A first-ever effort to quantify where humans fit in the food webs around us suggests a strategy for minimizing our negative effects on the natural world.
SFI Professor Jennifer Dunne and a team of archaeologists and ecologists from Idaho State University are studying Sanak Island, Alaska, where Aleut people lived for 5,000 years before recently moving to the mainland.
Using interviews, ecological observations, and archaeological studies, the team is reconstructing marine and terrestrial food webs for the entire Sanak archipelago. These complex ecological networks describe “who eats whom,” including humans, among the hundreds of species in local habitats. Surprisingly, such a “whole system” study of the human roles in a food web has never been done, Jennifer says.
Jennifer’s initial network analyses show that the Sanak Aleut were “super-generalists” and “super-omnivores” who ate a greater variety of plants and animals throughout the food web than other consumer species. In the intertidal food web, for example, Sanak Aleuts ate more than a quarter of all species at all levels of the web.
Historical and archeological records show that the Aleut also regularly switched what they ate, by hunting sea lions when the weather was good, harvesting salmon when they migrated up the local river, or digging for clams when other food items were unavailable or inaccessible.
Switching made sense – if one thing gets hard to find, eat another – but also helped keep the ecosystem healthy by giving plant and animal populations a chance to recover. Jennifer’s modeling demonstrates the importance of this behavior: a super-generalist can be a part of a stable ecosystem as long as they eat only a few species at a time, she says.
In the modern world, economic pressures can interfere, however. She cites blue fin tuna, which have been in the news recently because their value has skyrocketed as they have become rare due to overfishing for the sushi market. People’s failure to switch to other more available, but less pro table, species is driving drive blue fin tuna towards extinction.
Jennifer says this cycle also, and more alarmingly, introduces a potentially destabilizing dynamic: ripple effects in the food web could drive other species to extinction, altering the ecosystem’s fundamental structure and function and ultimately affecting what – and how much – food we humans have left.