Prediction of collapse process and tipping points for mutualistic and competitive networks with k-core method

Ecosystems generally have the self-adapting ability to resist various external pressures or disturbances,which is always called resilience.However,once the external disturbances exceed the tipping points of the system resilience,the consequences would be catastrophic,and eventually lead the ecosystem to complete collapse.We capture the collapse process of ecosystems represented by plant-pollinator networks with the k-core nested structural method,and find that a sufficiently weak interaction strength or a sufficiently large competition weight can cause the structure of the ecosystem to collapse from its smallest k-core towards its largest k-core.Then we give the tipping points of structure and dynamic collapse of the entire system from the one-dimensional dynamic function of the ecosystem.Our work provides an intuitive and precise description of the dynamic process of ecosystem collapse under multiple interactions,and provides theoretical insights into further avoiding the occurrence of ecosystem collapse.

Will the summer sea ice in the Arctic reach a tipping point?

The Arctic sea-ice cover has decreased in extent,area,and thickness over the last six decades.Most global climate models project that the summer sea-ice extent(SIE)will decline to less than 1 million(mill.)km^(2) in this century,ranging from 2030 to the end of the century,indicating large uncertainty.However,some models,using the same emission scenarios as required by the Paris Agreement to keep the global temperature below 2°C,indicate that the SIE could be about 2 mill.km^(2) in 2100 but with a large uncertainty of±1.5 mill.km^(2).Here,the authors take another approach by exploring the direct relationship between the SIE and atmospheric CO_(2) concentration for the summer-fall months.The authors correlate the SIE and In(CO_(2)/CO_(2)r)during the period 1979-2022,where CO_(2)r is the reference value in 1979.Using these transient regression equations with an R2 between 0.78 and 0.87,the authors calculate the value that the CO_(2) concentration needs to reach for zero SIE.The results are that,for July,the CO_(2) concentration needs to reach 691±16.5 ppm,for August 604±16.5 ppm,for September 563±17.5 ppm,and for October 620±21 ppm.These values of CO_(2)for an ice-free Arctic are much higher than the targets of the Paris Agreement,which are 450 ppm in 2060 and 425 ppm in 2100,under the IPCC SSP1-2.6 scenario.If these targets can be reached or even almost reached,the "no tipping point"hypothesis for the summer SIE may be valid.

On the Image Reconstruction of Zhuge Liang in ACGN Games Based on the Perspective of the Tipping Point Theory

Zhuge Liang,a well-known figure with rich cultural implications in Chinese history,has exerted profound influences on the spiritual life of the Chinese nation.In the ACGN context,new cultural implications have been attached to him,which offset some of the classic implications of the character forged over a long history.Meanwhile,the inherent traditional cultural spirit embodied by him is being reconstructed.In terms of content design,the ACGN games based on traditional realism tend to refresh people’s collective memories of Zhuge Liang to enhance the stickiness factor of the games,thus creating a sense of familiarity to make the transmitted information easier for the game players to accept.The modern fashionable games,however,are good at leveraging the advantages of technologies to form a tipping point and incorporating fashion elements into the traditional image of Zhuge Liang to attract players,thus enhancing the communication effect.In terms of environmental construction,the ACGN games have created a new industrial environment featuring“ACGN+traditional culture,”which changes the traditional image of Zhuge Liang by means of ACGN game technology while retaining its basic cultural characteristics to provide players with a better immersive and interactive experience.

Tipping Point

LIBYA is rapidly joining the ranks of Africa＇s better-known failed states： the Central African Re- public, Somalia and South Sudan. The North African country, once boasting one of the continent＇s highest per-capita GDPs, is a shadow of its former self： torn apart by armed conflict and now felled by falling oil prices and declining production.

