Revealing hidden extinction risks in China’s flora through dynamic habitat assessment

12.2 Riverine Habitat Dynamics

Riverine Habitat Dynamics

Simple SummaryThrough calculating landscape indexes and constructing an ecological risk assessment model, we assessed the landscape pattern and ecological risk of moose (Alces alces) habitat in the Nanwenghe National Nature Reserve of the Great Khingan Mountains in China. The results show that the areas with high habitat suitability for moose were mainly concentrated in forests and rivers. However, under the premise of global warming, the risk of landscape pattern fragmentation tends to increase from 2015 to 2020. Moose preference patch type is dispersed, the degree of polymerization is low, and the risk of patch type transformation is increased. In terms of ecological risk: the medium- and high-risk areas in the moose habitat are mainly concentrated in the river area and its nearby forests, showing a fine and scattered distribution. The low ecological risk area is mainly distributed on both sides of the road and the mountainous area, and the patch type is single. It shows that the moose habitat will have a weak ability to resist risk in the future. The study suggests that we should avoid further human intervention in forests and rivers, formulate reasonable forest protection and sustainable development plans in cold temperate zones, and effectively monitor and protect the dynamics of cold temperate forests and moose populations.The change in habitat pattern is one of the key factors affecting the survival of the moose population. The study of the habitat landscape pattern is the key to protecting the Chinese cold-temperate forest moose population and monitoring the global distribution of moose. Through the ecological risk assessment of the moose habitat landscape pattern in a cold-temperate forest, we hope to assess the strength of habitat resistance under stress factors. This study provides a theoretical basis for the protection of the moose population in the cold-temperate forest in China and the establishment of the cold-temperate forest national park. In the study, the MaxEnt model, landscape index calculation and ecological risk assessment model construction were used to analyze the field survey and infrared camera monitoring data from April 2014 to January 2023. The habitat suitability layer of the moose population in the Nanwenghe National Nature Reserve of the Great Khingan Mountains was calculated, and the range of the moose habitat was divided based on the logical threshold of the model. The landscape pattern index of the moose habitat was calculated by Fragstats software and a landscape ecological risk assessment model was established to analyze the landscape pattern and ecological risk dynamic changes of the moose habitat in 2015 and 2020. The results showed that under the premise of global warming, the habitat landscape contagion index decreased by 4.53 and the split index increased by 4.86 from 2015 to 2020. In terms of ecological risk: the area of low ecological risk areas increased by 0.88%; the area of medium ecological risk areas decreased by 1.11%; and the area of high ecological risk areas increased by 0.23%. The fragmentation risk of the landscape pattern of the moose habitat tends to increase, the preferred patch type is dispersed, the degree of aggregation is low, and the risk of patch type transformation increases. The middle and high ecological risk areas are mainly concentrated in the river area and its nearby forests, showing a fine and scattered distribution. Under the interference of global warming and human activities, the fragmentation trend of the moose habitat in the study area is increasing, and the habitat quality is declining, which is likely to cause moose population migration. For this reason, the author believes that the whole cold temperate forest is likely to face the risk of increasing the transformation trend of dominant patch types in the cold-temperate coniferous forest region mainly caused by global warming, resulting in an increase in the risk of habitat fragmentation. While the distribution range of moose is reduced, it has a significant impact on the diversity and ecological integrity of the whole cold-temperate forest ecosystem. This study provides theoretical references for further research on the impact of climate warming on global species distribution and related studies. It is also helpful for humans to strengthen their protection awareness of forest and river areas and formulate reasonable protection and sustainable development planning of cold-temperate forests. Finally, it provides theoretical references for effective monitoring and protection of cold-temperate forests and moose population dynamics.

Mangrove wetlands play a key role in global biodiversity conservation, though they have been damaged in recent decades. Therefore, mangrove habitats have been of great concern at the international level since the latter half of the 20th century. We focused on the key issue of the dynamics of mangrove habitats. A comprehensive review of their typicality and status from the global perspective was evaluated before the landscape dynamics of the mangrove habitats at the five sites were interpreted from Landsat satellite images covering 20 years, from 2000 to 2020. Ground-truthing was undertaken after comparing the results with the other published international mangrove datasets. We reached three conclusions: Firstly, within the period from 2000 to 2020, the mangrove area in Dongzhaigang increased by 414 ha, with an increase of 24.6%. In Sembilang NP, Sundarban, Kakadu NP, and RUMAKI, the mangrove area decreased by 1652 ha, 16,091 ha, 83 ha, and 2012 ha, with a decrease of 1.8%, 2.7%, 0.9%, and 3.9%, respectively. Secondly, other types of wetlands play a key role in degradating the mangrove wetlands in all of five protected areas. Thirdly, the rate of mangrove degradation has slowed dramatically based on the five sites over the past two decades, which are generally consistent with the findings of other researchers.

