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A major new report on the state of land in New Zealand has been released today (19 April 2018) - read it at the Ministry for the Environment site here.
The following is some commentary from Professor Rich McDowell, AgResearch principal scientist and Chief Scientist for the Our Land and Water national science challenge:
While this report does provide a snapshot of the state of the land as far as impacts, it is important to note that it does not provide insights into the trends in relation to phosphorus in the soil, and macroporosity of the soil – and how land use, and intensity of that use, contributes. Phosphorus in the soil is one measure, but there are other variables at play such as compaction of the soil, that will dictate whether there is phosphorus run-off into waterways to do damage.
What we do know is that the data for water quality (in regard to phosphorus) and sediment concentrations indicate that far more sites are showing improvements now (2004-2013) than before (1994-2003). This is despite changes in land use, land use intensity and indications that phosphorus under dairying is enriched, and macroporosity of the soil is impaired. These improvements may be due to greater awareness, farmers being more proactive or policy changes. Efforts include the isolation of critical source areas that contribute most phosphorus and sediment loss from farms or catchments, and targeting critical source areas with measures to mitigate these losses.
The question is always whether these efforts are enough to meet community aspirations of water quality. This is why the Our Land and Water National Science Challenge (hosted by AgResearch) is supporting work examining land use suitability, and providing indicators on what a parcel of land can produce, the potential of these land parcels to lose contaminants, and the effect of these contaminants on water according to a water quality objective. This work will also be expanded to examine objectives for soil.
You can read more about work in regard to land use suitability, and sources and flows of contaminants at pages 17 and 18 here.