The study is real, peer reviewed, and the claim's core is supported. The paper states that climate change impacts are often underestimated due to a lack of historical baselines, and that using recently discovered aerial imagery and subtidal quadrat data from 1972, the authors recreated historical baselines for kelps and associated benthic macroalgae in a hotspot within the northern Salish Sea in British Columbia, Canada.

Resurveying the same sites in 2023, they showed that half a century ago bull kelp (Nereocystis luetkeana) formed expansive forests exceeding 550 hectares, none of which remain today.

On the origin of the data: Timmer was examining old research at the University of Victoria when he found aerial and underwater photos of thick bull kelp forests in the northern Salish Sea covering 550 hectares of ocean around Comox and Denman Island in 1972, and over roughly a dozen years it all vanished.

The 1972 surveys were originally government aerial scans and scuba surveys intended to map a red algae species for commercial harvesting; the project was discontinued and the data sat in archives, but kelp was visible in the photos and the scuba survey locations were known.

On timing: Satellite records show that most of the bull kelp loss occurred between 1972 and 1984, well before the kelp losses documented during more recent marine heatwaves.

On the "before it was recognized" element: Timmer noted that most kelp loss research is recent and tied to well-known marine heatwaves such as the "Blob," while the decimation around Comox and Denman occurred much earlier.

Coverage of the study states that climate change had been altering ecosystems long before most people were aware anything was wrong.