Tipping Point

A MAFIA-LIKE criminal order inspired by a totalitarian ideology threatens North Africa and the Sahel, with Libya now as its centerpiece. As this radical, obscurantist and brutal form of Islam spreads and displaces traditional Islam in Libya, the emergence of the Benghazi Defense Brigades （BDB）, formed in June 2016 to oppose the Libyan national army, has plunged the coun- try into further chaos. The BDB is locked in con- flict with the Libyan army led by Major General Khalifa Haftar.

The Tipping Point

THE worst year on record for rhino poaching in South Africa＇s history makes 2013 a dismal period for the endangered animal. Figures released by the South African Department of Environmental Affairs in January show that in 2013, just over 1,000 rhinos were illegally killed in South Africa - the equivalent of nearly three animals a day. The figure is more than 1.5 times the official figure of 668 rhinos killed for their horns in 2012. This brings South Africa＇s white rhino population ever closer to the tipping point, where deaths outnumber births and the population begins a serious decline.

Significant tipping points of sediment microeukaryotes forewarn increasing antibiotic pollution

Antibiotic pollution imposes urgent threats to public health and microbial-mediated ecological processes.Existing studies have primarily focused on bacterial responses to antibiotic pollution,but they ignored the microeukaryotic counterpart,though microeukaryotes are functionally important(e.g.,predators and saprophytes)in microbial ecology.Herein,we explored how the assembly of sediment microeukaryotes was affected by increasing antibiotic pollution at the inlet(control)and across the outlet sites along a shrimpwastewater discharge channel.The structures of sedimentmicroeukaryotic community were substantially altered by the increasing nutrient and antibiotic pollutions,whichwere primarily controlled by the direct effects of phosphate and ammonium(−0.645 and 0.507,respectively).In addition,tetracyclines exerted a large effect(0.209),including direct effect(0.326)and indirect effect(−0.117),on the microeukaryotic assembly.On the contrary,the fungal subcommunity was relatively resistant to antibiotic pollution.Segmented analysis depicted nonlinear responses of microeukaryotic genera to the antibiotic pollution gradient,as supported by the significant tipping points.We screened 30 antibiotic concentration-discriminatory taxa of microeukaryotes,which can quantitatively and accurately predict(98.7%accuracy)the in-situ antibiotic concentration.Sediment microeukaryotic(except fungal)community is sensitive to antibiotic pollution,and the identified bioindicators could be used for antibiotic pollution diagnosis.

Do abrupt cryosphere events in High Mountain Asia indicate earlier tipping point than expected?

Tipping points of about 16 elements have been identified in Earth system,yet cryospheric tipping point of specific Alpine region has not been studied.Here we analyzed three tipping elements(mountain glacier,snow cover,and permafrost)identified in recent years,evidenced by the facts of frequent occurrence of abrupt massive collapse of glacier mass and the widespread thermakarst of permafrost.Since 2015,strikingly abrupt cryosphere events(ACEs)have been consistently observed over a large range of High Mountain Asia(HMA).Those events were un-precedentedly significant in history,leading to collapses of glaciers following by disconnection of glacier tongue from accumulation basin and recession of thermakarst towards higher elevation.Strong decreasing of snow depth in 2022 was also observed since 2021/2022 winter,coinciding with extreme warming of the year.The widespread high warming rates in the last two decades over HMA might have triggered above ACEs.The dynamic thresholds of ACEs depend largely on high temperature,especially extreme heat wave,for both glaciers and permafrost,closely related to meltwater as a key factor for reaching initial conditions of abrupt changes,suggesting HMA cryosphere is a tipping element under the global warming level of 1.1℃.The ACEs can cause tremendous damage to local ecosystem and socioeconomy,measures to mitigate risks should be taken when the tipping points are reached.

