Editors' Choice

Science  26 May 2017:
Vol. 356, Issue 6340, pp. 817
  1. Oceans

    Risks of reef erosion

    1. Julia Fahrenkamp-Uppenbrink

    The degradation of coral reefs is deepening their nearshore environments.

    PHOTO: K. K. YATES ET AL. BIOGEOSCIENCES 14, 1739 (2017) © EUROPEAN GEOSCIENCES UNION

    Coral reefs serve as natural barriers that protect coastal regions from storms and erosion, but climate change, ocean acidification, and other stressors from human activities are increasingly causing coral reefs to degrade. Yates et al. report evidence of seafloor erosion in five coral reef ecosystems in the Atlantic, Pacific, and Caribbean. Comparison with historical data shows that over the past few decades, seafloor elevation has decreased by 0.09 to 0.8 m at the study sites—far more than expected on the basis of model predictions. Together with sea level rise from climate change, the seafloor erosion at these sites results in deeper water and puts coastal populations at increased risk.

    Biogeosciences 14, 1739 (2017).

  2. Neurodevelopment

    Roadmaps for building the neonatal brain

    1. Pamela J. Hines

    In the postnatal mammalian brain, neurons continue to be generated and migrate to their home stations. Often, these neuroblasts travel along pathways defined by the blood vessels or the glial cells that surround and support neurons. García-González et al. also find that serotonergic axons establish neuroblast migratory pathways. Knockout of the serotonin receptor in transit-amplifying cells and neuroblasts of mice misguided and slowed migration of the new cells. The postnatal neuroblasts travel along the serotonergic axons and depend on serotonergic signaling to sustain and guide their migration. Similar serotonergic axons also characterize neuroblast migratory pathways in fish, birds, rabbits, nonhuman primates, and humans.

    Neuron 10.1016/j.neuron.2017.04.013 (2017).

  3. Environment and Health

    Burn to run in the U.S.A.

    1. Barbara R. Jasny

    Hotter summers in the future will make Americans more reluctant to exercise.

    PHOTO: ANTONIOGUILLEM/ISTOCKPHOTO

    Our willingness to be physically active in our free time is influenced by weather; common excuses for not exercising are that it is too hot, too cold, or too wet. Obradovich and Fowler analyzed historical meteorological data and exercise surveillance data from the Centers for Disease Control and Prevention, and they developed a model to predict human responses to climate change in the next few decades. The model incorporated variables to compensate for city-specific differences (e.g., infrastructure). It appears that by 2050, climate change might result in physically active person-months increasing by 40, on average, per 1000 individuals. Over the course of this century, Americans could become more physically active in their free time in northern areas of the country, but less active in the summer, especially in southern regions.

    Nat. Hum. Behav. 10.1038/s41562-017-0097 (2017).

  4. Asthma

    The NET effect of viral-triggered asthma

    1. Priscilla N. Kelly

    Infection with rhinovirus is a common cause of allergic asthma. Toussaint et al. studied how the virus triggers inflammation and stimulates an asthmatic attack. Rhinovirus infection causes the release of host double-stranded DNA and the formation of neutrophil extracellular traps (NETs). NETs are structures that capture microorganisms and activate immune cells and inflammatory responses. The authors show that rhinovirus-driven NETs promote the infiltration of inflammatory cells to the airways, causing the clinical features of an allergic response. Treatment with a compound blocking NET formation stopped the asthma from becoming worse.

    Nat. Med. 10.1038/nm.4332 (2017).

  5. Geophysics

    Building a better mantle with BEAMS

    1. Brent Grocholski

    Solid-state convection has operated in the mantle since Earth's formation 4.56 billion years ago. This is difficult to reconcile with evidence for ancient and isolated regions of the mantle, though. Ballmer et al. propose bridgmanite-enriched ancient mantle structures (BEAMS) as a solution to this riddle. BEAMS have a low Mg/Si ratio, and their presence would cause a relative increase in the mantle mineral bridgmanite, along with a 20-fold viscosity increase. BEAMS may square many odd features in the lower mantle with the geochemical signatures of ancient, isolated, and persistent mantle regions.

    Nat. Geosci. 10.1038/NGEO2898 (2017).

  6. Infectious Disease

    PPR a risk to Europe

    1. Caroline Ash

    Imagine the shock if your flock of sheep dropped dead, foaming at the mouth. This is a classic symptom of acute infection with peste de petits ruminants (PPR), a morbillivirus resembling the now eradicated rinderpest, which causes up to 80% mortality in small livestock. There are robust vaccines, but they are not deployed systematically, although PPR has been earmarked by the United Nations Food and Agriculture Organization for eradication by 2030. Baazizi et al. confirm that an East African strain of PPR virus is circulating in northern Algeria, Tunisia, and Morocco. This strain probably originated from an outbreak in Sudan in 2000 but has crossed the Sahara as a result of porous borders and high levels of illegal trade. The threat to Europe comes from two fronts because PPR virus is also present in western Turkey. Among other mammals, cervids are susceptible to the virus, which puts northern Europe at particular risk, owing to the high deer populations in this region.

    PLOS ONE 10.1371/journal.pone.0175461 (2017).

  7. Molecular Materials

    Perovskite ferroelectric bond-switching

    1. Phil Szuromi

    Ferroelectric materials are normally inorganic ceramics, such as barium titanate, but for flexible devices, molecular ferroelectrics that could readily form thin films are of interest. Xu et al. report that substitution of organic cations for potassium in an iron cyanide perovskite—[(CH3)3NOH]2[KFe(CN)6]—creates a ferroelectric with a high Curie temperature (402 K), where it undergoes a phase transition through a bond-switching mechanism from a low-temperature monoclinic ferroelectric phase (space group Cc) to a high-temperature cubic paraelectric phase (Fm3̄m). Thin films of this material showed rectangular polarization–electric field hysteresis loops at a relatively high driving frequency of 5 kHz and could be reversibly poled with the bias field from a probe tip.

    J. Am. Chem. Soc. 10.1021/jacs.7b01334 (2017).