There are an awful lot of insects. It’s hard to say exactly how many because 80% haven’t yet been described by taxonomists, but there are probably about 5.5m species. Put that number together with other kinds of animals with exoskeletons and jointed legs, known collectively as arthropods – this includes mites, spiders and woodlice – and there are probably about 7m species in all.
Despite their ubiquity in the animal kingdom, a recent report warned of a “bugpocalypse”, as surveys indicated that insects everywhere are declining at an alarming rate. This could mean the extinction of 40% of the world’s insect species over the next few decades.
What is particularly worrying is that we don’t know exactly why populations are declining. Agricultural intensification and pesticides are likely a big part of the problem, but it’s certainly more complicated than that, and habitat loss and climate change could also play a part.
Although some newspaper reports have suggested that insects could “vanish within a century” total loss is unlikely – it’s probable that if some species die out, others will move in and take their place. Nevertheless, this loss of diversity could have catastrophic consequences of its own. Insects are ecologically important and if they were to disappear, the consequences for agriculture and wildlife would be dire.
The sprawling kingdom of bugs
It’s difficult to overstate how many species there are. Indeed, the 7m estimate above is likely a major underestimate. Lots of insects that look alike – so-called “cryptic species” – are distinguishable only by their DNA. There are an average of six cryptic species for every easily recognisable kind, so if we apply this to the original figure, the potential total number of arthropods balloons to 41m.
Even then, each species has multiple kinds of parasites which are mostly specific to just one host species. Many of these parasites are mites which are themselves arthropods. Conservatively allowing just one kind of parasitic mite per host species brings us to a potential total of 82m arthropods. Compared with only around 600,000 vertebrates – animals with backbones – that’s 137 species of arthropod for every vertebrate species.
Astronomical numbers like these caused the physicist-turned-biologist Sir Robert May to observe that “To a good approximation, all [animal] species are insects.” May was good at guessing big numbers – he became the UK Government’s chief scientist – and his quip in 1986 now seems pretty close to the mark.
That’s just diversity though. How many individual insects would be lost in a mass extinction? And how much might they weigh? Their ecological importance will likely depend on both measures. It turns out that insects are so numerous that even though they are small, collectively their weight far outstrips that of the vertebrates.
Perhaps the most celebrated ecologist of his generation, the Harvard ant enthusiast E.O. Wilson estimated that each hectare (2.5 acres) of Amazonian rainforest is inhabited by only a few dozen birds and mammals but well over one billion invertebrates, almost all of which are arthropods.
That hectare would contain about 200kg dry weight of animal tissue, 93% of which would be made up of invertebrate bodies, and a third of that being just ants and termites. This is uncomfortable news for our vertebrate-centric view of the natural world.
The wriggling foundations of life
The role allotted to all these tiny creatures in the grand scheme of nature is to eat and be eaten. Insects are the key components of essentially every terrestrial food web. Herbivorous insects, which make up the majority, eat plants, using the chemical energy plants derive from sunlight to synthesise animal tissues and organs. The job is a big one, and is split into many different callings.
Caterpillars and grasshoppers chew plant leaves, aphids and plant hoppers suck their juices, bees steal their pollen and drink their nectar, while beetles and flies eat their fruits and devastate their roots. Even the wood of huge trees is eaten by wood-boring insect larvae.
In turn, these plant-eating insects are themselves eaten, being captured, killed or parasitised by yet more insects. All of these are, in their turn, consumed by still larger creatures. Even when plants die and are turned to mush by fungi and bacteria, there are insects that specialise in eating them.
Going up the food chain, each animal is less and less fussy about what kind of food it will eat. While a typical herbivorous insect might consume only one species of plant, insectivorous animals (mostly arthropods, but also many birds and mammals) don’t much care about what kind of insect they catch. This is why there are so many more kinds of insect than birds or mammals.
Because only a small fraction of the material of one kind of organism is transformed into that of its predators, each successive stage in the food chain contains less and less living matter. Even though efficiency in this process is known to be greater higher up the food chain, the animals “at the top” represent only a few percent of the total biomass. This is why big, fierce animals are rare.
And so it’s obvious that when insect numbers decrease everything higher up in the food web will suffer. This is already happening – falling insect abundance in Central American tropical forest has been accompanied by parallel declines in the numbers of insect-eating frogs, lizards and birds. We humans ought to be more careful about our relationship with the little creatures that run the world. As Wilson commented:
The truth is that we need invertebrates, but they don’t need us.
Knowing about insects and their ways is not a luxury. Wilson’s friend and sometime colleague Thomas Eisner said:
Bugs are not going to inherit the earth. They own it now.
If we dispossess them, can we manage the planet without them?
About the Author
Studio: University of Chicago Press
Label: University of Chicago Press
Publisher: University of Chicago Press
Manufacturer: University of Chicago Press
Ursula K. Heise argues that understanding these stories and symbols is indispensable for any effective advocacy on behalf of endangered species. More than that, she shows how biodiversity conservation, even and especially in its scientific and legal dimensions, is shaped by cultural assumptions about what is valuable in nature and what is not. These assumptions are hardwired into even seemingly neutral tools such as biodiversity databases and laws for the protection of endangered species. Heise shows that the conflicts and convergences of biodiversity conservation with animal welfare advocacy, environmental justice, and discussions about the Anthropocene open up a new vision of multispecies justice. Ultimately, Imagining Extinction demonstrates that biodiversity, endangered species, and extinction are not only scientific questions but issues of histories, cultures, and values.