Landscape dynamic network biomarker analysis reveals the tipping point of transcriptome reprogramming to prevent skin photodamage

Skin,as the outmost layer of human body,is frequently exposed to environmental stressors including pollutants and ultraviolet(UV),which could lead to skin disorders.Generally,skin response process to ultraviolet B(UVB)irradiation is a nonlinear dynamic process,with unknown underlying molecular mechanism of critical transition.Here,the landscape dynamic network biomarker(lDNB)analysis of time series transcriptome data on 3D skin model was conducted to reveal the complicated process of skin response to UV irradiation at both molecular and network levels.The advanced l-DNB analysis approach showed that:(i)there was a tipping point before critical transition state during pigmentation process,validated by 3D skin model;(ii)13 core DNB genes were identified to detect the tipping point as a network biomarker,supported by computational assessment;(iii)core DNB genes such as COL7A1 and CTNNB1 can effectively predict skin lightening,validated by independent human skin data.Overall,this study provides new insights for skin response to repetitive UVB irradiation,including dynamic pathway pattern,biphasic response,and DNBs for skin lightening change,and enables us to further understand the skin resilience process after external stress.

Critical transitions and tipping points in EMT

Background:Phase transition and phase separation as well as their tipping points are penetrating phenomena in biology and are intrinsic properties of biological systems ranging from basic molecule complexes to cells and all way up to entire ecosystems.Results:For example,phase separation has been established as a key mechanism for biological molecules such as protein or RNA to form membraneless organelles to perform complex biological functions.Phase transitions are commonly observed during cellular differentiation,and generally,there are the tipping points or critical states just before the phase transitions.And the stability of ecosystem and extinction of species are systematic manifestation of phase transitions.All phase transition and phase separation phenomena display switch-like behavior and critical transitions.Conclusion:Here we summarize the concepts regarding the epithelial-to・mesenchymal transition(EMT)as a type of phase changes and the implication of critical transitions in EMT,and discuss open questions and challenges in this fast-moving field.

Some Remarks on the Individual Contribution to Climate Change

Climate change is one of the most important challenges of the 21st Century. As greenhouse gas concentration of the atmosphere has reached the 400ppm threshold of a 2°C global warming on 9 May 2013 and irreversible tipping points of the climatic system at some point of time have got even more likely, the question of the individual contribution to climate change becomes more and more virulent. For a long time, the absorption capacity of the environment has been regarded as limitless, and based on this perception, the economic entities used the environment for hundreds of years without constraints. Today, with progress of scientific knowledge, we are now aware of the possible negative impacts of climate change to environmental, economic and social systems on Earth. This awareness, however, did not lead to a significant change of individual behavior, because the perceived individual contribution to both the anthropogenic cause of climate change and its mitigation is still regarded as marginal. To encounter this misperception or “diffusion of environmental responsibility”, this article presents an alternative calculation of the individual contribution to climate change taking the incremental approach to a tipping point or a 2°C global warming threshold into account.

Simulation of critical transitions and vulnerability assessment of Tibetan Plateau key ecosystems

Critical transitions in ecosystems may imply risks of unexpected collapse under climate changes,especially vegetation often responds sensitively to climate change.The type of vegetation ecosystem states could present alternative stable states,and its type could signal the critical transitions at tipping points because of changed climate or other drivers.This study analyzed the distribution of four key vegetation ecosystem types:desert,grassland,forest-steppe ecotone and forest,in Tibetan Plateau in China,using the latent class analysis method based on remote sensing data and climate data.This study analyzed the impacts of three key climate factors,precipitation,temperature,and sunshine duration,on the vegetation states,and calculated the critical transition tipping point of potential changes in vegetation type in Tibetan Plateau with the logistic regression model.The studied results showed that climatic factors greatly affect the vegetation states and vulnerability of the Tibetan Plateau.In comparison with temperature and sunshine duration,precipitation shows more obvious impact on differentiations of the vegetations status probability.The precipitation tipping point for desert and grassland transition is averagely 48.0 mm/month,70.7 mm/month for grassland and forest-steppe ecotone,and 115.0 mm/month for forest-steppe ecotone and forest.Both temperature and sunshine duration only show different probability change between vegetation and non-vegetation type,but produce opposite impacts.In Tibetan Plateau,the transition tipping points of vegetation and nonvegetation are about 12.1°C/month and 173.6 h/month for the temperature and sunshine duration,respectively.Further,vulnerability maps calculated with the logistic regression results presented the distribution of vulnerability of Tibetan Plateau key ecosystems.The vulnerability of the typical ecosystems in the Tibetan Plateau is low in the southeast and is high in the northwest.The meteorological factors affect tree cover as well as the transition probability that occurs in different vegetation states.This study can provide reference for local government agencies to formulate regional development strategies and environmental protection laws and regulations.

