Responses Of Ecological Indicators Research Articles

Effects of changing riparian topography on the decline of ecological indicators along the drawdown zones of long rivers in China

Riparian topographical features can drive a suite of ecological indicators (EIs) that shape the river ecosystem. The mechanisms that EIs reflect provide several ecosystem services. We know little about the responses of EIs (indicators of plant cover, regeneration, exotics, habitat, erosion, and stressors) to the changing stream-channel width, riparian width, and elevation of the lengthy drawdown zones (upstream, midstream, and downstream) of long rivers. We have discovered that changing topographical characteristics affect riparian buffer areas differently by using a rapid field-based method with 297 transects in inundated regions along the Yangtze River and other 36 linked tributaries in China. Changing stream-channel widths was most effective on downstream EIs and the least effective at midstream. The exotic parameters were the most affected (with a range of −0.36 < r < 0.401) by stream-channel widths, as determined using Pearson correlation (p < 0.05). In contrast, the changing riparian width had the uppermost impact on the upstream EIs and the lowermost impact downstream; riparian width had the most significant impact on habitat parameters (with r ≤ 0.787). The elevation followed the riparian width pattern and was negatively associated with habitat and exotics (r ≤ −0.645 and r ≤ −0.594) and positively correlated with regeneration (r ≤ 0.569). These results reaffirm the imperative need for studies on regionally dependent riparian areas maintained under the same management strategies regardless of their topographical features. Future policies should be formulated to enhance ecosystem service provision, promoting the sustainable use of extensive river ecosystems while considering EIs. Additionally, these future policies should acknowledge drawdown zone factors within the same river network. Furthermore, additional measures are imperative to conserve topographical features and prevent further destruction.

The responses of ecological indicators to compound extreme climate indices in Southwestern China

Global warming has been leading to frequent climate extremes, and a single variable of climate extremes is no longer sufficient to fully assess the impact of climate extremes on ecosystems, requiring a synergistic multivariate inquiry. We obtain the compound warm-dry index (CWD) and the compound cold-dry index (CCD), based on a Copula theory with a binary distribution of a standardized precipitation index (SPI) and a standardized temperature index (STI). Changes in the spatial and temporal patterns of the compound extreme climate indices (CECIs) and the direct and lag responses of ecological indicators (EIs) to the CECIs in Southwestern China (SWC) are analyzed using these two indices. We find that CECIs rise continually during 1980–2019 (p < 0.05), with spring CCD being particularly pronounced (74.8 %, p < 0.01). Moreover, there are regional asymmetries and seasonal asymmetries in the direct and lag responses of ecosystems to compound extreme climate events (CECEs). CWD promotes productivity in spring and the response diminishes in summer, with the response area shifting towards higher altitudes. Spring CWD has a strong lag effect that will suppress summer productivity at higher elevation (>3000 m). Spring CCD promotes the growth of vegetation at low elevation (<1000 m), while summer CCD inhibits it at high elevation. Meanwhile, spring CCD has a strong lag positive effect on summer vegetation growth at low elevation specifically in Sichuan Basin, especially for crops (46.8 %). Our findings highlight the impact of compound climatic conditions on vegetation at specific geographical terrain, and vegetation in different regions can have complex and different responses to compound climate extremes.

Unveiling the future of relict Mediterranean mountain peatlands by integrating the potential response of ecological indicators with environmental suitability assessments

Mediterranean mountain peatlands are unique ecosystems because of their distinct hydrology and environmental conditions, as well as being home to a vast array of rare and endemic species. Due to anthropogenic activities and ongoing climate change, mountain peatlands are one of the most endangered ecosystems in Mediterranean areas. Climate scenarios for the western Mediterranean area estimate a sharp decrease in annual precipitation and an upsurge in temperature, which may disrupt the structure and functioning of ground-water-dependent ecosystems. To predict how the environmental suitability of Mediterranean mountain peatlands would be impacted by climate-induced changes, a microscale climatic model was used to downscale 2 m hourly air temperature to a high spatial resolution of 100 m in protected area of North Portugal. The environmental suitability was assessed based on bioclimatic indices associated with mountain peatland indicator species. Climate change projections envisage a decline in the environmental suitability of Mediterranean mountain peatlands and their indicator species, which could compromise this relict ecosystem probability of occurrence. Specifically, environmental suitability was considered highly sensitive to increases in temperature, namely when coupled with decreases in precipitation, resulting in significant reshaping of potential evaporation, evapotranspiration, and soil water content of the areas where peatlands actually occur. Also, the importance of microclimatic information for detecting change in ecosystems that are more vulnerable to climate change and in defining the best management options and conservation priorities is highlighted. Considering their vital role in the conservation of biodiversity and provider of ecosystem services, actions to mitigate and restore Mediterranean mountain peatlands are urgent.

