A conceptual framework for urban ecological restoration and rehabilitation

Urban greenspace has gained considerable attention during the last decades because of its relevance to wildlife conservation, human welfare, and climate change adaptation. Biodiversity loss and ecosystem degradation worldwide require the formation of new concepts of ecological restoration and rehabilitation aimed at improving ecosystem functions, services, and biodiversity conservation in cities. Although relict sites of natural and semi-natural ecosystems can be found in urban areas, environmental conditions and species composition of most urban ecosystems are highly modified, inducing the development of novel and hybrid ecosystems. A consequence of this ecological novelty is the lack of (semi-) natural reference systems available for defining restoration targets and assessing restoration success in urban areas. This hampers the implementation of ecological restoration in cities. In consideration of these challenges, we present a new conceptual framework that provides guidance and support for urban ecological restoration and rehabilitation by formulating restoration targets for different levels of ecological novelty (i.e., historic, hybrid, and novel ecosystems). To facilitate the restoration and rehabilitation of novel urban ecosystems, we recommend using established species-rich and well-functioning urban ecosystems as reference. Such urban reference systems are likely to be present in many cities. Highlighting their value in comparison to degraded ecosystems can stimulate and guide restoration initiatives. As urban restoration approaches must consider local history and site conditions, as well as citizens’ needs, it may also be advisable to focus the restoration of strongly altered urban ecosystems on selected ecosystem functions, services and/or biodiversity values. Ecosystem restoration and rehabilitation in cities can be either relatively inexpensive or costly, but even expensive measures can pay off when they effectively improve ecosystem services such as climate change mitigation or recreation. Successful re‐shaping and re-thinking of urban greenspace by involving citizens and other stakeholders will help to make our cities more sustainable in the future.     

The Nature of Urban Soils and Their Role in Ecological Restoration in Cities

Current and predicted trends indicate that an increasing proportion of the world’s population is living in urban and suburban places. The nature of the urban environment becomes an important factor if we are concerned with the restoration and preservation of biodiversity and ecosystems in and around cities. This article highlights the varied impacts of cities on soils and their implications for restoration planning and expectations of restoration “success.” Urban soils exist in different historical and formational trajectories than their local nonurbanized counterparts due to direct anthropogenic disturbance and indirect environmental impacts from urbanization. Therefore, urban soils often exhibit altered physical, chemical, and biological characteristics in comparison to local nonurbanized soils. Several unique features of urban soils and urban ecosystems pose particular issues for ecological restoration or the improvement of degraded soil conditions in cities. The creation of novel soil types, conditions that promote invasion by non‐natives, the strong influence of past land use on soil properties, and the presence of strong interactions and alternative stable states set up unique difficulties for the restoration of urban soils. Soils in urban restorations are a medium that can be deliberately manipulated to improve site conditions or in the monitoring of soil conditions as indices of ecosystem status. Including an explicit role for strong manipulations of soils in urban ecosystems changes how we approach baselines, management, and reference conditions in urban ecological restoration. With an understanding of urban soil ecological knowledge, we can guide aspects of urban ecological restoration toward successful outcomes.     

Restoring streams in an urbanizing world

1. The world's population is increasingly urban, and streams and rivers, as the low lying points of the landscape, are especially sensitive to and profoundly impacted by the changes associated with urbanization and suburbanization of catchments. 2. River restoration is an increasingly popular management strategy for improving the physical and ecological conditions of degraded urban streams. In urban catchments, management activities as diverse as stormwater management, bank stabilisation, channel reconfiguration and riparian replanting may be described as river restoration projects. 3. Restoration in urban streams is both more expensive and more difficult than restoration in less densely populated catchments. High property values and finely subdivided land and dense human infrastructure (e.g. roads, sewer lines) limit the spatial extent of urban river restoration options, while stormwaters and the associated sediment and pollutant loads may limit the potential for restoration projects to reverse degradation. 4. To be effective, urban stream restoration efforts must be integrated within broader catchment management strategies. A key scientific and management challenge is to establish criteria for determining when the design options for urban river restoration are so constrained that a return towards reference or pre‐urbanization conditions is not realistic or feasible and when river restoration presents a viable and effective strategy for improving the ecological condition of these degraded ecosystems.     

