Degradation of the crocodile population in the Olifants River Gorge of Kruger National Park,South Africa

• 1. Top predators such as crocodiles often reflect ecosystem degradation. The recent spate of close to 200 Nile crocodile deaths may reflect the ecosystem state of the Olifants–Letaba River system in the Kruger National Park. This paper investigates whether the crocodile deaths were indeed the consequence of a rare and perhaps acute event given the variability in annual population growth rates of crocodilians.
• 2. Spotlight‐ and helicopter‐based surveys designed to correct for availability and detectability bias were used to estimate population sizes of crocodiles from 2008 to 2010 in and around the Olifants River Gorge, the focal area of crocodile deaths.
• 3. Correction factors derived from individually observed crocodiles for both spotlight‐ and helicopter‐based counts were lower than those typically used for Nile crocodiles as well as other crocodile species. Even so, corrected spotlight‐ and helicopter‐based estimates were comparable and the number of crocodiles in the focal study area declined significantly from 780 (95% CI: 637–1222) to between 460 (spotlight estimate, 95% CI 375–665) and 505 (aerial estimate, 95% CI: 559–1746) during the period of crocodile deaths. The average annual decline of 35% was at the lower end of the distribution of annual population growth rates across the rivers of Kruger National Park.
• 4. The crocodile deaths reflect a possible rare event that suggests a degraded crocodile population, possibly the consequences of broad‐scale cascades of environmental deterioration of the Olifants–Letaba River system.
• 5. Even so, the potential risk of local demise of the population in the focal study area in the short term may be diminished through evolutionary, demographic and spatial resilience inherent within crocodiles that can accommodate the as yet unknown disease dynamics of pansteatitis. Copyright © 2011 John Wiley & Sons, Ltd.

     

On the brink – investigating biodiversity in endangered crater lakes of the Amber Mountains National Park (Madagascar)

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鄱阳湖国家湿地公园湿地生态系统健康评价研究

湿地生态系统与森林、海洋生态系统一起被称为地球三大生态系统,在维持地球生命和全球生态平衡方面具有不可替代的作用。对湿地生态系统健康进行评价,识别影响其健康的重要因子,可为湿地健康的诊断和湿地保护与管理提供依据。以鄱阳湖国家湿地公园湿地生态系统为研究对象,在充分考虑湿地实际情况的基础上,从湿地自然环境、整体功能和社会环境3个子系统选取21项评价指标,运用模糊综合评价法对湿地生态系统健康状况进行了综合分析。结果表明,鄱阳湖国家湿地公园生态系统健康度为0.619,处于第Ⅱ等级(健康);3个子系统中,湿地的自然环境和整体功能分别在0.431和0.540的程度上属于较健康状态,湿地的社会环境健康状况最差,在0.452的程度上属于疾病状态;制约因素主要有土壤性状、物种多样性、物质生产功能、环保投资指数、化肥使用强度、农药使用强度以及人口自然增长率。从评价结果分析来看,湿地自然环境和整体功能受到的影响虽然没有社会环境受到的影响大,但也应引起足够的重视,这两类指标属于长期指标,在短时间不会产生巨大变化。     

Recreational angling markets to advance the conservation of a reach of the Western Ramganga River,India

• 1. Mahseer fishes of the genus Tor are ‘iconic species’ in Indian rivers, representing ‘flagship’ species for conservation purposes but with additional exploitable, cultural and economic values. Conservation action is required to address their vulnerability to numerous pressures on multiple habitats, and connections between them, across the extended aquatic ecosystems supporting different life stages.
• 2. Recreational angling for mahseer, along with associated wildlife and cultural tourism, is a growth industry dependent upon healthy river ecosystems.
• 3. A cyclic, ecosystem‐based model in which local people can benefit economically from sustainable mahseer exploitation through catch‐and‐release fisheries can form a basis for conservation of both mahseer and the wider river ecosystem.
• 4. Experience on the Western Ramganga River in the vicinity of the town of Bikhyasen, Uttarakhand State (in the Himalayas in northern India), demonstrates the importance of involving local people in the benefits associated with angling, wildlife and cultural tourism. This creates local incentives for river protection, and may be the most effective means for preventing destructive over‐exploitation in poor rural communities.
• 5. Recognition of this value and its recirculation to local people can form the basis for a ‘paying for ecosystems services’ (PES) market. This will benefit river ecosystems, local people, tour operators and visiting anglers, provided that local people benefit to a greater extent than through the killing of fish for non‐renewable consumption or sale.
• 6. This is the basis for a potentially transferable model which may support regional development through involving local people in markets for iconic species. Copyright © 2010 John Wiley & Sons, Ltd.

