Ecological Engineering Approaches Research Articles

Protecting threatened species from coastal infrastructure upgrades: The importance of evidence-based conservation

Increased coastal development and rising sea levels as a result of continuing climate-change put coastal regions at risk from flooding and inundation. A common mitigation response is the construction and upgrade of hard coastal protection structures, such as breakwaters, seawalls, and groynes. The alteration of the coast, together with the introduction of novel materials into coastal waters can negatively impact adjacent habitats and associated organisms. The implementation of management plans that involve scientists, as well as a variety of other stakeholders offer an opportunity to minimise adverse effects to biodiversity or even enhance it, while still protecting infrastructure and people. This study examines the management of an Australian breakwater upgrade and the progressive design finding process, including stakeholder engagement, determination of assessment criteria, and environmental impact assessment. In the course of the latter, scientific research led to the rediscovery of a presumed extinct algal species, Nereia lophocladia, which created an additional challenge and temporarily halted the upgrade. To accommodate this, the breakwater design solution was modified to avoid any impacts on the algal population and, in order to maximise the species' survival, novel ecological engineering approaches were proposed as mitigation strategies. Our case study underpins the value of evidence-based conservation and cooperation among stakeholders as important tools for minimising ecological impacts from coastal infrastructure upgrades.

Heavy metal contamination in the sediment and plants of the Sundarbans, India

ABSTRACTHeavy metals are one of the hazardous contaminants in the total environment. The present study shows that the Sundarbans soil is contaminated with sludge and moderately contaminated with Cd and Co according to Contamination factor (CF), Enrichment factor (EF), Index of geo-accumulation (Igeo), and Ecological risk factor (ERF). The correlation, principle component analysis and factor analysis showed that Mn and Fe might have lithogenic origin whereas Cu, Pb, Co and Cd have anthropogenic inputs. The screening quick reference table (SQuiRT) shows that Cu and Cd may exert a possible toxic effect on the sediment dwelling biota. The phytoremediation study revealed that the endangered Heritiera fomes leaves can accumulate 80% of cadmium from the soil, which is highest based on this study as compared to other mangroves. The study also indicated that threatened date palm Phoenix paludosa leaves can accumulate 74% and 73% of Cu and Fe, respectively, from the soil. Now a day, there has been a spurt in mangrove plantations worldwide for the conservation of mangrove ecosystem using ecological engineering approaches. The present study is very much useful to choose a proper plant to decontaminate the soil from various heavy metal pollutants for effective management of mangrove wetlands.

Decentralized wastewater treatment using passively aerated biological filter

ABSTRACTThis study aimed to evaluate the efficiency of a novel pilot-scale passively aerated biological filter (PABF) as a low energy consumption system for the treatment of municipal wastewater. It consists of four similar compartments, each containing 40% of a non-woven polyester fabric as a bio-bed. The PABF was fed with primary treated wastewater under a hydraulic retention time (HRT) of 3.5 hr and a hydraulic loading rate of 5.5 m2/m3/d. The effect of media depth, HRT, dissolved oxygen (DO) and surface area of the media on the removal efficiency of pollutants was investigated. Results indicated that increasing media depth along the axis of the reactor and consequently increasing the HRT and DO resulted in great removal of different pollutants. A significant increase in the DO levels in the final effluent up to 6.7 mg/l resulted in good nitrification processes. Statistical analysis using SPSS showed that the reactor performance has significant removal efficiency (p < .05) for all pollutants. Overall results indicated that PABF is a viable ecological engineering approach that can be optimized and applied to improve water quality with minimal consumption of energy and low sludge production compared with conventional activated sludge and trickling filter systems.

