Guano is a natural fertilizer made from the accumulated excrement of seabirds and bats. It is rich in nitrogen, phosphorus, and potassium, which are essential nutrients for plant growth. Guano has been used for centuries in agriculture to enhance soil fertility and improve crop yields. The most famous sources of guano are found on islands off the coasts of Peru and Chile, where large populations of seabirds nest. The harvesting of guano became a significant industry in the 19th century, leading to economic booms in these regions. Today, guano is still valued as an organic fertilizer in sustainable farming practices.