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Eat and be eaten: the fundamental role of insects in the food chain

The populations of insect-eating birds have declined more than any other bird group.
Credit: Insectarium de Montréal (André Sarrazin)
The populations of insect-eating birds have declined more than any other bird group.
  • The populations of insect-eating birds have declined more than any other bird group.
  • The dragonfly preys on other insects, but in turn will be eaten by another animal.
  • Ladybugs are important predators for the control of insect pest populations.
Eat and be eaten: the fundamental role of insects in the food chain

We’re talking about it and seeing it more and more: insect populations are collapsing. The thing is, in being eaten and feeding other organisms, insects occupy essential positions in the food chain. The grasshopper eats the plant, the bird eats the grasshopper, the fox eats the bird – each link transfers energy to the next level. So what would happen if the food pyramid were modified by the disappearance of insects?

Nature in balance thanks to insects

Insects overall have an apparently infinite dietary range. Whether they’re decomposers, herbivores or predators, their contribution to the food chain takes place at many levels. While some enjoy an assortment of choices to feed from, others are specialists, meaning they can count on only a specific species to survive. That’s the case, for example, of the red milkweed beetle, which feeds solely on milkweed.

Many insects are predators or parasites. They contribute to controlling insect pest populations, in a way that maintains balance. The decrease in insect populations would entail an imbalance between parasites and their hosts, which could have important consequences.

At the base of the pyramid

Because of their great numbers and the fact that they’re found in almost all habitats, insects hold a predominant position at the base of the food pyramid. Insects reproduce much more rapidly and are considerably more numerous than the animals that feed on them. Thus, the higher you go up the chain, the more non-specialized animals are in terms of what they eat. Which is why there are more species of insects than of birds, fish or mammals.

It’s obvious, therefore, that with a downturn in the number of insects, everything above them on the food chain will suffer.

Decline in insect-eating birds

We have really unhappy evidence of the importance of insects in the food chain. Over the last few years, populations of insectivore birds have dropped by 59 percent in Canada alone. That’s more than any other bird group. Possible causes of the decrease: the decline in insect populations, the intensification of agriculture, and climate change.

What do we do in the face of such a disaster? We act! Habitat restoration, associated with drastic cuts in pesticide use and an overhaul of our agricultural practice, is probably the most effective way of stopping the declines.

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