Landscape moderation of biodiversity patterns and processes - eight hypotheses

Understanding how landscape characteristics affect biodiversity patterns and ecological processes at local and landscape scales is critical for mitigating effects of global environmental change. In this review, we use knowledge gained from human-modified landscapes to suggest eight hypotheses, which we hope will encourage more systematic research on the role of landscape composition and configuration in determining the structure of ecological communities, ecosystem functioning and services. We organize the eight hypotheses under four overarching themes. Section A: 'landscape moderation of biodiversity patterns' includes (1) the landscape species pool hypothesis-the size of the landscape-wide species pool moderates local (alpha) biodiversity, and (2) the dominance of beta diversity hypothesis-landscape-moderated dissimilarity of local communities determines landscape-wide biodiversity and overrides negative local effects of habitat fragmentation on biodiversity. Section B: 'landscape moderation of population dynamics' includes (3) the cross-habitat spillover hypothesis-landscape-moderated spillover of energy, resources and organisms across habitats, including between managed and natural ecosystems, influences landscape-wide community structure and associated processes and (4) the landscape-moderated concentration and dilution hypothesis-spatial and temporal changes in landscape composition can cause transient concentration or dilution of populations with functional consequences. Section C: 'landscape moderation of functional trait selection' includes (5) the landscape-moderated functional trait selection hypothesis-landscape moderation of species trait selection shapes the functional role and trajectory of community assembly, and (6) the landscape-moderated insurance hypothesis-landscape complexity provides spatial and temporal insurance, i.e. high resilience and stability of ecological processes in changing environments. Section D: 'landscape constraints on conservation management' includes (7) the intermediate landscape-complexity hypothesis-landscape-moderated effectiveness of local conservation management is highest in structurally simple, rather than in cleared (i.e. extremely simplified) or in complex landscapes, and (8) the landscape-moderated biodiversity versus ecosystem service management hypothesis-landscape-moderated biodiversity conservation to optimize functional diversity and related ecosystem services will not protect endangered species. Shifting our research focus from local to landscape-moderated effects on biodiversity will be critical to developing solutions for future biodiversity and ecosystem service management.     

基于生物多样性和生态系统服务的青藏高原保护优先区和保护空缺识别

协同生物多样性保护和生态系统服务功能维持对制定系统性保护规划具有重要意义。研究以青藏高原为研究区,应用Maxent模型模拟了重点植物的空间分布,结合世界保护联盟(IUCN)重点动物空间分布数据和生态系统服务空间分布,利用Zonation模型依次识别了基于单一因素的保护优先区以及集成生物多样性和生态系统服务的保护优先区,评估了青藏高原现有自然保护地对保护优先区、重要物种及生态系统服务的保护状况和保护空缺。结果表明:(1)青藏高原保护优先区保护价值呈现由东南向西北递减趋势,优先区主要分布在青藏高原东南缘喜马拉雅山地、雅鲁藏布江中游河谷及横断山区等区域,生物多样性保护优先区和生态系统服务保护优先区分布略有差异,存在43.2%的空间重叠;(2)在重要物种保护上,自然保护地对两栖动物的保护率最高,平均保护了38.2%,哺乳动物次之(24%),爬行动物的保护率较低,仅为10.2%。对生态系统服务功能覆盖率分别是44.1%(防风固沙)、27.1%(水源涵养)、22.3%(土壤保持)、17.1%(碳固定)和16.6%(洪水调蓄);(3)自然保护地对研究识别的保护优先区存在保护空缺,仅覆盖了26.8%的集成保护优先区,Ⅰ级、Ⅱ级和Ⅲ级优先区保护空缺面积占青藏高原面积的7.2%、6.9%和7.7%。研究结果可为青藏高原以国家公园为主体的自然保护地体系优化提供科学依据与理论支撑。     

Response diversity determines the resilience of ecosystems to environmental change