Tiling the reef – Exploring the first step of an ecological engineering tool that may promote phase-shift reversals in coral reefs

Phase shifts from coral- to algal-dominated reefs have grave effects on reef biodiversity and key ecosystem functions, further influencing management approaches that have generated fewer returns than desired. Harnessing the ability of corals to ‘self-anchor’ to substrates and of tissue fusions between isogeneic fragments, we develop here a novel ecological engineering approach based on the 2D Coral Preparative (2D-CP) tool. Using this tool we propose to create flat, two dimensional coral units that are first grown in a mid-water coral nursery and then transplanted to overlay phase-shifted coral reef surfaces as floor tiles. Here, we assess the feasibility of the 2D-CP’s first stage- growth in the nursery. Ten coral colonies from each of the species: Stylophora pistillata, Pocillopora damicornis and Cyphastrea spp. were collected from localities at the northern Gulf of Eilat (Red Sea, Israel), fragmented into nubbins and glued onto flat surfaces (CDs) to create 235 2D-CP units (32 nubbins/unit). All 2D-CPs were hung in a mid-water coral nursery, in both horizontal and vertical positions, and were digitally photographed once a month for a year. Images of each 2D-CP were used to determine the percentages of live coral tissue coverage on the substrates and the nubbins’ survival percentage. Results revealed high survival rates, with >80% of the 2D-CPs possessing live coral tissues at 12 months post setup (mps). The nubbins of all three species displayed an extensive 2D growth on the substrates, and as of 6–7 months (species and genotype specific) many of the 2D-CPs were completely covered with coral tissue (20% of all the 2D-CPs showed >100% coral coverage at 12mps). The coral coverage of S. pistillata and P. damicornis 2D-CPs was significantly higher in the vertical placement position, 1.5 and 3 times, respectively.Overall, these results imply that the 2D-CP units can be successfully grown in a coral nursery for the purpose of creating ‘live tiles’ that can be placed directly over a denuded reef covered by turf algae, a novel ecological engineering tool to be used for coral-algae phase shifts reversals. We further anticipate that even in completely/partially dead 2D-CP units, newly exposed calcium carbonates would be expended as preferable substrates for either coral larval recruitment or coralline algae growth, boosting reef rehabilitation.

Approaches to defining deltaic sustainability in the 21st century

Deltas are among the most productive and economically important of global ecosystems but unfortunately they are also among the most threatened by human activities. Here we discuss deltas and human impact, several approaches to defining deltaic sustainability and present a ranking of sustainability. Delta sustainability must be considered within the context of global biophysical and socioeconomic constraints that include thermodynamic limitations, scale and embeddedness, and constraints at the level of the biosphere/geosphere. The development, functioning, and sustainability of deltas are the result of external and internal inputs of energy and materials, such as sediments and nutrients, that include delta lobe development, channel switching, crevasse formation, river floods, storms and associated waves and storm surges, and tides and other ocean currents. Modern deltas developed over the past several thousand years with relatively stable global mean sea level, predictable material inputs from drainage basins and the sea, and as extremely open systems. Human activity has changed these conditions to make deltas less sustainable, in that they are unable to persist through time structurally or functionally. Deltaic sustainability can be considered from geomorphic, ecological, and economic perspectives, with functional processes at these three levels being highly interactive. Changes in this functioning can lead to either enhanced or diminished sustainability, but most changes have been detrimental. There is a growing understanding that the trajectories of global environmental change and cost of energy will make achieving delta sustainability more challenging and limit options for management. Several delta types are identified in terms of sustainability including those in arid regions, those with high and low energy-intensive management systems, deltas below sea level, tropical deltas, and Arctic deltas. Representative deltas are ranked on a sustainability range. Success in sustainable delta management will depend on utilizing natural delta functioning and an ecological engineering approach.

Ecological engineering with high diversity vegetation patches enhances bird activity and ecosystem services in Philippine rice fields

This study examines the potential for ecological engineering to enhance the beneficial ecosystem services provided by birds in tropical rice fields. Bird activities were monitored at six sites in the Philippines with high-diversity vegetation patches (HDVPs) established as an ecological engineering approach to restore ecosystem services. Adjacent plots of conventional rice were monitored as controls. Predatory birds (shrikes, Lanius spp., grassbirds, Megalurus palustris, and kingfishers, Halcyon spp.) were more active in the ecological engineering fields where they foraged for arthropods and snails among the rice plants. Pied trillers, Lalage nigra, and yellow vented bulbuls, Pycnonotus goiavier, foraged more in the HDVPs than in rice. These birds mainly responded to the availability of bamboo for perching in the HDVPs, although patch vegetation beneath the bamboo was also used for perching by some species. Aerial hunters such as swallows, Hirundo spp., avoided HDVPs likely because the tall vegetation and bamboo stakes represented an obstacle for their flight. Small changes in the design of HDVPs could avoid any negative effects on foraging by swallows and swifts. The results indicate that ecological engineering of rice paddies can have multiple benefits for farmers and the environment, including improved nutrition for farming communities, the creation of habitat for wildlife, and the enhancement of regulatory ecosystem services provided by insectivorous and snail-eating birds.

