. 50, pp. 119-128, doi: 10.1111/1365-2664.12029.

1. We used an isolated floodplain of the river Danube as a model system to gain an understanding on the functioning of retention areas to predict future developments and to sustain their ecological services.
2. We applied correlation analysis and spline regression models to assess the effects of geomorphology, hydraulics, and seasonality on sediment characteristics, suspended solids, hydrochemistry and primary producers.
3. The spatio-temporal connection to the river is the primary factor influencing the hydrochemical characteristics and sediments. Allochthonous processes such as nutrient and sediment input during high waters dominate in connected parts of the floodplain, whereas autochthonous processes, for example, the release of phosphorus from the sediments and internally driven eutrophication, dominate in isolated parts. These conditions also affect the dominating primary producers, biodiversity, the degree of floodplain aggradation and thus the potential life span of aquatic habitats.
4. Measures to improve the functional basis for ecological services may use both allochthonous and autochthonous processes as a starting point, that is, minimizing sediment storage and nutrient input and improving the water balance to prolong the life span of isolated waters, and thus maximizing water body diversity and associated biodiversity.
5. Based on the results of our analysis and literature, eight alternative management measures have been evaluated. As a result, we propose a stepwise adaptive approach beginning with a controlled water supply with low sediments and nutrient loads. If these measures prove insufficient to sustain ecological functions and conservation value, more radical steps must be considered.
6. Synthesis and applications The increasing problems with catastrophic flooding have forced decision makers to seek basin-wide solutions with focus on ‘more room for the river’ and the reintegration of former floodplains as retention basins. Such reintegrations also represent opportunities to improve the ecological conditions for nature development in addition to their principal function, that is, the storage of water during floods. The results of our study can serve as an effective tool to predict the effects of alternative management options and to establish and define the design criteria of water retention areas with regard to their ecological functions, life spans and biodiversity.

Open Access

The vulnerability of Amazon freshwater ecosystems

Castello, L., D.G. McGrath, L.L. Hess, M.T. Coe, P.A. Lefebvre, P. Petry, M.N. Macedo, V.F. Renó, and C.C. Arantes, 2012: “The vulnerability of Amazon freshwater ecosystems.” Conservation Letters, doi: 10.1111/conl.12008.

The hydrological connectivity of freshwater ecosystems in the Amazon basin makes them highly sensitive to a broad range of anthropogenic activities occurring in aquatic and terrestrial systems at local and distant locations. Amazon freshwater ecosystems are suffering escalating impacts caused by expansions in deforestation, pollution, construction of dams and waterways, and overharvesting of animal and plant species. The natural functions of these ecosystems are changing, and their capacity to provide historically important goods and services is declining. Existing management policies—including national water resources legislation, community-based natural resource management schemes, and the protected area network that now epitomizes the Amazon conservation paradigm—cannot adequately curb most impacts. Such management strategies are intended to conserve terrestrial ecosystems, have design and implementation deficiencies, or fail to account for the hydrologic connectivity of freshwater ecosystems. There is an urgent need to shift the Amazon conservation paradigm, broadening its current forest-centric focus to encompass the freshwater ecosystems that are vital components of the basin. This is possible by developing a river catchment-based conservation framework for the whole basin that protects both aquatic and terrestrial ecosystems.

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‘Water war’ in the Mekong Basin?

Pearse-Smith, S.W.D., 2012: “‘Water war’ in the Mekong Basin?” Asia Pacific Viewpoint, v. 53, pp. 147–162, doi: 10.1111/j.1467-8373.2012.01484.x.

The Mekong River system provides a crucial source of natural resources for riparian nations. However, the increasingly rapid pace of hydro-development in the Mekong Basin is threatening the integrity of the river system, posing a real concern for Lower Basin states, which are particularly dependent on the basin. This scenario has led to warnings of armed conflict, or even ‘water war,’ between riparian states. Certainly, the expanding scale of hydro-development can be expected to continue increasing interstate tensions in the Mekong region; but are these tensions really likely to escalate to armed conflict? This paper explores this question by drawing on the water and conflict theory of Aaron Wolf. Ultimately, this paper concludes that interstate tensions over Mekong hydro-development are unlikely to generate armed conflict. This is in part due to the strategic impracticality of such a conflict as well as the presence of a river basin management institution. Most compellingly, though, armed conflict is unlikely because the economic imperative shared by Mekong states is better served by cooperation – or at least non-interference – than conflict, over regional hydro-development. In closing, the paper urges that the study of water and conflict in the Mekong Basin be refocused at the intrastate level.

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Effects of cascade hydropower dams on the structure and distribution of riparian and upland vegetation along the middle-lower Lancang-Mekong River

Li, J., S. Dong, Z. Yang, M. Peng, S. Liu, X. Li, 2012: “Effects of cascade hydropower dams on the structure and distribution of riparian and upland vegetation along the middle-lower Lancang-Mekong River.” Forest Ecology and Management, v. 284, pp. 251-259, doi: 10.1016/j.foreco.2012.07.050.

