Entrants in this year’s contest were invited to submit images that showcase Earth’s biodiversity and show some of the mounting threats to the natural world. These images originally appeared on bioGraphic, an online magazine about science and sustainability and the official media sponsor for the California Academy of Sciences’ BigPicture Natural World Photography Competition. The organizers were kind enough to share some of the winners and finalists here, selected from nearly 6,500 entries. The captions were written by the bioGraphic editorial staff, and lightly edited for style.

Daniel Dietrich / BigPicture Photography Competition

Boneyard Waltz: Terrestrial Wildlife Finalist. A trio of polar bears lumbers past a forbidding pile of whale bones along the coast of Barter Island in northern Alaska, their bloodstained noses hinting at a recent, fresher meal. As top predators, polar bears rule the Arctic ecosystem and are typically solitary hunters, except when learning from Mom, like the siblings pictured here. Eventually, the cubs will venture out on their own to patrol the nearby Arctic National Wildlife Refuge, a wilderness area encompassing more than 30,000 square miles. But these epic hunting grounds may not stay pristine forever: The region holds an estimated 7.7 billion barrels of recoverable oil. Moreover, climate change is forcing the bears to travel much longer distances in search of food. For this trio, however, there’s a more imminent threat. The smallest in the trio turns to catch a glimpse of a large male following the group before all three slip into the still chilly, though warming, waters of the Beaufort Sea. 

Jinggong Zhang / BigPicture Photography Competition

Bohemian Skirt: Aquatic Life Finalist. Looking lavish and looming large are key survival strategies for this female palmate octopus. While males of the species are dwarves, measuring only about 15 millimeters (less than an inch) in length, fully grown females often stretch up to 2 meters (6.6 feet), trailing eye-catching membranes from two of their elongated arms as they cruise the open ocean. When threatened, a female will extend her skirtlike membrane and wave it like a billowing banner. This dramatic display increases the size of her silhouette and is often enough to deter predators. In the face of a fiercely determined attacker, however, the octopus can quickly detach parts of her membrane along visible “fracture” lines and send a distracting chunk spiraling through the water like a bullfighter’s cape, giving her time to make her escape. 

James Gifford / BigPicture Photography Competition

The Human Touch: Human/Nature Winner. It’s no exaggeration to say that André Bauma, the head caretaker at the Senkwekwe Center for orphaned gorillas in Virunga National Park, risks his life daily for the animals in his care. In recent decades, more than 170 rangers have been killed in the park, and the Senkwekwe Center has been overrun by rebels on multiple occasions. Even in these moments, Bauma has never abandoned the center’s gorillas. "Gorilla caretakers with those gorilla orphans? We are the same family," he says. "They know we are their mums." 

Buddy Eleazer / BigPicture Photography Competition

Traveling to the Edge: Terrestrial Wildlife Finalist. In the Namib-Naukluft Desert of Namibia, a gemsbok sends a spray of fine sand cascading down the sheer flank of a rust-red dune. Although the ascent is strenuous and the sun blazing hot, relief awaits at the top. Along the ridge line, the antelope will find a cool, moist inland breeze blowing in from the nearby Atlantic Ocean. By simply inhaling this cooler air through its convoluted nasal passages, the animal is able to reduce the temperature of the blood destined for its brain, helping the desert dweller avoid overheating in this otherwise relentless environment.

Armand Sarlangue / BigPicture Photography Competition

Duality: Landscapes, Waterscapes, and Flora Winner. Although it’s not the country’s best-known destination, Norway’s Senja Island is quickly growing in popularity. One mountain in particular is largely responsible for that fame. Towering nearly 650 meters (2,100 feet) above the sea, Segla is a peak that epitomizes the ruggedness and wildness of northern Norway. Here, reindeer still roam the tundra while humpback whales, orcas, and sea eagles pursue herring along narrow fjords. Until recently, these ecosystems, which provide sustenance and a haven for wildlife as well as livelihoods for many Norwegians, were at risk from a fossil-fuel industry seeking another kind of bounty. Then, in April of this year, Norway’s Labour Party, the country’s parliamentary majority, surprised many by committing to permanently protect Senja and nearby islands and waterways in the Norwegian Arctic from oil drilling and exploration—a move that promises to keep these wild places wild for generations to come. 