One option, two countries, several strategies: subjacent mechanisms of assisted migration implementation in Canada and France

Climate change obliges societies to develop adaptive strategies in order to maintain sustainable management of resources and landscapes. However, the development and implementation of these strategies require dialogue between researchers and policy‐makers about what they understand for adaptation. This dialogue can be hindered by language differences, the hidden agendas, and conflicting concerns of those involved. In this research study, we explored the mechanisms that underlie the implementation process of assisted migration (AM), an adaptation strategy that aims to limit the impact of climate change. We conducted a comparative analysis of 80 semistructured interviews with actors in the forestry sectors in Canada and France. In Canada, our results show a division between the provinces strategies, causing a debate about AM because researchers are wary of the geoengineering and economic arguments that frame AM in areas where the effects of climate change remain unclear. In contrast, we found that the observation of climate impacts is a strong trigger for the application of AM despite an awareness of its associated risks. In France, we explained the absence of AM implementation by a lack of information flow between research and foresters regarding the concept of AM, a cultural attachment of French foresters to their forest landscapes and that climate change effects are not clear yet. Clarity on what implies a true ecological engineering approach in ecological restoration can help maintaining adaptive actions like AM within the general scope of ecosystem management and minimize simplistic applications of adaptation strategies because of climate change.

Evaluation of raising geese in cornfields based on emergy analysis: A case study in southeastern Tibet, China

Global agriculture faces a daunting challenge of feeding the increasing world population using the finite environmental resources. An efficient pathway is to integrate the agricultural and pastoral systems in rural regions. This study investigated the hypothesis of raising geese in cornfields (RGICF), which is an ecological engineering approach based on the principle of agro-pastoral integration, and whether this production pattern should be widely applied in southeastern Tibet, China. The core idea is to utilize available resources, such as weeds, the bottom leaves of crop plants, and insects in tillage systems to raise poultry. In this study, an emergy analysis method was used to better understand the performance, input-output status, and resource-use efficiency of RGICF compared to the conventional corn planting (CCP) production pattern that was used as a control. The results showed that, compared to CCP, RGICF had a lower emergy yield ratio by 0.62, lower systematic self-organization ability by 0.07, lower environmental loading ratio by 0.51, 1.32 times higher emergy sustainable index, and 2.14 times higher emergy index of product safety. The economic benefit of RGICF was higher than that of CCP, since the gross income and the net income of RGICF were 3.11 and 2.43 times higher than those of CCP, respectively. Overall, the results showed that RGICF led to greater economic benefits and had higher sustainability, lower environmental pressure, and higher product safety compared to CCP in the studied region. Therefore, RGICF has significant ecological–economic advantages compared to CCP, and its application is highly recommended for the area of southeastern Tibet.

Ecological Engineering Approaches to Improve Hydraulic Properties of Infiltration Basins Designed for Groundwater Recharge.

