Buzzing away: are insects on the verge of global extinction?

It's odd how some of these posts get initiated. For this particular one, there were two driving factors. One was passing a new house on my way to work where apart from the concrete driveway, the front garden consisted solely of a large square of artificial grass; the owners are clearly not nature lovers! The second inspiration was listening to a BBC Radio comedy quiz show, in which the panel discussed the recent report on global insect decline without being able to explain why this is important, apart from a vague mention of pollination.

Insect biologists have long sung the praises of these unrewarded miniature heroes, from JBS Haldane's supposed adage about God being "inordinately fond of stars and beetles" to EO Wilson's 1987 speech that described them as "the little things that run the world." In terms of numbers of species and individuals, invertebrates, especially insects, are the great success story of macroscopic life on our planet. So if they are in serious decline, does that spell trouble for Homo sapiens?

The new research claims that one-third of all insect species are currently endangered, extrapolating to wholesale extinction for the class Insecta over the next century. Although the popular press has started using evocative phrases such as "insect genocide" and even "insectageddon", just how accurate are these dramatic claims?

The United Nation's Red List currently describes three hundred insect species as critically endangered and a further seven hundred as vulnerable, but this is a tiny proportion of the total of...well, at lot more, at any rate. One oft-quoted figure is around one million insect species, although entomologists have estimated anywhere from 750,000 up to 30 million, with many species still lacking formal scientific identification. The hyperbole could therefore easily sound like unnecessary scaremongering, until you consider the details.

The new report states that butterflies and caddis flies are suffering the greatest decline, while cockroaches - as anyone who has faced a household infestation of them will know, they are likely to remain around until the end of world - and flies are the least affected orders. So, to paraphrase Monty Python, what have the insects ever done for us?

Pollination is of course of key importance, to both horticulture and un-managed 'wild' environments. Insects are near the base of many food webs; if numbers were much reduced, never mind removed, the impact on the rest of the ecosystem would be catastrophic. With the human population set to top ten billion in thirty years' time, we require ever larger regions of productive land for agriculture. They may be small at an individual level, but arthropods in general total about seventeen times the mass of all us H. sapiens. Insects replenish the soil, as alongside bacteria they break down dead matter and fecal material. So important is this latter function that New Zealand has been trialling non-native dung beetles to aid cattle farmers.

One key way to save fresh water and lessen the generation of the potent greenhouse gas methane is to reduce meat consumption in favour of insect protein. If insects are no longer around, then that will be an additional challenge in reducing environmental degradation. This of course also ignores the fact that insects are already a component in the diet of many developing nations. Last year I wrote about how scientists have been creating advanced materials derived from animals. Again, we are shooting ourselves in the foot if we allow this ready-made molecular library to be destroyed.

What is responsible for this global decline? Perhaps unsurprisingly, it turns out to be the usual suspects. Agricultural chemicals including pesticides have been associated with honey-bee colony collapse disorder (not incidentally, some tests have found honey samples with neonicotinoids - the mostly widely-used insecticides - exceeding the recommended human dosage) so clearly the same culprit is affecting other insects. Fresh waterways, home to many aquatic insect species, are frequently as polluted as the soil, either due to agricultural run-off or industrial contaminants. Wild landscapes are being converted with great haste into farm land and urban sprawl, with an obviously much-reduced biota.

Climate change is playing its part, with soil acidity increasing just as it is in the oceans. Even areas as remote as central Australia have seen marked decreases in insects as higher temperatures and lower rainfall outpaces the ability to adapt to the new conditions. I've often mentioned the role of invasive species in the decimation of indigenous vertebrates, but insects are equally prone to suffer from the arrival of newcomers. Although New Zealand has very strict biosecurity protocols, the likes of Queensland fruit flies and brown marmorated stink bugs are still occasionally found in or around ports of entry.

Many nations have no such procedures in place, resulting in local species being out-competed or killed by introduced species or pathogens to which they have no resistance. Until fairly recently, even New Zealand had a lax attitude to the issue, resulting in the decline of native species such as carabid beetles. When I conducted a brief survey of my garden in 2017 I found that one-third of the insect species were non-native, most of these being accidental imports since the arrival of European settlers.

