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"Long-term changes"
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Intensification of Mesoscale Convective Systems in the East Asian Rainband Over the Past Two Decades
by
Li, Puxi
,
Zhuang, Moran
,
Schiemann, Reinhard
in
Algorithms
,
Anthropogenic factors
,
atmospheric total column water vapor
2023
As one of the major producers of extreme precipitation, mesoscale convective systems (MCSs) have received much attention. Recently, MCSs over several hotpots, including the Sahel and US Great Plains, have been found to intensify under global warming. However, relevant studies on the East Asian rainband, another MCS hotpot, are scarce. Here, by using a novel rain‐cell tracking algorithm on a high spatiotemporal resolution satellite precipitation product, we show that both the frequency and intensity of MCSs over the East Asian rainband have increased by 21.8% and 9.8% respectively over the past two decades (2000–2021). The more frequent and intense MCSs contribute nearly three quarters to the total precipitation increase. The changes in MCSs are caused by more frequent favorable large‐scale water vapor‐rich environments that are likely to increase under global warming. The increased frequency and intensity of MCSs have profound impacts on the hydroclimate of East Asia, including producing extreme events such as severe flooding. Plain Language Summary Mesoscale convective systems (MCSs), accounting for more than half of the total rainfall in the East Asian rainband, frequently generate high‐impact extreme weather events, such as flooding. In the summer of 2020, large regions of East Asia suffered extensive flooding and damage. Therefore, understanding the long‐term changes of MCSs is crucial to gain insights into how extreme weather may change in the context of global warming. However, compared to several other MCS hotpots, the investigation of long‐term changes of MCSs is scarce over East Asia. Here, based on a high spatiotemporal resolution satellite precipitation product and a novel MCS tracking method, we find that MCSs have become more frequent and intense in the East Asian rainband and accounted for three quarters of the total rainfall increase during 2000–2021. It is further found that increases in atmospheric total column water vapor, which is mainly due to increased temperature caused by anthropogenic forcing, leads to more frequent large‐scale water vapor‐rich environments that are responsible for the intensification of MCSs. As water vapor increases with global warming, it is very likely that MCSs will continue to intensify in this region into the future. Key Points Mesoscale convective systems (MCSs) have become more frequent and intense in the East Asian rainband over the past two decades The significant increase of MCS precipitation accounted for three quarters of the total rainfall increase during 2000–2021 The increase of atmospheric total column water vapor, mainly driven by anthropogenic forcing, leads to more favorable environments for MCSs
Journal Article
Tracking of marine predators to protect Southern Ocean ecosystems
by
University of Sydney Institute of Marine Science (USIMS) ; The University of Sydney
,
Delord, Karine
,
Ratcliffe, Norman
in
631/158/1144
,
631/158/672
,
Animal Identification Systems
2020
Southern Ocean ecosystems are under pressure from resource exploitation and climate change1,2. Mitigation requires the identification and protection of Areas of Ecological Significance (AESs), which have so far not been determined at the ocean-basin scale. Here, using assemblage-level tracking of marine predators, we identify AESs for this globally important region and assess current threats and protection levels. Integration of more than 4,000 tracks from 17 bird and mammal species reveals AESs around sub-Antarctic islands in the Atlantic and Indian Oceans and over the Antarctic continental shelf. Fishing pressure is disproportionately concentrated inside AESs, and climate change over the next century is predicted to impose pressure on these areas, particularly around the Antarctic continent. At present, 7.1% of the ocean south of 40°S is under formal protection, including 29% of the total AESs. The establishment and regular revision of networks of protection that encompass AESs are needed to provide long-term mitigation of growing pressures on Southern Ocean ecosystems.