A growing body of evidence highlights the importance of biodiversity for ecosystem stability and the maintenance of optimal ecosystem functionality. Conservation measures are thus essential to safeguard the ecosystem services that biodiversity provides and human society needs. Current anthropogenic threats may lead to detrimental (and perhaps irreversible) ecosystem degradation, providing strong motivation to evaluate the response of ecological communities to various anthropogenic pressures. In particular, ecosystem functions that sustain key ecosystem services should be identified and prioritized for conservation action. Traditional diversity measures (e.g. ‘species richness’) may not adequately capture the aspects of biodiversity most relevant to ecosystem stability and functionality, but several new concepts may be more appropriate. These include ‘response diversity’, describing the variation of responses to environmental change among species of a particular community. Response diversity may also be a key determinant of ecosystem resilience in the face of anthropogenic pressures and environmental uncertainty. However, current understanding of response diversity is poor, and we see an urgent need to disentangle the conceptual strands that pervade studies of the relationship between biodiversity and ecosystem functioning. Our review clarifies the links between response diversity and the maintenance of ecosystem functionality by focusing on the insurance hypothesis of biodiversity and the concept of functional redundancy. We provide a conceptual model to describe how loss of response diversity may cause ecosystem degradation through decreased ecosystem resilience. We explicitly explain how response diversity contributes to functional compensation and to spatio‐temporal complementarity among species, leading to long‐term maintenance of ecosystem multifunctionality. Recent quantitative studies suggest that traditional diversity measures may often be uncoupled from measures (such as response diversity) that may be more effective proxies for ecosystem stability and resilience. Certain conclusions and recommendations of earlier studies using these traditional measures as indicators of ecosystem resilience thus may be suspect. We believe that functional ecology perspectives incorporating the effects and responses of diversity are essential for development of management strategies to safeguard (and restore) optimal ecosystem functionality (especially multifunctionality). Our review highlights these issues and we envision our work generating debate around the relationship between biodiversity and ecosystem functionality, and leading to improved conservation priorities and biodiversity management practices that maximize ecosystem resilience in the face of uncertain environmental change.     

Species richness facilitates ecosystem resilience in aquatic food webs

1. Many studies indicate that biodiversity in ecosystems affects stability, either by promoting temporal stability of ecosystem attributes or by enhancing ecosystem resistance and resilience to perturbation. The effects on temporal stability are reasonably well understood and documented but effects on resistance and resilience are not. 2. Here, we report results from an aquatic mesocosm experiment in which we manipulated the species richness and composition of aquatic food webs (macrophytes, macro‐herbivores and invertebrate predators), imposed a pulse disturbance (acidification), and monitored the resistance (initial response) and resilience (recovery) of ecosystem productivity and respiration. 3. We found that species‐rich macroinvertebrate communities had higher resilience of whole‐ecosystem respiration, but were not more resistant to perturbations. We also found that resilience and resistance were unaffected by species composition, despite the strong role composition is known to play in determining mean levels of function in these communities. 4. Biodiversity’s effects on resilience were probably mediated through complex pathways affecting phytoplankton and microbial communities (e.g. via changes in nutrient regeneration, grazing or compositional changes) rather than through simpler effects (e.g. insurance effects, enhanced facilitation) although these simpler mechanisms probably played minor roles in enhancing respiration resilience. 5. Current mechanisms for understanding biodiversity’s effects on ecosystem stability have been developed primarily in the context of single‐trophic level communities. These mechanisms may be overly simplistic for understanding the consequences of species richness on ecosystem stability in complex, multi‐trophic food webs where additional factors such as indirect effects and highly variable life‐history traits of species may also be important.     

Community involvement in management for maintaining coral reef resilience and biodiversity in southern Caribbean marine protected areas

Climate change is posing new challenges to conservation because management policies on protected coral reefs are less effective than they were before the current ecosystem degradation. Coral reefs, the most diverse and complex marine ecosystem provide economic services for millions, but are seriously threatened worldwide because reef-building corals are experiencing bleaching phenomena and a steady decline in abundance. The resources of a Marine Protected Area (MPA) in Cartagena, Colombia, are in constant decline, despite a current management plan and on-site staff, urging new conservation actions. A multidisciplinary team gathered to evaluate management effectiveness including biophysical, socioeconomic and governance indicators. Coral cover and fish diversity and abundance were low both inside and outside the MPA, which suggests a limited efficiency of management. Currently, the MPA is a reef with low coral cover and high algae cover as well as large dead coral areas, which are generally signs of highly degraded reef habitats. Live coral cover in the MPA was represented by pioneer coral species such as Agaricia tenuifolia and Porites astreoides. Nonetheless, 35% of the scleractinian species sampled in the area harbored more than one zooxanthellae symbiont, which suggests potential resistance and resilience against coral bleaching. Maintenance of trophic structure and functional diversity is an important endeavor that should be a priority for management in order to allow ecosystem resilience. Social and governance indicators showed low-income levels and few opportunities for communities living in and around the park, low governability, weak communication among stakeholders and with authorities at different levels. As a result, problems related to over exploitation of resources were commonplace in the MPA. These results reflect low adaptive capacity of communities to comply with restrictive conservation rules, showing that establishment of a protected area is a necessary but insufficient condition to guarantee conservation goals. Ignoring the role of local communities only will exacerbate the problems associated with natural resources. Involvement of communities in strategic ecosystems management appears to be a requisite to improve effectiveness of protected areas, and participatory strategies, such as co-management, offer opportunities to improve governability while letting communities adapt to MPA needs.     

