The Insect Crisis

I hesitated before reading Oliver Milman's The Insect Crisis: The Fall of the Tiny Empires that Run the World.  I knew it would be depressing.  I made myself read it anyway because it's important not to look away.

I was right, it was a depressing read.  There are multiple strands of evidence that the past few decades have seen substantial, sometimes dramatic, falls in insect populations around the world.  Various longitudinal surveys in different places - primarily Europe and the USA - show declines in insect numbers that are generally in the range of 20-50% but in some places are as much as 90%.  Some formerly abundant species, like North America's Monarch Butterflies or some species of European and North American bumblebees, are now threatened, but even species that are far from being threatened, like our common domesticated honeybees, are facing increasing pressure.  

A caveat is in order.  None of these are comprehensive region-wide studies, let alone national or continental.  Many parts of the globe (including Australia) have very little insect data at all.  What we have are snapshots of different locations, taken over time.  

Yet with this in mind, the story remains remarkably consistent, and is backed up by wider anecdotal stories from around the globe.  Insects seem to be declining.  This is bad news for the insects, but its effects also ripple through the rest of the ecosystem.  Insects are vital as food for other species - birds, reptiles, small mammals, other insects - and also play a vital role in pollinating plants including a large number of our food crops.  Without insects, all sorts of creatures suffer, including us.

What is causing this decline?  There's no single culprit, but the list of causes is familiar - habitat loss, pollution (in this case, insecticides) and climate change.  

The main culprit for habitat loss is agriculture, although logging, mining, urban sprawl and bushfires (linked to climate change) also play a role.  There are many aspects to it, because insects live in diverse habitats.  The loss of forests, especially rainforests, devastates complex webs of insect life. Modern industrial farming removes pockets of insect habitat such as hedgerows, native grasslands and tree cover which co-existed with more traditional farming methods. Urban lawns, with their manicured monocultures of couch and concrete, do the same.  Insects that rely on flowering plants for their food need diverse plant communities to live on because different plants flower at different times of the year - if whole swathes of country are devoted to a single crop they have a glut (provided the crop is something they can eat from) then a famine.  As habitats shrink, populations of a species become increasingly 'islanded' - unable to move from habitat to habitat, stuck with a small gene pool, and with nowhere to migrate to if disaster hits.  

Insecticides are of course, by definition, harmful to insects.  Back in the 1960s and 1970s, Rachel Carson's Silent Spring drew the attention of millions to the problem of DDT, and it was eventually banned around the world.  Seemingly we never learned the fundamental lesson, because now we have a new generation of insecticides called neonicotinoids which are even more potent.  They are heavily promoted by massive agricultural conglomerates and many famers, following the modern trend of industrial agriculture, sow mono-cultural fields, often using proprietary seeds that are coated in pesticides, and then spraying at intervals to control pests.  Of course, pretty much any insect is caught in the crossfire and the deaths spread as the poison is blown on the air, washed into streams and finds its way to the most unlikely places.  

Interestingly, Milman suggests that while this is hugely profitable for the ag companies, it is not necessarily a huge net benefit to the farmers.  They find themselves caught in a cycle where they have to buy pesticide resilient seeds from the companies, then spray expensive pesticides in increasing quantities as the pests develop resistance.  Meanwhile, natural predator insects are also decimated.  If farmers cut out or reduce pesticides they may get more pests which would result in increased crop losses, but this would be offset both by increased natural protection and decreased costs.  

Finally, of course, climate change changes all sorts of things.  At the simplest level, insects that are temperature sensitive can no longer live where they used to.  They could, perhaps, move to cooler latitudes or altitudes provided they have access to these, but islanded habitats can prevent this, and the plants they need may not move with them.  More complex things happen too.  For instance, if plants flower based on the length of the day while insects hatch and pupate based on temperature (or vice versa), then the mutual benefit of feed and pollination don't meet up any more.  Too much rain, or not enough, can interfere with life cycles.  

The source of hope here is that insects can bounce back.  Most insects breed prolifically, and in the right conditions their populations can boom. If we just take our foot off their throat they will have a chance to rebound - allow more diverse plant communities, pull back on the pesticides, move quickly to mitigate climate change.  Nothing beyond our capabilities, and most of this would be good for us in so many other ways.

