Guano is a fertiliser made from the accumulated waste products of birds, bats, and seals.
The majority of bird guano originates from islands off the shores of Africa, Baja (Lower) California, and Peru that are home to cormorants, pelicans, and gannets in large numbers. All around the world, caverns contain bat guano.
On the Isla Lobos de Tierra and Islas Lobos de Afuera (Lobos Islands), off northwest Peru, seal guano has collected to tremendous depths. Bird guano, which has a nitrogen content of 11 to 16 percent, a phosphoric acid content of 8 to 12 percent, and a potash content of 2 to 3 percent, has a higher fertiliser value than bat and seal guano.
Bat guano is found in caves throughout the world. Many cave ecosystems are wholly dependent on bats to provide nutrients via their guano which supports bacteria, fungi, invertebrates, and vertebrates. The loss of bats from a cave can result in the extinction of species that rely on their guano.
However, unsustainable harvesting of bat guano may cause bats to abandon their roost.
https://en.wikipedia.org/wiki/Guano