Responses of ecological indicators to fishing pressure under environmental change: exploring non-linearity and thresholds

Abstract Marine ecosystems are influenced by multiple stressors in both linear and non-linear ways. Using generalized additive models (GAMs) fitted to outputs from a multi-ecosystem, multi-model simulation experiment, we investigated 14 major ecological indicators across ten marine ecosystems about their responses to fishing pressure under: (i) three different fishing strategies (focusing on low-, high-, or all-trophic-level taxa); and (ii) four different scenarios of directional or random primary productivity change, a proxy for environmental change. From this work, we draw four major conclusions: (i) responses of indicators to fishing mortality in shapes, directions, and thresholds depend on the fishing strategies considered; (ii) most of the indicators demonstrate decreasing trends with increasing fishing mortality, with a few exceptions depending on the type of fishing strategy; (iii) most of the indicators respond to fishing mortality in a linear way, particularly for community and biomass-based indicators; and (iv) occurrence of threshold for non-linear-mixed type (i.e. non-linear with inflection points) is not prevalent within the fishing mortality rates explored. The conclusions drawn from the present study provide a knowledge base in indicators’ dynamics under different fishing and primary productivity levels, thereby facilitating the application of ecosystem-based fisheries management worldwide.

Making ecological indicators management ready: Assessing the specificity, sensitivity, and threshold response of ecological indicators

Moving toward ecosystem-based fisheries management (EBFM) necessitates a suite of ecological indicators that are responsive to fishing pressure, capable of tracking changes in the state of marine ecosystems, and related to management objectives. In this study, we employed the gradient forest method to assess the performance of 14 key ecological indicators in terms of specificity, sensitivity and the detection of thresholds for EBFM across ten marine ecosystems using four modelling frameworks (Ecopath with Ecosim, OSMOSE, Atlantis, and a multi-species size-spectrum model). Across seven of the ten ecosystems, high specificity to fishing pressure was found for most of the 14 indicators. The indicators biomass to fisheries catch ratio (B/C), mean lifespan and trophic level of fish community were found to have wide utility for evaluating fishing impacts. The biomass indicators, which have been identified as Essential Ocean Variables by the Global Ocean Observing System (GOOS), had lower performance for evaluating fishing impacts, yet they were most sensitive to changes in primary productivity. The indicator B/C was most sensitive to low levels of fishing pressure with a generally consistent threshold response around 0.4*FMSY (fishing mortality rate at maximum sustainable yield) across nine of the ten ecosystems. Over 50% of the 14 indicators had threshold responses at, or below ∼0.6* FMSY for most ecosystems, indicating that these ecosystems would have already crossed a threshold for most indicators when fished at FMSY. This research provides useful insights on the performance of indicators, which contribute to facilitating the worldwide move toward EBFM.

Power analysis as a tool to identify statistically informative indicators for monitoring coral reef disturbances.

Extensive biological field surveys are costly and time consuming. To optimize sampling and ensure regular monitoring on the long term, identifying informative indicators of anthropogenic disturbances is a priority. In this study, we used 1800 candidate indicators by combining metrics measured from coral, fish, and macro-invertebrate assemblages surveyed from 2006 to 2012 in the vicinity of an ongoing mining project in the Voh-Koné-Pouembout lagoon, New Caledonia. We performed a power analysis to identify a subset of indicators which would best discriminate temporal changes due to a simulated chronic anthropogenic impact. Only 4% of tested indicators were likely to detect a 10% annual decrease of values with sufficient power (>0.80). Corals generally exerted higher statistical power than macro-invertebrates and fishes because of lower natural variability and higher occurrence. For the same reasons, higher taxonomic ranks provided higher power than lower taxonomic ranks. Nevertheless, a number of families of common sedentary or sessile macro-invertebrates and fishes also performed well in detecting changes: Echinometridae, Isognomidae, Muricidae, Tridacninae, Arcidae, and Turbinidae for macro-invertebrates and Pomacentridae, Labridae, and Chaetodontidae for fishes. Interestingly, these families did not provide high power in all geomorphological strata, suggesting that the ability of indicators in detecting anthropogenic impacts was closely linked to reef geomorphology. This study provides a first operational step toward identifying statistically relevant indicators of anthropogenic disturbances in New Caledonia's coral reefs, which can be useful in similar tropical reef ecosystems where little information is available regarding the responses of ecological indicators to anthropogenic disturbances.

