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Over on The Daily Beast, the marine biologist Callum Roberts has a good essay (excerpted from his new book) on a topic that doesn’t get nearly enough attention: the declining state of the oceans.

According to Roberts, “with an ever-accelerating tide of human impact, the oceans have changed more in the last 30 years than in all of human history before.” Today, he adds, “in most places, the seas have lost upwards of 75 percent of their megafauna-large animals such as whales, dolphins, sharks, rays, and turtles-as fishing and hunting spread in waves across the face of the planet.”

Roberts touches on the familiar villain of overfishing and gives the standard (and relevant) advice that consumers should strive to “eat low in the food web, so favor smaller fish like anchovies, herring, and sardines over big predators like Chilean sea bass, swordfish, and large tunas (you will be doing yourself a favor, as these predators also concentrate more toxins).”

But he makes an even more important point that I fear often gets lost amid the fishery labels and the “avoid” and “recommended” lists (as important as those things are): The oceans represent contain highly complex ecosystems that are intimately related to their terrestrial counterparts in ways that transcend fishing trends. Overfishing is “only one small piece in a much larger puzzle of interacting impacts,” Roberts writes. To put it in another way, consumer choices about which sea creatures to devour and which to shun, while important, only exert so much influence over the fate of the oceans.