生态系统保护现状及保护等级评估——以江西省为例

基于生态系统的保护是防止生物多样性丧失的重要手段,已成为保护生物学研究的热点。对生态系统保护等级进行划分,确定局域、区域和全球尺度上生态系统保护的优先性,可为制定生态系统保护方案提供重要依据。目前,生态系统保护等级划分的常用指标包括面积流失率、幅度和代表性。以江西省生态系统为例,基于20世纪80年代的江西省植被图、生态系统图、2010年土地利用图和自然保护区图,在GIS环境下进行图层叠加运算和重分类,再进行定量评估和归一化,将江西省生态系统划分为极重要、重要和一般3个级别。结果表明:过去的30年间江西省自然生态系统面积共减少了82613.83km2,减少率超过了60%。全省的37个自然生态系统类型中有19个类型建有国家级自然保护区,但得到保护的面积比例较低。森林生态系统中极重要、重要和一般生态系统类型分别占省国土面积的16.7374%、5.5310%和3.8242%,受国家级自然保护区保护的比例分别为0.51%、3.73%和5.76%;灌丛生态系统中极重要、重要和一般生态系统类型分别占0.0975%、0.9335%和0.0100%,保护比例分别为1.72%、0.17%和0.70%;草地生态系统中极重要、重要和一般生态系统类型分别占0.2647%、0.0005%和0.1064%,保护比例分别为0.21%、0.00%和3.49%;湿地生态系统中极重要、重要和一般生态系统类型分别占0.3532%、0.0345%和1.5650%,保护比例分别为1.87%、0.00%和18.01%。从各级生态系统空间分布来看,极重要生态系统分布范围最广,主要分布在江西省的东南部和西北部;重要生态系统主要分布在西北部和东北部;一般生态系统分布范围最小,主要分布在北部。中部地区的自然生态系统多数由于经济发展而退变为农田、城市等人工生态系统。结合江西省生态系统现状,将极重要的生态系统作为重点保护范围,因而占江西省国土面积17.46%的生态系统应该得到优先保护。这一结果为有效地开展生态系统管理,制定有针对性的生态系统的保护规划具有重要参考价值。     

Resilience of New?Zealand indigenous forest fragments to impacts of livestock and pest mammals

A number of factors have combined to diminish ecosystem integrity in New?Zealand indigenous lowland forest fragments surrounded by intensively grazed pasture. Livestock grazing, mammalian pests, adventive weeds and altered nutrient input regimes are important drivers compounding the changes in fragment structure and function due to historical deforestation and fragmentation. We used qualitative systems modelling and empirical data from Beilschmiedia tawa dominated lowland forest fragments in the Waikato Region to explore the relevance of two common resilience paradigms ? engineering resilience and ecological resilience ? for addressing the conservation management of forest fragments into the future. Grazing by livestock and foraging/predation by introduced mammalian pests both have direct detrimental impacts on key structural and functional attributes of forest fragments. Release from these perturbations through fencing and pest control leads to partial or full recovery of some key indicators (i.e. increased indigenous plant regeneration and cover, increased invertebrate populations and litter mass, decreased soil fertility and increased nesting success) relative to levels seen in larger forest systems over a range of timescales. These changes indicate that forest fragments do show resilience consistent with adopting an engineering resilience paradigm for conservation management, in the landscape context studied. The relevance of the ecological resilience paradigm in these ecosystems is obscured by limited data. We characterise forest fragment dynamics in terms of changes in indigenous species occupancy and functional dominance, and present a conceptual model for the management of forest fragment ecosystems.     

