Grass is integral to our agricultural sector, and therefore to our economy. Pasture grasses are exotic species introduced from Europe, and not always suited to our soils or environment. So how is it that pasture-farming has been so successful in New Zealand, despite the relative lack of fertile soils? The answer is phospate-based fertiliser. But another fragile island environment has paid a high price for the artificial fertility of our soils.
As Brooking, Hodge and Wood outline in “The grasslands revolution reconsidered” (Chapter 11, Environmental Histories of New Zealand), the term “grasslands revolution” was coined to celebrate the phenomenal increase in farming productivity which occurred, despite only a small increase in land.
This “revolution” was made possible by the acquistion of Nauru Island in 1919, which Australia and New Zealand plundered for its phosphate-rich limestone and guano rock over the succeeding decades, causing irreparable environmental damage.* The introduction of aerial top-dressing in 1949 made the application of fertiliser a far more efficient process. The application of superphosphate peaked at over 3 million tonnes in 1985, or about 2 per cent of the world’s total. At the same time, sheep numbers on our farms peaked in 1982 to 70 million.
However, the conversion of much of New Zealand’s countryside to grasslands has not been an unmitigated “success” – the conversion of hill country in particular to pasture has led to erosion, landslides and flooding – and further loss of fertility as a result of lost topsoil.
[Photo right: Posphate mining on Nauru]
* 80% of the island is now a barren wasteland, with the the island’s residents living on a small strip along the coast. The inhabitants have to import most of their food as agriculture is not possible on the land stripped of top-soil.