Infiltration systems are increasingly used in urban areas for groundwater recharge. The reduction of sediment permeability by physical and/or biological processes is a major problem in management of infiltration systems often requiring expensive engineering operations for hydraulic performance maintenance. To reduce these costs and for the sake of sustainable development, we proposed to evaluate the ability of ecological engineering approaches to reduce the biological clogging of infiltration basins. A 36-day field-scale experiment using enclosures was performed to test the influences of abiotic (light reduction by shading) and biotic (introduction of the macrophyte Vallisneria spiralis (L.) or the gastropod Viviparus viviparus (Linnaeus, 1758)) treatments to limit benthic biofilm biomass and to maintain or even increase hydraulic performances. We coupled biological characterization of sediment (algal biomass, bacterial abundance, total organic carbon, total nitrogen, microbial enzymatic activity, photosynthetic activity, and photosystem II efficiency) with hydraulic conductivity measurements to assess the effects of treatments on sediment permeability. The grazer Viviparus viviparus significantly reduced benthic biofilm biomass and enhanced hydraulic conductivity. The other treatments did not produce significant changes in hydraulic conductivity although Vallisneria spiralis affected photosynthetic activity of biofilm. Finally, our results obtained with Viviparus viviparus are promising for the development of ecological engineering solutions to prevent biological fouling in infiltration systems.

DIVECOSYS: Bringing together researchers to design ecologically-based pest management for small-scale farming systems in West Africa

Crop pests are a major constraint to the intensification of agricultural production in the tropics, with novel issues related to global change (climate, land use, biological invasions, etc.), food security and preservation of natural resources and biodiversity. A research, extension and education network called DIVECOSYS (Diversity of cropping systems and ecologically-based pest management in West Africa) was launched in 2010 to synergize applied research actions in response to growing concerns on the vulnerability of agricultural systems to pest management in West Africa. This scientific network brings together research and academic institutions, with expertise spanning a multidisciplinary perspective from biology and ecology to remote sensing, agronomy and integrated pest management. Its main scientific objective is to explore the potential of biodiversity and ecological processes such as pest regulation, enabling novel ecologically-based models for productive systems, reduction of pesticide use, and adaptation or resilience of farming systems in the face of environmental disruptions. From Northern Senegal to Southern Benin, the research group explores a wide range of ecoregions and socio-ecological contexts, including stakeholders and their objectives, land use and agricultural practices, and management of biodiversity for enhancing biological control. Main challenges to be turned into opportunities include (i) encouraging collaborations amongst researchers from different scientific fields, (ii) fostering interactive research and synergies among research institutions and among countries, and (iii) developing an ecological engineering approach for the design of sustainable agricultural systems for smallholder farmers.

Passive co-treatment of acid mine drainage and sewage: Anaerobic incubation reveals a regeneration technique and further treatment possibilities

The passive co-treatment of municipal wastewater and acid mine drainage is an ecological engineering approach that has recently shown promise for the sustainable remediation of common liquid wastes. In order to investigate a possible regeneration technique and illuminate further treatment possibilities, four replicate columns containing limestone overlain with inert biofilm media that had been processing a passively pre-treated mixture of high-strength acid mine drainage and raw municipal wastewater were pulled offline, kept filled, sealed and incubated. The incubation period (91 d) was presumed to far exceed that required to reach a pseudo-steady state to drive reactions closer to completion than the standard residence time (42-h and 18-h in the inert media and limestone stages of the columns, respectively). Further nitrate reduction, alkalinity generation, and pH increase resulted. Further Al, Mn, and Zn removal was observed. Dissolved Fe increased from 45.3 to 147mg/L, a likely result of Fe-reducing bacterial activity, indicating that accumulated Fe in solid phases could be transformed, remobilized, and flushed from the unit process. This phenomenon could serve to passively regenerate treatment cells by removing accumulated solids to avoid clogging and preferential flowpaths. Phosphate and other trace metals (e.g., As, Cd, Pb) associated with solid phases were not released into solution, indicating the stability of the phosphate-related solids formed during standard operation or the availability of further re-sorption sites. Overall, results revealed that most anaerobic treatment reactions were near completion under the previous treatment regime, that further Zn processing was likely practical, and a possible passive media regeneration technique, thus illuminating further options regarding high-strength acid mine drainage and raw municipal wastewater passive co-treatment.

L’agriculture africaine face aux changements globaux : recherches et innovations basées sur les sciences de l’écologie

In the context of environmental and socio-economic changes, the agriculture of Sub-Saharan African countries will have to ensure food security of the population, while reducing its environmental footprint. The biophysical and social systems of agricultural production are complex. Innovative agricultural practices will be based on an intensification of ecological processes that determine the functioning of the soil–plant system, farmers’ fields and agro-ecosystems. This ecological engineering approach is useful to take up the challenge of Sub-Saharan agricultures in the future, as shown in researches conducted by IESOL International Joint Lab “Intensification of agricultural soils in West Africa” (ISRA, UCAD, TU, OU, INERA, IRD).

