You wouldn’t typically expect to see a whale shark in California, but that’s exactly what some local fishermen encountered earlier this week. These gentle giants prefer the warm waters of Mexico, and rarely venture north of the border. But this year’s El Niño has changed that. El Niño happens when the trade winds that normally push warm surface water toward Asia weaken, letting that warm water slosh back east across the Pacific. Off California, that’s pushed water temperatures up to 4°C higher than usual, inviting in unlikely visitors, including hammerhead sharks and sicklefin devil rays. While the sightings can be exciting, this warm water can turn local ecosystems upside down. California’s marine life depends on upwelling — the process by which cold, nutrient-dense water rises from the depths to replace the warm surface water usually pushed west. That cold water is what nourishes the kelp forests. During El Niño, the kelp forests lose their food source, and native species like abal...