That’s only a problem for people who are getting high just about every single day. It’s super easy to use weed on and off without any problems.

It’s true that climate change does contribute, but it’s also worth noting that without human disruption of natural biogeochemical cycles (like the nitrogen cycle), even with climate change, we’d see significantly fewer harmful algal blooms. Algae do like the warm water, so when combined with excess nutrients the algal blooms only get worse. It’s just not really reasonable to point to climate change without mentioning nutrient pollution, which is far more impactful on algal blooms.

Red tides are more than anything due to nutrient pollution. Development of coastal and riverine wetlands has significantly decreased the nutrient uptake that occurs before water flows out to the sea, and agriculture and home fertilizer use cause large amounts of nitrogen and phosphorus to be present in run off when it rains. Nitrogen is the limiting factor for the growth of marine plants and algae, so adding excess nitrogen significantly contributes to these blooms.