If insects are so vital to our survival, why has there been so little interest in their well-being? There are some fairly obvious suggestions here. Firstly, at least in Western cultures, insects have been deemed dirty, ugly things that can be killed without a second thought. Wasps, ants and cockroaches in particular are seen in this light of being unwelcome pests, with typical insect-related phrases including "creepy crawlies" and "don't let the bed bugs bite".

It's fairly well-known that malaria-carrying mosquitoes are the most dangerous animals for us humans in terms of fatalities. The widespread outbreaks of the Zika virus haven't done them any favours either. As Brian Cox's television series Wonders of Life showed, their small size has given them veritable super powers compared to us lumbering mammals, from climbing up sheer surfaces (as a praying mantis was doing a few nights' ago on my window) to having amazing strength-to-weight ratios. All in all, insects are a bit too alien for their own good!

Clearly, scale prejudice is also a key factor. On a recent trip to Auckland Central Library I only found one book on insects versus dozens on birds. Photographic technology has been a double-edged sword when it comes to giving us a clearer picture of insects: close-ups are often greeted with revulsion, yet until Sir David Attenborough's 2005 BBC series Life in the Undergrowth, there was little attempt to film their behaviour with the same level of detail as say, the lions and antelopes of the Serengeti. It should also be mentioned that when Rachel Carson's ground-breaking book about the dangers of pesticides, Silent Spring, was published in 1962, the resulting environmentalism was largely in support of birds rather than insects.

Among all this doom and gloom, are there any ways to prevent it? One thing is for certain, and that is that it won't be easy. The agricultural sector would have to make drastic changes for a start, becoming much smarter in the use of chemicals and be held responsible for the local environment, including waterways. Vertical farming and other novel techniques could reduce the need for new agricultural land and water usage, but developing nations would be hard-pressed to fund these themselves.

Before any major undertaking, there's going to have to be either a fundamental crisis, such as food shortages, in a rich nation or a massive public relations exercise to convince people to consider insects in the same light as giant pandas or dolphins. This is not going to be easy, but as David Attenborough put it: "These small creatures are within a few inches of our feet, wherever we go on land - but often, they're disregarded. We would do very well to remember them."

Core solidification and the Cambrian explosion: did one begat the other?

Let's face it, we all find it easier to live our lives with the help of patterns. Whether it's a daily routine or consultation of an astrology column (insert expletive of choice here) - or even us amateur astronomers guiding our telescopes via the constellations - our continued existence relies on patterns. After all, if we didn't innately recognise our mother's face or differentiate harmless creatures from the shape of a predator, we wouldn't last long. So it shouldn't be any surprise that scientists also rely on patterns to investigate the complexities of creation.

Richard Feynman once said that a scientific hypothesis starts with a guess, which should perhaps be taken with a pinch of salt. But nonetheless scientists like to use patterns when considering explanations for phenomena; at a first glance, this technique matches the principle of parsimony, or Occam's Razor, i.e. the simplest explanation is usually the correct one - excluding quantum mechanics, of course!

An example in which a potential pattern was widely publicised prior to confirmation via hard data was that of periodic mass extinction, the idea being that a single cause might be behind the five greatest extinction events. Four years after Luis Alvarez's team's suggestion that the 66 million year-old Chicxulub impactor could have caused the Cretaceous-Paleogene extinction, paleontologists David Raup and Jack Sepkoski published a 1984 paper hypothesising extinctions at regular intervals due to extraterrestrial impacts.

This necessitated the existance of an object that could cause a periodic gravitational perturbation, in order for asteroids and comets to be diverted into the inner solar system. The new hypothesis was that we live in binary star system, with a dwarf companion star in an highly elliptical, 26 million-year orbit. This would be responsible for the perturbation when it was at perihelion (i.e. closest approach to the sun).

What's interesting is that despite the lack of evidence, the hypothesis was widely publicised in popular science media, with the death-dealing star being appropriately named Nemesis after the Greek goddess of retribution. After all, the diversification of mammals was a direct result of the K-T extinction and so of no small importance to our species.

