“Why?” he will ask, lowering his raised hand. His brow will furrow and his eyes will be wide with not only confusion, but the determination of a curious student to understand the answer. “Why did nobody stop it? Why did nobody try?”

“We tried,” the reply will come, spilling from her lips with a tired sigh. She is not that old, not yet, but in this room surrounded by twelve year olds, she will feel ancient. She will know of a world alien to the younger boy asking the question, a world lost with her generation. “It was too late.”

That has not happened yet. In this life, in this time, she is standing on a boat, shoving her little brother out of the way so she can talk to her friends. A waterproof camera is clutched in her hands, her best friend peering over the railing and pointing at the crystal blue waters. “Look,” she gasps, “oh, this is going to make such a good Instagram post.” They giggle and bet on who will get more likes and her younger brother pouts indignantly up at them for being excluded and then it’s actually time for them to go, sliding off the side of the boat and into the chilly seawater.

She shivers and manages to smile at her friend. “What global warming? It’s freezing.” They laugh at that and laugh even harder when it’s time to pull their snorkels on, snapping a picture with the camera before following their guide. He promises that he knows where the best reefs are, that he knows where they will see the most fish, and they do not give voice to the fact that years ago they would not have needed a guide, because the best reefs would have been everywhere, and the waters would have been teeming with fish. They laugh at climate change jokes but they do not comment on the coral bleached bone-white that they must swim past, the skeleton of what had been. She clicks the camera shutter once, twice. These pictures will not go on her Instagram but she thinks that this deserves to be remembered.

The image will appear on the screen in front of the class, projected in cold unforgiving light: an ocean devoid of life, and the worst part is that this will elicit no reaction from the class because this, from what they have seen, is all the ocean contains. Though maybe that is wrong, because these students will never have been in the ocean. No, the reaction she will get is one of surprise, demanding to know: “How did you get those pictures? I thought the ocean was too acidic to go in!” She will use that to explain how carbon entering the oceans caused there to be too little oxygen, and how fish suffocated. How bacteria thrived in the lack of competition, and how microbes decomposed the fishes’ corpses to produce even more carbon. How it became a vicious cycle, a feedback loop, throwing in some vocab that the kids will need to know for their test, and how in this way, death spread throughout the ocean, fish choking to death in the waters that had once breathed life into them. How eventually the oceans gave off gas that promised death, gas that crept towards the land and will soon, in these children’s lives, poison the plants and the animals and finally, them.

For now, she quietly files away the sight of the coral graveyard spread out before her and swims on, unaware of what it means. Besides, she reasons, scientists will save it. Science can fix everything nowadays. There are kaleidoscopes of fish in the waters just ahead of them, a rainbow of color splattered across the ocean floor, and these she takes pictures of, beaming at the camera before diving underwater to document them up close. What she doesn’t know is that even this coral is fighting a losing battle. The waves creep higher and higher every day, too deep for the coral to survive in. It is trying, but it reaches for the shore at a sickeningly slow pace. This she cannot see. So she will post these pictures and caption them ocean life, not knowing that the life she sees is drowning before her eyes.

The effects of climate change will be a large unit, so she will give her students a quiz halfway through. It won’t be hard; they will review extensively. Here is a preview: question 5, multiple choice. Coral reefs take up 1% of the ocean floor, but they once held over ___ % of marine life. A. 5, B. 2, C. 12, D. 25. Choice D will be the correct answer, and when they get the graded papers back, for a moment they will be shocked to see how much was lost. But then they will leave the classroom, comparing grades and pushing through the crowded hallways to get to their next class, and what they learned today in class will be forgotten. Perhaps they will bring it up at the dinner table: mom, dad, did you ever see the coral reefs? When were they lost? Was there really nothing we could do? We talked about it in science today. What’s going to the beach like? Their parents will exchange glances; their shoulders will slump and eyes will be closed and the smell of saltwater and the feeling of cool waves lapping at their feet will play in their memory. Maybe they will pull up old pictures of white sands and turquoise seas and bright smiles, and their children’s fingertips will hover over the image, reconciling it with what they have seen of the beaches: contaminated by hydrogen sulfide, some of them will say, a term proudly learned in chemistry. A mere ghost of what had been, the wind that had once carried the tang of salt now bearing a heavy rotting scent: a death sentence to life on Earth. It has killed us before and will kill us again. Too little, too late, goes the old saying—we were right about one thing, at least.