Ancient and dead trees are declining habitats harbouring many threatened species. These habitats are naturally patchy, and inhabiting species might exhibit metapopulation dynamics at a small spatial scale. In this study, the demography and metapopulation dynamics was analysed forOsmoderma eremita, which is an endangered beetle species associated with tree hollows in Europe. Extinction risks ofO. eremitapopulations were predicted using Monte Carlo simulations based on time series of population assessments. Predicted occurrence patterns were consistent with field observations from an area with many small stands in which the populations are believed to have been more or less isolated from each other during the last 150–200 yr. Population growth was found to be density dependent. Carrying capacity was proportional to the volume of wood mould (i.e. loose material of dead wood in the tree hollows), which varied widely between hollow trees. This generates large differences in local extinction risks between hollow trees. The predicted metapopulation extinction risk was much higher if the habitat dynamics (formation, gradual increase and deterioration of tree hollows) were taken into consideration than in predictions yielded by models in which the amount of wood mould was assumed to be constant over time. Thus, this system has features from both mainland‐island metapopulations and habitat‐tracking metapopulations, and is rather far from a classic metapopulation. For the long‐term persistence of the species in hollow trees, the habitat dynamics seem to be more important than demographic processes. Since the formation and deterioration of suitable tree are partly stochastic processes, there is a considerable extinction risk for manyO. eremitapopulations, because they mainly rely on only one or a few trees with large amounts of wood mould.

In the face of biodiversity loss worldwide, it is paramount to quantify species' extinction risk to guide conservation efforts. The International Union for the Conservation of Nature (IUCN)'s Red List is considered the global standard for evaluating extinction risks. IUCN criteria also inform national extinction risk assessments. Bayesian models, including the state‐of‐the‐art JARA (‘Just Another Red List Assessment’) tool, deliver probabilistic statements about species falling into extinction risk categories, thereby enabling characterisation and communication of uncertainty in extinction risk assessments. We coupled the state‐of‐the‐art VAST (‘Vector Autoregressive Spatio‐Temporal’) modelling tool and JARA, for better informed Red List assessments of marine fishes. In this framework, VAST is fitted to scientific survey catch rate data to provide indices to JARA whose uncertainty is propagated to JARA outcomes suggesting extinction risk categories (under the population reduction criterion). In addition, VAST delivers a valuable habitat assessment to better understand what may be driving extinction risk in the study region. Here, we demonstrate the coupled VAST‐JARA modelling framework by applying it to five contrasting North Sea species, with or without a quantitative stock assessment and with different conservation statuses according to the latest global Red List assessments. The North Sea application coupled with previous assessments and studies suggest that, among the three elasmobranchs, starry ray is in most need of urgent research (and conservation actions where appropriate), followed by spurdog, while lesser‐spotted dogfish is increasing in biomass. Moreover, both the VAST‐JARA modelling framework and previous research indicate that, while European plaice is not of conservation concern, cod has likely met the IUCN criteria for being listed as Endangered recently. Synthesis and applications. The predictions of the VAST‐JARA modelling framework for North Sea species, including JARA output and VAST habitat assessment, constitute valuable supporting information to make interpretations based on Red List guidelines, which will help decision‐makers in their next North Sea Red List assessment. We foresee applications of the modelling framework to assist Red List assessments of numerous marine fishes worldwide. Our modelling framework has many potential advantageous uses, including informing resource management about climate change impacts on species' extinction risks.

