30 April, 2024

Lucy Sherriff Los Angeles Spring is a vital season for many species in the air, oceans and on land – whether it's time to migrate, mate or metamorphose. Climate change, meanwhile, is making life harder for animals that already have gruelling journeys ahead. Sometimes those journeys are short, like the fish that flop their way onto California's beaches for a peculiar mating ritual. For migratory birds, those journeys can span half the world. In this animal-packed edition of Future Earth, we see how changes we can make as humans can aid animals' chance of survival – beginning with those curious Californian fish.

CLIMATE CONVERSATION  Grunion greetings A grunion greeter greets grunion on the beach. Credit: Karen Martin The silvery fish flip-flop on the cool southern Californian sand. It's a new Moon, and so my headtorch comes in handy. ‌ I'm careful not to shine the light on the hundreds of tiny anchovy-like fish that have flung themselves onto the sand. It startles them, so Karen Martin, scientist and long-time grunion-lover, informs me, and might interrupt their mating ritual. ‌ I'm trying to be a good "grunion greeter" – the name Martin has given to the thousands of citizen scientists she's roped into her project over the past 22 years. ‌ Martin, who is a distinguished professor emeritus of biology at Malibu's Pepperdine University, has made it her mission to find out what is happening to the thousands of grunion that come to California's beaches to spawn. They're hard to monitor because they don't take hooks like other fish, and they avoid trawler nets. They also have some rather interesting – and specific – spawning habits.

Grunion mating on the beach. Credit: Doug Martin They only come to shore during the four high tides following a full and a new moon, and only between February and September, although peak season is April until June. That doesn't deter Martin's grunion greeters though – members of the public who diligently fill in Martin's questionnaire with information about where they've seen the grunion, any unusual sightings, how many they've seen, and so on.

Greeters to the rescue Climate change is a challenge to the grunion's survival. As carbon dioxide levels in the atmosphere rise, so does ocean acidity. The eggs of the grunion, like many other fish, are highly sensitive to acidity. ‌ In decades past, there would often be so much grunion spawning on a beach that it was impossible to see the sand. Now, their numbers are less and less every year. ‌ They're trapped by locals for food and sport when they come on shore to spawn. Their spawning grounds are also threatened by development, pollution, erosion, and the fact that these beaches are some of the most popular tourist destinations in California. ‌ Actions to make beaches safer for grunion – such as refraining from raking them at key parts of the year – could be crucial to helping the fish survive. Which is where the grunion greeters come in. Our understanding of these fish would be much less without citizen scientists, whose data has led to several protective measures to help the fish survive. ‌ Against the odds, Martin is hopeful – she's fighting for the survival of this rare fish, as are her army of grunion greeters. ‌ Read my full report on the citizen scientists trying to preserve this natural phenomenon.

NUMBER OF THE WEEK 33 million The number of children who faced closed schools due to extreme heat in Bangladesh, as temperatures surge past 42C (108F).