     

Bridging the divide: Social–ecological coherence in Marine Protected Area network design

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A new map of mangroves for Kakadu National Park,Northern Australia,based on stereo aerial photography

• 1. Using colour aerial photography, a set of fine (～1 m) spatial resolution orthomosaics and accompanying Digital Elevation Models (DEMs) were generated for the majority of mangroves in Kakadu National Park, Northern Australia, from which their extent and canopy height have been mapped.
• 2. The orthomosaics and DEMs, which were based on 68 stereo pairs acquired in 1991, cover an area of approximately 742 km² and a coastal distance of 86 km. The DEMs have a height resolution of approximately ± 1 m.
• 3. The entire mosaic represents a key historical baseline data set of the extent and height of mangroves within the Park against which to observe and quantify changes in response to, for example, sea‐level rise.
• 4. The data sets will be available to assist management of the coastal environment and also to provide a unique insight into the distribution, dynamics and condition of mangroves. The techniques used are applicable to mangroves and other forested wetlands in other regions of Australia and elsewhere.

Copyright © 2007 John Wiley & Sons, Ltd.     

Strong fisheries management and governance positively impact ecosystem status

Fisheries have had major negative impacts on marine ecosystems, and effective fisheries management and governance are needed to achieve sustainable fisheries, biodiversity conservation goals and thus good ecosystem status. To date, the IndiSeas programme (Indicators for the Seas) has focussed on assessing the ecological impacts of fishing at the ecosystem scale using ecological indicators. Here, we explore fisheries ‘Management Effectiveness’ and ‘Governance Quality’ and relate this to ecosystem health and status. We developed a dedicated expert survey, focused at the ecosystem level, with a series of questions addressing aspects of management and governance, from an ecosystem‐based perspective, using objective and evidence‐based criteria. The survey was completed by ecosystem experts (managers and scientists) and results analysed using ranking and multivariate methods. Results were further examined for selected ecosystems, using expert knowledge, to explore the overall findings in greater depth. Higher scores for ‘Management Effectiveness’ and ‘Governance Quality’ were significantly and positively related to ecosystems with better ecological status. Key factors that point to success in delivering fisheries and conservation objectives were as follows: the use of reference points for management, frequent review of stock assessments, whether Illegal, Unreported and Unregulated (IUU) catches were being accounted for and addressed, and the inclusion of stakeholders. Additionally, we found that the implementation of a long‐term management plan, including economic and social dimensions of fisheries in exploited ecosystems, was a key factor in successful, sustainable fisheries management. Our results support the thesis that good ecosystem‐based management and governance, sustainable fisheries and healthy ecosystems go together.     

Examining horizontal and vertical social ties to achieve social–ecological fit in an emerging marine reserve network

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Stewardship and management of freshwater ecosystems: From Leopold's land ethic to a freshwater ethic

