The food web, a metaphor for the relationships between organisms in the environment, tells us that all living things rely on one another. These dependencies can be immediate, like an eagle catching a salmon for a meal, but can also be more distant like the bees that pollinate the apple flower which produces an apple for you to eat.
Since organisms are so interconnected, the loss of a single species can mean the loss of others. This is part of the reasoning behind the Endangered Species Act–protect things before there’s nothing left to protect. But what happens to food webs when we maintain species, but the abundance of each species starts to crash?
This crash in species’ abundance is happening now and could be happening worldwide, as shown by a recent study published by researchers in Germany.
We’ve known for some time that we are currently experiencing (and humans are the culprit behind) the sixth mass extinction in the history of Earth, but this drop in the number of individuals across the board for thousands of species is a new wrinkle in our understanding of our changing world.
The type of study conducted by these researchers is hard to come by; it focuses on the same locations over a long period of time. Such studies are invaluable as they can tell you about long-term trends that would otherwise go unnoticed, but they are exceedingly hard to accomplish considering the twists and turns people’s lives have taken over the past decades.
In this study, the authors collected flying insects at sites across Germany, encompassing an array of habitat types, over the course of 27 years. There are a lot of things that can affect insect abundance, so the researchers kept track of what they thought might affect it, like weather patterns at each location to see how the climate changed over the 27 years. They also recorded changes in the types of plants found at each site, as well as changes in the surrounding landscape.
Insects are one of the biggest components of our planetary food web. Insects help decompose dead and dying organisms by recycling their nutrients back to the land for other organisms to use. Insects kill a lot of animals (including other insects) that may otherwise be a nuisance or cause serious disease to humans. Insects are the favored food of a variety of organisms from bears to fungi to birds. For songbirds, insects can make up over 50 percent of their diet during the springtime.
The researchers found an alarming 76 percent decrease in total mass of insects caught from the beginning of the study period compared to the end. A drop of this magnitude for any group of organisms is alarming, but a drop of this magnitude for insects is especially significant considering their crucial role on our planet.
The authors could not explain this drop in abundance using any of the other information they collected, suggesting this could be a large-scale phenomenon happening worldwide.
What’s even more startling is that each one of the 63 sites used in this study are situated within nature reserves. Such a drop in insect abundance might not be so surprising in an area without protection from habitat destruction. But nature reserves are meant to act as a last bastion for wildlife, providing a source-sink of the human dominated landscape.
We have been trained to think of the loss of a species, or extinction, as the paramount biological risk of our era. But lost in this focus is the effect of functional extinction, which occurs when a species is still around, but no longer able to carry out its typical role in the food web.
As insects and other organisms become less and less abundant, the food web unravels just as if it has lost a species entirely. More research is needed immediately if we are to uncover the causes behind this decline and conserve the world as we know it.
Kevin Keegan is a campus correspondent for The Daily Campus. He can be reached via email at firstname.lastname@example.org.