The littoral zone in the Three Gorges Reservoir, China: challenges and opportunities

For flood control purpose, the water level of the Three Gorges Reservoir (TGR) varies significantly. The annual reservoir surface elevation amplitude is about 30 m behind the dam. Filling of the reservoir has created about 349 km(2) of newly flooded riparian zone. The average flooding period lasts for more than 6 months, from mid-October to late April. The dam and its associated reservoir provide flood control, power generation, and navigation, but there are also many environmental challenges. The littoral zone is the important part of the TGR, once its eco-health and stability are damaged,which will directly endanger the ecological safety of the whole reservoir area and even the Yangtze River Basin. So, understanding the great ecological opportunities which are hidden in littoral zone of TGR (LZTGR) and putting forward approaches to solve the environmental problems are very important. LZTGR involves a wide field of problems, such as the landslides, potential water pollution, soil erosion, biodiversity loss, land cover changes, and other issues. The Three Gorges dam (TGD) is a major trigger of environmental change in the Yangtze River. The landslides, water quality, soil erosion, loss of biodiversity, dam operation, and challenge for land use are closely interrelated across spatial and temporal scales. Therefore, the ecological and environmental impacts caused by TGD are necessarily complex and uncertain. LZTGR is not only a great environmental challenge but also an ecological opportunity for us. In fact, LZTGR is an important structural unit of TGR ecosystem and has special ecosystem services function. Vegetation growing in LZTGR is therefore a valuable resource due to accumulation of carbon and nutrients. Everyone thinks that the ecological approach to the problem is needed. If properly designed, dike-pond systems, littoral woods systems, and re-created waterfowl habitats will have the capacity to capture nutrients from uplands and obstruct soil erosion. Ecological engineering approaches can therefore reduce environmental impacts of LZTGR and optimize ecological services. In view of the current situation and existing ecological problems of LZTGR, according to function demands such as environmental purification, biodiversity conservation, and vegetation carbon sink enhancement, we should explore the eco-friendly utilization mode of resources in LZTGR. Ecological engineering approaches might minimize the impacts or optimize the ecological services. Natural regeneration and ecological restoration in LZTGR are valuable for soil erosion decrease, pollutant purification, biodiversity conservation, carbon sink increase, and ecosystem health maintenance in TGR.

Linking sediment trapping efficiency with morphological traits of Salix tiller barriers on marly gully floors under ecological rehabilitation

Soil erosion is considered to be a major threat for soil quality worldwide. Overgrazing and deforestation are the main causes of a recent increase in soil erosion. When devoid of vegetation, marly terrains are particularly prone to severe hydric erosion with gully formation. It is commonly acknowledged that the presence of vegetation interacts with the sediment yield, especially in the gully floor. In the southern Alps, there is a promising ecological engineering approach used to decrease the sediment yield at marly gullies, consisting in implanting bioengineering works to trap sediment in gully floors. Here, vegetation barriers are made of a line of Salix purpurea cuttings (non-native species but widely used in bioengineering), arranged perpendicularly to the flow, on a dead-wood sill, resprouting and forming tillers. Our objective was to better understand how morphological traits of Salix tiller barriers can explain their sediment trapping efficiency. The history of sediment trapping has been recorded on a sample of 77 Salix barriers since their implantation, from 2002 to 2008. Then, focusing on still visible and homogeneous segments of tiller barriers only (49 segments), the basal diameter, basal stem density and basal shoot branching of the tillers, as well as the sediment deposit heights were measured in spring 2010. The results showed that Salix tillers barriers are able to trap sediment in marly gully floors under ecological rehabilitation. The sediment trapping records showed that there is a structural efficient threshold beyond which Salix barriers can trap sediment. We suggest that this threshold is explained by the fact that the basal stem diameter also reaches a threshold value of about 6mm, usually during the 3rd year after Salix cuttings are implanted. Beyond this threshold, the results suggest that the main tiller morphological trait which explains the efficiency of sediment-trapping barriers is the basal shoot branching. The present study is innovative in the sense that the sediment flow conditions in gully beds are much stronger than those found in previous studies. The results found here provide practitioners with useful data for designing gullies restoration with Salix cuttings.

