Making a meal of our insect life

Eat, drink and be merry, for tomorrow we die? That’s just the attitude humans don’t need, writes Bob Holderness-Roddam

HAVING a barbecue? Uninvited guests such as mozzies turn up to join the party and a drink of red: not the wine, but your blood. Then there are the myriad insects that dine out on our farm and garden crops — the cabbage white butterfly caterpillars, aphids, fruit flies and weevils. Termites dine out on the timber that supports our homes, and cicadas disrupt our sleep.

But it’s just like other things in life. We notice the bad behaviour, whilst the good work of many insect species goes unnoticed. Life on Earth would be very different without them. They are an essential part of the food chain; ensuring the survival of many bird species such as our iconic blue wrens, swallows, robins, grey fantails and many other species.

Micro Chiroptera (bats), frogs, lizards and Australia’s unique egg-laying mammals, the echidna and platypus, also rely upon insects for much of their diet.

Insects provide essential ecosystem services: pollination of our crops and gardens rely upon the services of bees, moths, flies, wasps and other insects Other insects help to break down the fallen timber, releasing nutrients back into the soil.

Ladybird beetles help to control the aphids which attack our garden plants.

Insects play an essential role in dealing with dead animals and dung. Without them, we would soon be snowed under in dead animals and up to our eyes in s — t!

But all this is threatened. The Mercury carried a story, “Insects’ time may be up”, referring to a paper by

Francisco Sanchez-Bayo from Sydney University and Kris Wyckhuys from the University of Queensland in the journal Biological Conservation. They assessed 73 studies on insect populations and concluded that 41 per cent of all insect species were in decline globally, with an annual decrease of 1 per cent. If this rate is maintained, insects will be virtually extinct within a few decades.

Most of the papers assessed dealt with European and North American insect species, not a deliberate bias, but simply because most of the studies are from these areas. Very few studies have been made of African, Asian, Australian and South American insect populations. However, those that are available support the paper’s findings. For example, in Puerto Rico there has been a decline in ground-foraging and canopy dwelling insects of 78 per cent over 36 years. This, in turn, has led to fewer frogs and lizards because their food is disappearing.

The authors provide many other examples from a wide group of insects to support their argument. In Sweden, 269 butterfly species have been monitored in a nature reserve for 50 years. The species decline has been 45 per cent, with 159 species not being found in 2004. Spanish butterflies have also fared poorly, with 46 of the 66 species monitored declining in the 20 years since 1994.

Honeybee colonies declined in the US by nearly 50 per cent since 1947, initially due to DDT exposure. Bumble bee populations have also tumbled, with 48 of 60 species declining over a 136-year period. Thirty per cent of these species are threatened and another four are extinct. Half of 14 bumblebee species in Ontario, Canada declined between 1971 and 2006.

Other studies have shown that insects that rely upon water habitats for at least a part of their life cycle are at particular risk due to pollution from agricultural chemicals. These include dragonflies, damselflies, stoneflies, mayflies and caddisflies.

What is the reason for these massive decline in insect numbers? The authors blame massive increase in intensive agriculture. Land clearance has destroyed the habitat for many species, clearing native grasslands and woodlands and draining wetlands. The development of feedlots and stalls for livestock has removed dung from the environment, resulting in a dramatic fall in dung beetle numbers.

Intensive agriculture has increased use of insecticides, fungicides, herbicides and fertilisers. The development of DDT provided the initial hit on insects and other species, so well chronicled in Rachel Carson’s iconic Silent Spring. Many other insecticides, such as neonicotinoids, are a serious threat to insects such as bees. Herbicides don’t directly kill insects, but they kill plant species which some insects rely upon for food. Fertilisers such as nitrogen end up in our waterways resulting in increased algal growth. This decreases the available oxygen, resulting in the deaths of aquatic insects and fish.

Biological factors have been blamed for other insect declines. In South Africa, introduced rainbow trout reduced the range of a threatened dragonfly species. Dragonflies have also been affected by exotic tree planting on river banks in South Africa.

The obvious culprit of climate change has received little attention. However, I suggest that as our climate becomes increasingly unpredictable this will become

a major player in further insect decline.

How do we reverse this threat to our own survival? We must stop ripping up our natural areas, allow damaged areas to regenerate and stop draining our wetlands. Instead of massive applications of pesticides and fertilisers, we need to rethink pest control. Options include biological controls, such as encouraging ladybird beetles to deal with aphids.

It is vital that research into the situation in Australia is increased in order to determine the local situation.

Finally, we absolutely must ditch our “Eat, drink and be merry, for tomorrow we die” attitude. If we don’t, it won’t just be the insects that die — most other organisms — plants and animals — will disappear along with them, including us. Bob Holderness-Roddam is an associate in the Discipline of Geography and Spatial Sciences/ School of Technology, Environments and Design in the Colleges of Science and Engineering at the University of Tasmania. He has a diploma in Agriculture and a masters degree in Environmental Management.