(CNN)Some hot commodities are obvious: gold, oil, corn and more recently, hand sanitizer, are clearly worth a lot.
But some valuable products are less evident -- and much more off-putting.
New research has revealed that the waste produced by seabirds -- that's right, the poop of seagulls, pelicans, and penguins -- could be worth nearly half a billion dollars annually.
That's because seabird feces, also known as guano, can be used as commercial fertilizer and is vital for contributing nutrients to marine ecosystems.
In an effort to raise awareness about the importance of seabirds and conserving their habitats, scientists set out to quantify the contributions of seabirds and illustrate the actual cost of declining seabird populations by valuing their waste.
It's not petty cash: Its value is estimated at more than $473 million each year and possibly much more, according to a new paper published today in the journal Trends in Ecology & Evolution.
"Guano production is an ecosystem service made by seabirds at no cost to us -- I can go to an island, collect the guano, and sell it at market price as fertilizer," study coauthor Marcus V. Cianciaruso, an ecology professor at the Federal University of Goiás in Brazil, said in a press release.
"Because there is this scientific and biological importance, it's possible to quantify seabird ecosystem services in a language that the general public and policymakers can begin to understand."
Not just commercial value
Although only a few seabird species produce guano that is currently commercialized in Peru, Chile and other countries, the waste of other birds contributes vital nutrients to marine ecosystems and is also important for coastal economies.
Seabirds bodily functions are nature's way of pumping nutrients back and forth "between marine and terrestrial habitats," wrote Cianciaruso and his coauthor, Daniel Plazas-Jiménez, a doctoral student at the Federal University of Goiás, in the paper.
"They release high concentrations of nitrogen (N) and phosphorus (P) through their faeces, causing important environmental changes in these ecosystems," according to the study.