"Preventing the extinction of bears" is a way to say "阻止熊的灭亡" in Engpsh.

The term "extinction" refers to the disappearance or death of a species, meaning that there are no longer any individuals of that species left on Earth. "Preventing the extinction" means taking actions to ensure that a species does not become extinct.

Here are a few examples of sentences using this phrase:

"Conservation efforts are focused on preventing the extinction of bears in the region." (保护活动致力于阻止该地区熊的灭亡。)
"The organization works to prevent the extinction of endangered species, including bears." (该组织致力于阻止濒危物种的灭亡，包括熊。)
"Scientists are studying the behaviors of bears in an effort to prevent their extinction." (科学家们正在研究熊的行为，以阻止它们的灭亡。)