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This is my continent
A young narrator learns about continents! This book explores what a continent is, looks at differences in geographical features and climates, and provides examples of different cultures.
Book
Cold winter extremes in northern continents linked to Arctic sea ice loss
The satellite record since 1979 shows downward trends in Arctic sea ice extent in all months, which are smallest in winter and largest in September. Previous studies have linked changes in winter atmospheric circulation, anomalously cold extremes and large snowfalls in mid-latitudes to rapid decline of Arctic sea ice in the preceding autumn. Using observational analyses, we show that the winter atmospheric circulation change and cold extremes are also associated with winter sea ice reduction through an apparently distinct mechanism from those related to autumn sea ice loss. Associated with winter sea ice reduction, a high-pressure anomaly prevails over the subarctic, which in part results from fewer cyclones owing to a weakened gradient in sea surface temperature and lower baroclinicity over sparse sea ice. The results suggest that the winter atmospheric circulation at high northern latitudes associated with Arctic sea ice loss, especially in the winter, favors the occurrence of cold winter extremes at middle latitudes of the northern continents.
Journal Article
Earth's continents
\"This book presents a focused, clear, age-appropriate look at Earth's continents [for] young readers\"--Amazon.com.
Book
A global atlas of the dominant bacteria found in soil
Soil bacteria play key roles in regulating terrestrial carbon dynamics, nutrient cycles, and plant productivity. However, the natural histories and distributions of these organisms remain largely undocumented. Delgado-Baquerizo et al. provide a survey of the dominant bacterial taxa found around the world. In soil collections from six continents, they found that only 2% of bacterial taxa account for nearly half of the soil bacterial communities across the globe. These dominant taxa could be clustered into ecological groups of co-occurring bacteria that share habitat preferences. The findings will allow for a more predictive understanding of soil bacterial diversity and distribution. Science , this issue p. 320 Relatively few soil bacterial taxa dominate terrestrial ecosystems worldwide, with predictable distributions and ecology. The immense diversity of soil bacterial communities has stymied efforts to characterize individual taxa and document their global distributions. We analyzed soils from 237 locations across six continents and found that only 2% of bacterial phylotypes (~500 phylotypes) consistently accounted for almost half of the soil bacterial communities worldwide. Despite the overwhelming diversity of bacterial communities, relatively few bacterial taxa are abundant in soils globally. We clustered these dominant taxa into ecological groups to build the first global atlas of soil bacterial taxa. Our study narrows down the immense number of bacterial taxa to a “most wanted” list that will be fruitful targets for genomic and cultivation-based efforts aimed at improving our understanding of soil microbes and their contributions to ecosystem functioning.
Journal Article
Climate change contributes to widespread declines among bumble bees across continents
Climate change could increase species’ extinction risk as temperatures and precipitation begin to exceed species’ historically observed tolerances. Using long-term data for 66 bumble bee species across North America and Europe, we tested whether this mechanism altered likelihoods of bumble bee species’ extinction or colonization. Increasing frequency of hotter temperatures predicts species’ local extinction risk, chances of colonizing a new area, and changing species richness. Effects are independent of changing land uses. The method developed in this study permits spatially explicit predictions of climate change–related population extinction-colonization dynamics within species that explains observed patterns of geographical range loss and expansion across continents. Increasing frequencies of temperatures that exceed historically observed tolerances help explain widespread bumble bee species decline. This mechanism may also contribute to biodiversity loss more generally.
Journal Article
Water‐Induced Mantle Overturns Leading to the Origins of Archean Continents and Subcontinental Lithospheric Mantle
The origins of Archean continents and subcontinental lithospheric mantle (SCLM) were important events in the early Earth. The mechanisms for the origins of Archean continents and the SCLM remain unclear. This study suggests that these events were controlled by the evolution of the hydrous magma ocean (MO). With solidification, the basal MO eventually became gravitationally unstable because of the enrichment of water. The triggered massive mantle overturns resulted in the major pulses of the crust and thick SCLM generations. The model avoids a fatal drawback of the oceanic plateau model for the origin of continents: the source of H2O needed for the formation of tonalite‐trondhjemite‐granodiorite (TTG). The model can also account for why the TTG and thick SCLM basically occurred in the Archean. Plain Language Summary Among the inner solar system planets, the Earth is the only planet that has continental crust, plate tectonics, and life. The formation of Archean continents, which should play a crucial role in the initiation of plate tectonics and the evolution of life, remains hotly debated. In this study, we show that water in the basal magma ocean plays a fundamental role in the formation of Archean continents. With progressive crystallization, the basal magma ocean becomes increasingly enriched in water because the major lower‐mantle minerals have limited water storage capacity. The basal magma ocean eventually becomes gravitationally unstable because of the enrichment of water and generates mantle overturns. The mantle overturns transported a large amount of water upward to the shallow part of the Earth and controlled the formation of the continental crust and can account for many observations including the source of H2O needed for generation of the continental crust and the major pulse of crustal growth around the end of the Archean. Key Points Water in the basal magma ocean plays a fundamental role in the formation of Archean continents and subcontinental lithospheric mantle The basal magma ocean eventually became gravitationally unstable and generated the mantle overturns because of the enrichment of water The water‐induced mantle overturns resulted in the major pulses of the thick subcontinental lithospheric mantle and continental crust generations in the Neoarchean
Journal Article
The influence of human disturbance on wildlife nocturnality
As the human population grows, there are fewer places for animals to live out their lives independently of our influence. Given our mostly diurnal tendencies, one domain that remains less affected by humans is the night. Gaynor et al. found that across the globe and across mammalian species—from deer to coyotes and from tigers to wild boar—animals are becoming more nocturnal (see the Perspective by Benítez-López). Human activities of all kinds, including nonlethal pastimes such as hiking, seem to drive animals to make use of hours when we are not around. Such changes may provide some relief, but they may also have ecosystem-level consequences. Science , this issue p. 1232 ; see also p. 1185 Human activities are pushing animals towards a more nocturnal existence. Rapid expansion of human activity has driven well-documented shifts in the spatial distribution of wildlife, but the cumulative effect of human disturbance on the temporal dynamics of animals has not been quantified. We examined anthropogenic effects on mammal diel activity patterns, conducting a meta-analysis of 76 studies of 62 species from six continents. Our global study revealed a strong effect of humans on daily patterns of wildlife activity. Animals increased their nocturnality by an average factor of 1.36 in response to human disturbance. This finding was consistent across continents, habitats, taxa, and human activities. As the global human footprint expands, temporal avoidance of humans may facilitate human-wildlife coexistence. However, such responses can result in marked shifts away from natural patterns of activity, with consequences for fitness, population persistence, community interactions, and evolution.
Journal Article