Resistance,Resilience and Restoration

Disturbances (pulse, press and ramp) constitute a major force influencing, even determining, the structure and functions of ecological components – populations, communities and ecosystems. The capacity to weather a disturbance without loss is defined as resistance, whereas resilience is the capacity to recover from a disturbance after incurring losses, which may be considerable. This article seeks to resolve differences in the ecological definition of resistance and of resilience and to examine the importance of resilience as applied to ecological restoration. In restoration, interventions are designed and implemented with the aim of strengthening the resilience, that is, the capacity to recover, of degraded systems. In response to restorative measures, degraded systems may have both resistance and negative resilience to remain in the degraded state. The key aim of restoration is to overcome the resistance and negative resilience of the degraded state by strengthening positive resilience, the capacity to recover to the intact undegraded state. Restoration may be hindered by a lack of knowledge of acting disturbances (both past and present), of the previous intact condition and of appropriate interventions to implement. Resilience to a disturbance is determined after the disturbance has ceased. Thus, for current ongoing press and ramp disturbances, resilience can be hard to determine.     

Waste Not,Want Not: The Need to Utilize Existing Artificial Structures for Habitat Improvement Along Urban Rivers

Urban rivers have often experienced substantial engineering modification and consequently are highly degraded aquatic ecosystems with minimal riparian habitat. Habitat restoration and improvement efforts are needed within urban rivers to support ecological communities and increase ecosystem integrity. Most river restoration techniques are not feasible within large urban rivers, and so there is a need to develop novel methodologies. Artificial structures such as river walls can function as habitat for plant and invertebrate species in urban rivers, and in some cases can be more diverse than remnant habitat. Along the River Thames through central London, plant species richness was found to be significantly higher on river walls than intertidal foreshore, which represents the only remnant habitat for riparian species. Both this survey and other studies have suggested that the physical and environmental characteristics of river walls are likely to influence their capacity to function as ecological habitat, for example, walls composed of more complex construction materials (brick and boulders) being more diverse than simpler structures (concrete and sheet piling). The opportunity exists to use river walls and other artificial structures (e.g., jetties) to improve habitat along urban rivers by installing walls which are designed to be more complex, or by adding modifications to existing walls. Some trial modifications, such as the addition of wall ledges and timber fenders to sheet piling, have been installed at Deptford Creek along the River Thames, and have so far greatly supported the colonization and development of plant communities. The restoration possibilities of such modifications should be considered, and further development and rigorous testing of installations is required in urban rivers to make sound restoration recommendations.     

Initial soil amendments still affect plant community composition after nine years in succession on a heavy metal contaminated mountainside

Many efforts to restore disturbed landscapes seek to meet ecological goals over timescales from decades to centuries. It is thus crucial to know how different actions available to restoration practitioners may affect ecosystems in the long term, yet few such data exist. Here, we test the effects of seed and compost applications on plant community composition 9 years after their application, by taking advantage of a well‐controlled restoration experiment on a mountainside severely degraded by over 80 years of zinc smelting emissions. We asked whether plots have converged on similar plant communities regardless of initial seed and compost treatments, or if these initial treatments have given rise to lasting differences in whole plant communities or in the richness and abundance of native, exotic, and planted species. We found that compost types significantly affected plant communities 9 years later, but seed mix species composition did not. Observed differences in species richness and vegetative cover were negatively correlated, and both were related to the differences in plant communities associated with different compost types. These observed differences are due primarily to the number and abundance of species not in original seed mixes, of which notably many are native. Our results underscore the importance of soils in shaping the aboveground composition of ecosystems. Differences in soil characteristics can affect plant diversity and cover, which are both common restoration targets. Even in highly polluted and devegetated sites, compost and seed application can reinstate high vegetative cover and allow continued colonization of native species.     