Evaluating the sensitivity of ecological indicators with a perspective of temporal scales

This simulation study tests the sensitivity of 12 candidate ecological indicators (EIs) that characterise fish abundance, body size and trophodynamics with respect to temporal scales. Size-spectrum models that explicitly account for trophic interactions are used to simulate community dynamics under different levels of fishing pressure, including a specific model of the fish community in Haizhou Bay, China, and trait-based models of generalised fishery systems. The sensitivity of EIs is characterised by (1) responsiveness, which refers to the dynamics of EI values with respect to the magnitude of changes in fishing effort, and (2) detectability, which measures the relative changes of EI with respect to reference baselines. The response of EIs is substantially non-linear over time. Most EIs are responsive to the reduction of fishing effort and have low detectability under high fishing pressure. Both characteristics of sensitivity tend to increase in the early years and level off in 2 decades, suggesting transient behaviours in EI dynamics. The results suggested the essential non-linear dynamics of EIs resulting from underlying trophic interactions and the potential misinterpretation of the temporal EIs dynamics. We highlight the necessity of considering temporal scales and fishing characteristics in applying EIs in fishery management.

Management performance of ecological indicators in the Georges Bank finfish fishery

Abstract Successful implementation of Ecosystem-Based Fisheries Management (EBFM) requires appropriate action as informed by reference points in an ecosystem context. Thresholds in the response of ecological indicators to system drivers have been suggested as reference points for EBFM, though the management performance of these indicators and possible values for their reference points have not been widely evaluated. We used Management Strategy Evaluation to test the performance of control rules that used ecological indicators to adjust the advice from single-species stock assessments, using the Georges Bank finfish fishery as a case study. We compare the performance of control rules that used ecological indicators to that of single-species FMSY control rules when the system dynamics were governed by the same multispecies population model. Control rules that used indicator-based reference points were able to perform better against catch and biodiversity objectives than when harvests were based on single-species advice alone. Indicators and values for reference points associated with good performance varied depending on the management objective. We quantified tradeoffs between total catch, biodiversity, and interannual variability in catch, noting that it was possible in some instances to achieve higher than average biodiversity while maintaining high catches using indicator-based control rules. While improved performance was noted using ecological indicators, outcomes were variable, and the gains in performance obtained may be similar to alternative methods of implementing precaution in single-species fishery control rules.

Eco-morphological response of floodplain forests (Populus euphratica Oliv.) to water diversion in the lower Tarim River, northwest China

The Tarim River is about 1,320 km long and is one of the longest continental inland waterways in the world. In an undisturbed state, it is accompanied on both sides by floodplain forests of Euphrates poplar (Populus euphratica Oliv.). The rising water consumption in the upper and middle reaches, and massive hydro-technical interventions in the development of uncultivated land for cotton farming, especially during the last decades, have led to a widespread destruction of the natural ecosystems. This is the case particularly in the lower reaches of the river, where 320 km of the floodplain forests are either highly degraded or dead. Since the year 2000, the Chinese government has made efforts to restore these ecosystems and conducted man-made water diversion project into the affected area. The starting phase of recovering measures needs an efficient and extensive long-term monitoring. A combined approach of remote sensing and terrestrial samples can meet these demands. This study is based on the data from a small-scale ecological monitoring in the past 7 years and combination of QuickBird image information of the floodplain forests along the lower reaches of the Tarim River within the purview of the man-made restoration project. The effects of the artificial water diversion on the dynamics of the groundwater layer and the revitalization of P. euphratica floodplain forests have been analysed in the Arghan transect. The results showed that the groundwater level has risen from 12.6 to 5.5–6.2 m below the surface in the vicinity of the river beds. Some eco-morphological parameters of the P. euphratica trees have different levels of response to the ecological water diversion. To specify, in the vertical direction, the farther the trees are from the river, the weaker the response of ecological indicators. These parameters include tree vitality level, crown diameter, under branch height as well as newly developed crown types of P. euphratica trees. Generally, the floodplain forests within 200 m to the riverbed recovered remarkably, and those between 200 and 800 m from the river showed a medium response to the water transfer, while forests further away than 800 m from the river bed showed less sign of recovery.