Binding: Kindle Edition
Format: Kindle eBook
Studio: Cosmology Science Publishers
Label: Cosmology Science Publishers
Publisher: Cosmology Science Publishers
Manufacturer: Cosmology Science Publishers
Table of Contents
I: History, Origins & Causes of Mass Extinctions
1. The History, Origins, and Causes of Mass Extinctions,
Ashraf M. T. Elewa, and R. Joseph, - 4
2. Extinction, Metamorphosis, Evolutionary Apoptosis, and
Genetically Programmed Species Mass Death. R. Joseph, - 26
3. The Cronus Hypothesis: Extinction as a Necessary and Dynamic Balance to
Evolutionary Diversification Corey J. A. Bradshaw, and Barry W. Brook, - 86
4. Mass Extinction of Species: The Role of External Forcing. Andrew Glikson, - 103
5. The Biological Cosmology of Global Warming and Global Freezing.
R. Joseph, - 110
II: Asteroids, Comets, Meteors & Mass Extinctions
6. Comets, Catastrophes, and Earth's History. W. M. Napier, -138
7. The Case for the Younger Dryas Extraterrestrial Impact Event:
Mammoth, Megafauna, and Clovis Extinction, 12,900 Years Ago.
Richard B. Firestone, - 163
8. What Caused the Megafaunal Extinctions? The Case Against
Bolide Impact. Stuart J. Fiedel, - 191
9. Archaeological and Paleobiological Problems with the
Case for the Extraterrestrial Younger Dryas Impact Event
Marcus J. Hamilton and Briggs Buchanan - 196
10. Desperately Seeking a Cosmic Catastrophe 12,900 B.P.
Richard Gillespie, - 201
11. Large-Body Impacts and Global Mass Extinctions:
How Compelling is the Causal Relationship? Jonathan T. Hagstrum, - 208
12. Archaeological Perspectives on the ExtraTerrestrial
Impact Hypothesis, 12,900 B.P.: A View from Western North America
Terry L. Jones, - 214
13. Asteroids & Extinction Risks: Pebbles From Heaven.
A. Cellino, and A. Dell'Oro, - 221
14. Asteroid Impacts the Earth: The Tsunami Hazard. D. Isvoranu and V. Badescu, - 237
III: The Next Mass Extinction & Eradication of Humans
15. The Threat of Nuclear War. Victor W. Sidel, and Barry S. Levy, - 252
16. The Next Mass Extinction: Human Evolution or Human Eradication
Andrew R. Jones, - 259
17. Contemporary Mass Extinction and the Human Population Imperative
Jeffrey K. McKee, - 278
18. The Sixth Extinction Crisis: Loss of Animal Populations and Species
Gerardo Ceballos, Andrés García, and Paul R. Ehrlich, - 287
19. Preventing the Next Mass Extinction: Ethical Obligations.
Bruce Tonn, - 301
IV Threats to the Biosphere, Climate Change & Extinction
20. Atmospheric and Marine Pluralea Interactions and
Species Extinction Risks. Merrill Singer, - 314
21. Homo Sapiens, the Anthropocene Carbon Oxidation Event
and the Shift in the State of the Atmosphere. Andrew Glikson, - 322
22. Threats to the Biosphere: Eight Interactive Global Crises. John Cairns, Jr., - 342
23. Is Civilization Facing a Monumental Crisis? Is the End Near? Peter Leigh, - 355
V. Solar Activity & The Next Mass Extinction
24. Is the Sun Heading for Another Maunder Minimum?
Precursors of the Grand Solar Minima. Hiroko Miyahara et al., 362
25. The Forthcoming Grand Minimum of Solar Activity. S. Duhau, and C. de Jager, - 379
Format: Kindle eBook
- Lee Hannah
- Thomas Lovejoy
Studio: Island Press
Label: Island Press
Publisher: Island Press
Manufacturer: Island Press
Saving a Million Species reconsiders the central question of that paper: How many species may perish as a result of climate change and associated threats? Leaders from a range of disciplines synthesize the literature, refine the original estimates, and elaborate the conservation and policy implications.
examines the initial extinction risk estimates of the original paper, subsequent critiques, and the media and policy impact of this unique studypresents evidence of extinctions from climate change from different time frames in the pastexplores extinctions documented in the contemporary recordsets forth new risk estimates for future climate changeconsiders the conservation and policy implications of the estimates.
Saving a Million Species offers a clear explanation of the science behind the headline-grabbing estimates for conservationists, researchers, teachers, students, and policy-makers. It is a critical resource for helping those working to conserve biodiversity take on the rapidly advancing and evolving global stressor of climate change-the most important issue in conservation biology today, and the one for which we are least prepared.