Crunch the numbers and help our habitat

udging by the responses, there is a lot of interest in world over-population. It seems to me that most people react to this emotionally, having pre-conceived opinions based on their experiences and beliefs formed over their lifetime. They have no interest in researching current accepted science.

I am the same. But my experiences lead me to accept current science from the Intergovernmental Panel on Climate Change.

I was born in England. I spent many holidays at a rural village in Kent, near Canterbury. We used to walk through the countryside - up the lane, through a wheatfield, past apple orchards and hopfields. There was a stream and a bridge; where we played. There were minnows, tadpoles and frogs, dragonflies, water beetles, midges; the stream was full of life.

But when I visited for the last time before I left in 1963, there was a council estate on the wheatfield, and the stream was gone - just a greasy ditch full of cans and litter.

In New Zealand, we lived at a harbourside village near Katikati. There were two frogs in a neighbour's pond. But we were told that in previous years there had been hundreds of frogs in the area.

When we arrived from the UK, the water in all the streams, rivers and lakes in New Zealand was drinkable. After a few years giardia moved into fresh wild water, and now no one can drink the wild water in New Zealand because it is so polluted. There was a report recently in the Chronicle, showing that Wanganui water has various levels of pollution.

These changes in the environment are not just climate change but also from over-population. Not only of humans, if one compares the farming methods of today with those of the past, the stocking rate of just one species in one area has often increased dramatically.

Now there are huge dairy farms, sometimes with hundreds or even thousands of cows.

The family farms of the 1800s had a mixture of products: cows, sheep, pigs, poultry and crops, trees and vegetables. So the manure from the animals could be used on the crops.

There was rotation on the farms from animals to crops; so the farms were ecologically balanced. It is still possible to see something of that today, with farms that grow maize as well as running sheep and cattle.

And, of course, now chemical fertilisers and pesticides are widely used with their consequent ill-effects.

Certainly we should all do what we can to make our air, water and land cleaner. But to reduce, re-use and recycle will not be nearly enough. We must change our ways drastically and most importantly tackle the fundamental problem of world over-population.

Frogs are a measurement of water quality. Frogs cannot live in a toxic environment, nor - eventually - will we.

Sara Dickon is ex-convener of the Environment Standing Committee, NCWNZ