Recent environmental changes in the Bay of Quinte, Lake Ontario, have coincided with a decline in the stocks of walleye Sander vitreus. Suitable habitat supply was estimated in three sections of the bay during the summers of 1972–2001 to assess its role in the decline. An empirical model was developed to predict suitable habitat area for walleyes based on their preferences for cool water and low light intensity. The results indicated that lack of suitable light limits walleye habitat in the bay. Walleye habitat in the shallow upper bay has decreased at the rate of 34 ha/year since the invasion of dreissenid mussels in 1994, while that in the middle and lower bays has remained abundant. Walleye stocks and suitable habitat in the upper bay have both declined since the early 1990s. However, this pattern has not been consistent through time and suggests that other factors have also affected the Bay of Quinte walleye population. The analyses developed here can be used as a tool to enhance the assessment of walleye habitat dynamics in the Bay of Quinte and allow us to examine the impact of oligotrophication on the habitat of an important recreational and commercial species.

The ecological indicator values are the most common and sufficiently effective method of habitat assessment. The aim of our research review is to analyze current studies from 2020 to 2022 in which researchers have used Ellenberg indicator values to address a variety of problems. We limited the study to papers that are published in journals indexed by Scopus and Web of Science. The total number of records examined was 358. The number of records selected was 98. Visualization of the distribution of studies by country is based on the GeoCharts library. The results revealed that about half of the studies were conducted in Germany and Poland, and the most common objects were forests and grasslands. Almost half of the studies were devoted to ecological niches, habitat analysis, assessment of vegetation dynamics, and influence of various factors on plants. The analyzed articles are actively cited. In general, our research analysis revealed the effectiveness of Ellenberg indicator values for solving a wide range of urgent problems for a variety of plant communities, and different climate zones. The results of our research confirmed the advisability of actively using this approach.

Changes in fluvial characteristics, water flow regimes, and anthropogenic pressure have severely impacted the middle Ganga River, leading to resource scarcity for aquatic biodiversity. Despite the importance of habitat assessment in managing these ecosystems, gaps remain in understanding the process to fluvial stress factor, maintenance of minimum water to sustain Environmental flow (E-flow) and delineating potential riverine habitats for biodiversity. This study aims to identify clusters of riverine habitats. We used Geographic Information System (GIS) and Analytical Hierarchical Process (AHP) to undergo Multi Criteria Decision Making (MCDM) analysis. Weights assigned to variables based on their ecological significance, achieving a favourable consistency ratio of 0.0276 in model validation. The resulting potential habitat areas are categorized into four classes i.e., high, moderate, and low potential area along with restoration area. Key findings indicate that Ganga River from Sirsa to Kaithi has high potential habitat for aquatic biodiversity. Stretch between Jhilmil Jheel Conservation Reserve to Bijnor and Narora to Kannauj need more conservation effort for aquatic biodiversity. Particularly, stretches downstream of tributary confluences possess high potentiality for supporting species, such as the Gangetic dolphin (Platanista gangetica), whereas, sand bars and islands are important habitat for Smooth coated otter (Lutrogale perspicillata), Gharial (Gavialis gangeticus), Turtles and birds. River sections between barrages, particularly those lacking tributary input, are critical for species survival. This study underscores the need for effective management strategies to address fluvial stressors and enhance habitat conservation for aquatic biodiversity in the Ganga River system.

Predictions of population viability can provide valid information for guiding the management and conservation of species. However, such studies are rarely conducted on cetaceans due to limited basic data. In this study, a detailed assessment of the population dynamics of Indo-Pacific humpback dolphins (Sousa chinensis) in Xiamen Bay, China was carried out using a Vortex model that was based on model parameters that were derived from monitoring data and published sources. Then, sensitivity analyses were conducted to test the relative importance of the uncertainty of the model parameters. Moreover, potential management models were evaluated to determine their effectiveness in assisting with species recovery. The baseline model projected a decline in the population abundance with a growth rate (r) of -0.031, and the probability of extinction was 58.7% over the next 100 years. The sensitivity analyses revealed that juvenile mortality and fertility were the most pivotal factors for the viability of this population. All the conservation measures, including habitat improvement, catastrophe control, and individual supplementation, contributed to population increases when compared with the baseline model. In particular, decreasing calf and juvenile mortality through habitat improvement, at high levels, was the only way to generate positive growth rates. The findings suggest that these practical management activities can reduce the risk of extinction for this species.

