In 2018, a marine heat wave appeared off the coast of New Zealand and helped spike land temperatures to record highs. Along the coast of Tasmania, giant kelp once stretched over 9 million square meters. Today, thanks to warmer water and a subsequent invasion of urchins, the kelp covers fewer than 500,000 meters. In 2021, a blob of hot water bubbled up in 130,000 square miles of ocean off the Uruguayan coast, an area nearly twice as big as Uruguay itself. It caused a die-off of clams and mussels, an important food source for tens of thousands of people who live on the coast.
