Here’s an image for you: A starfish, technically known as a sea star, eats by basically vomiting up its stomach, sticking it inside the shell of a tasty morsel—say a mussel—and hanging out all day like this until it has fully digested its prey.

This delightful description is provided by Brian Helmuth, a professor of marine and environmental sciences, who studies the effects of global warming on creatures that live in the intertidal zone—that part of the ocean floor revealed at low tide.

As you might imagine, this whole out-of-body eating experience saps a lot of energy out of the poor sucker. Once a starfish goes into dining mode, it’s pretty committed. While the meal begins under water, the tide eventually drops, leaving the starfish and its prey exposed to the air and the heat.

Without any water around, the starfish has to cool itself off by “moving water around in its body,” Helmuth tells me. As it gets hotter, it has to suck water out of its arms to protect the vital organs in the core of its body. When it does this, it sometimes loses an arm … or two.

Of course, growing back an arm is no big deal for a starfish. But in the meantime, its ability to function is compromised, since a starfish uses its arms to move, store nutrients, and, get this, to house its sexual organs. So, sacrificing arms, while not lethal, isn’t a terrific idea for a starfish.

So what does this all have to do with climate change? 

Helmuth says the impact from global warming will be a slow process, but one in which the ultimate collapse, if it occurs, will be rather sudden. For this reason, it’s important to understand the signs of distress long before creatures die off.

Increasing rates of arm loss, increasing rates of sterility, or decreasing rates of growth might be signs of a bigger blow yet to come. As with many species, he said, everything will appear to be OK until one day there’s a huge drop-off in numbers. But if we pay attention to the early warning signs, perhaps we can do something to prevent the devastation.

Helmuth’s contention is that “local conditions are going to matter more than global conditions to many organisms.” He says that “local” can be as minute as the rock the organism happens to be lounging on, or the beach where it lives. With information from his starfish research, scientists can tell a little better which populations are likely to survive and which are not.

“If it’s a habitat where the organisms can stay out of the sun, they’re more likely to survive,” he says. “It’s these nit-picky details that make a huge impact.”


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Angela Herring is Northeastern’s science writer. Contact her via twitter, at her blog, iNSolution, or via email.