I've had quite a bit feedback on the column I wrote two weeks ago on the world's threatened mass insect extinction.

It had an impact on people, as the study I quoted had made an impact on me.

I surprised myself with the frustration, anger, and indeed guilt that I felt on learning about the rapid insect decline happening globally. Those feelings flowed into what I wrote.

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Two weeks later, I want to respond to some points made by people who read the column.

The central claim of the study by Dr Francisco Sánchez-Bayo (University of Sydney) and Kris Wyckhuys (University of Queensland) was that the mass of the world's insects had declined by 80 per cent over the last 25-30 years. They reached this conclusion by looking at 73 historical reports on insect decline around the world.

Some scientists, in response to the study, have expressed scepticism that the 80 per cent figure could be confidently arrived at.

The situation is bad, very bad and getting worse, it's agreed, but many experts on insects don't believe we have enough information to put a figure on it. This doesn't make Sánchez-Bayo's and Wyckhuys's claim necessarily wrong, but the global situation does require further investigation.

What's uncontested is that human activity is causing the extinction of species and a rapid drop in the mass of insects. (The global economy has nearly quadrupled since 1990.)

Two different New Zealand grasshopper species - Phaulacridium marginale (right larger) and Phaulacridium otagoense - have been found to mate due to landscape changes.
Two different New Zealand grasshopper species - Phaulacridium marginale (right larger) and Phaulacridium otagoense - have been found to mate due to landscape changes.

One reaction to my previous column, however, was that this situation didn't apply to New Zealand and we shouldn't be concerned.

Maybe the decline of insect numbers hasn't been as bad because of our relatively low population to land mass. We need more studies to find out.

That said, factors contributing to the insect decline worldwide are definitely occurring here.

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Our pesticide use is mid-range compared to other countries: 9.88 kilograms per hectare in 2009. But our use of synthetic fertilisers is one of the absolute highest in the world. Figures from 2014 showed 1.5 tonnes of artificial fertiliser used per hectare of land.

According to Greenpeace, who wants synthetic fertilisers banned because of their contribution to global warming, New Zealand has increased by seven-fold the use of synthetic fertilisers since 1990.

It is mostly used to grow grass for a cow population that's doubled.

It's fair to say that this increased use will have had consequences for insects and microbes in and above the soil.

Synthetic fertiliser is being used in increasing quantities because the soil isn't being given a chance to regenerate itself naturally.

The cycle of growth and decay of plant and animal matter is being compromised by a synthetic process which is harmful to insects and other beneficial life.

The soil is being degraded and is only 'working' because synthetic fertilisers are constantly reapplied at increasing cost. That included the cost in carbon emissions released in the manufacturing process and in the application of the fertilisers to the land.

Everything is interconnected. Save the insects through moving to organic farming techniques primarily for local consumption, and we reduce our carbon emissions as well.

Is this the vision the Northland Regional Council has for agriculture in Northland? I'm not sure it is.