Journal Article
Stratospheric Ozone Loss Enhances Summer Precipitation Over the Southern Slope of the Tibetan Plateau
2023
Heavy summer precipitation over the southern slope of the Tibetan Plateau has dramatic influences on water resources and hydrological disasters in South Asia. It experienced increasing trends over 1979–1996 and decreasing trends over 1996–2022, which are not yet well understood. Here we show observational and numerical evidence that stratospheric ozone has significant impacts on long‐term trends of summer precipitation in this strong convection area. It is found that stratospheric ozone depletion, by modulating the lower stratospheric temperature and upper‐tropospheric static stability, enhances deep convection and precipitation over the southern slope of the Tibetan Plateau. The results suggest that the ozone recovery in the future may reduce the summer precipitation over the southern slope of the Tibetan Plateau in the first half of the 21st century, which would be imperative for future water resource management in South Asia. Plain Language Summary South Asia, with a population of more than 1.8 billion, is among the most vulnerable regions in the world in response to climate change and a global hotspot for water security. Heavy summer precipitation over the southern slope of the Tibetan Plateau, which directly affects North India and Nepal with a population of more than 200 million and has dramatic influences on water resources and hydrological disasters in South Asia, experienced increasing trends over 1979–1996 and decreasing trends over 1996–2022 (Figure 1). We find that the long‐term variations of the summer precipitation are likely related to the stratospheric ozone depletion and recovery over the Tibetan Plateau in recent decades. The convective precipitation over the southern slope of the Tibetan Plateau is modulated by the upper tropospheric static stability which is affected by the lower‐stratospheric temperature. We find that stratospheric ozone depletion, which radiatively cools the lower stratosphere, enhances the deep convection and precipitation. This work helps to understand the stratospheric contributions to the changes in the summer precipitation over the southern slope of the Tibetan Plateau and future water resource management in South Asia. Key Points Trends in heavy summer precipitation over the southern slope of the Tibetan Plateau are positive in 1979–1996 and negative in 1996–2022 Stratospheric ozone depletion led to lower stratospheric cooling and a reduction of upper‐tropospheric static stability Stratospheric ozone depletion enhanced the deep convection and precipitation over the southern slope of the Tibetan Plateau
Journal Article
Substantial changes in the depth distributions of benthic invertebrates in the eastern Kattegat since the 1880s
by
Rolandsson, Johan
,
Josefson, Alf B.
,
Loo, Lars‐Ove
in
Benthic environment
,
Benthic fauna
,
bottom communities
2018
Bottom trawling and eutrophication are well known for their impacts on the marine benthic environment in the last decades. Evaluating the effects of these pressures is often restricted to contemporary benthic data, limiting the potential to observe change from an earlier (preimpact) state. In this study, we compared benthic species records from 1884 to 1886 by CGJ Petersen with recent data to investigate how benthic invertebrate species in the eastern Kattegat have changed since preimpact time. The study shows that species turnover between old and recent times was high, ca. 50%, and the species richness in the investigation area was either unchanged or higher in recent times, suggesting no net loss of species. Elements of metacommunity structure analysis of datasets from the 1880s, 1990s, and 2000s revealed a clear change in the depth distribution structure since the 1880s. The system changed from a Quasi‐nested/Random pattern unrelated to depth in the 1880s with many species depth ranges over a major part of the studied depth interval, to a Clementsian pattern in recent times strongly positively correlated with depth. Around 30% of the 117 species recorded both in old and in recent times, including most trawling‐sensitive species, that is large, semiemergent species, showed a decrease in maximal depth of occurrence from the deeper zone fished today to the shallower unfished zone, with on average 20 m. Concurrently, the species category remaining in the fished zone was dominated by species less sensitive to bottom trawling like infauna polychaetes and small‐sized Peracarida crustaceans, most likely with short longevity. The depth interval and magnitude of the changes in depth distribution and the changes in species composition indicate impacts from bottom trawling rather than eutrophication. Furthermore, the high similarity of results from the recent datasets 10 years apart suggests chronic impact keeping the system in an altered state. Because impacts of several threats to marine benthic habitats in recent times in eastern Kattegat are water depth dependent, we ask the question whether benthic invertebrate species depth distributions have changed since preimpact times in the late 1800s. EMS analyses suggest dramatic change in depth distribution structure in the eastern Kattegat from a quasi‐nested/random structure with great overlaps between species distributions in the 1880s, to Clementsian patterns in the 1990s and 2000s strongly correlated with water depth. These results suggest that some factor(s) has reinforced the influence of water depth on species distributions in the Kattegat since hypothetically pristine times and underpin suggestions that chronic fishing disturbance has changed benthic community structure over wide areas of the shelf seas using a temporal reference.