Trophic networks: How do theories link ecosystem structure and functioning to stability properties? A review

In the context of present global changes, interest in understanding how systems respond to anthropogenic environmental pressures and stress has increased. Indices that characterize ecosystem state are helpful tools for the interpretation of ecosystem responses. The central question is how to link these responses to ecosystem structure and functioning and to quantify ecosystem persistence, resistance or resilience. Quantification and characterization of trophic networks by ecological network analysis (ENA) indices is proceeding rapidly, especially in the field of coastal ecology. In this contribution, we review several theories that relate ecosystem structure and function to stability. The structure and functioning of ecosystems change during the maturation of ecosystems. In the first section, the maturation of ecosystems is described using thermodynamics. In the second and third parts of this paper, we define some concepts for analysing structure and functioning of food webs and discuss their relation to stability. In the last section, we describe three ENA indices and their link to stability. We demonstrate that ENA provides powerful tools for describing local stability, combining quantitative and qualitative concepts. However, it remains incomplete for describing real conservation cases that combine local and global stability.     

Meta‐analysis on pulse disturbances reveals differences in functional and compositional recovery across ecosystems

Most ecosystems are affected by anthropogenic or natural pulse disturbances, which alter the community composition and functioning for a limited period of time. Whether and how quickly communities recover from such pulses is central to our understanding of biodiversity dynamics and ecosystem organisation, but also to nature conservation and management. Here, we present a meta‐analysis of 508 (semi‐)natural field experiments globally distributed across marine, terrestrial and freshwater ecosystems. We found recovery to be significant yet incomplete. At the end of the experiments, disturbed treatments resembled controls again when considering abundance (94%), biomass (82%), and univariate diversity measures (88%). Most disturbed treatments did not further depart from control after the pulse, indicating that few studies showed novel trajectories induced by the pulse. Only multivariate community composition on average showed little recovery: disturbed species composition remained dissimilar to the control throughout most experiments. Still, when experiments revealed a higher compositional stability, they tended to also show higher functional stability. Recovery was more complete when systems had high resistance, whereas resilience and resistance were negatively correlated. The overall results were highly consistent across studies, but significant differences between ecosystems and organism groups appeared. Future research on disturbances should aim to understand these differences, but also fill obvious gaps in the empirical assessments for regions (especially the tropics), ecosystems and organisms. In summary, we provide general evidence that (semi‐)natural communities can recover from pulse disturbances, but compositional aspects are more vulnerable to long‐lasting effects of pulse disturbance than the emergent functions associated to them.     

The fundamental role of ecological feedback mechanisms for the adaptive management of seagrass ecosystems – a review

Seagrass meadows are vital ecosystems in coastal zones worldwide, but are also under global threat. One of the major hurdles restricting the success of seagrass conservation and restoration is our limited understanding of ecological feedback mechanisms. In these ecosystems, multiple, self‐reinforcing feedbacks can undermine conservation efforts by masking environmental impacts until the decline is precipitous, or alternatively they can inhibit seagrass recovery in spite of restoration efforts. However, no clear framework yet exists for identifying or dealing with feedbacks to improve the management of seagrass ecosystems. Here we review the causes and consequences of multiple feedbacks between seagrass and biotic and/or abiotic processes. We demonstrate how feedbacks have the potential to impose or reinforce regimes of either seagrass dominance or unvegetated substrate, and how the strength and importance of these feedbacks vary across environmental gradients. Although a myriad of feedbacks have now been identified, the co‐occurrence and likely interaction among feedbacks has largely been overlooked to date due to difficulties in analysis and detection. Here we take a fundamental step forward by modelling the interactions among two distinct above‐ and belowground feedbacks to demonstrate that interacting feedbacks are likely to be important for ecosystem resilience. On this basis, we propose a five‐step adaptive management plan to address feedback dynamics for effective conservation and restoration strategies. The management plan provides guidance to aid in the identification and prioritisation of likely feedbacks in different seagrass ecosystems.     