Extreme events as ecosystems drivers： Ecological consequences of anomalous Southern Hemisphere weather patterns during the 2001/2002 austral spring-summer

The frequency and severity of extreme events associated with global change are both forecast to increase with a concomitant increase expected in perturbations and disruptions of fundamental processes at ecosystem, community and population scales, with potentially catastrophic consequences. Extreme events should thus be viewed as ecosystem drivers, rather than as short term deviations from a perceived ＇norm＇. To illustrate this, we examined the impacts associated with the extraordinary weather pattern of the austral spring/summer of 2001/2002, and find that patterns of ocean-atmosphere interactions appear linked to a suite of extreme events in Antarctica and more widely across the Southern Hemisphere. In the Antarctic, the extreme events appear related to particular ecological impacts, including the substantial reduction in breeding success of Ade1ie penguins at sites in the Antarctic Peninsula as well as for Adelie penguin and snow petrel colonies in East Antarctica, and the creation of new benthic habitats associated with the disintegration of the Larsen B Ice Shelf. Other major impacts occurred in marine and terrestrial ecosystems at temperate and tropical latitudes. The suite of impacts demonstrates that ecological consequences of extreme events are manifested at fundamental levels in ecosystem processes and produce long-term, persistent effects relative to the short-term durations of the events. Changes in the rates of primary productivity, species mortality, community structure and inter-specific interactions, and changes in trophodynamics were observed as a consequence of the conditions during the 2001/2002 summer. Lasting potential consequences include reaching or exceeding tipping points, trophic cascades and regime shifts.

Response of runoff and its components to climate change in the Manas River of the Tian Shan Mountains

A warming-wetting climate trend has led to increased runoff in most watersheds in the Tian Shan Mountains over the past few decades.However,it remains unclear how runoff components,that is,rainfall runoff(Rrain),snowmelt runoff(Rsnow),and glacier meltwater(Rglacier),responded to historical climate change and how they will evolve under future climate change scenarios.Here,we used a modified Hydrologiska Byrans Vattenbalansavdelning(HBV)model and a detrending method to quantify the impact of precipitation and temperature changes on runoff components in the largest river(Manas River)on the northern slope of the Tian Shan Mountains from 1982 to 2015.A multivariate calibration strategy,including snow cover,glacier area,and runoff was implemented to constrain model parameters associated with runoff components.The downscaled outputs of 12 general circulation models(GCMs)from the Sixth Coupled Model Intercomparison Project(CMIP6)were also used to force the modified HBV model to project the response of runoff and its components to future(2016-2100)climate change under three common socio-economic pathways(SSP126,SSP245,and SSP585).The results indicate that Rrain dominates mean annual runoff with a proportion of 42%,followed by Rsnow(37%)and Rglacier(21%).In terms of inter-annual variation,Rrain and Rsnow show increasing trends(0.93(p<0.05)and 0.31(p>0.05)mm per year),while Rglacier exhibits an insignificant(p>0.05)decreasing trend(-0.12 mm per year),leading to an increasing trend in total runoff(1.12 mm per year,p>0.05).The attribution analysis indicates that changes in precipitation and temperature contribute 8.16 and 10.37 mm,respectively,to the increase in runoff at the mean annual scale.Climate wetting(increased precipitation)increases Rrain(5.03 mm)and Rsnow(3.19 mm)but has a limited effect on Rglacier(-0.06 mm),while warming increases Rrain(10.69 mm)and Rglacier(5.79 mm)but decreases Rsnow(-6.12 mm).The negative effect of glacier shrinkage on Rglacier has outweighed the positive effect of warming on Rglaciers resulting in the tipping point(peak water)for Rglacier having passed.Runoff projections indicate that future decreases in Rglacier and Rsnow could be offset by increases in Rrain due to increased precipitation projections,reducing the risk of shortages of available water resources.However,management authorities still need to develop adequate adaptation strategies to cope with the continuing decline in Rgacier in the future,considering the large inter-annual fluctuations and high uncertainty in precipitation projection.