Journal Article
Non-random extinctions dominate plant community changes in abandoned coppices
by
Kopecký, Martin
,
Hédl, Radim
,
Szabó, Péter
in
Animal, plant and microbial ecology
,
Applied ecology
,
Biodiversity
2013
1. The plant community structure of European lowland forests has changed dramatically in the twentieth century, leading to biodiversity decline at various spatial scales. However, due to methodological difficulties associated with simultaneous changes in species diversity and composition, ecological processes behind the changes are still poorly understood. 2. We analysed temporal changes in forest plant community after the mid-twentieth-century abandonment of coppicing in a typical Central European forest, which had been managed as coppice for centuries. We used 122 semi-permanent plots first surveyed in the 1950s shortly after the last coppicing and again in the 2000s after half a century of natural succession. We used a novel temporal nestedness analysis to disentangle the immigration and extinction processes underlying temporal changes in community structure and tested whether species gains and losses were ecologically random. 3. The studied vegetation has shifted from the species-rich assemblages of a relatively open and low-nutrient forest towards the impoverished flora of a closed-canopy forest dominated by a few shade-adapted species. The significant reduction in beta diversity, that is, compositional heterogeneity among plots, indicated taxonomic homogenization of the forest understorey. Temporal species turnover was only a minor component of the community change, and recent assemblages are nested subsets of the former ones. Ecologically non-random extinctions dominated these changes. Light-demanding species with a persistent seed bank were the most prone to extinction, while species with high specific leaf area substantially increased in frequency. 4. Synthesis and applications. The dominant process after the abandonment of coppicing was the ecologically non-random extinction of light-demanding species, leading to an impoverished, temporally nested plant community structure. This development is typical for many abandoned coppices and poses a significant threat to forest biodiversity in Europe. If forestry and conservation policies continue to prefer closed-canopy stands, many endangered species are likely to pay their extinction debts. To restore declining or even locally extinct species, canopy opening in abandoned coppices is urgently needed.
Journal Article
Decadal change and inter-annual variability of net primary productivity on the Tibetan Plateau
by
Zhou, Bingrong
,
Xu-Ri
,
Cuo, Lan
in
Annual precipitation
,
Annual variations
,
atmospheric precipitation
2021
Net primary productivity (NPP) is an important indicator of plant dynamics and the net carbon exchange between the terrestrial ecosystem and atmosphere. Both the long-term shifts in climate mean (climate change) and short-term variations around the climate mean (climate variability) have impacts on NPP but studies examining both aspects of climate variations are rare especially in the data-scarce regions such as the Tibetan Plateau (TP). Here, we used a dynamic vegetation model to investigate the impacts of the changes and variabilities in temperature, precipitation, cloud cover and CO
2
on NPP on the TP. The simulated NPP was evaluated using field and Moderate-Resolution Imaging Spectroradiometer NPP and was found to be reasonable. At monthly time scale, NPP significantly correlated concurrently and at 1-month lag with temperature, precipitation and cloud cover (coefficient of determination, R
2
, in 0.52–0.77). Annual NPP variability was high (low) where mean annual NPP was low (high). The effects of annual precipitation, cloud cover and temperature variability on annual NPP variability were spatially heterogeneous, and temperature variability appeared to be the dominant factor (R
2
of 0.74). Whereas, NPP changes were very similar to CO
2
increases across the TP (spatial correlation of 0.60), indicating that long-term changes in NPP were dominated by CO
2
increases. For both variability and long-term changes in NPP, temperature was the major factor of influence (highest spatial correlation of 0.67). These findings could assist in making informed mitigation policies on the impacts of climate change and variability on ecosystem and local nomadic communities.