淡水湖泊生态系统退化驱动因子及修复技术研究进展

目前我国多数淡水湖泊污染、退化问题非常严重,诸多修复技术也已初见成效。影响淡水湖泊生态系统退化的驱动因子众多,既有生物因素也有非生物因素,它们之间相互联系,相互作用,且作用机理错综复杂。首先介绍了淡水湖泊生态系统退化的含义及形式;其次,分析、总结了淡水湖泊生态系统退化的驱动因子,从退化的生态学完整性意义和退化修复的技术手段上看,淡水湖泊生态系统主要受物理、化学和生物三大驱动因子影响,且基本遵循"环境变化-驱动力-压力(阈值)-状态-响应"原理;再次,在厘清湖泊生态系统退化驱动原理的基础上,从淡水湖泊生态系统功能模块和湖泊生态系统修复实践经验总结的角度出发,构建了淡水湖泊生态系统修复模块技术体系,并就湖泊富营养化和湖滨湿地生态系统退化修复的技术进行了讨论和对比;最后,对淡水湖泊生态系统修复的环境变化驱动因子的作用机制、作用途径和修复技术的长效机制等方面进行了展望。     

热带亚热带退化生态系统的恢复与复合农林业

我国热带亚热带是人口和环境压力最大的区域之一。原有自然生态系统遭到很大的破坏,退化生态系统大面积增加,这是严重制约农业生产发展的重要因素。长期的恢复生态学定点研究表明,通过综合整治,使退化生态系统得以恢复与重建,具有重大的生态效益、经济效益和社会效益。在丘陵山区进行退化生态系统的恢复与重建实践中所构建的“林果草(牧)鱼”复合生态系统,是高产、高质、高效的复合农林业模式,是促进地方农业经济发展的有效途径。     

Collaborative research partnerships inform monitoring and management of aquatic ecosystems by Indigenous rangers

Aquatic ecosystems are critical to the long-term viability and vibrancy of communities and economies across northern Australia. In a region that supports significant cultural and ecological water values, partnerships between Indigenous and non-Indigenous stakeholders can benefit aquatic ecosystem management. We present, as a case study from the Kimberley region of Western Australia, a collaborative research program that successfully documented Indigenous and Western Scientific knowledge of remote wetlands, using a variety of field-based activities, questionnaires, interviews and workshops. The sharing of knowledge between Indigenous and non-Indigenous research partners facilitated a comprehensive understanding of ecosystem values, threats, processes, management priorities and aspirations. These formed the basis of a management plan and monitoring tools, designed to build the capacity of an Indigenous ranger group to engage in research, monitoring and management of wetlands. The project provides a useful example of the benefits of collaborations in the context of remote-area management where local communities are responsible for environmental management and monitoring, such as is the case in northern Australia and presumably other areas of the world.     

Defining ecological restoration of peatlands in Central Kalimantan,Indonesia

Indonesia declared an ambitious plan to restore its degraded and fire‐prone peatlands, which have been a source of significant greenhouse gas and haze. However, the progress has been slow and the plan cannot succeed without sustained social supports and political will. Although many previous studies argued for the need to see ecological restoration in socio‐economic contexts, empirical assessments have been lacking for how restoration is operationalized on the ground. We interviewed 47 key informants involved in four different projects in Central Kalimantan, Indonesia, and assessed their definitions, goals, and practices of peatland restoration. Most of the actors we interviewed defined peatland restoration primarily in an ecological context following the global concept of ecological restoration. However, all four restoration projects were designed without determining reference and trajectory conditions. Their intermediate goals and practices were more focused on engaging local communities and developing sustainable livelihood options than improving the ecological conditions of peatlands. To be internally consistent, peatland restoration needs to recognize a social dimension in its process, as well as in its goal. Setting clear trajectory conditions is also important to clarify achievable goals and measurable intermediate outcomes. We propose the following definition of peatland restoration: a process of assisting the recovery of degraded peatland ecosystems to achieve the appropriate trajectories defined through multi‐stakeholder collaboration within social‐ecological contexts. We hope to generate healthy debates to further refine the definition that encompasses both social and ecological dimensions to generate broader support for sustaining and expanding peatland restoration projects in Indonesia.     

