An unexpectedly large count of trees in the West African Sahara and Sahel.

Autor: Brandt M; Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark. mabr@ign.ku.dk.; Science Systems and Applications Inc., NASA Goddard Space Flight Center, Greenbelt, MD, USA. mabr@ign.ku.dk., Tucker CJ; NASA Goddard Space Flight Center, Greenbelt, MD, USA. compton.j.tucker@nasa.gov., Kariryaa A; Science Systems and Applications Inc., NASA Goddard Space Flight Center, Greenbelt, MD, USA.; HCI Group, University of Bremen, Bremen, Germany., Rasmussen K; Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark., Abel C; Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark., Small J; Science Systems and Applications Inc., NASA Goddard Space Flight Center, Greenbelt, MD, USA.; NASA Goddard Space Flight Center, Greenbelt, MD, USA., Chave J; Laboratoire Evolution and Diversité Biologique, CNRS, UPS, IRD, Université Paul Sabatier, Toulouse, France., Rasmussen LV; Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark., Hiernaux P; Science Systems and Applications Inc., NASA Goddard Space Flight Center, Greenbelt, MD, USA.; Pastoralisme Conseil, Caylus, France., Diouf AA; Centre de Suivi Ecologique, Dakar, Senegal., Kergoat L; Geosciences Environnement Toulouse (GET), Observatoire Midi-Pyrénées, UMR 5563 (CNRS/UPS/IRD/CNES), Toulouse, France., Mertz O; Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark., Igel C; Department of Computer Science (DIKU), University of Copenhagen, Copenhagen, Denmark., Gieseke F; Department of Computer Science (DIKU), University of Copenhagen, Copenhagen, Denmark.; Department of Information Systems, University of Műnster, Műnster, Germany., Schöning J; HCI Group, University of Bremen, Bremen, Germany., Li S; Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark., Melocik K; Science Systems and Applications Inc., NASA Goddard Space Flight Center, Greenbelt, MD, USA.; NASA Goddard Space Flight Center, Greenbelt, MD, USA., Meyer J; Science Systems and Applications Inc., NASA Goddard Space Flight Center, Greenbelt, MD, USA.; NASA Goddard Space Flight Center, Greenbelt, MD, USA., Sinno S; Science Systems and Applications Inc., NASA Goddard Space Flight Center, Greenbelt, MD, USA.; NASA Goddard Space Flight Center, Greenbelt, MD, USA., Romero E; Science Systems and Applications Inc., NASA Goddard Space Flight Center, Greenbelt, MD, USA.; NASA Goddard Space Flight Center, Greenbelt, MD, USA., Glennie E; Science Systems and Applications Inc., NASA Goddard Space Flight Center, Greenbelt, MD, USA.; NASA Goddard Space Flight Center, Greenbelt, MD, USA., Montagu A; Département de Géosciences, Ecole Normale Supérieure, Paris, France., Dendoncker M; Earth and Life Institute, Environmental Sciences, Université Catholique de Louvain, Louvain-la-Neuve, Belgium., Fensholt R; Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark.
Jazyk: angličtina
Zdroj: Nature [Nature] 2020 Nov; Vol. 587 (7832), pp. 78-82. Date of Electronic Publication: 2020 Oct 14.
DOI: 10.1038/s41586-020-2824-5
Abstrakt: A large proportion of dryland trees and shrubs (hereafter referred to collectively as trees) grow in isolation, without canopy closure. These non-forest trees have a crucial role in biodiversity, and provide ecosystem services such as carbon storage, food resources and shelter for humans and animals 1,2 . However, most public interest relating to trees is devoted to forests, and trees outside of forests are not well-documented 3 . Here we map the crown size of each tree more than 3 m 2 in size over a land area that spans 1.3 million km 2 in the West African Sahara, Sahel and sub-humid zone, using submetre-resolution satellite imagery and deep learning 4 . We detected over 1.8 billion individual trees (13.4 trees per hectare), with a median crown size of 12 m 2 , along a rainfall gradient from 0 to 1,000 mm per year. The canopy cover increases from 0.1% (0.7 trees per hectare) in hyper-arid areas, through 1.6% (9.9 trees per hectare) in arid and 5.6% (30.1 trees per hectare) in semi-arid zones, to 13.3% (47 trees per hectare) in sub-humid areas. Although the overall canopy cover is low, the relatively high density of isolated trees challenges prevailing narratives about dryland desertification 5-7 , and even the desert shows a surprisingly high tree density. Our assessment suggests a way to monitor trees outside of forests globally, and to explore their role in mitigating degradation, climate change and poverty.
Databáze: MEDLINE
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