Periods Of Abrupt Change Research Articles

Vulnerabilities of northern Peruvian small-scale fishing communities revealed by the COVID-19 pandemic

During periods of abrupt change, understanding sources of resilience for adaptability in small-scale fisheries (SSF) is important for enhancing their sustainability. This study aimed to understand the vulnerability of five diverse SSF communities in northern Peru amid COVID-19, by analyzing key sensitivity indicators that influence their response to the immediate impacts caused by the lockdown and their short-term adaptive capacity. We established a baseline for each fishing community, through socio-economic, fishery-related, and commercialization characteristics. We then assessed fishery changes before and during the first and most restricted lockdown and community responses to the pandemic impact. These were used to generate a score value that ranked the adaptive capacity of each community. Through a regression tree we identified key SI that most influence the communities´ response to COVID-19 impacts. Our results show that the ‘fishing area related to distance from the coast’ was the most important sensitivity indicator as offshore fisheries were riskier (i.e. higher travel costs) than inshore fisheries. The communities that responded better to COVID-19 impacts had high social capital (i.e. self-organization and social learning); while, the least successful communities responded passively. The adaptive strategies of SSF here identified included diversification of fishing activities (i.e., shifting to fishery areas closer to the coast), selling marine products at local markets, fishing fewer days, establishing agreements with authorities, using technology (i.e., digital platforms) in creative ways to enhance local seafood value chains, and combining different types of knowledge from different actors. These strategies fostered the re-organization of the supply chain in which a shift to local markets became a trend. We include a list of recommendations for decision-makers and principal insights related to community resilience.

Study on the Influence of Water Level on Earth Dam Reinforced by Cut-Off Wall: A Case Study in Wujing Reservoir

The construction of a cut-off wall is a common reinforcement method for earth rock dams. At present, compared with the in-depth study on homogeneous earth dams, more and more attention is being paid to the stability and deformation of earth dams strengthened by a concrete cut-off wall. In this study, aiming at the Wujing project of the earth dam strengthened by cut-off wall, the influence of the water level rise and fall on the stability of the dam slope, the deformation of the dam body, and the crack width on dam crest were analyzed by numerical calculation and in situ measurement. The analysis results show that when the reservoir encounters a sudden drawdown, the safety factor of the dam slope decreases sharply. The faster the sudden drawdown, the faster the safety factor decreases. When the reservoir water level rises, the dam’s horizontal displacement shifts to the upstream direction, and the change of horizontal displacement of the downstream slope is significantly larger than that at the measuring point of the upstream slope. The water level of the reservoir rises, and the surface of the dam body rises, and the fluctuation of settlement deformation shows that the upstream side is larger than the downstream side, especially during the period of abrupt change in the reservoir water level. The longitudinal cracks on the dam crest show a tendency of shrinkage when the reservoir water level rises, and opening decreases with the decrease of deformation gradient increment and increases with the increase of gradient increment.

Spatio-Temporal Extraction of Surface Waterbody and Its Response of Extreme Climate along the Upper Huaihe River

The upper Huaihe River is the water-producing area of the Huaihe River Basin and the major grain and oil-producing area in China. The changing global climate over the recent years has increased the frequency of extreme weather in the upper reaches of the Huaihe River. Research on the responses of surface water bodies to extreme climates has become increasingly important. Based on all utilizable Landsat 4–8 T1–SR data and frequency mapping, the spatio-temporal extraction of surface water and its response to extreme climate were studied. We generated high-precision frequency maps of surface water, and a comparison of cartographic accuracy evaluation indices and spatial consistency was also carried out. The high-precision interpretation of small waterbodies constructs a surface water distribution with better continuity and integrity. Furthermore, we investigated the effect of El Niño/La Niña events on precipitation, temperature, and surface water along the upper Huaihe River, using the Mann–Kendall mutation tests. The results show: in 1987–2018, periods of abrupt changes in precipitation coincide with EI Niño/La Niña events, indicating that the precipitation was sensitive to EI Niño/La Niña events, which also strongly correlated with surface water area during wet and dry years. The effect of extreme events on seasonal water was smaller than permanent water. Surface water area showed an insignificant declining trend after 1999 and a significant drop in 2012. The phenomenon of topographic enhancement of precipitation controlled the spatial distribution of permanent water, with human activities having a substantial effect on the landscape pattern of seasonal water. Finally, discussions and applications related to the Markov Chain probability calculation theory in the paper contributed to enriching the theories on frequency mapping. The relevant results provide a theoretical basis and case support for the formulation of long-term water resources utilization and allocation policies.