Meeting the relational challenge of ecological engineering within ecological sciences

Due to the current environmental problems human societies have to face and the lack of sustainability of most of their activities, the time of Ecological Engineering (EE) has surely come. To assess the development of EE within the academic world we conducted a literature survey based on an exhaustive count of all articles mentioning EE and related terms since the 1980s, and a classification of all articles published in 2008 and 2009 in the journal Ecological Engineering. This survey reveals that EE has quickly developed, and that the journal Ecological Engineering plays a preponderant role in this development. In comparison, articles mentioning the expression “ecological restoration” or “agroecology” were published in many more journals than articles referring to “ecological engineering”. This analysis showed that EE is highly dominated by China and the USA, and by studies aimed at improving the chemical quality of waters (either in natural ecosystems or to treat wastewaters) and aquatic system restoration. Hence, our survey suggests that EE approaches could be widened. These results emphasize the existence of an internal relational challenge for EE, i.e. inside the academic world of ecological sciences. Scientists and engineers from all environmental and ecological sciences must be convinced to take part in the development of this discipline. We explain why meeting this challenge is required for the full development of EE and why this would also highly benefit fundamental ecology. Finally, we give some hints on how to meet this challenge. Reaching this objective should help to bridge the gap between fundamental and applied ecologies and to unify applied ecology.

Ecological perspectives in restoring mine waste management areas

Ecological Engineering (EE) in mining waste restoration aims to apply knowledge of natural biological systems known to be present on rocks or minerals, and in sediments to practically and beneficially achieve human and industrial objectives in a natural self-sustaining way. Omitting or discarding ecological processes in the engineering of the mine waste management areas severely prolongs the longevity of current mining practices, when chemical treatment must be provided for hundreds of years. The potential biological controls on contaminant generation and the biological strategies available to reverse sulphide oxidation in mine wastes provide pathways toward less expensive, more energy-efficient and ecologically more acceptable strategies for mine waste management. The application of EE to mining has been demonstrated in several field projects and numerous publications, where the relevant bio-mineralization processes have been well-documented. Unfortunately, the EE approach has not been widely accepted, not because of its lack of a scientific foundation or successful implementation, but due to the challenge of effectively communicating the importance of ecosystem function and the associated geochemical and biological processes to the engineering fraternity. The mining industry needs to adapt to the values and aims of contemporary environmental engineering, to develop systems, structures, methods, tools and infrastructures to protect human and environmental health. The progress made in our EE projects has been brought about through the enhancement of ecosystem function. We will here briefly describe the transformation of an acid mine drainage dump into a productive, biologically-active polishing lake.

Biochemical oxygen demand and nutrient processing in a novel multi-stage raw municipal wastewater and acid mine drainage passive co-treatment system

A laboratory-scale, four-stage continuous flow reactor system was constructed to test the viability of high-strength acid mine drainage (AMD) and municipal wastewater (MWW) passive co-treatment. The synthetic AMD had pH 2.60 and 1860 mg/L acidity as CaCO3 equivalent with 46, 0.25, 2, 290, 55, 1.2 and 390 mg/L of Al, As, Cd, Fe, Mn, Pb and Zn, respectively. The AMD was introduced to the system at a 1:2 ratio with raw MWW from the City of Norman, Oklahoma USA containing 265 ± 94 mg/L BOD5, 11.5 ± 5.3 mg/L PO4−3, and 20.8 ± 1.8 mg/L NH4+–N. During the 135 d experiment, PO4−3 and NH4+–N were decreased to <0.75 and 7.4 ± 1.8 mg/L, respectively. BOD5 was generally decreased to below detection limits. Nitrification increased NO3− to 4.9 ± 3.5 mg/L NO3−–N, however relatively little denitrification occurred. Results suggest that the nitrogen processing community may require an extended period to mature and reach full efficiency. Overall, results indicate that passive AMD and MWW co-treatment is a viable ecological engineering approach for the developed and developing world that can be optimized and applied to improve water quality with minimal use of fossil fuels and refined materials.

