What is killing kelp?

Could you please elaborate on the factors that are responsible for the decline of kelp populations? I'm particularly interested in understanding the environmental pressures and anthropogenic impacts that might be driving this trend. Could climate change be a significant contributor? Are there any specific pollutants or human activities that are known to harm kelp? Additionally, are there any natural predators or diseases that might be affecting kelp populations? It would be helpful if you could provide some insights into these questions and explain how they might be interconnected in causing the decline of kelp.