Modern global earthquake fatalities can be separated into two components: (1) fatalities from an approximately constant annual background rate that is independent of world population growth and (2) ...fatalities caused by earthquakes with large human death tolls, the frequency of which is dependent on world population. Earthquakes with death tolls greater than 100,000 (and 50,000) have increased with world population and obey a nonstationary Poisson distribution with rate proportional to population. We predict that the number of earthquakes with death tolls greater than 100,000 (50,000) will increase in the 21st century to 8.7±3.3 (20.5±4.3) from 4 (7) observed in the 20th century if world population reaches 10.1 billion in 2100. Combining fatalities caused by the background rate with fatalities caused by catastrophic earthquakes (>100,000 fatalities) indicates global fatalities in the 21st century will be 2.57±0.64 million if the average post-1900 death toll for catastrophic earthquakes (193,000) is assumed.
Synopsis Understanding how animals maximize reproductive success in variable environments is important in determining how populations will respond to increasingly extreme weather events predicted in ...the face of changing climates. Although temperature is generally considered a key factor in reproductive decisions, rainfall is also an important predictor of prey availability in arid environments. Here, we test the impact of weather (i.e., rainfall and temperature) on female reproductive investment in an arid-dwelling bird (i.e., clutch size and egg volume) and tradeoffs between the two. We predicted that female chestnut-crowned babblers (Pomatostomus ruficeps), endemic to the arid region of Australia, would increase clutch size at the expense of egg volume in response to variation in rainfall and temperature. We found that over 14 breeding seasons, clutch size decreased with increasing temperature, but increased following more rain. Egg volume, on the other hand, became larger as temperatures increased and, although not related to the amount of rain, was related to the number of days since the last rainfall. Finally, egg size decreased as clutch size increased, indicating a tradeoff between the two reproductive parameters. Our results suggest that chestnut-crowned babblers breed reactively in response to variable environments. We expect that clutch size variation in response to rain may reflect the impact of rain on arthropod abundance, whereas the effect of temperature may represent an established decline in clutch size observed in other seasonal breeders. As the tradeoff between clutch size and egg volume was modest and clutch sizes were modified to a greater extent than egg volumes in response to rainfall, we suggest selection is more likely to increase offspring number than quality, at least in favorable years. Our results support the idea that reproductive investment is variable in fluctuating environments, which has implications for species living in habitats experiencing more extreme and less predictable weather as the global climate changes.
Among species with variable numbers of individuals contributing to offspring care, an individual's investment strategy should depend upon both the size of the breeding group and the relative ...contributions of each carer. Existing theoretical work on carer investment rules has, however, largely focused on biparental care, and on modelling offspring provisioning in isolation from other stages of investment. Consequently, there has been little exploration of how maternal investment prior to birth might be expected to influence carer provisioning decisions after birth, and how these should be modified by the number of carers present. In particular, it is unclear whether mothers should increase or decrease their investment in each offspring under favourable rearing conditions, and whether this differs under alternative assumptions about the consequences of being ‘high quality’ at birth. We develop a game-theoretical model of cooperative care that incorporates female control of prebirth investment, and allow increased maternal investment to either substitute for later investment (giving offspring a ‘head start’) or raise the value of later investment (a ‘silver spoon’). We show that mothers reduce prebirth investment under better rearing conditions (more helpers) when investment is substitutable, leading to concealed helper effects. In contrast, when maternal prebirth investment primes offspring to benefit more from postbirth care, mothers should take advantage of good care environments by investing more in offspring both before and after birth. These results provide novel mechanisms to explain contrasting patterns of maternal investment across cooperative breeders.
•We model maternal investment in offspring quality in breeding groups with helpers.•Optimal maternal tactics vary with group size and consequences of investment.•Greater maternal investment can give offspring a ‘head start’ or a ‘silver spoon’.•Mothers providing a ‘silver spoon’ should raise offspring quality in larger groups.•Mothers providing a ‘head start’ should lower offspring quality in larger groups.
Global flood models (GFMs) and earth observation (EO) play a crucial role in characterising flooding, especially in data-sparse, under-resourced regions of the world. However, validation studies are ...often limited to a handful of historic events and do not directly assess the ability of these products to simulate flood hazard-the probability that flooding will occur in a given location. As a result, it is difficult for stakeholders to decipher the ability of either models or observations to identify flood hazard and make decisions to mitigate for flooding. Here, we leverage flood observations from 20 years of MODIS data to compare the recorded flooding with what would be expected given the hazard simulated by a GFM. We devise an approach, Flood Expectation Per Pixel, and apply it across four large basins in Africa-Congo, Niger, Nile and Volta representing a variety of biomes. We estimate the uncertainty of EO to capture flood events due to burned areas, cloud cover and vegetation, incorporating uncertainty estimates when comparing to modelled hazard. We found that at lower return periods (RPs) (<20 years), the EO data records less flooding than the GFM, suggesting GFMs overpredict frequent flooding. For RPs between 50 and 100 years, GFM and EO data show greater consistency given the uncertainties we consider. For large RPs (100 years) the EO observations show more flooding than expected given the GFM data, potentially due to data errors and non-fluvial flooding, however there are too few observations to draw significant conclusions at these RPs. The EO record indicates that the GFM can differentiate between flood RPs. We find EO and GFM complement each other and thus should be used in tandem to inform strategies to mitigate floods across the hazard spectrum from frequent to extreme flood events.