Julie Fletcher / BigPicture Photography Competition

Resilience: Terrestrial Wildlife Finalist. In 2018, Australia experienced its third-hottest year on record—temperatures that, coupled with historic droughts, created prime conditions for bushfires. For slow-moving koalas, the odds of surviving fast-burning blazes like these are slim. Which made photographer Julie Fletcher’s discovery on this day all the more surprising. Having set out to document the desolate, fire-ravaged forests on Kangaroo Island off South Australia, Fletcher watched as the determined koala, its fur tinged burnt sienna, climbed a tree and began to munch charred, crispy leaves. "He was watching me the whole time," she says, "with an intensity that told the story." 

Audun Rikardsen / BigPicture Photography Competition

Taking Center Stage: Grand Prize Winner. While the beauty of Norway’s spectacular northern coastline might be lost on this male black grouse, the prime vantage point offered by its perch is certainly not. For a ground-dwelling bird known for exuberant territorial displays during the breeding season, what better place to see and be seen than this branch, which provides an eagle’s-eye perspective of the terrain below. What initially drew photographer Audun Rikardsen to this spot high above the sea was, in fact, a resident golden eagle that frequented the perch. Having constructed a blind nearby, Rikardsen spent many frigid winter days photographing the eagle. But by spring, it had been replaced by a new subject: a black grouse in proud display. Not only did the grouse quickly become accustomed to Rikardsen’s rapidly firing camera shutter and flash, he says, it was almost as if the bird enjoyed being in the spotlight. 

Pier Mané / BigPicture Photography Competition

Sea Dragon: Aquatic Life Winner. The bottom of the ocean seems an unlikely place for a lizard to find itself. In fact, marine iguanas of the Galápagos Islands are the only lizards to venture beneath the waves—and they make a habit of it. With food options scarce along the islands’ volcanic coastlines, marine iguanas have evolved to forage at sea. Diving to depths of up to 25 meters on a single breath, they graze on algae that grow in the cold, nutrient-rich waters here. A carpet of healthy green and red algae like that seen in this image by Pier Mané makes the dive itself and the time spent sunbathing on the shore to regain body heat worthwhile. 

Piotr Naskrecki / BigPicture Photography Competition

Losing Wings: Winged Life Winner. Most mound-building termites in sub-Saharan Africa are eyeless, wingless, subterranean creatures. But once a year, termite queens produce winged offspring that are destined for a different existence. When the first heavy rains mark the end of the dry season, millions of these ecosystem engineers make a dramatic appearance, emerging en masse in a synchronized, if short-lived, nuptial flight. “A few minutes after landing on the ground, most individuals break off their wings and start looking for partners,” says the scientist and photographer Piotr Naskrecki. Within a day, the ground can literally be carpeted with discarded wings, providing padded walkways for a variety of other creatures—including the small, winged carpenter ants in this photo, which had just completed a mating flight of their own. 

Chiara Salvadori / BigPicture Photography Competition

Clouds of Salt: Art of Nature Winner. On the high plains of northwestern Argentina, the photojournalist Chiara Salvadori encountered a truly magical scene. Standing at an elevation of 3,900 meters (12,795 feet) surrounded by the stark beauty of the Salar de Antofalla, one of the world’s largest salt pans, she watched as the landscape’s colors changed and were shaped by the shadows of clouds that flowed fast overhead. One of the things that stood out most to Salvadori was the absence of humanity here. Indeed, the Salar’s dry salt bed supports little in the way of life. Even along its edges and on the slopes of towering volcanoes nearby, only the hardiest plants and animals survive. Shaped largely by wind and drought, the region’s harshness will, in all likelihood, continue to guard its surreal beauty. 

Mikhail Korostelev / BigPicture Photography Competition

Curiosity: Terrestrial Wildlife Winner. Capturing an underwater photograph of a massive brown bear as it fishes for salmon might seem like an impossible—and impossibly dangerous—feat. But with ingenuity, patience, and an abundance of bears, the wildlife photographer Mikhail Korostelev managed to do just that. To improve his chances, Korostelev ventured to the South Kamchatka Sanctuary, an isolated, 795,000-acre federally protected reserve on the tip of Russia’s easternmost peninsula. Not only is this home to the largest of all protected brown-bear populations in Russia, the sanctuary’s rivers see some of the largest salmon runs along the Pacific Coast. Along the Ozemaya River, one of the bears’ favorite fishing haunts, Korostelev submerged a remotely operated camera and waited. Before long, a curious bear happened upon the unusual object sitting on the river bottom, and, as it began to investigate, Korostelev snapped this breathtaking photograph.