Volume 525 Issue 7568, 10 September 2015

A three-dimensional representation of a world of trees� based on a new map of global tree density. Features and countries you can see have trees, the others (like the Sahara) have virtually none. Until now, our understanding of global forest ecosystems has been generated from satellite information that can tell us about the area of forest. Policy makers and environmental scientists have relied heavily on this information when considering trees� involvement in patterns of biodiversity, biogeochemical cycles and their contribution to ecosystem services. Thomas Crowther et al. have extended the scope of this information by generating a map of global tree density that reveals what is going on below the canopy. The map, which was generated using more than 400,000 ground-sourced measurements of tree density, reveals patterns in tree numbers at regional and global scales. Using this map, the authors are able to estimate that the current global tree number stands at approximately 3 trillion. Cover art: Jan Willem Tulp using Processing (http://processing.org/)

Editorial

  • Editorial |

    The plight of a record number of refugees is something the West cannot ignore. Humanitarian values should be upheld, and people fleeing war and persecution must be offered protection. 

  • Editorial |

    It is not how much people have, it is how much we know they have that stokes inequality.

  • Editorial |

    There can be more to a question than appears at first sight.

World View

Research Highlights

Social Selection

Seven Days

News

News Feature

Comment

  • Comment |

    Cities need to understand and manage their carbon footprint at the level of streets, buildings and communities, urge Kevin Robert Gurney and colleagues.

    • Kevin Robert Gurney
    • , Paty Romero-Lankao
    • , Karen C. Seto
    • , Lucy R. Hutyra
    • , Riley Duren
    • , Christopher Kennedy
    • , Nancy B. Grimm
    • , James R. Ehleringer
    • , Peter Marcotullio
    • , Sara Hughes
    • , Stephanie Pincetl
    • , Mikhail V. Chester
    • , Daniel M. Runfola
    • , Johannes J. Feddema
    •  & Joshua Sperling

Books & Arts

  • Books & Arts |

    Nathaniel Comfort takes issue with the second instalment of the evolutionary biologist's autobiography.

    • Nathaniel Comfort
  • Books & Arts |

    Barbara Kiser reviews five of the week's best science picks.

    • Barbara Kiser
  • Books & Arts |

    Cartoonist and former robotics researcher Jorge Cham wowed graduate students with The PhD Movie in 2011. With the follow-up The PhD Movie 2: Still in Grad School — an astute, funny look at more academic tribulations — set to screen at campuses worldwide from the end of September, Cham talks about crowdfunding, the grim scrabble for grants, the under-representation of women in science and coaxing a cameo from a Nobel laureate.

    • Zoë Corbyn

Correspondence

Obituary

News & Views

  • News & Views |

    An analysis of energy markets with prices that vary according to demand finds that this market design unexpectedly serves to amplify, rather than dampen, fluctuations in power use.

    • Alex Pentland
  • News & Views |

    Two studies find that a lipid-exchange cycle mediates the enrichment of the lipid phosphatidylserine in the cell membrane compared with the membrane of an organelle called the endoplasmic reticulum, where the lipid is produced.

    • Anant K. Menon
    •  & Tim P. Levine
  • News & Views |

    People who died of the neurodegenerative condition Creutzfeldt-Jakob disease after treatment with cadaver-derived human growth hormone also developed some of the pathological traits of Alzheimer's disease. See Letter p.247

    • Mathias Jucker
    •  & Lary C. Walker
  • News & Views |

    Ice clouds in marine regions at high latitudes might form in warmer and drier air than was previously believed because of freezing induced by airborne particles that contain organic materials from ocean surface waters. See Letter p.234

    • Lynn M. Russell
  • News & Views |

    The first well-resolved images of local-galaxy stellar nurseries that are poor in elements heavier than helium give the best picture yet of the conditions in which stars may have formed in the early Universe. See Letter p.218

    • Adam Leroy
  • News & Views |

    The development of an algorithm called RaceID enables the identification of rare cell types by single-cell RNA sequencing, even when they are part of a complex mixture of similar cells. See Letter p.251

    • Lu Wen
    •  & Fuchou Tang
  • News & Views |

    An in silico, three-dimensional model of tumour evolution suggests that cell motility is a key factor in the initial growth of a tumour mass. The model also reveals the dynamics of mutation spread. See Letter p.261

    • Natalia L. Komarova
  • News & Views |

    The finding that genes encoding enzymes that modify histone proteins are among the targets of certain mutant forms of the p53 protein sheds light on how these mutations cause cancer beyond p53 inactivation. See Article p.206

    • Carol Prives
    •  & Scott W. Lowe

Article

  • Article |

    Ground-sourced tree density data is assembled to provide a global map of tree density, which reveals that there are three trillion trees (tenfold more than previous estimates); tree numbers have declined by nearly half since the start of human civilization and over 15 billion trees are lost on an annual basis.