Cluster analysis offers a simple visual exploratory tool for the initial investigation of regional Global Positioning System (GPS) velocity observations, which are providing increasingly precise ...mappings of actively deforming continental lithosphere. The deformation fields from dense regional GPS networks can often be concisely described in terms of relatively coherent blocks bounded by active faults, although the choice of blocks, their number and size, can be subjective and is often guided by the distribution of known faults. To illustrate our method, we apply cluster analysis to GPS velocities from the San Francisco Bay Region, California, to search for spatially coherent patterns of deformation, including evidence of block‐like behavior. The clustering process identifies four robust groupings of velocities that we identify with four crustal blocks. Although the analysis uses no prior geologic information other than the GPS velocities, the cluster/block boundaries track three major faults, both locked and creeping.
Key Points
Cluster analysis helps visualize and organize regional GPS velocity fields
Clustering offers an objective approach for constructing tectonic block models
Cluster analysis finds major faults in the SF Bay region, creeping and locked
We present a transparent and validated
climate-conditioned catastrophe flood model for the UK, that simulates
pluvial, fluvial and coastal flood risks at 1 arcsec spatial resolution
(∼ 20–25 m). ...Hazard layers for 10 different return periods
are produced over the whole UK for historic, 2020, 2030, 2050 and 2070
conditions using the UK Climate Projections 2018 (UKCP18) climate simulations. From these, monetary losses
are computed for five specific global warming levels above pre-industrial
values (0.6, 1.1, 1.8, 2.5 and 3.3 ∘C). The analysis contains a
greater level of detail and nuance compared to previous work, and represents
our current best understanding of the UK's changing flood risk landscape.
Validation against historical national return period flood maps yielded
critical success index values of 0.65 and 0.76 for England and Wales,
respectively, and maximum water levels for the Carlisle 2005 flood were
replicated to a root mean square error (RMSE) of 0.41 m without calibration. This level of skill is similar to local modelling with site-specific data. Expected annual damage in 2020 was GBP 730 million, which compares favourably to the observed
value of GBP 714 million reported by the Association of British Insurers. Previous UK flood loss estimates based on government data are
∼ 3× higher, and lie well outside our modelled loss
distribution, which is plausibly centred on the observations. We estimate
that UK 1 % annual probability flood losses were ∼ 6 %
greater for the average climate conditions of 2020 (∼ 1.1 ∘C of warming) compared to those of 1990 (∼ 0.6 ∘C of warming), and this increase can be kept to around
∼ 8 % if all countries' COP26 2030 carbon emission reduction
pledges and “net zero” commitments are implemented in full. Implementing
only the COP26 pledges increases UK 1 % annual probability flood losses by 23 % above average 1990 values, and potentially 37 % in a “worst case” scenario where carbon reduction targets are missed and climate sensitivity
is high.
Abstract
Dams and reservoirs aid economic development but also create significant negative impacts. Dams fragment rivers and reduce longitudinal connectivity on a network scale. However, dams may ...also alter discharge regimes and flood peaks, consequently reducing floodplain inundation and lateral channel floodplain connectivity, which impacts floodplain associated ecosystems. Strategic planning has emerged as a promising approach to find a balance between dam impacts and benefits. Yet, strategic planning has predominantly focused on longitudinal connectivity due to the difficulty of including the complex interactions between dam design and operations, hydrologic regime alteration, and the hydrodynamic processes controlling downstream flood extent. Here, we present how to reduce conflicts between hydropower development and loss of floodplain inundation extent by jointly optimizing siting and design of many dams in a data scarce basin. We deploy a coupled hydrological—hydraulic simulation model linked to a multiobjective optimization framework to find development options with the least trade-offs between power generation and downstream impacts on floodplains. Our results for the Pungwe Basin in Mozambique indicate that whilst portfolios of many small storage and run-of-river diversion hydropower plants might create less impacts on the downstream floodplains, installation of some large storage dams would be necessary to attain higher levels of hydropower generation.
