Image credit: Wikimedia Commons
Perhaps it's because humans sit at the top of the food chain, or maybe it's that big predators so capture the imagination, but much of the attention given to the web of predators and prey focuses on this upper edge—the polar bears, the tigers, the wolves.
If the residents of an ecosystem piled into a pyramid, these predators would be at the peak and plants and microbes would form the foundation. Now, new research indicates that the middle—small insectivorous birds and lizards—are critically important to overall health of an ecosystem, and actually help promote greater biomass.At first glance, this seems obvious; that all parts of a natural system would play an important roll in overall health and success. Previous theories, however, suggested that the net effect of insectivores was negligible. The thought was that for every herbivorous insect a bird ate, a carnivorous one—like a spider—would also be eaten.
New research, however, shows that this is not the case. Daniel Gruner, a researcher at the University of Maryland Department of Entomology, explained:
Our study shows that despite feeding on predatory insects, birds, bats and lizards still act as plant protectors by having net negative effects on plant-feeding insects
Gruner and a team of other researchers looked at more than 100 studies insect predation by birds, bats or lizards and found that, regardless of the predator in question, their presence was associated with a 40 percent reduction in damage to plants. In turn, a healthy population of insectivores was linked to a 14 percent increase in plant biomass.
Sunshine Van Bael, a scientist at the Smithsonian Tropical Research Institute and coauthor of the study, commented:
It's no longer apt to say that one 'eats like a bird'...our study shows that birds, bats and lizards act as one big vacuum cleaner up in the treetops. Everything's on the menu.
Unfortunately, these specialized species in the middle of the food chain are especially vulnerable to habitat loss and fragmentation. When they go, the valuable roll they play in the ecosystem is also lost, leading to increased chances of insect infestation and disease outbreaks.
Read more about the food chain:
Global Warming Not the Only Thing Threatening Polar Bears
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DDT Concentrations May Be Increasing in Northern Oceans