At the end of each year, wildlife ecologist David Steen compiles a list of critters that have likely gone extinct. The 2017 list includes a bat, cat, and multiple lizards, although other creatures may be gone for good — we just don't know it yet. Steen, an ecologist at Auburn University, started the annual extinction list in 2012 to establish a clear, reliable source for the planet's extinctions. Educating the public about the loss of species, in his view, is as important as it is dispiriting. SEE ALSO: Trump slurps shark fin soup as U.S. works to remove itself from the shark fin trade "It is depressing, frankly, to think about all the creatures we will never see again but I think it is important for us to perceive extinction as a loss of actual species and not just numbers and rates," Steen said via email. Steen notes that listing any particular species is "surprisingly tricky." Some species have disappeared from the wild, but are still kept alive in captive settings, like zoos. Some might have been gone for years, but we hadn't yet figured out or officially established they were gone. Others species have disappeared from entire regions of the world — but could cling to existence elsewhere. The fishing cat, Prionailurus viverrinus, of Southeast Asia.Image: wikimedia commonsThe fishing cat in Southeast Asia is a good example. Researchers can't find any of these medium-sized cats on the island of Java in Indonesia where they were once abundant. They're likely now extinct across the entire nation, but Steen says "they persist in low numbers elsewhere." Those cats are on Steen's list. Island species, said Steen, are particularly "vulnerable to extinction and we are seeing a number of these animals blinking out." Once a predatory foreign species, such as a rat or snake, is introduced to an island, there's no place for native species to run. On Christmas Island, northwest of Australia, three lizards — Lister's gecko, the blue-tailed skink, Christmas Island forest skink — and a bat are widely presumed to be gone. They also make Steen's list. Exotic, or non-native, species are a likely culprit, but perhaps not the only one. Some scientists argue that we are now living during one of Earth's mass extinction events — which would be the sixth known such occurrence. Regardless of how scientists define a "great extinction event," Steen notes that a significant extinction crisis is inarguably happening now. The Christmas Island pipistrelle, a bat, is now considered extinct.Image: Lindy Lumsden/IUCN"All the evidence points to us having a rapid and disproportionate effect on the species around us," he said. "It is not a stretch to say that we are living through the sixth great extinction." Still, Steen believes it's important to give progress it's due — in places where it's deserved. Conservation areas, both in the oceans and on land, are being established. In November, Mexico designated North America’s largest ocean reserve, Revillagigedo Archipelago National Park in the Pacific Ocean. This 58,000 square miles of protected space is home to sharks, turtles, and hundreds of species of fish (dozens of which live nowhere else). Nothing can be legally fished here. "There's a lot to be discouraged about," said Steen. "But when it comes to conservation, I try to perceive our progress as ‘two steps forward, one step back.' "We will continue to lose species and their habitats, but we need to pay attention to all the new conservation areas that are established, the species we are reintroducing to their old habitats, and perhaps most importantly, the passionate people that are making it all possible." WATCH: The world’s tallest mammal is now threatened with extinction read more Disclaimer: Chances are that this post was requested by an advertiser.