“The unnoticed insect apocalypse” should sound alarm bells, according to nature conservation advocates who argue that if it is not stopped, it will have significant consequences for humans and all life on Earth.
theguardian.com, 13 November
Nothing in this world is eternal, not even the Earth and the Sun themselves, let alone species. 99% of all species that have ever lived on Earth are extinct. It is considered that the average lifespan of a species is about one million years, and the usual rate of evolutionary turnover, in the absence of mass extinction, fluctuates between 0.1 and 2 species losses per million species-years. Assuming there are about 5 million species living on Earth, we have to resign ourselves to losing some 10 species a year. Over the last 500 years, mostly due to human's insatiable economic activity, 322 land-dwelling vertebrate species have disappeared, which is an average of 1.6 species per year. About 158 fish species are also considered recently extinct. When measured against the total number of all possible species, this seems like a mere trifle; however, compared to the number of mammal (currently 5,416) and bird (currently about 10,000) species, this is an extinction rate at least 20 times faster than would be expected in the course of evolution undisturbed by civilisation.
On 13 November 2019, the British newspaper The Guardian once again sounded the alarm regarding threats to biodiversity, this time focusing on the decline of insects. The publication was prompted by a report prepared by Professor Dave Goulson, a Fellow of the Royal Entomological Society, on behalf of a nature conservation organisation: “Insect declines and why they matter”.
Goulson's report, as is usual for works aimed at the general public, describes the situation more subjectively than would be permissible in a scientific publication, sparing no colour to depict the drama of the situation and calling on the public to take immediate action to save what can still be saved. The report does not use the author's own research results, but instead recounts purposefully selected publications that summarise data on insect species numbers and occurrence collected over several decades in various countries.
Lately, insects have become as popular in articles dedicated to nature conservation as birds or plants. Goulson reports, for example, that the biomass of flying insects in Germany has decreased by 75% since 1989, the number of butterflies in the British countryside has decreased by 46% since 1976, and the range of 13 (out of 23) bumblebee species has halved, while 41% of insect species in Europe and North America are threatened with extinction. It is thus concluded that “we are experiencing the largest mass extinction since the late Permian period” 250 million years ago. The drama of the perception of the situation is sharpened by the terms “insect armageddon” and the “Brexit”-inspired “insectageddon”, which have been in circulation for several years.
Insects are a significant part of the ecosystem. Having arrived in the world 400 million years ago, they have managed to sting plesiosaurs and, as amber formed, became stuck in ancient pine resin like flypaper. Even then, they achieved astonishing diversity and distribution. Today, nearly a million insect species have been described – more than half of all known species. It is estimated that at least another three million insect species are waiting for their naming ceremony. The total calculated mass of terrestrial insects exceeds the living weight of humanity by 3-4 times, despite the latter's tendencies towards obesity. The presence of insects is necessary for maintaining balance in nature, the coordinated functioning of food chains, the subsistence of insectivorous animals, especially birds, the pollination of plants, and the formation of soil structure. From the perspective of human selfish interests, the most economically important task of insects would be providing the harvest for 75% of crops that cannot do without pollinators. In the spirit of folk songs, we could refer to honey and wax, but let's not forget the bright culinary prospects of crickets and insect larvae, as well as silk, chitin, carmine, bee venom, and so on and so forth.
If we accept that the figures presented in Goulson's report are true and that in the current “insect armageddon” of the sixth mass extinction, species are disappearing eight times faster than vertebrate species, we can roughly estimate that about 3,900 insect species would have disappeared over 500 years. Given that the possible total number of insect species is 4 million, such an extinction rate still falls within the standard evolutionary cycle: let us remember, up to two lost species per million species-years.
Apocalyptic visions of the insect future should perhaps be assessed not as species extinction, but as a demographic crisis and biomass reduction of insect species – their “peoples”. And this too is a path to destruction; here too, civilisation has shown its volcanic power. If the sixth mass extinction is gaining momentum right now, it, just like the previous five, is destroying familiar habitats, poisoning the environment, and causing climate change; only their cause is not natural disasters, but the “eruption” of civilisation. It is not volcanic lava, but humans, livestock, and crops that are taking over natural territories and displacing native species. All elephants, giraffes, lions, bears, hyenas, raccoons, and others together make up about one-fifteenth of the total biomass of livestock, primarily cows and pigs.
At the same time, it should be pointed out that insects exhibit much greater plasticity than mammal or bird populations; insect populations are capable of both rapidly multiplying in favourable environmental conditions and shrinking in poor ones. One must understand which point in time we choose as the baseline for comparison. Just as in economics: in any given year, we can have both GDP growth and a decline if we take the previous year, 2008, 1989, or 1913 as a comparison. Several of the sources used in Goulson's report can be accused of biased selection of data documenting population decline, and insufficiently long or fragmented time series of observations. Thus, a study conducted in Great Britain that showed a gradual decrease in the number of moths after 1982 would be another drop in the bucket for the armageddon mill, if it were not known that in the period from 1967 to 1982, the number of these insects increased rapidly, and currently, there are more moths in Great Britain than there were before the great student protests in Europe and the occupation of Czechoslovakia.
In conclusion, when speaking about natural disasters, mass extinctions, and crises, one must remember that, in addition to all the destruction, they also possess a creative force. Had there not been the fifth mass extinction 66 million years ago, when a natural disaster caused by an asteroid swept away the hegemony of the dinosaurs, our mammalian ancestors would not have had the opportunity to ride the evolutionary wave, and most likely we would still be hiding in caves to this day, in the form of proto-primates, from the teeth of nasty reptiles. Likewise, diversity has its dark sides – even without mentioning the connectors for mobile phone chargers. Had there not been the Toba volcanic eruption 75,000 years ago and the freezing of our Homo genus cousins in a volcanic winter, perhaps we would have to fight yetis, bigfoots, and snowmen for a seat on the tram.
However, let us not get carried away with revolutionary ideas. To date, mass extinctions of species in Earth's history have ended with the demise of the dominant species – be they graptolites, trilobites, or dinosaurs. At the moment, we are the ones in charge, so let us quote Goethe: “Linger, you are so fair!”
Article first published in the January 2020 issue of Rīgas Laiks magazine