Loss of biodiversity
Many of New Zealand’s tens of thousands of native species are not found anywhere else in the world. More than 50 species of bird are known to have become extinct since the arrival of humans, and an unknown number of invertebrate animals and plants have also been lost and continue to decline. In 2007 there were 2,788 species (including birds, bats, fish and plants) listed as threatened.
The establishment and expansion of farms, orchards, and vineyards – with their exotic plants and animals – have been key drivers of the land clearance and changing patterns of habitat that have led to diminishing biodiversity. Agricultural activities destroy the habitats of some species and create habitats for other, usually introduced, species.
Proponents of organic farming believe that a holistic approach to production, and not using synthetic fertilisers and pesticides, will benefit not only consumers of organic produce, but also the farm environment. Biodiversity is important from the farmers’ perspective – many farmers and researchers believe that the more diverse the ‘agro-ecosystem’, the better its chances against disease and pests. Ongoing research is investigating this.
The contribution of agriculture to New Zealand’s total greenhouse gas emissions is significant – over 50%, compared to the global average of 14%. In 2004 livestock contributed 90% of methane emissions and over 95% of nitrous oxide. Since 1990 New Zealand’s agricultural emissions have grown by about 1% each year.
As agriculture changed from sheep-dominated to mixed farming – with intensive dairy farming increasing since the 1980s – its role in New Zealand’s greenhouse gas emissions has become significant. In 2004, carbon dioxide comprised nearly half of New Zealand’s total greenhouse gas emissions, but subtracting the carbon dioxide removed from the atmosphere through activities such as forestry, reduces it to a net 19%. The major net contributors were methane (54%), and nitrous oxide (26%). Nitrous oxide emissions have grown with the increasing use of nitrogen fertilisers in farming.
Methane, a by-product of animal rumination (released in sheep and cow burps), is still of concern, with outputs increasing by 10% between 1990 and 2006. In 2003 the New Zealand Parliament considered an emissions tax (commonly called the ‘fart tax’) to control the amount of methane produced on farms. There was so much opposition from farmers that the idea was rejected.
Given the dairy industry’s commitment to continued growth, it will be difficult to reduce agricultural greenhouse gas emissions. Solutions may lie in regulatory approaches (such as amendments to the Resource Management Act 1991 to control nitrogen fertiliser use), market-based initiatives (such as tradeable pollution permits), and incentives to encourage practices to reduce nitrous oxide emissions (such as applying nitrification inhibitors to pasture).