Life wouldn’t be possible without insects, yet we know precious little about them, besides their immediate purpose. Bees pollinate flowers, dung beetles move nutrients around and bats eat mosquitoes. The millions of different kinds of insects — the world’s most populous of all species — have evolved over millions of years to form the base of the ecosystems that allow life on Earth to continue.
Our attention has focused on the decimation of charismatic vertebrates such as rhinos and elephants, but scientists are now investigating what they call the “insect apocalypse”. One way they do this is with the windscreen test.
It’s pretty crude: drive along a road and see how many insects end up smashed on the windscreen (or in a net hanging out the window). It is a fitting test for counting how many are killed by something that exists solely for humans. Around the world, scientists (and other people) have anecdotally reported that this number has been decreasing. Remember how many insects used to splat on the windscreen when your parents took you on holiday?
The growing concern about the decline in insect species numbers has now led to the first comprehensive look at how many kinds exist, and how their numbers are changing. Scientists from universities and research institutions in Vietnam, Australia and China studied 653 publications — across 40 years of research — that examined insect populations. Their findings in an article titled Worldwide Decline of Entomofauna: A Review of Its Drivers, was published in the journal Biological Conservation this month.
The headline figure is that no less than 45% of all insect species could become extinct in the next few decades. The scientists noted: “It is evident that we are witnessing the largest extinction event on Earth since the late Permian and Cretaceous period [65-million years ago]. Such an event cannot be ignored and should prompt decisive action to avert a catastrophic collapse of nature’s ecosystems.”
About half of the world’s ecosystems are being encroached on and altered by human activities and farming and cities are the main drivers. Forests are being cut down at an unsustainable rate, 12% of all land has been converted to farming, which destroys ecosystems, residential and industrial areas expand and land not being farmed is affected by air and water pollution from industrial chemicals.
This conversion of land dramatically intensified during the so-called Green Revolution of the 1950s, when agriculture turned to industrial fertilisers, irrigation and intensive farming with the aim of growing enough food for rapidly expanding populations.
The Green Revolution was hailed as one of the greatest achievements of our species — the man behind it, American Norman Ernest Borlaug, got a Nobel peace prize — but this latest research exposes the cost of the revolution.
“The current rates of species decline — which could progress into extinction — are unprecedented,” say the researchers. The rate has accelerated in the past two decades, reaching “alarming proportions”.
The destruction of ecosystems affects insects, which have spent 400-million years evolving to be the base of so many ecosystems, in a variety of ways. In South Africa, beekeepers lose a third of their colonies each year. One reason for this is that bee populations, which have historically been able to coexist with pathogens, are being destroyed because the pesticide contamination of their pollen has weakened their immune systems.
Of the 155 dragonfly species in this country, 13 are in decline and four are extinct. The introduction of rainbow trout has hit the already endangered Ecchlorolestes peringueyi dragonfly.
Data for the effects on South Africa’s insects is in short supply — research data on insects in developing countries is generally inadequate, because scientists focus on other problems. Most of the data for this latest research on insects is from the northern hemisphere. Even then, it is inadequate.
Regarding the ant and wasp populations, the researchers say: “The status [of how many there are] remains practically unknown to this date.”
When insects die off in large numbers, the researchers warn: “The repercussions this will have for the planet’s ecosystems are catastrophic to say the least, as insects are the structural and functional base for many of the world’s ecosystems.”
And this is without the accelerated change brought about by climate change, which is already being felt. Animals are unable to evolve fast enough to survive their habitats getting hotter or colder, drier or wetter. That change will be felt hardest in the tropics, for which there is the least data on insect numbers.
Given the apocalyptic nature of their findings, the researchers say urgent action is needed: “A rethinking of current agricultural practices, in particular a serious reduction in pesticide usage and its substitution with more sustainable, ecologically based practices, is urgently needed to slow or reverse current trends, allow the recovery of declining insect populations and safeguard the vital ecosystem services they provide.”