Identifying restoration hotspots that deliver multiple ecological benefits

Ecological restoration principally seeks to restore lost or degraded ecosystems. Restoration can, however, also deliver a suite of wider ecological, social, and economic benefits. To optimize performance it is, therefore, important to plan the design and placement of restoration initiatives with a view to maximizing joint effects on ecosystems, animal populations, ecological functions, and ecosystem services. We measured the effects of multiple (13) restored oyster reefs on a suite of restoration benefits (oyster settlement and growth, fish diversity and abundance, the ecological functions of scavenging and predation) in the Noosa River estuary, Australia, and used distribution models to identify potential restoration sites with the greatest overall benefits. Oysters recruited to reefs, and reefs enhanced the diversity and abundance of fishes and had higher rates of ecological functions than control sites. However, the growth of oyster reefs was most correlated with the proximity of restoration sites to urbanized shorelines and the estuary mouth, and the area of mangroves around the site. By contrast, fish diversity and abundance, and the rates of ecological functions, were typically negatively correlated with the proximity of reefs to both mangroves and seagrasses. This complex spatial mosaic resulted in distinct areas predicted to achieve all restoration benefits that were significantly smaller than the total area that could be restored. Applying a systematic and defensible method to identify potential restoration sites that maximize multiple benefits while lowering costs is a sensible social, economic, and ecological strategy.     

Spider community responses to grassland restoration: balancing trade‐offs between abundance and diversity

Spiders (Araneae) play key roles in ecosystems, not only as common and abundant generalist predators, but also as major contributors to biodiversity in many areas. In addition, due to their short generation times and high mobility, spiders respond rapidly to small changes in their environment, potentially making them useful indicators for restoration monitoring. However, few studies have focused on spider responses to grassland restoration in the United States. We compared degraded, native, and restored grassland sites to examine how spider communities and habitat respond to arid grassland restoration. We also examined how responses varied with the age of the restoration project. Spider communities in native sites differed from those in restored and degraded sites in several ways: native sites had fewer spiders and a different community composition than degraded and restored sites. However, native and restored sites had more species than degraded sites. Chronosequence data showed trends for lower abundance, higher species richness, and changing community composition as restoration projects mature. Several habitat variables were closely linked to variation in spider communities including cover of invasive annual grasses, litter, and biological soil crusts. Our data suggest that spider and vegetation responses to grassland restoration efforts can be successful in the long term—with resulting communities becoming more similar to native ones—and that spiders are useful indictors of grassland restoration. Our results also suggest that restoration may involve balancing trade‐offs between ecosystem services, with potential losses in predatory control offset by increases in biodiversity with restoration effort.     

Restoration,soil organisms,and soil processes: emerging approaches

Better understanding of the connection between aboveground plant communities and belowground soil organisms and processes has led to an explosion in recent research on the applications of this link to the field of ecological restoration. Research is only beginning to have the capacity to link soil organisms and specific ecosystem functions. Establishing general ecological principles of the role microbial communities have during ecological restoration is also still in its infancy. As such, the literature is at a critical point to generate a Special Feature that brings together novel approaches of linking soil and restoration to promote more regular inclusion and consideration of soil organisms and soil‐based processes in ecological restoration. In this special feature, we bring together nine research articles from different ecosystems that study the relationship between restoration activities, soil microbial communities, and soil properties. From these research articles, we describe two primary themes: (1) research on the impacts of ecosystem‐specific restoration activities on soil organisms and processes and (2) research testing methods of soil manipulation to improve restoration outcomes. We hope to inspire readers and restoration practitioners to consider soil microbes and soil processes in their research, restoration projects, and world views.     

西北干旱荒漠区生态系统可持续管理理念与模式

结合对西北干旱区水资源短缺、资源开发中的生态与经济矛盾突出、气候变暖可能加剧干旱区荒漠化以及生态水权与长效保障机制缺失等问题的分析诊断,探讨了荒漠区生态系统可持续管理面临的问题与难点,分析提出了荒漠生态系统植被保育的生态水位与生态阈值,阐述了荒漠-绿洲过渡带生态融合以及绿洲生态系统安全的生态防护梯度等干旱区生态系统管理理念;结合干旱区极端环境自然条件,在多年现场试验基础上,研发集成了退化群落改造与生态多样性构建技术、植物群落结构优化配置、组装与生态融合技术、生态系统恢复水分利用与生态自维持技术以及胡杨萌蘖更新技术等多种适宜荒漠植被恢复与重建的技术模式,并进行了成功实践和试验示范,为干旱荒漠区生态系统可持续管理提供了重要科技支撑。     

