Sadly, most of this decline is due to human activity.

And sadly, most of this decline is attributable to human activities. Historically, penguins have had to deal with multiple disturbances. The mass collection of penguin eggs and the harvesting of the seabird guano they nested in caused the dramatic decline of several penguin species. If you're wondering what humans would want with seabird poop, it was used as an ingredient in fertilizer and in gunpowder, being so valuable that in the 19th century, it was known as white gold. Current threats to penguins include the destruction of both marine and terrestrial habitats, introduced predators, entrapment in fishing nets, and pollution from plastics and chemicals.