Macrofaunal Functional Diversity Provides Resilience to Nutrient Enrichment in Coastal Sediments

The degradation of ecosystems is often associated with losses of large organisms and the concomitant losses of the ecological functions they mediate. Conversely, the resilience of ecosystems to stress is strongly influenced by faunal communities and their impacts on processes. Denitrification in coastal sediments is a process that may provide ecosystem resilience to eutrophication by removing excess bioavailable nitrogen. Here, we conducted a large-scale field experiment to test the effect of macrofaunal community composition on denitrification in response to two levels of nutrient enrichment at 28 sites across a biologically heterogeneous sandflat. After 7 weeks of enrichment, we measured denitrification enzyme activity (DEA) along with benthic macrofaunal community composition and environmental variables. We normalised treatment site specific DEA values by those in ambient sediments (DEA_CN) to reveal the underlying response across the heterogeneous landscape. Nutrient enrichment caused reductions in DEA_CN as well as functional changes in the community; these were both more pronounced under the highest level of nutrient loading (on average DEA_CN was reduced by 34%). The degree of suppression of DEA_CN following moderate nitrogen loading was mitigated by a key bioturbating species, but following high nitrogen loading (which reduced the key species density) the abundance and diversity of other nutrient processing species were the most important factors alleviating negative effects. This study provides a prime example of the context-dependent role of biodiversity in maintaining ecosystem functioning, underlining that different elements of biodiversity can become important as stress levels increase. Our results emphasise that management and conservation strategies require a real-world understanding of the community attributes that facilitate nutrient processing and maintain resilience in coastal ecosystems.     

Biodiversity and species competition regulate the resilience of microbial biofilm community

The relationship between biodiversity and ecosystem stability is poorly understood in microbial communities. Biofilm communities in small bioreactors called microbial electrolysis cells (MEC) contain moderate species numbers and easy tractable functional traits, thus providing an ideal platform for verifying ecological theories in microbial ecosystems. Here, we investigated the resilience of biofilm communities with a gradient of diversity, and explored the relationship between biodiversity and stability in response to a pH shock. The results showed that all bioreactors could recover to stable performance after pH disturbance, exhibiting a great resilience ability. A further analysis of microbial composition showed that the rebound of Geobacter and other exoelectrogens contributed to the resilient effectiveness, and that the presence of Methanobrevibacter might delay the functional recovery of biofilms. The microbial communities with higher diversity tended to be recovered faster, implying biofilms with high biodiversity showed better resilience in response to environmental disturbance. Network analysis revealed that the negative interactions between the two dominant genera of Geobacter and Methanobrevibacter increased when the recovery time became longer, implying the internal resource or spatial competition of key functional taxa might fundamentally impact the resilience performances of biofilm communities. This study provides new insights into our understanding of the relationship between diversity and ecosystem functioning.     

Enhancing the conservation status and resilience of a narrowly distributed forest: A challenge to effectively support ecosystem services in practice

The conservation and sustainable management of forests has become an important issue, especially in ecosystems where keystone species form unique and marginal forest habitats with narrow distribution. With increasing pressures and threats to nature, the establishment of Protected Areas has been recognized as a major tool for maintaining well-functioning forest ecosystems and their associated ecosystem services (ES). This study aims at assessing the changes in the status of a narrowly distributed Mediterranean forest through the perspective of land cover dynamics and the ES framework. Using the priority habitat of Cedrus brevifolia forest as a case study, the distribution of land use and land cover (LULC) was mapped and simulated, together with the supply of multiple ES before and after the implementation of conservation measures. The results prior applying the management actions revealed a general pattern of forest densification that did not act fully in favor of C. brevifolia due to competitions among forest species. From an ES viewpoint, forest densification led to landscape homogenization affecting important ES such as the increase in the supply of regulating services, and the decrease in the ability to support nursery populations and habitats. By contrast, the future simulation of LULC integrated with afforestation and thinning measures showed an expected increase in both high-density vegetation and cedar trees, benefiting multiple ES. The current findings highlight the importance of sustainable forest management in enhancing the co-occurrence of several ES and supporting the overall multi-functionality of ecosystems. The holistic approach presented in this study can offer new insights into the relation between ES and natural ecosystem and/or habitats’ management while avoiding potential negative impacts on human well-being and ecosystem resilience.     

