Why do we need to phase out synthetic nitrogen fertiliser?

Between 1990 and 2023, the number of dairy cows in Aotearoa New Zealand increased by 71%, from 3.4 million to 5.9 million. All those cows need to eat. Nitrogen fertiliser is used to make grass grow. Growing more grass faster with fertiliser has facilitated intensive dairy farming. Between 1991 and 2019, synthetic nitrogen fertiliser use increased by 629%.

Using nitrogen fertiliser has serious impacts. This includes the pollution of rivers, lakes and groundwater. Over a third of our monitored groundwaters saw a rise in nitrate levels in the last two decades. It also poses risks to human health through nitrate contamination of community drinking water supplies.

The manufacture and use of synthetic fertiliser contributes to climate change, and has tipped the natural nitrogen cycle out of balance.