It is estimated that the worldwide population of sea otters once numbered between several hundred thousand to over one million before being nearly hunted to extinction by fur traders in the 1700s and 1800s. Sea otters finally gained protections with the signing of the International Fur Seal Treaty of 1911, and became listed under the Marine Mammal Protection and Endangered Species Acts in the 1970s. Worldwide, numbers have slowly recovered but still stand far below original population numbers. While sea otters are vulnerable to natural predators, their populations are significantly impacted by several human factors as well.

Oil spills from offshore drilling or shipping are an immense threat to sea otter populations. When sea otters come into contact with oil, it causes their fur to mat, which prevents it from insulating their bodies. Without this natural protection from the frigid water, sea otters can quickly die from hypothermia. The toxicity of oil can also be harmful to sea otters, causing liver and kidney failure as well as severe damage to their lungs and eyes.