Defining trends and thresholds in responses of ecological indicators to fishing and environmental pressures

Abstract Large, S. I., Fay, G., Friedland, K. D., and Link, J. S. 2013. Defining trends and thresholds in responses of ecological indicators to fishing and environmental pressures. – ICES Journal of Marine Science, 70: 755–767. Both fishing and environmental forces can influence the structure of marine ecosystems. To further understand marine ecosystems and to implement ecosystem-based fisheries management (EBFM), an evaluation of ecosystem indicators is warranted. In this context, it is particularly important to identify thresholds where fishing and environmental pressures significantly influence ecological indicators. We empirically determined numerical values of environmental forces and fishing pressure that significantly altered the response of ecological indicators for the Northeast Shelf Large Marine Ecosystem. Generalized additive models predicted a non-linear relationship for each pressure–response pairing. With this smoother, 95% confidence intervals (CI) for estimated first and second derivatives for each relationship were determined via parametric bootstrap. A significant trend or threshold was noted when the CI for the first or second derivative was greater or less than zero, delineating the level at which pressure variables influence the rate and direction of ecosystem indicator responses. We identify reference levels where environmental forces and fishing pressure result in ecosystem change by collectively examining the responses of multiple ecological indicators. Individual indicators showed unique responses to pressures, however, similar values for the pressures were associated with significant changes for multiple indicators. These reference levels establish a foundation for implementation of EBFM.

SPATIAL VARIATION OF STRUCTURAL AND FUNCTIONAL INDICATORS IN A LARGE NEW ZEALAND RIVER

ABSTRACTThe ecological responses of large rivers to human pressure can be assessed at multiple scales using a variety of indicators, but little is known about how the responses of ecological indicators vary over small spatial scales. We sampled phytoplankton, zooplankton and macroinvertebrates and measured river metabolism and cotton strip breakdown rates (loss in tensile strength) in contrasting habitats along a 21‐km urban‐industrial reach on a constrained section of the Waikato River, New Zealand's longest river. Rates of gross primary production (2.8–7.8 g O2/m2/d) and ecosystem respiration (3.5–12.7 g O2/m2/d) did not differ consistently between near‐shore (2–3 m from river side) and far‐shore (ca. 10 m from side) locations, urban and industrial reaches or between autumn and spring sampling occasions. Rates of cotton decay (−k) ranged from 0.014 to 0.112 per day and were typically faster at far‐shore locations and in the section of river receiving industrial inputs, but slower in spring compared with autumn. Nonmetric multidimensional scaling analysis of phytoplankton and zooplankton data did not reveal spatial patterns relating to pressure or location (embayment, edge, mid‐river). However, the macroinvertebrate ordination suggested distinct communities for the mid‐river benthos compared with near‐shore communities and a distinction between sites in the urban reach and the industrial reach. Our results suggest that large‐river macroinvertebrate communities and cotton decay rates can be influenced to varying degrees by reach‐scale pressures and local habitat conditions. Monitoring designs in spatially complex rivers should account for habitat heterogeneity that can lead to differences in structural and functional indicator responses. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Ranking the ecological relative status of exploited marine ecosystems

Abstract Coll, M., Shannon, L. J., Yemane, D., Link, J. S., Ojaveer, H., Neira, S., Jouffre, D., Labrosse, P., Heymans, J. J., Fulton, E. A., and Shin, Y-J. 2010. Ranking the ecological relative status of exploited marine ecosystems. – ICES Journal of Marine Science, 67: 769–786. A set of simple, data-based ecological indicators was used to rank exploited ecosystems regarding fishing impacts with respect to their status, trends, and ecosystem EAF attributes. Expected theoretical changes in indicators with respect to increasing fishing impacts were considered, and ecosystems were compared by examining the mean values of indicators in the most recent three years for which data were available and over time (1980–2005 and 1996–2005). Systems were classified into nine potential categories according to whether they were most, moderately, or least impacted, and whether they were becoming more or less impacted, or remaining stationary. The responses of ecological indicators to additional environmental and socio-economic explanatory factors were tested. Ecosystems ranked using short- and long-term trends and states differed because of differences in trends, underscoring the importance of analysing both states and trends in ecosystem analyses. The number of ecosystems classified as unclear or intermediately impacted has increased recently, the proportion of ecosystems classified as less strongly impacted has been maintained, but more now fall within the category more strongly impacted in terms of long-term trends and states. Ecosystem type, fisheries enforcement, primary production, sea temperature, and fishing type were important variables explaining the ecological indicators. The results reflect different changes and processes in the ecosystems, demonstrating that information on ecological, environmental, and fishery histories is crucial to interpreting indicators correctly, while disentangling the effects of fishing and of the environment.