Journal Article
Winners and losers over 35 years of dragonfly and damselfly distributional change in Germany
by
Isaac, Nick J.B.
,
Spengler, Torsten
,
Bruelheide, Helge
in
Anisoptera (Odonata)
,
Aquatic insects
,
biodiversity monitoring
2021
Aim Recent studies suggest insect declines in parts of Europe; however, the generality of these trends across different taxa and regions remains unclear. Standardized data are not available to assess large‐scale, long‐term changes for most insect groups but opportunistic citizen science data are widespread for some. Here, we took advantage of citizen science data to investigate distributional changes of Odonata. Location Germany. Methods We compiled over 1 million occurrence records from different regional databases. We used occupancy‐detection models to account for imperfect detection and estimate annual distributions for each species during 1980–2016 within 5 × 5 km quadrants. We also compiled data on species attributes that were hypothesized to affect species’ sensitivity to different drivers and related them to the changes in species’ distributions. We further developed a novel approach to cluster groups of species with similar patterns of distributional change to represent multispecies indicators. Results More species increased (45%) than decreased (29%) or remained stable (26%) in their distribution (i.e. number of occupied quadrants). Species showing increases were generally warm‐adapted species and/or running water species, while species showing decreases were cold‐adapted species using standing water habitats such as bogs. Time series clustering defined five main patterns of change—each associated with a specific combination of species attributes, and confirming the key roles of species’ temperature and habitat preferences. Overall, our analysis predicted that mean quadrant‐level species richness has increased over most of the time period. Main conclusions Trends in Odonata provide mixed news—improved water quality, coupled with positive impacts of climate change, could explain the positive trends of many species. At the same time, declining species point to conservation challenges associated with habitat loss and degradation. Our study demonstrates the great value of citizen science and the work of natural history societies for assessing large‐scale distributional change.
Journal Article
Global climate change‐driven impacts on the Asian distribution of Limassolla leafhoppers, with implications for biological and environmental conservation
2024
Knowing the impacts of global climate change on the habitat suitability distribution of Limassolla leafhoppers contributes to understanding the feedback of organisms on climate change from a macroecological perspective, and provides important scientific basis for protecting the ecological environment and biodiversity. However, there is limited knowledge on this aspect. Thus, our study aimed to address this gap by analyzing Asian habitat suitability and centroid shifts of Limassolla based on 19 bioclimatic variables and occurrence records. Selecting five ecological niche models with the outstanding predictive performance (Maxlike, generalized linear model, generalized additive model, random forest, and maximum entropy) along with their ensemble model from 12 models, the current habitat suitability of Limassolla and its future habitat suitability under two Shared Socio‐economic Pathways (SSP1‐2.6 and SSP5‐8.5) in the 2050s and 2090s were predicted. The results showed that the prediction results of the five models are generally consistent. Based on ensemble model, 11 potential biodiversity hotspots with high suitability were identified. With climate change, the suitable range of Limassolla will experience both expansion and contraction. In SSP5‐8.52050s, the expansion area is 118.56 × 104 km2, while the contraction area is 25.40 × 104 km2; in SSP1‐2.62090s, the expansion area is 91.71 × 104 km2, and the contraction area is 26.54 × 104 km2. Furthermore, the distribution core of Limassolla will shift toward higher latitudes in the northeast direction, and the precipitation of warmest quarter was found to have the greatest impact on the distribution of Limassolla. Our research results supported our four hypotheses. Finally, this research suggests establishing ecological reserves in identified contraction to prevent habitat loss, enhancing the protection of biodiversity hotspots, and pursuing a sustainable development path with reduced emissions. This study conducted a comprehensive analysis of the distribution of Limassolla based on different Shared Socio‐economic Pathways and climate scenarios, incorporating theories and methods from insect ecology, environmental ecology, and biogeography. The results indicated that Limassolla is mainly distributed in East Asia, South Asia, and Southeast Asia, and the precipitation of warmest quarter has been found to have the greatest impact on the distribution of Limassolla. With climate change, the suitable range of Limassolla will experience both expansion and contraction, with the distribution core shifting toward higher latitudes in the northeast direction.