The extensive number of hydropower dams being planned in southwest China has attracted much attention in recent years. Eight cascading dams along the middle and lower reaches of the Lancang-Mekong River basin were selected to assess the riparian and upland vegetation. A total of 24 transects and 126 quadrats perpendicular to the river channel were surveyed from upstream to downstream. By using two-way indicator species analysis (TWINSPAN), the vegetation types in this region were classified into 21 vegetation classes. The ecological gradient analysis was completed using canonical correspondence analysis (CCA) and demonstrated that the dominant environmental factors impacting vegetation distribution were the variations in latitude and altitude. The vegetation impact index (VII) was developed as a quantitative index to assess the impact of dam inundation and operation on the upland and riparian vegetation. The values of VII showed that the most endangered vegetation communities were the shrub and herb communities in riparian habitats along this river. The effects of cascading hydropower dams on riparian and upland vegetation distribution were more complex than those of single dams. Cascading hydropower dams can enhance habitat fragmentation, reduce the distribution ranges (latitude and altitude) of primary vegetation and reduce the complexity of the vegetation types along the river as well as induce the loss of primary vegetation in the whole watershed.

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A method for gauging landscape change as a prelude to urban watershed regeneration: The case of the Carioca River, Rio de Janeiro

Schlee, M.B., K.R. Tamminga, and V.R. Tangari, 2012: “A method for gauging landscape change as a prelude to urban watershed regeneration: The case of the Carioca River, Rio de Janeiro.” Sustainability, v. 4, no. 9, pp. 2054-2098, doi: 10.3390/su4092054.

Natural systems undergo processes, flows, and rhythms that differ from those of urban sociocultural systems. While the former takes place over eras or many generations, the latter may occur within years or even months. Natural systems change includes no principle of intentional progress or enhancement of complexity. In contrast, sociocultural systems change occurs through inherited characteristics, learning, and cultural transmission. Both are dynamic, heterogeneous, and vulnerable to regime shifts, and are inextricably linked. The interrelations among natural and anthropogenic factors affecting sustainability vary spatially and temporally. This paper focuses on landscape changes along the Carioca River valley in Rio de Janeiro, located in the Brazilian Neotropical Southeastern Region, and its implications for local urban sustainability. The study incorporates a transdisciplinary approach that integrates landscape ecology and urban morphology methodologies to gauge landscape change and assess social-ecological systems dynamics. The methodology includes a variety of landscape change assessments; including on-site landscape ecological, landscape morphology, biological and urbanistic surveys, to gauge urban watershed quality. It presents an adapted inventory for assessment of urban tropical rivers, Neotropical Urban Stream Visual Assessment Protocol (NUSVAP), and correlates the level of stream and rainforest integrity to local urban environmental patterns and processes. How can urban regional land managers, planners and communities work together to promote shifts toward more desirable configurations and processes? An understanding of the transient behavior of social-ecological systems and how they respond to change and disturbance is fundamental to building appropriate management strategies and fostering resilience, regenerative capacity, and sustainable development in urban watersheds. The sociocultural patterns, processes and dynamics of Rio’s hillsides suggest that increasing the multifunctionality, flexibility, adaptability and connectivity of open spaces may influence carrying, adaptive and regenerative capacities of urban landscape systems.

Open Access

Riparian forest restoration: Conflicting goals, trade-offs, and measures of success

Bateman, H.L., D.M. Merritt, and J.B. Johnson, 2012. “Riparian forest restoration: Conflicting goals, trade-offs, and measures of success.” Sustainability, v. 4, no. 9, pp. 2334-2347, doi: 10.3390/su4092334.

Restoration projects can have varying goals, depending on the specific focus, rationale, and aims for restoration. When restoration projects use project-specific goals to define activities and gauge success without considering broader ecological context, determination of project implications and success can be confounding. We used case studies from the Middle Rio Grande (MRG), southwest USA, to demonstrate how restoration outcomes can rank inconsistently when narrowly-based goals are used. Resource managers have chosen MRG for restoration due to impacts to the natural flood regime, reduced native tree recruitment, and establishment of non-native plants. We show restoration “success” ranks differently based upon three goals: increasing biodiversity, increasing specific ecosystem functions, or restoring native communities. We monitored 12 restored and control sites for seven years. Treatments ranked higher in reducing exotic woody populations, and increasing proportions of native plants and groundwater salvage, but generally worse at removing fuels, and increasing species and habitat structural diversity. Managers cannot rely on the term “restoration” to sufficiently describe a project’s aim. Specific desired outcomes must be defined and monitored. Long-term planning should include flexibility to incorporate provisions for adaptive management to refine treatments to avoid unintended ecological consequences.

