請問facingtheenvironment的英文句型 - 社會議題

請問這句英文的句型：
Perhaps the most serious problem facing the environment is global warming.
當中的facing the environment的寫法，
我覺得有些奇怪，是子句簡化而來的嗎?
感覺整句的寫法應該是：
Perhaps the most serious problem of environment that we are facing is global warming.
麻煩英文高手解惑，十分感謝。