Response of runoff to change of atmospheric 0°C level height in summer in arid region of Northwest China

Based on the daily observed data from eight sounding stations and the daily mountain runoff data from nine rivers in summer from 1960 to 2009 in four typical study areas located in arid region of Northwest China (ARNC), the change trends, abrupt change points, and their significance of runoff and 0°C level height (FLH) were analyzed in ARNC in the last 50 years by using Mann-Kendall (MK) nonparametric test, and the quantitative relationship between runoff and FLH in summer was also analyzed with the linear regression and elastic coefficient methods. The results are indicated as follows: (1) in recent 50 years, there is a similar changing trend between the summer runoff and FLH in ARNC and each region has its own unique feature. The summer runoff has been significantly ascending in the Tianshan Mountains and on the northern slope of the Qilian Mountains (NSQM) compared to that of the northern slope of the Kunlun Mountains (NSKM). Likewise, the FLH has been taking on a markedly rising trend on the northern slopes of the Tianshan and Qilian Mountains (NSTM and NSQM) in comparison with the southern slope of the Tianshan Mountains (SSTM). However, the FLH on NSKM has been decreasing with the speed of 2.33 m every year. (2) Abrupt change analysis indicates that the period of abrupt change happened for summer runoff and FLH is totally different among the four typical study regions, and even in same region. (3) There is a positive significant relation between the summer runoff and FLH in ARNC (NSQM P <0.05; other three regions P <0.01). Therefore, the ascending and descending of the summer FLH is a vital factor inducing the change of summer runoff in ARNC. (4) The elastic coefficient of summer runoff to the change of summer FLH on NSKM, NSTM, NSQM, and SSTM are 7.19, 3.80, 2.79, and 6.63, respectively, which indicates that there exists the regional difference in the sensibility of summer runoff to the change of summer FLH in ARNC. The distinct proportion of glacial meltwater runoff is an important cause resulting in the regional difference of sensibility.

Analysis of the seasonal dynamics of river phytoplankton based on succession rate indices for key event identification

The seasonal dynamics of river phytoplankton was analyzed using succession rate indices based on data collected from year-round observations of two small plain rivers in the Upper Ob Basin (Western Siberia). The study revealed a generally clear seasonal pattern of structural changes in the phytoplankton of the lower reaches of the studied rivers. The dynamics of succession rate indices reflects the key events in the life of phytoplankton in the Bolshaya Losikha and Barnaulka Rivers, showing mainly changes in the dominant species during the main phases of the hydrological cycle. The most significant changes in phytoplankton structure tend to occur in the period between the spring flood decline and the beginning of summer–autumn low water. These changes coincide with the most drastic changes in both environmental conditions and phytoplankton successional stages. Use of succession rate indices to analyze the seasonal dynamics of phytoplankton allowed us to distinguish between periods of abrupt change and periods of comparatively low-intensity changes in plankton composition in small lowland temperate rivers.

ADAPTIVE GOVERNANCE OF SOCIAL-ECOLOGICAL SYSTEMS

▪ Abstract We explore the social dimension that enables adaptive ecosystem-based management. The review concentrates on experiences of adaptive governance of social-ecological systems during periods of abrupt change (crisis) and investigates social sources of renewal and reorganization. Such governance connects individuals, organizations, agencies, and institutions at multiple organizational levels. Key persons provide leadership, trust, vision, meaning, and they help transform management organizations toward a learning environment. Adaptive governance systems often self-organize as social networks with teams and actor groups that draw on various knowledge systems and experiences for the development of a common understanding and policies. The emergence of “bridging organizations” seem to lower the costs of collaboration and conflict resolution, and enabling legislation and governmental policies can support self-organization while framing creativity for adaptive comanagement efforts. A resilient social-ecological system may make use of crisis as an opportunity to transform into a more desired state.

Synchronized evolution in lineages of land snails in oceanic islands

Synchronous episodes of phenotypic change in five lineages of the endemic land snail genus Mandarina of the oceanic Bonin (Ogasawara) Islands through 40,000 years were documented by morphological analyses of radiocarbon-dated fossil specimens. Adult shell traits of these lineages show mostly synchronous patterns of change with longer intervals of stability and rapid shifts to other states of stability. Although there are intermediates between these different phenotypic states, the net interval of the phenotypic shift was relatively short, i.e., no longer than 7000 years. Extinction of a lineage and speciation occurred during the intervals of the rapid phenotypic shift. This period of abrupt change corresponds to the period of lowest sea level and end of the last glacial period. This implies that climatic change is one of the causes of these episodes of simultaneous rapid phenotypic shifts, speciation, and extinction in different lineages. These findings suggest that major phenotypic changes in phyletic evolution, separation of different species, and extinction of lineages may occur synchronously in many lineages during an extremely short interval.