1. In 1949, Aldo Leopold formalized the concept of the ‘land ethic’, in what emerged as a foundational and transformational way of thinking about natural resource management, biodiversity conservation, and stewardship in terrestrial systems. Yet, the land ethic has inherent linkages to aquatic ecosystems; Leopold himself conducted research on rivers and lakes, and freshwater ecosystems figured widely in his writing.
2. We reflect on the land ethic and other aspects of Leopold's scholarship to identify key messages that provide insight into the stewardship and management of freshwater ecosystems around the globe. We also frame what we call the ‘freshwater ethic’ around Leopold's legacy. Although Leopold could not have envisaged the stressors affecting modern aquatic ecosystems, his core principles remain salient. These apply not only to ecosystem protection, but also to the ethics of modern conservation economics, sustainability, and the protection of natural capital, in which lakes, rivers, and wetlands now figure prominently.
3. We identify key ‘Aldo-inspired’ recommendations for protecting and restoring freshwater ecosystems in the Anthropocene that emanate directly from his writings (e.g. adopt an ecosystem approach, identify win–win–win scenarios, recognize the irreplaceability of wild waters, and strive for freshwater optimism).
4. In an epoch where links between people and nature are becoming more explicit in environmental management, policy, and governance, we suggest that Aldo Leopold's work illustrates how inspirational, seminal thinkers have offered leadership in this domain. We contend that today there is still much that can be learned from Leopold, especially by the next generation of environmental practitioners, to ensure the effective stewardship of our aquatic ecosystems.
5. We submit that the adoption of a freshwater ethic in parallel with Leopold's land ethic will enhance the stewardship of the world's increasingly threatened fresh waters by raising the profile of the plight of fresh waters and identifying enduring actions that, if embraced, will help conserve and restore biodiversity.

     

Ecological and eco‐social models for the introduction of the abalone Haliotis discus hannai into benthic systems of north‐central Chile: sustainability assessment

• 1. Loop models of ecological and socio‐economic systems were developed to analyse and predict the impact of a possible accidental introduction (escapes) of the abalone Haliotis discus hannai into a benthic community of north‐central Chile.
• 2. Although the ‘new’ ecological system resulting from a successful invasion of abalone would be locally stable, the establishment of a self‐enhanced dynamic of recruits would transform this into an unstable system.
• 3. The harvest of the kelp, Lessonia trabeculata and other macroalgae is not recommended because this destabilizes the system. The harvest of abalone adults is only sustainable if they do not exert a negative effect upon other native invertebrates.
• 4. The eco‐social model showed three important results: (1) if the variables ‘Price’ and ‘Farming’ are in expansion and stationary dynamics, then the models were found unstable; (2) a self‐enhanced dynamic of abalone recruits tends toward instability; and (3) the harvest of the kelp L. trabeculata and other macroalgae would be non‐sustainable.
• 5. Based on our results, the sustainable development of extensive farming of H. discus hannai in the sea would be not reached. If it is done, an intensive monitoring of the community after introduction into the system is strongly recommended. Likewise, the farming of macroalgal species (source of food for abalone) should be promoted in order to avoid harvesting of macroalgae from natural systems.

Copyright © 2006 John Wiley & Sons, Ltd.     

Assessing the conservation status of mangroves in Rakhine,Myanmar

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Frameworks for marine conservation — non‐hierarchical approaches and distinctive habitats

• 1. Conservation efforts have traditionally been directed to ‘flagship’ species (whales, seals, migratory birds, etc.) that capture public attention. Often these flagship species occupy distinctive habitats. Distinctive habitats appear to be distinguished because of anomalous physical structures and unique oceanographic processes occurring within them, whereas representative habitats are not notable in this way. Distinctive habitats are found in areas of various physical anomalies described primarily by temperature, chlorophyll and topography.
• 2. Several different kinds of distinctive habitats can be defined by their anomalous physical structures and oceanographic and biological processes. Species diversity may be either higher or lower in distinctive than in representative habitats. Distinctive habitats predominantly belong to a class of environments called ‘ergoclines’, and are typically associated with elevated resources at some ‘trophic level’.
• 3. These elevated resources may be either the product of true production (i.e. they are generated (in situ), or they are the product of physical accumulation due to circulation mechanisms. These processes lie at the heart of the ecology of distinctive habitats, and are fundamental to maintenance of ecosystem health, ecological integrity, distributions, abundances and recruitment of species, patterns of animal migrations, and potential or actual fisheries yields.
• 4. Conservation strategies need to examine the relationships between distinctive and representative habitats and species diversity. A strategy, leading from studies on flagship or other focal species, could have several advantages. It should rejuvenate the inherent appeal and significance of ‘species’ approaches to marine conservation, provide a rationale for human interest and a new foundation for examination of marine ecological interactions. It would also require a novel synthesis of relationships between ‘species’ and ‘spaces’ approaches to marine conservation by asking how we can take the best advantage of both approaches, rather than seeing them as in conflict.

Copyright © 2002 John Wiley & Sons, Ltd.     