Unfortunately, further research has shown that mass extinctions don't fall into a neat 26 million-year cycle. In addition, orbiting and ground-based telescopes now have the ability to detect Nemesis and yet have failed to do so. It appears that the hypothesis has reached a dead end; our local corner of the universe probably just isn't as tidy as we would like it to be.

Now another hypothesis has appeared that might appear to belong in a similar category of neat pattern matching taking precedence over solid evidence. Bearing in mind the importance of the subject under scrutiny - the origin of complex life - are researchers jumping the gun in order to gain kudos if proven correct? A report on 565 million year-old minerals from Quebec, Canada, suggests that at that time the Earth's magnetic field was less than ten percent of what it is today. This is considerably lower than earlier estimate of forty percent. Also, the magnetic poles appear to have reversed far more frequently during this period than they have since.

As this is directly related to the composition of the Earth's core, it has led to speculation that the inner core was then in the final stage of solidification. This would have caused increased movement in the outer liquid, iron-rich core, and thus to the rapid generation of a much higher magnetic field. In turn, the larger the magnetic field dipole intensity, the lower the amount of high energy particles that reach the Earth's surface, both cosmic rays and from our own sun. What is particularly interesting about this time is that it is just (i.e. about twenty million years) prior to the so-called Cambrian explosion, following three billion years or so of only microbial life. So were these geophysical changes responsible for a paradigm shift in evolution? To confirm, we would need to confirm the accuracy of this apparently neat match.

It's well known that some forms of bacteria can survive in much higher radiation environments than us larger scale life forms; extremophiles such as Deinococcus radiodurans have even been found thriving inside nuclear reactors. Therefore it would seem obvious that more complex organisms couldn't evolve until the magnetic field was fairly high. But until circa 430 million years ago there was no life on land (there is now evidence that fungi may have been the first organisms to survive in this harsh environment). If all life was therefore in the sea, wouldn't the deep ocean have provided the necessary radiation protection for early plants and animals?

By 600 million years ago the atmospheric oxygen content was only about ten percent of today's value; clearly, those conditions would not have been much use to pretty much any air-breathing animals we know to have ever existed. In addition, the Ediacaran assemblage, albeit somewhat different from most subsequent higher animals, arose no later than this time - with chemical evidence suggesting their development stretched back a further 100 million years. Therefore the Canadian magnetic mineral evidence seems to be too late for the core solidification/higher magnetic field generation to have given the kick start to a more sophisticated biota.

In addition, we shouldn't forget that it is the ozone layer that acts as an ultraviolet shield; UVB is just as dangerous to many organisms, including near-surface marine life, as cosmic rays and high-energy solar particles. High-altitude ozone is thought to have reached current density by 600 million years ago, with blue-green algae as its primary source. O2 levels also increased at this time, perhaps driven by climate change at the end of a global glaciation.

Although the "Snowball Earth" hypothesis - that at least half of all ocean water was frozen solid during three or four periods of glaciation - is still controversial, there is something of a correlation in time between the geophysical evidence and the emergence of the Ediacaran fauna. As to the cause of this glacial period, it is thought to have been a concatenation of circumstances, with emergent plate tectonics as a primary factor.

How to conclude? Well, we would all like to find neat, obvious solutions, especially to key questions about our own origin. Unfortunately, the hypothesis based on the magnetic mineral evidence appears to selectively ignore the evolution of the Ediacaran life forms and the development of the ozone layer. The correlation between the end of "Snowball Earth" and the Ediacaran biota evolution is on slightly firmer ground, but the period is so long ago that even dating deposits cannot be accurate except to the nearest million years or so.

It's certainly a fascinating topic, so let's hope that one day the evidence will be solid enough for us to finally understand how and when life took on the complexity we take for granted. Meanwhile, I would take any speculation based on new evidence with a Feynman-esque pinch of salt; the universe frequently fails to match the nice, neat, parcels of explanations we would like it to. Isn't that one of the factors that makes science so interesting in the first place?