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EXPLORER, APRIL 2021 (AD) DIGITAL CREDITS: COVER: © YASHPAL RATHORE/NATUREPL.COM. TABLE OF CONTENTS: (BACKGROUND) PRIMEIMAGES/E+/GETTY IMAGES; (ELEPHANT) WILLIAM PERSSON; (STONE) ED DARACK; (LAKE) ROLF HICKER PHOTOGRAPHY/ALAMY STOCK PHOTO. CURING WHAT AILS YOU: (LEAF DESIGN ELEMENTS) VIKIVECTOR/SHUTTERSTOCK; (ELEPHANTS OUTSIDE) HEMIS/ALAMY STOCK PHOTO; (ELEPHANTS EATING UNDER ROOF) ATTILA KLEB/ALAMY STOCK PHOTO; (SPIKY PLANT) THEWET/ISTOCK/GETTY IMAGES PLUS; (ELEPHANTS LOGGING) DANITA DELIMONT/ALAMY STOCK PHOTO; (MAPS) MAPPING SPECIALISTS, LTD; (SINGLE ELEPHANT EATING) KISZON PASCAL/MOMENT/GETTY IMAGES; (ALL OTHER IMAGES) WILLIAM PERSSON. NATURE’S MYSTERIES: (STONE) ED DARACK; (MAPS/GLOBES) LEONELLO CALVETTI/SHUTTERSTOCK; (CIRCLES IN SAND) LEE FROST/GETTY IMAGES; CIRCLE CLOSE UP) CHRIS AND SALLY GABLE/AGE FOTOSTOCK; (NORBERT JUERGENS) DETLEV KALDINSKI; (SAND TERMITES) CHROMORANGE/MARTINA RAEDLEIN/ALAMY STOCK PHOTO; (TERMITE SPOTS AERIAL) MARTIN HARVEY/THE IMAGE BANK/GETTY IMAGES; (PUFFERFISH CIRCLE PHOTO & YOJI OKATA PORTRAIT) © YOJI OKATA/NATURE PRODUCTION/MINDEN PICTURES; (PUFFERFISH VIDEOS BOTH) BBC NATURAL HISTORY/BBC CREATIVE/GETTY IMAGES; (SAILING STONE) MICHA PAWLITZKI/GETTY IMAGES; (MAN IN DEATH VALLEY) OSCITY/SHUTTERSTOCK; (DEATH VALLEY VIDEO) PRO_STUDIO/SHUTTERSTOCK; (RALPH LORENZ) RALPH LORENZ; (STONE BACKGROUND) ANTON SOROKIN/ALAMY STOCK PHOTO. LAKE TOUR: (BACKGROUND) ROLF HICKER PHOTOGRAPHY/ALAMY STOCK PHOTO; (TOP CENTER) PAUL & PAVEENA MCKENZIE/OXFORD SCIENTIFIC/GETTY IMAGES; (BOTTOM CENTER) PHOTOGRAPHY BY BYRON TANAPHOL PRUKSTON/MOMENT/GETTY IMAGES; (BOTTOM LEFT) MICHAEL WHEATLY/ALAMY STOCK PHOTO; (UPPER RIGHT) © PETER VERHOOG/BUITEN-BEELD/MINDEN PICTURES; (SPOTTED LAKE) GUNTER MARX PHOTOGRAPHY/CORBIS DOCUMENTARY/GETTY IMAGES; (LAKE NATRON) © GERRY ELLIS/MINDEN PICTURES; (FLAMINGOS) DAVID TIPLING PHOTO LIBRARY/ALAMY STOCK PHOTO; (LAKE BAIKAL) © OLGA KAMENSKAYA/NATUREPL.COM; (SEAL) GERALD NOWAK/IMAGE BROKER/GETTY IMAGES; (DIVER) MICHELE WESTMORLAND/NATUREPL.COM; (JELLYFISH CLOSE UP) © PETER VERHOOG/BUITEN-BEELD/MINDEN PICTURES; (BOILING LAKE VIDEO) LADRONES/POND 5; (BOILING LAKE IMAGE) GEORGE H.H. HUEY/ALAMY STOCK PHOTO; (GREENLAND) JASON EDWARDS/NATIONAL GEOGRAPHIC IMAGE COLLECTION; (GREENLAND VIDEO) SEAN GALLUP/GETTY IMAGES EDITORIAL FOOTAGE/GETTY IMAGES. THE END PHOTO: JMWSCOUT/ISTOCK/GETTY IMAGES PLUS.