Why is kelp disappearing?

Could you please enlighten me as to the reason behind the disappearance of kelp? I've noticed a significant decline in its presence and am curious to understand the factors contributing to this phenomenon. Could it be due to environmental changes, such as rising water temperatures or altered nutrient levels? Or could human activities, like pollution or overfishing, be playing a role? I'm eager to gain insights into this puzzling trend and would greatly appreciate your expertise in addressing this question.