Open Access

Long-term cottonwood forest dynamics along the upper Missouri River, USA

Scott, M.L., G.T. Auble, M.D. Dixon, W. Carter Johnson, and L.A. Rabbe, 2012: “Long-term cottonwood forest dynamics along the upper Missouri River, USA.” River Research and Applications, doi: 10.1002/rra.2588.

The upper Missouri River bottomland in north-central Montana, USA, retains much of the physical character it had when traversed by Lewis and Clark around 1805. We used geospatial data to quantify long-term changes in the distribution of bottomland vegetation, land use patterns and channel planform for a 257-km segment of the Missouri River above Fort Peck Reservoir. This segment is less ecologically altered than downstream segments, but two dams completed in the mid-1950s have decreased the frequency and magnitude of floods. The area of forest is sparse because of geomorphic setting but, contrary to public perception, has remained relatively constant during the past century. However, the stability of forest area obscures its spatial and temporal dynamics. We used state and transition models to quantify fates and sources of forest during two periods: 1890s–1950s and 1950s–2006. Total forest area was 6% greater in 2006 than it was in the 1890s, largely due to reduced forest loss to erosional processes and gains related to progressive channel narrowing. Channel narrowing resulted in part from human-caused peak flow attenuation. A modified transition matrix, used to examine future steady-state conditions, projected little change in forest area; however, these projections are likely an overestimate. The extent to which 2006 forest area represents a transient adjustment to a new flow regime versus a dynamic, quasi–steady state will be determined by the long-term interplay among hydrologic factors, channel processes, water management and land use practices.

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Riparian vegetation and water yield: A synthesis

Salemi, L.F., J.D. Groppo, R. Trevisan, J.M. de Moraes, W. de Paula Lima, and L.A. Martinelli, 2012: “Riparian vegetation and water yield: A synthesis.”Journal of Hydrology, vv. 454–455, pp. 195-202, doi: 10.1016/j.jhydrol.2012.05.061.

Forested riparian zones perform numerous ecosystem functions, including the following: storing and fixing carbon; serving as wildlife habitats and ecological corridors; stabilizing streambanks; providing shade, organic matter, and food for streams and their biota; retaining sediments and filtering chemicals applied on cultivated/agricultural sites on upslope regions of the catchments. In this paper, we report a synthesis of a different feature of this type of vegetation, which is its effect on water yield. By synthesizing results from studies that used (i) the nested catchment and (ii) the paired catchment approaches, we show that riparian forests decrease water yield on a daily to annual basis. In terms of the treated area increases on average were 1.32 ± 0.85 mm/day and 483 ± 30 mm/yr, respectively; n = 9. Similarly, riparian forest plantation or regeneration promoted reduced water yield (on average 1.25 ± 0.34 mm/day and 456 ± 125 mm/yr on daily and annual basis, respectively, when prorated to the catchment area subjected to treatment; n = 5). Although there are substantially fewer paired catchment studies assessing the effect of this vegetation type compared to classical paired catchment studies that manipulate the entire vegetation of small catchments, our results indicate the same trend. Despite the occurrence of many current restoration programs, measurements of the effect on water yield under natural forest restoration conditions are still lacking. We hope that presenting these gaps will encourage the scientific community to enhance the number of observations in these situations as well as produce more data from tropical regions.

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Threats to Riparian Ecosystems in Western North America: An Analysis of Existing Literature

Poff, B., K.A. Koestner, D.G. Neary, and V. Henderson, 2011: “Threats to Riparian Ecosystems in Western North America: An Analysis of Existing Literature.” Journal of the American Water Resources Association, v. 47, no. 6, pp. 1241-1254, doi: 10.1111/j.1752-1688.2011.00571.x.

A total of 453 journal articles, reports, books, and book chapters addressing threats to riparian ecosystems in western North America were analyzed to identify, quantify, and qualify the major threats to these ecosystems as represented in the existing literature. Publications were identified either as research, policy, literature review, historical comparison, or management papers. All papers were evaluated based on year of publication, area of interest, and type(s) of threats addressed. Research papers, however, were assessed in more depth. The publications ranged from the 1930s to 2010 and addressed the following threats: dams, pollution (point and nonpoint), grazing, land use change, timber harvesting, water diversion, road construction, recreation, mining, groundwater pumping, invasive species, climate change, salinity, fire, insect and diseases, woody encroachment, watershed degradation, elimination of native vegetation, beavers, fire suppression, and fuel management. While the types of threats vary on spatial and temporal scales, some persist through decades in western North America. This analysis shows that grazing has been perceived as a dominant threat since the 1980s, but has been diminishing in the past decade, while invasive species, dams and, in recent years, climate change are increasingly represented in the literature as threats to riparian ecosystems in western North America.

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