Top‐down conservation targets and bottom‐up management action: creating complementary feedbacks for freshwater conservation

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Comparing the stability of successional transient models in kelp forests and barrens (south-east Pacific): Implications for conservation monitoring

1. Ecological stability based on statistical variability was contrasted with the asymptotical local stability of transient states during successional changes in community structure in kelp forests and barren grounds.
2. Simplified semi-quantitative ecological models with different levels of complexity were constructed to represent transient successional states in kelp and barrens, and Routh–Hurwitz's criteria and Levins' criterion of local stability were also estimated.
3. The results suggest that ecological stability based on statistical variation does not match local (mathematical) stability, since although successional changes in kelp exhibited less variability (measured as percentage coefficient of variation), barren beds were more locally stable. The local stability criteria used in the current work could be a suitable technique for evaluating the likelihood of transient ecological states to resist or change, since it considers states at equilibrium to maintain their properties only against small disturbances.
4. These outcomes are relevant because the natural alternation between kelp and barrens could be disrupted by the intensive harvest of kelp species carried out over the last 10 years on the central-north Chilean coast and in other temperate ecosystems.
5. Additionally, the negative effects of harvesting kelp species could have a synergetic relationship with other drivers such as climate change and coastal pollution. Thus, strict policy managements to limit the kelp harvest are deeply encouraged. A monitoring programme for assessing the current conditions of benthic–pelagic ecosystems along the Chilean coast is also required.

     

Decadal changes (1996–2006) in coastal ecosystems of the Chagos archipelago determined from rapid assessment

• 1. The atolls and islands comprising Chagos are a biodiversity hotspot of global conservation significance in a remote part of the central Indian Ocean.
• 2. This study examines the condition of the archipelago's coastal ecosystems by rapid environmental assessment at 21 sites/islands, which were also investigated a decade earlier using the same methodology. Major changes in ecosystem structure and environmental disturbance were determined.
• 3. Coral fish abundance was significantly lower in 2006 than 1996. Decrease in the physical structural complexity of the reefs, as a result of coral bleaching and mortality induced by the 1998 warming event, may have been a contributing factor.
• 4. Evidence of collecting/fishing was significantly greater in 2006 than 1996. This is attributed mainly to an illegal fishery for holothurians (sea cucumbers), which has expanded over recent years and now exerts substantial pressure on the resource. The significant decline observed in beach wood, a readily accessible fuel for fishing camps, is consistent with this.
• 5. Solid waste on islands was high (median 2 to 20 items m^?1 beach) in both 1996 and 2006. Potentially harmful biological impacts, determined from other studies, include entanglement, toxic effects and provision of transport for invasives or other ‘hitchhiker’ species.
• 6. Significantly higher bird abundances were recorded in protected areas than ‘unprotected’ areas, attributed mainly to absence of predation by rats.
• 7. Rapid assessment augments more comprehensive ecosystem investigations. It provides a valuable snapshot of environmental conditions based upon a broad suite of features (ecosystems and disturbances) determined, concurrently, within the same site inspection quadrats and using the same scale of assessment.

Copyright © 2009 John Wiley & Sons, Ltd.     

A window to the past: documenting the status of one of the last remaining ‘megapopulations’ of the threatened staghorn coral Acropora cervicornis in the Dominican Republic

• 1. Acropora cervicornis (staghorn coral) and Acropora palmata (elkhorn coral), once common features of shallow Caribbean reefs observed growing as large stands or thickets, are now found mainly as remnant pockets or isolated colonies at a fraction of their historical areal extent.
• 2. In February 2010, a large, surviving population of A. cervicornis was surveyed at Cabezos del Cayo, Punta Rusia, Dominican Republic to document its present condition and potential threats to its persistence.
• 3. The A. cervicornis surveyed at Cabezos del Cayo provides a rare glimpse of the habitat structure that these keystone components of coral reefs once provided. The staghorn population covers an area of 2 ha and is formed by interlocking skeletons of unusually large and thick A. cervicornis colonies.
• 4. The large size of its colonies (maximum branch length 250 cm; average linear length of live tissue 471 cm; maximum number of branch tips 141 per colony; maximum branch diameter 5 cm) and the complex open canopy of these colonies, have not been described, to our knowledge, in the recent literature.
• 5. The site is within Montecristi National Park but there is no active protection in this area and signs of overfishing are evident based on low fish abundance and complete lack of fish >20 cm in length.
• 6. The stressors associated with this population include significant predation by gastropods and fireworms, overgrowth by macroalgae, damselfish ‘gardening’ activities, and white band disease.
• 7. The management priority for the staghorn population at Cabezos del Cayo, Dominican Republic, should be to enforce the legal framework that is already in place for the protection of Montecristi National Park, limiting unsustainable and damaging fishing practices, and limiting land‐based sources of pollution associated with increasing population numbers and future coastal development. Copyright © 2010 John Wiley & Sons, Ltd.