***

Milman points out that a lot of our conservation efforts focus on a few charismatic mammals - white rhinos, tigers, giant pandas, koalas.  Meanwhile, the loss of insects barely registers.  We have an ambivalent relationship towards them - we love colourful butterflies, iridescent beetles, ladybirds, even praying mantises.  On the other hand, we do our best to eliminate flies, mosquitoes and cockroaches and have a visceral response maggots.  Even the species we love we often don't notice.  Mostly, if insects aren't annoying us we don't think about them.  This means that we also don't notice their disappearance.

One example of this is the 'windscreen test'.  In my youth I remember driving through rural Queensland.  If we travelled at night, by the time we arrived at our destination the front of the car would be plastered with dead insects - grasshoppers, moths, beetles, butterflies.  First order of business the next morning would be to call in at the nearest servo and give the windscreen a good scrub so Dad could see out for that day's driving.  

I can't remember any such journey in recent years.  If I have one critter splatted on the front of my car, that is an unusual event.  Milman records such changes from around the world.  There's a man in Denmark who has turned the issue into a detailed scientific investigation, with he and his graduate students driving nightly down the same roads at the same speeds for years, logging the number of insects they kill on a massive database.  You guessed it - a lot fewer insects now than when they started.  

But the childhood experience of insects that sits closes to my heart is the story of Rhopaea magnicornis, a species of scarab beetle most often known as the Brown Cockchafer.  When we were kids our parents called these Christmas Beetles - as English immigrants they got them mixed up with their  more beautiful golden-carapaced cousins.  When I lived in Maryborough in the heart of Queensland's cane country in the 1980s everyone called them cane beetles.  

These beetles appear each Spring here in South-East Queensland. They don't live long as beetles.  For most of their lives they live underground as white larvae that people refer to as 'curl grubs'.  These munch away at organic matter - you might find them in your garden, where they don't do any real harm - if they chew on the roots of your plants a little, they make up for it by aerating the soil and breaking down organic matter.  They pupate under ground, and the spring rain stimulates them to come out, find a mate, lay some eggs and then pass out of this life.

In my childhood, each October featured hundreds of them banging on our windows at night, trying to get to our lights.  Every morning the verandah and garage would be littered with them wriggling on their backs, and they would be lying under every window.  We would try to set them on their feet and sometimes they would try to crawl off but they wouldn't get far.  If we tried to keep them in boxes they would be dead within 24 hours.  But their children would be back the next Spring, and the one after.  

It was the same in Maryborough.  The grubs loved the canefields and each spring when the rains came they would pour out and fly around town.  You could tell they were around because they gave off a faint bitter smell.  

Yet last Spring I don't think I saw one.  We still have curl grubs in our garden so not sure where the adults go, and they could be from a different species - the grubs can be hard to tell apart.  I haven't found any wriggling in the ground.  I haven't seen them when I'm out walking.  

I wondered if it might be urban sprawl and me living closer to the city now - after all, we were pretty close to the edge of town as kids.  So I asked some Maryborough friends if they still get them now.  Same story - they have declined slowly and they hardly see any now.  Yet the town is still the same, the cane fields are as close as ever.

What's happened to them?  Short answer is, no idea.  No-one has researched it, as far as I can find.  No-one even has any record of numbers.  The Atlas of Living Australia has a few recorded sightings of it around SEQ but nothing around Maryborough - but this is dependent on ordinary enthusiasts taking an interest.  Still, four specimens from around Brisbane in two years is a meagre record of a beetle which once appeared by the hundreds at my house. 

Certainly around Maryborough, insecticides could be part of the problem.  These little critters don't do much damage to cane but there are closely related beetles that do, and the insecticides don't distinguish.  In Brisbane perhaps habitat loss is more significant - they seem to live in my garden, but the big numbers are likely to come from bushland areas and these have been progressively cleared to make way for urban sprawl.  Meanwhile, the farmers on our outskirts presumably use insecticides too.  What role does climate change play?  Have our hot dry years placed them under stress?  

But this is all speculation.   In fact, no-one cares enough to really find out, to understand their lifecycles deeply and find out what is going on for them.  Perhaps they are not yet rare enough to go on the endangered list but how would we know?  Beyond a few iconic species, like the Bogong Moth, we really have no idea what is happening to Australian insects. But one thing is for sure - there are a lot fewer of them than there used to be.  

***

The British evolutionary biologist JBS Haldane is reported as saying that God has 'an inordinate fondness for beetles'.  There are about 300,000 documented beetle species, and almost certainly thousands more not described and classified by scientists.  If some went extinct, we probably wouldn't even know.  No-one would notice, or mourn their passing.

Except for God, who we assume, given he marks the death of every sparrow, is also marking the death of his beloved beetles, and mourning every species that passes.