粤港澳大湾区城市群生态保护优先区识别研究

生态保护优先区识别对于城市群的整体性生态保护和区域生态安全具有重要意义。基于生态保护重要性评价识别城市群生态保护优先区,有助于保障生态系统服务的供给水平和维持生态系统的稳定性。以粤港澳大湾区(以下简称“大湾区”)为研究对象,首先通过增加粮食供给等生态系统服务指标和土地利用强度等生态脆弱性指标构建新的生态保护重要性评价指标体系,以弥补原指标体系忽略部分生态系统服务价值或者关乎生态脆弱性的重要因素所导致的评价结果片面性问题;然后运用结合空间主成分分析法和有序加权平均算子(Ordered Weighted Averaged, OWA)的主客观结合赋权法进行生态保护重要性评价的多情景模拟,并基于保护效率和权衡度进行多情景择优,由此所得最优情景的生态保护优先区的整体生态保护价值相对最高,且一定程度上减小了指标间权衡问题可能导致的评价误差;最终大湾区生态保护优先区面积为26406.04 km²,占大湾区陆域国土总面积的47.69%,主要分布在大湾区中部以外的肇庆、惠州、香港、广州北部、江门外环以及深圳东部沿海,同时优先区识别结果基本覆盖现有生态保护红线和周边大部分一般生态空间...     

Functional roles of remnant plant populations in communities and ecosystems

A hypothesis is suggested for functional roles of remnant plant populations in communities and ecosystems. A remnant population is capable of persistence during extended time periods, despite a negative population growth rate, due to long‐lived life stages and life‐cycles, including loops that allow population persistence without completion of the whole life cycle. A list of critera is suggested to help identification of remnant plant populations. Several community and ecosystem features may result from the presence of remnant plant populations. Apart from increasing community and ecosystem resilience just by being present, remnant populations may contribute to resilience through enhancing colonization by other plant species, by providing a persistent habitat for assemblages of animals and microorganisms, and by reducing variation in nutrient cycling. It is suggested that the common ability of plants to develop remnant populations is a contributing factor to ecosystem stability. Remnant populations are important for the capacity of ecosystems to cope with the present‐day impact caused by human society, and their occurrence should be recognized in surveys of threatened plant species and communities.     

国家公园生态系统健康测度模型构建及黄山实证研究

国家公园是中国生态文明建设的重要制度实践,其生态系统健康的科学评估是国家公园分区管理、空间管制、生态保护的基础。国家公园生态系统具有特殊性和复合性,区别于城市、流域、湿地等生态系统,亟需建立一套适合国家公园生态系统的生态系统健康测度模型。基于国家公园生态系统的特殊性和生态系统健康概念的多维性,探讨了现有模型存在的问题和不足,从生态系统与人类活动交互的视角,建立了"VSR"(生态活力Vigor、服务能力Service、抗干扰力Resilience)国家公园生态系统健康测度模型。此外,将"VSR"模型应用到黄山国家公园生态系统健康的测度中,可视化了黄山国家公园生态系统健康的时空过程和格局,通过随机森林回归模型和增强回归树模型验证了"VSR"模型的有效性和稳定性。"VSR"国家公园生态系统健康测度模型有效量化了国家公园生态系统健康的时空差异性和时空动态性,为国家公园空间管制、生态保护等目标实施提供了科学支撑。     

Conserving Biodiversity in a Human-Dominated World: Degradation of Marine Sessile Communities within a Protected Area with Conflicting Human Uses

Conservation research aims at understanding whether present protection schemes are adequate for the maintenance of ecosystems structure and function across time. We evaluated long-term variation in rocky reef communities by comparing sites surveyed in 1993 and again in 2008. This research took place in Tigullio Gulf, an emblematic case study where various conservation measures, including a marine protected area, have been implemented to manage multiple human uses. Contrary to our prediction that protection should have favored ecosystem stability, we found that communities subjected to conservation measures (especially within the marine protected area) exhibited the greatest variation toward architectural complexity loss. Between 1993 and 2008, chronic anthropogenic pressures (especially organic load) that had already altered unprotected sites in 1993 expanded their influence into protected areas. This expansion of human pressure likely explains our observed changes in the benthic communities. Our results suggest that adaptive ecosystem-based management (EBM), that is management taking into account human interactions, informed by continuous monitoring, is needed in order to attempt reversing the current trend towards less architecturally complex communities. Protected areas are not sufficient to stop ecosystem alteration by pressures coming from outside. Monitoring, and consequent management actions, should therefore extend to cover the relevant scales of those pressures.     