    • T. W. Crowther
    • , H. B. Glick
    • , K. R. Covey
    • , C. Bettigole
    • , D. S. Maynard
    • , S. M. Thomas
    • , J. R. Smith
    • , G. Hintler
    • , M. C. Duguid
    • , G. Amatulli
    • , M.-N. Tuanmu
    • , W. Jetz
    • , C. Salas
    • , C. Stam
    • , D. Piotto
    • , R. Tavani
    • , S. Green
    • , G. Bruce
    • , S. J. Williams
    • , S. K. Wiser
    • , M. O. Huber
    • , G. M. Hengeveld
    • , G.-J. Nabuurs
    • , E. Tikhonova
    • , P. Borchardt
    • , C.-F. Li
    • , L. W. Powrie
    • , M. Fischer
    • , A. Hemp
    • , J. Homeier
    • , P. Cho
    • , A. C. Vibrans
    • , P. M. Umunay
    • , S. L. Piao
    • , C. W. Rowe
    • , M. S. Ashton
    • , P. R. Crane
    •  & M. A. Bradford
  • Article |

    A ChIP-seq analysis of the DNA-binding properties of mutant gain-of-function p53 protein compared to wild-type p53 reveals the gain-of-function proteins bind to and activate a distinct set of genes including chromatin modifying enzymes such as the histone methyltransferase MLL; small molecular inhibitors of MLL function may represent a new target for cancers with mutant p53.

    • Jiajun Zhu
    • , Morgan A. Sammons
    • , Greg Donahue
    • , Zhixun Dou
    • , Masoud Vedadi
    • , Matthäus Getlik
    • , Dalia Barsyte-Lovejoy
    • , Rima Al-awar
    • , Bryson W. Katona
    • , Ali Shilatifard
    • , Jing Huang
    • , Xianxin Hua
    • , Cheryl H. Arrowsmith
    •  & Shelley L. Berger

Letter

  • Letter |

    To understand the birth of stars, observations of the clouds in which they form are key; here, interferometric observations are reported of carbon monoxide clouds in the galaxy WLM, which has a metallicity that is 13 per cent of the value of our Sun.

    • Monica Rubio
    • , Bruce G. Elmegreen
    • , Deidre A. Hunter
    • , Elias Brinks
    • , Juan R. Cortés
    •  & Phil Cigan
  • Letter |

    Measurements of a steady emission of single photons from a quantum dot demonstrate that the fluctuations of the electric field can periodically be 3% below the fundamental quantum limit and confirm the long-standing prediction that the quantum state of single photons can be squeezed.

    • Carsten H. H. Schulte
    • , Jack Hansom
    • , Alex E. Jones
    • , Clemens Matthiesen
    • , Claire Le Gall
    •  & Mete Atatüre
  • Letter |

    Subtle anomalies in how the structure of metallic osmium evolves with pressure are detected using powder X-ray diffraction measurements at ultra-high static pressures; the anomaly at 440 gigapascals is attributed to an electronic transition caused by pressure-induced interactions between core electrons.

    • L. Dubrovinsky
    • , N. Dubrovinskaia
    • , E. Bykova
    • , M. Bykov
    • , V. Prakapenka
    • , C. Prescher
    • , K. Glazyrin
    • , H.-P. Liermann
    • , M. Hanfland
    • , M. Ekholm
    • , Q. Feng
    • , L. V. Pourovskii
    • , M. I. Katsnelson
    • , J. M. Wills
    •  & I. A. Abrikosov
  • Letter |

    Computational protein design is used to create a protein–DNA co-assembling nanomaterial; by varying the arrangement of protein-binding sites on the double-stranded DNA, a ‘nanowire’ with single-molecule width can be spontaneously formed by mixing the protein and double-stranded DNA building blocks.

    • Yun Mou
    • , Jiun-Yann Yu
    • , Timothy M. Wannier
    • , Chin-Lin Guo
    •  & Stephen L. Mayo
  • Letter |

    The presence of ice in clouds can influence cloud lifetime, precipitation and radiative properties; here, organic material at the sea–air interface, possibly associated with phytoplankton cell exudates, is shown to nucleate ice under conditions relevant for ice cloud formation in the atmospheric environment.

    • Theodore W. Wilson
    • , Luis A. Ladino
    • , Peter A. Alpert
    • , Mark N. Breckels
    • , Ian M. Brooks
    • , Jo Browse
    • , Susannah M. Burrows
    • , Kenneth S. Carslaw
    • , J. Alex Huffman
    • , Christopher Judd
    • , Wendy P. Kilthau
    • , Ryan H. Mason
    • , Gordon McFiggans
    • , Lisa A. Miller
    • , Juan J. Nájera
    • , Elena Polishchuk
    • , Stuart Rae
    • , Corinne L. Schiller
    • , Meng Si
    • , Jesús Vergara Temprado
    • , Thomas F. Whale
    • , Jenny P. S. Wong
    • , Oliver Wurl
    • , Jacqueline D. Yakobi-Hancock
    • , Jonathan P. D. Abbatt
    • , Josephine Y. Aller
    • , Allan K. Bertram
    • , Daniel A. Knopf
    •  & Benjamin J. Murray
  • Letter |

    Computed tomography and phylogenetic analysis of the Eunotosaurus africanus skull suggests that not only is Eunotosaurus an early relative of the group that eventually evolved into turtles, but that it is also a diapsid caught in the act of evolving towards a secondarily anapsid state.

