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There are a lot of insects. It is difficult to say exactly how much because the taxonomists have not yet described 80% of the cases, but there are probably about 5.5 million species. Count this number with other types of animals with exoskeletons and articulated legs, known collectively as arthropods – this includes mites, spiders and woodlice – and it There are probably about 7 million species.
Despite their omnipresence in the animal kingdom, a recent report warned of a "bug disease", as surveys have indicated that insects are declining everywhere at an alarming rate. This could mean the extinction of 40% of the world's insect species in the coming decades.
What is particularly worrying is that we do not know exactly why populations are declining. Intensification of agriculture and pesticides are probably an important part of the problem, but it is certainly more complicated than that; habitat loss and climate change may also play a role.
Although some newspaper articles have suggested that insects could "disappear in a century", a total loss is unlikely – it is likely that if some species die, others will settle and take their place. Nevertheless, this loss of diversity could have catastrophic consequences. Insects are important ecologically and if they were to disappear, the consequences for agriculture and wildlife would be terrible.
EPA-EFE / Jaipal Singh
The sprawling kingdom of insects
It is difficult to overestimate the number of species present. Indeed, the estimate of 7 million above is probably a major underestimate. Many similar insects – what are called "cryptic species" – are distinguished only by their DNA. There is an average of six cryptic species for each easily recognizable type, so if we apply this to the original figure, the total potential number of balloon arthropods will reach 41 m.
Even in this case, each species has several types of parasites that are mainly specific to a single host species. Many of these pests are mites that are themselves arthropods. By allowing only one type of parasite mite per host species, we have a total potential of arthropods of 82 million. Compared to only about 600 000 vertebrates – backbone animals – there are 137 species of arthropods for each vertebrate species.
It is these astronomical figures that led the physicist-turned-biologist, Sir Robert May, to observe that "to a good approximation, all [animal] the species are insects. "May was good at guessing the big numbers – he became the chief scientist of the British government – and his password in 1986 now seems very close to the goal.
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It's just diversity. How many individual insects would be lost during a massive extinction? And how much could they weigh? Their ecological importance will probably depend on both measures. It turns out that insects are so numerous that, even if they are small, their weight far exceeds that of vertebrates.
Perhaps the most famous ecologist of his generation, E. E., ants enthusiast at Harvard. Wilson estimated that a few acres of birds and mammals, but more than a billion invertebrates, almost all arthropods, inhabited every hectare of Amazonian rainforest.
This hectare would contain about 200 kg of animal tissue dry weight, of which 93% would be invertebrates, and one third of it would consist solely of ants and termites. It's an unpleasant news for our vision centered on the vertebrates of the natural world.
Ryan M. Bolton / Shutterstock
The unstable foundations of life
The role attributed to all these little creatures in the grand scheme of nature is to eat and be eaten. Insects are the key components of virtually every terrestrial food web. Herbivorous insects, which make up the majority, eat plants, using the chemical energy produced by sunlight to synthesize animal tissues and organs. The work is important and is divided into several different calls.
Caterpillars and grasshoppers chew plant leaves, plant aphids and larvae suck juice, bees steal their pollen and drink their nectar, beetles and flies eat their fruit and devastate their roots. Even gigantic tree wood is eaten by larvae of xylophagous insects.
In turn, these phytophagous insects are themselves devoured, captured, killed or parasitized by other insects. All these elements are, in turn, consumed by even larger creatures. Even when plants die and fungi and bacteria destroy them, some insects feed on them.
Going up the food chain, each animal is less and less agitated as to the type of food that it will eat. While a typical herbivore insect may consume only one plant species, insectivorous animals (mainly arthropods, but also many birds and mammals) do not care what type of insect they catch. This is why there are so many more species of insects than birds or mammals.
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Since only a small fraction of the material of one type of organism is transformed into that of its predators, each successive stage of the food chain contains less and less living matter. Although it is known that the efficiency of this process is higher in the food chain, the animals at the top represent only a few percent of the total biomass. This is why big ferocious animals are rare.
It is obvious that when the number of insects decreases, at the very top of the food chain will suffer. This is already happening – the decline in insect abundance in the tropical forests of Central America is accompanied by a parallel decrease in the number of frogs, lizards and eaters. insectivorous birds. We humans should pay more attention to our relationship with the little creatures that rule the world. As commented Wilson:
The truth is that we need invertebrates, but they do not need us.
Knowing the insects and their way of life is not a luxury. Thomas Eisner, a friend and sometimes Wilson's colleague, said:
Insects are not going to inherit the land. They own it now.
If we dispossess them, can we manage the planet without them?
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