AimMany vertebrate species globally are dependent on forests, most of which require active protection to safeguard global biodiversity. Forests, however, are increasingly either being disturbed, planted or managed in the form of timber or food plantations. Because of a lack of spatial data, forest management has commonly been ignored in previous conservation assessments.LocationGlobal.MethodsWe combine a new global map of forest management types created solely from remote sensing imagery with spatially explicit information on the distribution of forest‐associated vertebrate species and protected areas globally. Using Bayesian logistic regressions, we explore whether the amount of forested habitat available to a species as well as information on species‐specific threats can explain differences in IUCN extinction risk categories.ResultsWe show that disturbed and human‐managed forests dominate the distributional ranges of most forest‐associated species. Species considered as non‐threatened had on average larger amounts of non‐managed forests within their range. A greater amount of planted forests did not decrease the probability of species being threatened by extinction. Even more worrying, protected areas are increasingly being established in areas dominated by disturbed forests.ConclusionOur results imply that species extinction risk and habitat assessments might have been overly optimistic with forest management practices being largely ignored so far. With forest restoration being at the centre of climate and conservation policies in this decade, we caution that policy makers should explicitly consider forest management in global and regional assessments.

Spring-fed streams in Tokyo are important habitats for various aquatic species, whereas urbanization as well as introduction of invasive species is threatening the sustainability of such aquatic ecosystems. This study applies the System for Environmental Flow Analysis (SEFA) in a small urban river in Tokyo to assess the dynamics of the suitable habitats for the endangered freshwater fish Lefua echigonia (Jordan and Richardson 1907). A set of Habitat Suitability Curves (HSCs) for water depth, velocity and substrate was developed to evaluate the suitable habitats. The habitat assessment indicated that the Area Weighted Suitability (AWS) reached the maximum at 0.02 m3/s, which is close to the base flow of the target river; a gradual decrease in AWS was observed for higher flows. The temporal distribution of AWS, during forty-one consecutive months, showed that, on average, the best habitat conditions for adult L. echigonia occur during the period between January and July, whereas the worst situation occurs during the period between August and December. This work presents information and tools for instream habitat analysis that should help managers to conserve this aquatic species and prioritize actions to further rehabilitate urban rivers, using L. echigonia as a case study.

Biodiversity managers face a dilemma of choosing between “coarse-filter” approaches that deal with the habitats of several species and “fine-filter” approaches that address population viability of one or a few species. We present an approach for local spatial scales that integrates habitat-based and population-based methods to focus research and management on the species in a community that are most at risk of extinction and on the places in the landscape most important to these species. The steps in Dynamic Habitat and Population (DHP) Analysis are: 1) determine which species in the planning area most merit field study based on existing data; 2) use local field data to select species that most merit demographic study; 3) use demographic data to model population viability of the species deemed most at risk; 4) design and evaluate alternative management strategies for key species and landscape settings. We review each step and provide an example for land birds in a portion of the Greater Yellowstone Ecosystem. Among the 143 species of land birds likely in the study area, we selected 13 species most at risk of extinction. These were mostly neotropical migrant passerines that specialized on low-elevation deciduous habitats that may serve as population source areas. We present a management plan for the multiple ownerships of the study area that seeks to maintain/restore population source habitats for key species. DHP Analysis provides a framework for biodiversity management for those regions identified as high priority for conservation by continental-scale assessment programs such as Gap Analysis. Our approach is designed to minimize local extinctions, which should reduce the risk of range-wide extinctions.

How patch configuration affects the impact of disturbances on metapopulation persistence

In human dominated landscapes, ecosystems are under increasing pressures caused by urbanization and infrastructure development. In Alpine valleys remnant natural areas are increasingly affected by habitat fragmentation and loss. In these contexts, there is a growing risk of local extinction for wildlife populations; hence assessing the consequences on biodiversity of proposed land use changes is extremely important. The article presents a methodology to assess the impacts of land use changes on target species at a local scale. The approach relies on the application of ecological profiles of target species for habitat potential (HP) assessment, using high resolution GIS-data within a multiple level framework. The HP, in this framework, is based on a species-specific assessment of the suitability of a site, as well of surrounding areas. This assessment is performed through spatial rules, structured as sets of queries on landscape objects. We show that by considering spatial dependencies in habitat assessment it is possible to perform better quantification of impacts of local-level land use changes on habitats.