Subtle ecological chains worldwide are being damaged by human influence, leading to significant losses of population in different ecosystems.
One of the longest ecological chains ever found has just been discovered in the remote Palmyra Atoll, in the Pacific Ocean. This area is useful to science because there are relatively untouched ecosystems that are in close proximity to human-influenced ones.
Researchers there have now documented how something as simple as replacing native trees with non-native palms can lead to a collapse of seabird, plankton, and manta ray populations around an island.
The findings were almost accidental, as the researchers involved were there for a different study involving manta rays and their predator-prey interactions.
As they were doing the study though, they noticed that the manta rays kept returning to the coastlines of certain islands.
At the same time, a different researcher was in the area doing a study on the effects that non-native palm trees had on seabird communities and native habitats.
While interacting with each other, the overlap of the research began to become apparent.
“As the frequencies of these different conversations mixed together, the picture of what was actually happening out there took form in front of us,” Douglas McCauley, one of the researchers, and a graduate student from Stanford University, is quoted as saying.
The research was done using tracking and field surveys, along with nitrogen isotope analysis. The researchers found that the replacement of native trees with non-native palms led to about five times fewer roosting seabirds, less bird droppings fertilizing the soil, less nutrients washing into the sea, smaller plankton and less of them, and fewer manta rays feeding around the island.
“This is an incredible cascade,” said researcher Rodolfo Dirzo, a professor of environmental science and senior fellow with the Stanford Woods Institute for the Environment. “As an ecologist, I am worried about the extinction of ecological processes. This dramatically illustrates the significance of such extinctions.”
“Such connections do not leave any trace behind,” said researcher Fiorenza Micheli, an associate professor of biology affiliated with the Stanford Woods Institute. “Their loss largely goes unnoticed, limiting our understanding of and ability to protect natural ecosystems.”
Adding to that, McCauley said, “What we are doing in some ecosystems is akin to popping the hood on a car and disconnecting a few wires and rerouting a few hoses. All the parts are still there — the engine looks largely the same — but it’s anyone’s guess as to how or if the car will run.”
Researcher Robert Dunbar, a professor of earth sciences at Stanford Woods Institute, brings up the historical example of what happened when the water levels in Central California’s rivers were lowered because of increased water demands. When the water levels were lowered, the salmon runs collapsed, leading to a massive loss of nutrients in the ecosystem, as well as a loss of agricultural fertilizer, which has now been replaced with the application of millions of dollars of artificial fertilizers every year.
“Humans can really snip one of these chains in half,” Dunbar said.
The research has just been published in the journal Scientific Reports.
Source: Stanford University
Image Credits: Gareth Williams, Kydd Pollock