Multi-level assessment of ecological coastal restoration in South Texas

Adaptive management can be a very useful tool for assessing and improving coastal ecological engineering restoration projects. A shoreline restoration project using ecological engineering approaches to mitigate coastal erosion was developed and implemented in 2003 at Loyola Beach, Baffin Bay, TX. The project incorporated riprap, fiber matting, geotextile, and vegetation as an alternative to conventional hard structures for erosion control. As part of the restoration expansion, a detailed evaluation of the previous project was completed at several levels, including the landscape, geotechnical design, environmental and ecological considerations, and social and economic factors. The findings indicated that the vegetation and its underlying geotechnical integrity have played an important role in erosion mitigation. Overall the project was successful in the protection of the shoreline and was shown to be more ecologically beneficial than other hard structures. Based on the preliminary success of the initial project, the restoration techniques were adapted for another beach extension to the west. The assessment did reveal some weaknesses in the original project design including the need for more substantial toe protection and periodic maintenance requirements. Based on these assessments, some additional new methods for the restoration extension were proposed and implemented. The broader applicability of this restoration approach outside the local region has been presented through several outreach activities and delivered to coastal planners and land owners throughout the Texas Coastal Bend and Northern Mexico.

Ecohydrological principles to underpin the restoration of Cyperus papyrus at Lake Naivasha, Kenya

Degradation of C. papyrus (papyrus) at Lake Naivasha is the result of a combination of lowered lake levels and destruction by large grazing mammals, buffalo and cattle, followed by several smaller species, in addition to more limited direct human clearance. Restoration of papyrus is considered to be of great importance for the future sustainability of the lake ecosystem. Two different interventions for papyrus (wetland) restoration have been proposed: one located around the delta of the Malewa river, based on ecohydrological principles, the other on land adjacent to the Gilgil river, adopting more of an ecological engineering approach. Both interventions are ecologically feasible. However, the principal limitations of both projects relate to anthropogenic factors and, in this respect, restoration of the Gilgil river is regarded as the more pragmatic of the two proposals at the present time. Future action should facilitate the involvement of local communities in any restoration projects at Lake Naivasha, with particular emphasis placed on the development of economic goods derivable from papyrus swamps.

Tropical treatment wetlands dominated by free-floating macrophytes for water quality improvement in Costa Rica

Five tropical treatment wetlands dominated by floating aquatic plants and constructed to deal with a variety of wastewaters were compared for their effectiveness in treating organic matter and nutrients in the Parismina River Basin in eastern Costa Rica. Wastewaters were from a dairy farm, a dairy processing plant, a banana paper plant, and a landfill. Four of the five wetland systems were effective in reducing nutrient levels of effluents before water was discharged into rivers. Ammonia levels in water entering most wetlands were considerably higher than ambient (i.e., riverine) levels; concentrations were reduced by as much as 92% in the wetlands and retained at a maximum rate of 166 g N m −2 year −1. Nitrate nitrogen removal was variable, but occurred in low concentrations in the inflows (less than 1 mg N L −1). Phosphate phosphorus was present in high levels but was effectively reduced through the wetlands (92 and 45% reductions through dairy farm wetlands, 83% reduction through banana paper wetlands, and 80% reduction through dairy processing wetlands). Retention of phosphate phosphorus ranged from 0.1 to 10.7 g P m −2 year −1 in the treatment wetlands. Dissolved oxygen in the wetland outflows were ≤2 mg L −1 in three of the sampled wetlands, most likely a result of the abundant free-floating macrophytes that sheltered the water from diffusion and shaded aquatic productivity. The efficacy of these created wetlands to treat effluents from different sources varied, and modified wetland designs or active management may be necessary to improve water quality even further. Recommendations on tropical wetland design and management are presented, as are suggestions for implementing this ecological engineering approach with farmers in Central America.