Conservation and restoration of New Zealand Island ecosystems

An ecological collapse has precipitated pioneering conservation initiatives in New Zealand. Many terrestrial communities in t he New Zealand archipelago have been devastated by over-exploitation, introduced mammals and habitat destruction. More recently, marine ecosystems have been depleted by over-harvesting. To mitigate against these losses, conservation in terrestrial environments has focused on protection of species and habitats. A similar approach is now under way in marine environments with the establishment of ‘no-take’ marine reserves. On land, conservation is now reaching beyond protection t o the eradication of pests from islands and restoration of their terrestrial ecosystems. Restoration on islands not only reduces threats to rare species; it also raises opportunities to investigate how species interact. In the sea, marine reserves not only enhance the diversity of depleted marine communities; they may also augment stocks of commercially harvested species. These initiatives provide many lessons that could be applied to degraded habitats elsewhere.     

Are Socioeconomic Benefits of Restoration Adequately Quantified? A Meta‐analysis of Recent Papers (2000–2008) in Restoration Ecology and 12 Other Scientific Journals

Many ecosystems have been transformed, or degraded by human use, and restoration offers an opportunity to recover services and benefits, not to mention intrinsic values. We assessed whether restoration scientists and practitioners use their projects to demonstrate the benefits restoration can provide in their peer‐reviewed publications. We evaluated a sample of the academic literature to determine whether links are made explicit between ecological restoration, society, and public policy related to natural capital. We analyzed 1,582 peer‐reviewed papers dealing with ecological restoration published between 1 January 2000 and 30 September 2008 in 13 leading scientific journals. As selection criterion, we considered papers that contained either “restoration” or “rehabilitation” in their title, abstract, or keywords. Furthermore, as one‐third of the papers were published in Restoration Ecology, we used that journal as a reference for comparison with all the other journals. We readily acknowledge that aquatic ecosystems are under‐represented, and that the largely inaccessible gray literature was ignored. Within these constraints, we found clear evidence that restoration practitioners are failing to signal links between ecological restoration, society, and policy, and are underselling the evidence of benefits of restoration as a worthwhile investment for society. We discuss this assertion and illustrate it with samples of our findings—with regards to (1) the geographical and institutional affiliations of authors; (2) the choice of ecosystems studied, methods employed, monitoring schemes applied, and the spatial scale of studies; and (3) weak links to payments for ecosystem service setups, agriculture, and ramifications for public policy.     

Detecting restoration impacts in inter-connected habitats: Spring invertebrate communities in a restored wetland

Habitat restoration that improves the ecological status of a target ecosystem may have undesired effects in adjoining ecosystems. We assessed how restoration of a mire influenced benthic macroinvertebrates in associated freshwater springs. We included springs affected by restoration and compared these to remote control springs. We collected pre-restoration samples in May 2001 and post-restoration samples in May 2003, 2005 and 2010. Following restoration, water table rose in the whole mire. Restoration also caused profound changes to groundwater quality but, for the most part, water quality returned close to pre-restoration conditions within two years. Reflecting these chemical and hydrological changes, restoration altered spring invertebrate communities, especially the relative abundances of species, but had only weak effect on species richness. The proportional abundance of spring-dependent macroinvertebrates decreased in the restoration area, whereas their proportion remained stable in the remote control sites. Macroinvertebrate community structure at the remote control sites remained almost unchanged throughout the study, whereas communities in the restoration-area springs showed profound changes after restoration, followed by a slow recovery toward the initial conditions. Our results suggest that restoration planning and monitoring should be extended to adjoining ecosystems, and not only species richness but more complete compositional analysis of communities and species abundances should be used to indicate restoration impacts.     

