For me, Laysan was both the endpoint and beginning of a lifelong quest. As a kid with a bicycle and a fishing rod, I searched the near horizons of local Long Island beaches for signs of terns that would lead me to bluefish, striped bass, or weakfish, which I reeled in, flopping, onto the pebbly shore or over the side of my tiny, 12-foot boat. I loved the terns so much that I followed them not just to many fresh meals but to a Ph.D., a realization of deep changes in the sea, a career, and personal acquaintances with some of the most extreme athletes of the world’s remotest seas and far-flung lands. We owe seabirds a great debt. For me, it’s personal. And in the face of climate change, Laysan helped give me a global sense of how we’re returning their favor: At the rate we’re going, if we don’t drown them, we’ll starve them.

Scientists predict up to three feet of sea-level rise during this century. After that, melting glaciers will increasingly lift rising oceans. In the same number of years that have passed since the Pilgrims landed in Massachusetts, sea level will likely climb roughly 10 feet. But storms and washovers will begin scouring islands long before they’re completely submerged. Continental beaches, too, where migrating shorebirds forage and terns, gulls, and sea turtles nest, will get increasingly eroded, squeezed between water and buildings and roads.

Other effects of changing climate on seabirds will be less obvious. Even small shifts in temperature or chemistry or salinity can have cascading effects. Warming is reducing the basic amount of food produced by oceans. It’s also changing the proportions of what lives in the sea—the ratio of sardines to anchovies, for example.

Visualization by Pitch Interactive. Data compiled by Brooke Borel and Susan Matthews. Data: Climate Change 2013: The Physical Science Basis, Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, IPCC

The same carbon dioxide that is warming the planet is making oceans more acidic, creating unfavorable conditions for planktonic animals, corals, and shellfish, further affecting the food chain by benefiting jellyfish. The result is what ocean ecologist Jeremy Jackson calls “the rise of slime.” If that sounds ominous, it is.

For the many seabirds that are specialized feeders, adaptation to new climates may come too slow and hard. In general, colder seas are more productive. Cool winds mix the upper ocean, keeping more nutrients in the sunlight, where plankton can use them to grow and breed. Cooler water also holds more oxygen. So when water warms, productivity declines. The results can be catastrophic. Adult birds fail to breed, abandon their nests, or worse. Entire colonies can starve and die.

Credit: Same as above

In parts of the Southern Ocean, changing temperatures and ice conditions appear to be responsible for halving Emperor Penguin breeding numbers in Adélie Land during a stretch of warm water and poor krill production. Southern Fulmars skip breeding altogether in warmer years. More warmer years seem headed their way.

In the North Atlantic, one species of oil-rich copepod, Calanus finmarchicus, which is about the size of a grain of rice, gets eaten by everything from pencil-size sandeels to right whales. They form dense swarms in certain places and at certain times. Think of them metaphorically as giant bowls of rice in the sea, and you won’t be far off. The sandeels, herring, and mackerel that eat those copepods are in turn breakfast, lunch, and dinner for terns, puffins, shearwaters, and gannets. The copepods’ abundance and productivity falls when seawater warms or—as when sea ice melts—the oceans become less salty.

Visualization by Pitch Interactive. Data: Kawaguchi et. al, Nature Climate Change, July 2013

Often, timing is everything. In the Bering Sea, the year’s first plankton bloom drives the entire marine food bus. That so-called phytoplankton spins the first strand in the annual food web, using photosynthesis to turn sunlight into food enough for everything that will follow. But much depends on exactly when that first massive proliferation of plankton happens. And that depends heavily upon when the winter’s sea ice melts. Under cold conditions, it melts in April to May. At that time of year, the sunlight is strong enough to fuel phytoplankton proliferation, but temperatures remain too cold to support a burst of the tiny animal “zooplankton” that grazes the phytoplankton. So the ungrazed phytoplankton drifts down to the seafloor, becoming food for amphipods and clams, which feed diving seabirds such as the Spectacled Eider and mammals like walruses and gray whales. In warmer conditions, ice melts when the days are too short to spark the bloom. By the time there’s sufficient light, the water has warmed enough for zooplankton and larval fish. Zooplankton and fish eat and carry off the phytoplankton before it reaches the seafloor. Result: The abundance of shellfish Spectacled Eiders rely on has declined.

Meanwhile, the normally cold California Current off the West Coast is one of the world’s most productive ocean systems, supporting one million to two million seabirds of about 30 species over a vast moving system of water that runs from British Columbia to Baja California. Up and down the coast, recent increases in sea temperature have caused plunging plankton density. Researchers report major declines in numbers of Sooty Shearwaters that formerly swarmed this vast conveyor of water. Cold-water divers like Rhinoceros Auklets and Cassin’s Auklets appear to be withdrawing from warming Southern California waters. “It is now apparent,” write BirdLife International researchers, “that even modest temperature rises can have a profound impact on marine ecosystems.”