Rivers in peril inside and outside protected areas: a systematic approach to conservation assessment of river ecosystems

This paper establishes a framework within which a rapid and pragmatic assessment of river ecosystems can be undertaken at a broad, subcontinental scale, highlighting some implications for achieving conservation of river biodiversity in water‐limited countries. The status of river ecosystems associated with main rivers in South Africa was assessed based on the extent to which each ecosystem had been altered from its natural condition. This requires consistent data on river integrity for the entire country, which was only available for main rivers; tributaries were thus excluded from the analyses. The state of main river ecosystems in South Africa is dire: 84% of the ecosystems are threatened, with a disturbing 54% critically endangered, 18% endangered, and 12% vulnerable. Protection levels were measured as the proportion of conservation target achieved within protected areas, where the conservation target was set as 20% of the total length of each river ecosystem. Sixteen of the 112 main river ecosystems are moderately to well represented within protected areas; the majority of the ecosystems have very low levels of representation, or are not represented at all within protected areas. Only 50% of rivers within protected areas are intact, but this is a higher proportion compared to rivers outside (28%), providing some of the first quantitative data on the positive role protected areas can play in conserving river ecosystems. This is also the first assessment of river ecosystems in South Africa to apply a similar approach to parallel assessments of terrestrial, marine, and estuarine ecosystems, and it revealed that main river ecosystems are in a critical state, far worse than terrestrial ecosystems. Ecosystem status is likely to differ with the inclusion of tributaries, since options may well exist for conserving critically endangered ecosystems in intact tributaries, which are generally less regulated than main rivers. This study highlights the importance of healthy tributaries for achieving river conservation targets, and the need for managing main rivers as conduits across the landscape to support ecological processes that depend on connectivity. We also highlight the need for a paradigm shift in the way protected areas are designated, as well as the need for integrated river basin management plans to include explicit conservation visions, targets, and strategies to ensure the conservation of freshwater ecosystems and the services they provide.     

Seasonal and spatial variability of zooplankton diversity in the Poyang Lake Basin using DNA metabarcoding

Freshwater ecosystems face multiple threats to their stability globally. Poyang Lake is the largest lake in China, but its habitat has been seriously degraded because of human activities and natural factors (e.g. climate change), resulting in a decline in freshwater biodiversity. Zooplankton are useful indicators of environmental stressors because they are sensitive to external perturbations. DNA metabarcoding is an approach that has gained significant traction by aiding ecosystem conservation and management. Here, the seasonal and spatial variability in the zooplankton diversity were analyzed in the Poyang Lake Basin using DNA metabarcoding. The results showed that the community structure of zooplankton exhibited significant seasonal and spatial variability using DNA metabarcoding, where the community structure was correlated with turbidity, water temperature, pH, total phosphorus, and chlorophyll‐a. These results indicated habitat variations affected by human activities and seasonal change could be the main driving factors for the variations of zooplankton community. This study also provides an important reference for the management of aquatic ecosystem health and conservation of aquatic biodiversity.     

Scaling up the diversity–resilience relationship with trait databases and remote sensing data: the recovery of productivity after wildfire

Understanding the mechanisms underlying ecosystem resilience – why some systems have an irreversible response to disturbances while others recover – is critical for conserving biodiversity and ecosystem function in the face of global change. Despite the widespread acceptance of a positive relationship between biodiversity and resilience, empirical evidence for this relationship remains fairly limited in scope and localized in scale. Assessing resilience at the large landscape and regional scales most relevant to land management and conservation practices has been limited by the ability to measure both diversity and resilience over large spatial scales. Here, we combined tools used in large‐scale studies of biodiversity (remote sensing and trait databases) with theoretical advances developed from small‐scale experiments to ask whether the functional diversity within a range of woodland and forest ecosystems influences the recovery of productivity after wildfires across the four‐corner region of the United States. We additionally asked how environmental variation (topography, macroclimate) across this geographic region influences such resilience, either directly or indirectly via changes in functional diversity. Using path analysis, we found that functional diversity in regeneration traits (fire tolerance, fire resistance, resprout ability) was a stronger predictor of the recovery of productivity after wildfire than the functional diversity of seed mass or species richness. Moreover, slope, elevation, and aspect either directly or indirectly influenced the recovery of productivity, likely via their effect on microclimate, while macroclimate had no direct or indirect effects. Our study provides some of the first direct empirical evidence for functional diversity increasing resilience at large spatial scales. Our approach highlights the power of combining theory based on local‐scale studies with tools used in studies at large spatial scales and trait databases to understand pressing environmental issues.