北極暖化使北極熊面臨更高的疾病風險

As the Arctic region continues to warm, polar bears are increasingly at risk of developing health issues due to a rise in exposure to various pathogens. This alarming trend has been highlighted in a recent study that indicates polar bears are spending more time on land, which exposes them to viruses, bacteria, and parasites that were less common just three decades ago. Researchers conducted a thorough examination of blood samples from polar bears inhabiting the Chukchi Sea, located between Alaska and Russia. They compared samples collected between 1987 and 1994 with those gathered from 2008 to 2017, revealing a significant increase in the presence of chemical markers indicating infections from five different pathogens. Wildlife biologist Dr. Karyn Rode, who is affiliated with the US Geological Survey, emphasized that while it is challenging to determine the exact impact of these infections on the bears' overall health based solely on blood samples, the findings suggest that the entire Arctic ecosystem is undergoing significant changes. The researchers focused on six distinct pathogens, which are primarily associated with land-dwelling animals but have also been detected in marine species that polar bears prey upon. Dr. Rode noted that the study spanned three decades during which there was a considerable reduction in sea ice and an increase in land use by polar bears. The goal was to assess whether the bears' exposure to these pathogens had changed, particularly for those that are typically linked to land-based animals. The five pathogens identified in the study include two parasites responsible for toxoplasmosis and neosporosis, two types of bacteria that cause rabbit fever and brucellosis, and a virus known to cause canine distemper. Dr. Rode explained that while polar bears are generally resilient to diseases, the increasing prevalence of these pathogens highlights the ongoing changes occurring in the Arctic environment. The polar bear population is estimated to be around 26,000, with the majority residing in Canada, while others can be found in the US, Russia, Greenland, and Norway. The International Union for Conservation of Nature has classified polar bears as vulnerable to extinction, with climate change being a significant factor contributing to their decline. Adult male polar bears can reach lengths of approximately 3 meters and weigh close to 600 kilograms. They are capable of consuming up to 45 kilograms of blubber in a single meal and possess an exceptional sense of smell, allowing them to detect prey from distances of up to 16 kilometers. Additionally, polar bears are strong swimmers, often spotted as far as 100 kilometers offshore, and can swim at speeds of around 10 kilometers per hour due to their slightly webbed paws. In the United States, polar bears are classified as a threatened species, and scientists assert that the ongoing loss of sea ice habitat poses the greatest threat to their future. This ice is crucial for polar bears, as it serves as a platform for hunting marine prey. Previous research utilizing collar cameras on polar bears has demonstrated that as these animals spend more time on land during the ice-free summer months, they are increasingly exposed to pathogens. Dr. Rode explained that polar bears are apex predators, and the changes in pathogen exposure observed in their population reflect broader shifts affecting other species in the Arctic ecosystem. The findings of this study underscore the urgent need to address climate change and its impact on polar bears and the delicate balance of life in the Arctic.