Ian McLean Green candidate for Tauranga

When Bill Clinton said 'It's the economy, stupid”, he had it only half right. It is true, that to have a successful society, one needs a functioning economy. But to have a functioning economy, one needs a healthy environment.

Take rivers. When elected to government, the Greens will place resource charges on commercial use of water, introduce controls on dairy intensification into the National Policy Statement on water management and support the planting of riparian strips and fencing of waterways.

Throughout human existence, we have taken the environment for granted. We assumed that it existed to service our needs and provided infinite capacity to absorb whatever we threw at it. Call this the Absorption Hypothesis (AH).

Many societies have failed because the intensity of human enterprise overwhelmed the capacity of the local environment. In other words, we have already tested the AH many times and it has failed us.

For the Greens, this issue is fundamental. If we work with the environment, it will cheerfully provide the services that we need. If we fight it in order to maximise profitability, it will eventually fail us.

Agrichemicals, fertiliser, irrigation, grass or pine monocultures and forest clearance on steep slopes are all examples of our attempts to subjugate the environment in pursuit of profitability.

We use rivers as the cheapest option for transporting our agricultural and industrial wastes away from source. Rivers used for these services need strong flows because we rely on dilution to minimise downstream effects (AH again).

But we also remove the water (for irrigation), need it to be clean (for drinking, tourism, wildlife conservation and fishing) or change its flow and ecology (for energy production). Many of our rivers are already beyond their capacity to provide the (conflicting) services that we demand. We have become better at controlling point source pollutants from heavy industry. But our management of diffuse agricultural waste products is still inadequate.

And it shows: Our ‘clean, green' brand, worth an estimated $18 billion, is under threat. But more to the point, there are many rivers where our children can no longer swim or fish.

Farmers are at their wits end. Like anybody else, they want clean rivers and they want to run a profitable business without creating downstream effects. But we now know that an endless supply of diffuse pollution cannot be indefinitely absorbed by our environment.

Change is necessary. So are clean rivers.