Impact of climate change on biodiversity and associated key ecosystem services in Africa:a systematic review

Introduction:Biodiversity and biodiversity-based ecosystems services are intrinsically dependent on the climate.During the twentieth century,climate change has posed major threats to biodiversity in Africa,and impacts are expected to increase as climate change continues and perhaps even accelerates.Outcomes:Our review shows that the multiple components of climate change are projected to affect all levels of biodiversity,from genes over species to biome level.Loss of biodiversity as a result of climate change can alter the structures and functions of African ecological systems.As a result,the provision of biodiversity-based ecosystem services and the wellbeing of people that rely on these services are being modified.Of particular concerns are“tipping points”where the exceedance of ecosystem thresholds will possibly lead to irreversible shifts of the structure of ecosystems and their services.In recent years,climate prediction models have portended continued warming and more frequent extreme weather events across the region.Such weather-related disturbances such as El Niño will place a premium on biodiversity and biodiversity-based ecosystem services that people rely on.Conclusion:As biodiversity underlies all goods and services provided by ecosystems that are crucial for human survival and well-being,this paper synthesizes and discusses observed and anticipated impacts of climate change on biodiversity and biodiversity-based ecosystem service provision and livelihoods,and what strategies might be employed to decrease current and future risks on the well-being of human in Africa.

Fast action on short-lived climate pollutants and nature-based solutions to help countries meet carbon neutrality goals

Scientific studies show that fast actions to reduce near-term warming are essential to slowing self-reinforcing climate feedbacks and avoiding irreversible tipping points.Yet cutting CO_(2) emissions only marginally impacts near-term warming,This study identifies two of the most ffective mitigation strategies to limit near-term warming beyond CO_(2) mitigation,namely reducing short-lived climate pollutants(SLCPs)and promoting targeted nature-based solutions(NbS),and comprehensively reviews the latest scientifie progress in these fields.Studies show that quickly reducing SLCP emissions,particularly hydrofuorocarbons(HFCs),methane,and black carbon,from ll relevant sectors can avoid up to 0.6℃ of warming by 2050.Additionally,promoting targeted NbS that protect and enhance natural carbon sinks ncluding in forests,wetlands,grasslands,and agricultural lands,can avoid emssions of 23.8 Gt of CO_(2)e per year in 2030,without jeopardizing food security and biodiversity.Based on the scientific evidence,we provided a series of policy recommendations on SLCPs and NbS,including:1)implementing the Kigali Amendment to reduce HFC emissions;2)deploying cost-effective,sector-based measures to reduce methane and black carbon emissions;and 3)implementing targeted NbS to protect and enhance existing carbon sinks and shifting away from forest-burning bioenergy.These fast-acting strategies on SLCPs and NbS will play a key role in securing the most avoided warming in the near-term and help countries meet their mid-century carbon neutrality goals.Finally,we proposed future research topics,including:improving measurement and monitoring systems and techniques for SLCP emissions;developing and improving assessments of marginal abatement costs for SLCP mitigation in dfferent sectors;better quantifying the avoided warming potential from protecting dfferent types of natural carbon sinks by 2030,2050,and over longer periods;and identifying whether there are any biomass types for energy sources that are consistent with the United Nations Environment Assembly's 2022 resolution adopting a definition of NbS.Further research in these areas could help address barriers to adoption and assist countries with better integrating the most effective SLCP and NbS strategies into their climate policies.