Journal Article
Half a century of succession in a temperate oakwood: from species-rich community to mesic forest
by
Kopecký, Martin
,
Hédl, Radim
,
Komárek, Josef
in
Animal, plant and microbial ecology
,
Applied ecology
,
Biodiversity
2010
Aim Lowland woodlands in Europe went through dramatic changes in management in the past century. This article investigates the influence of two key factors, abandonment of coppicing and increased pressure of ungulates, in thermophilous oakwoods. We focused on three interconnected topics: (1) Has the assumed successional trend lead to impoverishment of the vegetation assemblages? (2) Has it resulted in vegetation homogenization? (3) Are the thermophilous oakwoods loosing their original character? Location Czech Republic, Central Europe. Methods The vegetation in 46 semi-permanent plots was recorded three times: firstly, shortly after the abandonment of coppicing (1953) and then, after four to six decades of secondary succession and strong game impact (1992 and 2006).Overall trends and changes in species spectra were analysed. Results There is a marked successional shift towards species-poorer communities growing in cooler, moister and nutrient-richer conditions. The change was significantly different in parts affected and unaffected by high numbers of ungulates yet only for herbs, not the woody species. However, observed change in species composition was not accompanied by significant homogenization process that is the general process reported from elsewhere. A sharp decline in plant species typical for thermophilous woodland communities and in endangered species indicates that the original character of the woodland has been gradually lost. Main conclusions Thermophilous oakwoods have been largely replaced by mesic forests. Lowland oakwoods in continental parts of Europe historically depended on active management, which kept the understorey conditions light and warm.Successional processes in the 20th century caused a critical loss of species diversity at various spatial levels. However, artificially high numbers of ungulates, which otherwise have a negativeimpact, probably held up succession, so that the changes may still be reversible.
Journal Article
Global vegetation biomass change (1988–2008) and attribution to environmental and human drivers
by
van Dijk, Albert I. J. M.
,
McCabe, Matthew F.
,
Liu, Yi Y.
in
Animal and plant ecology
,
Animal, plant and microbial ecology
,
Atmospheric conditions
2013
AIM: Vegetation optical depth (VOD) is an indicator of the water content of both woody and leaf components in terrestrial aboveground vegetation biomass that can be derived from passive microwave remote sensing. VOD is distinct from optical vegetation remote sensing data such as the normalized difference vegetation index in that it is: (a) less prone to saturation in dense canopies; (b) sensitive to both photosynthetic and non‐photosynthetic biomass; and (c) less affected by atmospheric conditions. Our primary objective was to analyse a recently developed long‐term VOD record and investigate how the vegetation water content of various land‐cover types responded to environmental changes and human influences from 1988 to 2008. LOCATION: Global. METHODS: We first conducted Mann–Kendall trend tests on annual average VOD to identify regions with significant changes over the period 1988–2008. To diagnose the underlying cause of the observed changes, patterns for these identified regions were further compared with independent datasets of precipitation, crop production, deforestation and fire occurrence. RESULTS: (1) Over grassland and shrubland, VOD patterns corresponded strongly to temporal precipitation patterns. (2) Over croplands, annual average VOD showed a general increase that corresponded to reported crop production patterns and was attributed to a combination of precipitation patterns and agricultural improvements. (3) Over humid tropical forest, the spatial pattern of VOD decline agrees well with deforestation patterns; the 2005 Amazon drought corresponded with a temporary VOD decrease. (4) Over boreal forests, regional VOD declines are attributed to a combination of fires and clear cutting. MAIN CONCLUSIONS: Passive microwave remote sensing of VOD can be used to monitor global changes in total aboveground vegetation water content and biomass over various land‐cover types. This new observational record can help in hydrological, agricultural, ecological and climate change studies, and provides new insights into large‐scale vegetation change and its drivers.
Journal Article