Assessing Simple Versus Complex Restoration Strategies for Industrially Disturbed Forests

Assessing the community‐level consequences of ecological restoration treatments is essential to guide future restoration efforts. We compared the vegetation composition and species richness of restored sites that received a range of restoration treatments and those of unrestored sites that experienced varying levels of disturbance. Our study was conducted in the industrially degraded landscape surrounding Sudbury, Ontario, Canada. The Great Lakes–St. Lawrence Forest once present in this area was degraded through logging, mining, and smelting activities beginning in the late 1800s until restoration of the most visibly degraded areas began in 1974. Restoration treatments ranged from simple abiotic enhancements to complex, multistage revegetation treatments using native and non‐native species, which included fertilizing, spreading of ground dolomitic limestone, understory seeding, and tree planting. Canonical correspondence analysis was used to determine which restoration treatments explained differences in the community structure among sites. We found that native understory vascular species richness was similar in restored sites that received more complex restoration treatments and unrestored sites that were mildly disturbed; however, the role of planted trees and non‐native species in the restored communities remains unclear. Understory vascular seeding played a key role in determining community composition of vascular understory and overstory communities, but the time since restoration commenced was a more important factor for nonvascular communities because they received no direct biotic enhancements. The use of non‐native species in the vascular seed mix seems to be slowly encouraging the colonization of native species, but non‐natives continue to dominate restored sites 25 years after restoration began.     

Species ecological strategy and soil phosphorus supply interactively affect plant biomass and phosphorus concentration

Excess soil phosphorus often constrains ecological restoration of degraded semi-natural grasslands in Western-Europe. Slow-growing species, often target of restoration (measures), are at a disadvantage because they are outcompeted by fast-growing species. Gaining insight into the responses of plant species and communities to soil phosphorus availability will help understanding restoration trajectories of grassland ecosystems. We set up two pot experiments using twenty grassland species with contrasting growth forms (i.e. grasses versus forbs) and nutrient use strategies (i.e. acquisitive versus conservative nutrient use). We quantified the nutrient use strategy of a species based on the stress-tolerance value of the CSR framework (StrateFy et al. 2017). We grew these species (1) as monocultures and (2) in mixtures along a soil phosphorus gradient and measured the aboveground biomass and plant phosphorus concentrations. Plant phosphorus concentration generally increased with soil phosphorus supply and biomass increased with soil phosphorus supply only in conservative communities. Forbs had higher plant phosphorus concentrations compared to grasses both in monocultures and mixtures. The species’ nutrient use strategy had contrasting effects on plant tissue phosphorus concentrations, depending on soil phosphorus supply (interaction effect) and vegetation biomass (dilution effect). Our findings contribute to the knowledge required for successful ecological restoration of species-rich grasslands. Our results suggest that under specific conditions (i.e. nitrogen limitation, no dispersal limitation, no light limitation), slow-growing species can survive and even thrive under excess soil phosphorus availability. In the field, competition by fast-growing species may be reduced by increased mowing or grazing management.     

恢复及演替过程中的土壤生态学考虑

 人类社会的日益扩张,导致人类加速占据地球表面景观,并胁迫地球上生态系统提供不断增长的资源需求和废物吸收能力。所以保护尚未“开放”的自然生态系统及恢复退化的生态系统成为人类长期生存的重要保证。该文着重讨论了恢复过程中的土壤生态学问题。土壤是所有陆地生态系统的结构与功能基础。土壤微生物与动物的种群变化,土壤有机质的积累,及主要元素地球化学循环的改变是恢复生态的重要环节。生态恢复与演替有许多共性,所以演替理论对于认识生态系统恢复中的结构与功能变化有着很大帮助。与自然演替不同的是,人的积极参与在生态恢复中占有中心位置。从最初样地的确立与物种的选择,到后续的灌溉与施肥管理,人的选择影响着土壤的演化,生态系统的发展方向,和最终恢复生态的结果。为保障恢复生态系统的可持续性,短期的工作目标,如提供养分促进植物生长,务必与长期的工作目标,如土壤的恢复相结合。植物与土壤的相互反馈是生态恢复成功的重要标志。成功的生态恢复不仅是对现有生态学理论的“试金检验”,也是推动生态学学科发展的重要原动力。