Why so much fatalism? From what I understand, this seems like a one-off situation, and could swing back into full restoration once the urchins die off from starvation.

If nature is anything, it's most certainly resilient! Mt. Saint Helens erupting caused more pollution than the entire industrial revolution combined, and a year of worldwide lockdown cleared up metric shedloads of air pollution.

Why trust what so-called experts say about 20 years out when their models suck for the next few years?