     

Combining eight research areas to foster the uptake of ecosystem‐based management in fresh waters

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Quantifying acceptable levels of visitor use on Red Sea reef flats

• 1. The effects of trampling by visitors walking over the reef flat to snorkel or swim along the reef edge were studied at Ras Um Sidd, a popular fringing reef site at Sharm El Sheikh, and in the Ras Mohammed National Park, South Sinai, Egypt. Twelve stations showed a sequence of events linked to increased frequency and extent of trampling, with the intensities of trampling ranging from 0.1 to 324 tramplers m^?2 yr^?1.
• 2. Heavily trampled stations had a reduced coral cover (in particular branching corals), higher amounts of coral damage, less old dead coral, less obligate corallivorous fishes and more herbivores.
• 3. Wave exposure was crucial in determining the susceptibility of coral communities to trampling. Exposed communities were dominated by branching corals and were mechanically more resistant, since wave stress had favoured stockier growth forms.
• 4. The applicability of the ‘carrying capacity concept’ was investigated as a management tool for determining how much use is sustainable. Examination of the relationship between hard coral cover and intensity of trampling suggested that carrying capacity could be set at approximately 50 tramplers m^?2 yr^?1. The actual amount of damage caused by trampling showed a linear increase with increasing trampling intensities, so that the carrying capacity concept, as defined in this study, was not applicable to the relationship since no threshold existed. Instead, the ‘limits of acceptable change’ approach would be more practicable, with managers deciding what amount of coral damage they permit before limiting access. To establish meaningful limits of change, more knowledge is required about ecological as well as social consequences (e.g. visitor satisfaction) of such limits.

Copyright © 2007 John Wiley & Sons, Ltd.     

Determining keystone species complexes and macroscopic properties for improving ecosystem‐based conservation practices in coral reefs along the western Caribbean Sea (Mexico and Honduras)

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Historical distribution of freshwater fishes and the reference conditions concept in a large Mediterranean basin

1. The European Water Framework Directive 2000/60/EC (WFD) defines the ecological status of aquatic systems as the deviation between their present biological state and that which would be expected in the absence of any major human disturbance, referred to by the WFD as the ‘reference condition’ (RC). It assumes that their biotic composition should remain balanced and constant over time. This study tested both assumptions against an analysis of the historical distribution of the fish fauna in a large and highly disturbed Mediterranean basin. If fish communities change substantially over time, it will mean that the validity of the RC concept comes into question.
2. Using presence/absence data for historical native fish fauna from the Guadalquivir Basin, distribution changes among sub-basins were quantified by mapping between the nineteenth century and today.
3. The range of two native species (Anguilla anguilla and Salmo trutta) has changed significantly. In addition, the diadromous species assemblage has almost become locally extinct, with the exception of the eel. Finally, most Guadalquivir sub-basins (94.7%) have suffered major changes in the composition of their fish communities, either by losing native species or by adding new non-native species.
4. These results render the definition of any RC unlikely. In Mediterranean areas, the WFD objective of ‘good ecological status’ recovery based on the integrity of aquatic communities is a theoretical rather than a real goal. Nonetheless, the WFD provides an ecological guiding principle that can also be transferred to the conservation of freshwater ecosystems.
5. As an alternative to the RC concept in Mediterranean lotic ecosystems, specific multimetric indices can be used, based on expert criteria, the metrics of which can also relate to the conservation value of water bodies, and not only to their ecological status.