Animals can gain large benefits from living in groups but must coordinate with their groupmates in order to do so. Social interactions between groupmates drive overall group coordination and are ...influenced by the characteristics of individual group members. In particular, consistent inter-individual differences in behaviour (e.g. boldness) and familiarity between individuals in groups profoundly affect the individual interactions that mediate group coordination. However, the effects of boldness and familiarity have mostly been studied in isolation. Here we describe how familiarity and boldness interact to affect individual performance, leadership, and group coordination in small shoals of three-spined sticklebacks (Gasterosteus aculeatus) solving a novel foraging task. Groups of higher average boldness were less cohesive, but only when group members were familiar with one another. Familiarity affected shy and bold individuals’ foraging performance and leadership tendencies differently depending on group characteristics: the shyest group member experienced declining foraging success and leadership with increased group boldness in familiar groups, but experienced the opposite effect on foraging and no effect on leadership in unfamiliar groups. The boldest group member, in contrast, exhibited the opposite pattern: leading and eating more with increasing group boldness in familiar groups, but eating less with increasing group boldness in unfamiliar groups. These results suggest that both boldness and familiarity are important for establishing group behaviour and coordination, and that consistent inter-individual differences in behaviour may primarily impact group coordination once familiarity has been established.
•-Personality affects group cohesion only when group members are already familiar with one another.•-Familiarity affects shy and bold group members differently.•-Personality seems to impact group coordination primarily when familiarity is established.
Family living is a stepping stone to higher-order social structures including cooperatively breeding groups, but understanding why offspring remain with parents by delaying dispersal remains a ...challenge. One rarely studied aspect of family living is communal huddle roosting, where individuals group together overnight for thermoregulatory and/or anti-predator benefits. Here, we use a PIT-tag detection system to investigate the potential for direct and indirect nepotism in roosting huddles of cooperatively breeding chestnut-crowned babblers (
Pomatostomus ruficeps
) living in extended families with female immigrants. This species habitually roosts communally in single-chambered domed nests; an average of 8.5 (± 4.4 SD) individuals taking ~6 min to enter roost nests roosted together in this study. We found that the order in which individuals settled in the roost was negatively associated with their exit order, and those settling late were more likely to be detected at the nest entrance during the night, suggesting that settlement order influences individual roosting positions. Juveniles entered the roost in mid-rank positions, and their entries were associated with increased activity levels of carers, suggesting direct nepotistic assistance. In addition, immigrant females more often settled in the roosts later than others, suggesting indirect nepotism through exclusion of immigrants from more central roosting positions. This exclusion was not obviously confounded by age or sex. As those settling later are expected to experience reduced thermoregulatory benefits and increased predation risk, our results suggest that direct and indirect nepotistic benefits during communal roosting might offer part of the explanation for family living through delayed dispersal in this species.
Significance statement
Nepotism—preferential treatment towards kin or against non-kin—may lead to individuals benefiting from staying in their natal group rather than dispersing, and so increasing the propensity for family living and the subsequent evolution of cooperative breeding. One possible route through which delayed dispersers might gain nepotistic benefits is in communal roosting huddles, as individuals roosting more centrally are likely to receive greater thermoregulatory and/or predator avoidance benefits. To our knowledge, studies have yet to discover an advantage of natal individuals beyond care received as young during communal roosting. We show that immigrant females settle in the communal roosts later than nutritionally independent natal females and may occupy peripheral positions in roosts of the cooperatively breeding chestnut-crowned babbler (
Pomatostomus ruficeps
) using a remote PIT-tag system. This apparent immigrant disadvantage might be significant in promoting delayed dispersal.
Parental care strategies occupy a continuum from fixed investments that are consistent across contexts to flexible behaviour that largely depends on external social and environmental cues. ...Determining the flexibility of care behaviour is important, as it influences the outcome of investment games between multiple individuals caring for the same brood. We investigated the repeatability of provisioning behaviour and the potential for turn taking among breeders and helpers in a cooperatively breeding bird, the rifleman, Acanthisitta chloris. First, we examined whether nest visit rate is an accurate measure of investment by assessing whether carers consistently bring the same size of food, and whether food size is related to nest visit rate. Our results support the use of visit rate as a valid indicator of parental investment. Next, we calculated the repeatability of visit rate and food size to determine whether these behaviours are fixed individual traits or flexible responses to particular contexts. We found that riflemen were flexible in visit rate, supporting responsive models of care over ‘sealed bids’. Finally, we used runs tests to assess whether individual riflemen alternated visits with other carers, indicative of turn taking. We found little evidence of any such coordination of parental provisioning. We conclude that individual flexibility in parental care appears to arise through factors such as breeding status and brood demand, rather than as a real-time response to social partners.
•We studied offspring care in a cooperatively breeding bird, the rifleman.•Our results support the use of visit rate as a measure of investment.•Carers are flexible, but we found no evidence they negotiate their investment.•Neither sealed bid nor turn-taking models appear to fit this system.
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