    • G. S. Bever
    • , Tyler R. Lyson
    • , Daniel J. Field
    •  & Bhart-Anjan S. Bhullar
  • Letter |

    Treatment of children with human cadaver-derived growth hormone (c-hGH) contaminated with prions resulted in transmission of Creutzfeldt–Jakob disease (CJD); unexpectedly, in an autopsy study of eight such iCJD patients, the authors found amyloid-β deposition in the grey matter typical of that seen in Alzheimer's disease and amyloid-β in the blood vessel walls characteristic of cerebral amyloid angiopathy, consistent with iatrogenic transmission of amyloid-β pathology in addition to CJD and suggests that healthy c-hGH-exposed individuals may also be at risk of Alzheimer's disease and cerebral amyloid angiopathy.

    • Zane Jaunmuktane
    • , Simon Mead
    • , Matthew Ellis
    • , Jonathan D. F. Wadsworth
    • , Andrew J. Nicoll
    • , Joanna Kenny
    • , Francesca Launchbury
    • , Jacqueline Linehan
    • , Angela Richard-Loendt
    • , A. Sarah Walker
    • , Peter Rudge
    • , John Collinge
    •  & Sebastian Brandner
  • Letter |

    An algorithm that allows rare cell type identification in a complex population of single cells, based on single-cell mRNA-sequencing, is applied to mouse intestinal cells, revealing novel subtypes of enteroendocrine cells and showing that the Lgr5-expressing population consists of a homogenous stem cell population with a few rare secretory cells, including Paneth cells.

    • Dominic Grün
    • , Anna Lyubimova
    • , Lennart Kester
    • , Kay Wiebrands
    • , Onur Basak
    • , Nobuo Sasaki
    • , Hans Clevers
    •  & Alexander van Oudenaarden
  • Letter |

    This study finds that the epithelial-to-mesenchymal (EMT) transition program, which is common to both mammary gland reconstituting stem cells and mammary tumour-initiating cells, is differentially regulated by two distinct EMT factors, Slug and Snail; the findings illustrate that although they appear similar, normal tissue stem cells and tumour-initiating cells are controlled by distinct regulatory processes.

    • Xin Ye
    • , Wai Leong Tam
    • , Tsukasa Shibue
    • , Yasemin Kaygusuz
    • , Ferenc Reinhardt
    • , Elinor Ng Eaton
    •  & Robert A. Weinberg
  • Letter |

    A new model of tumour evolution is presented to explain how short-range migration and cell turnover within the tumour can provide the basic environment of rapid cell mixing, allowing even a small selective advantage to dominate the mass within relevant time frames.

    • Bartlomiej Waclaw
    • , Ivana Bozic
    • , Meredith E. Pittman
    • , Ralph H. Hruban
    • , Bert Vogelstein
    •  & Martin A. Nowak
  • Letter |

    Insights derived from the crystal structures of the extracellular domain of PSKR, the receptor for the plant hormone phytosulfokine (PSK) that affects plant growth and development, reveal that PSK interacts with PSKR and enhances PSKR interaction with its co-receptor SERK allosterically.

    • Jizong Wang
    • , Hongju Li
    • , Zhifu Han
    • , Heqiao Zhang
    • , Tong Wang
    • , Guangzhong Lin
    • , Junbiao Chang
    • , Weicai Yang
    •  & Jijie Chai
  • Letter |

    Structural view of a dynamic molecular switch mechanism that governs repression and activation of the jasmonate plant hormone pathway.

    • Feng Zhang
    • , Jian Yao
    • , Jiyuan Ke
    • , Li Zhang
    • , Vinh Q. Lam
    • , Xiu-Fang Xin
    • , X. Edward Zhou
    • , Jian Chen
    • , Joseph Brunzelle
    • , Patrick R. Griffin
    • , Mingguo Zhou
    • , H. Eric Xu
    • , Karsten Melcher
    •  & Sheng Yang He
  • Letter |

    A single-molecule optical tweezer assay is developed to monitor transcription initiation in eukaryotic RNA polymerase II in real-time, making use of a highly purified preinitiation complex (PIC) from yeast; observations show that a large bubble is opened up in the DNA template during initiation, driven by the TFIIH helicase that forms part of the PIC, along with synthesis of an extended transcript before the transition from transcription initiation into elongation.

    • Furqan M. Fazal
    • , Cong A. Meng
    • , Kenji Murakami
    • , Roger D. Kornberg
    •  & Steven M. Block

Corrigendum

Feature

  • Feature |

    As institutions attempt to redefine the postdoctoral position, early-career researchers are joining together to wage a battle for proper benefits.

    • Helen Shen

Q&A

  • Q&A |

    A funds manager explains how his physics PhD helped him to transition into the world of finance and investments.

    • Julie Gould

Futures

  • Futures |

    Standard United Galactic Treaty Dictionary, 2nd edn, Caelum Univ. Press (11 June 2287).

    • Felicia Davin
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