Waiheke Channel
At Pōnui Island, under the shade of picturesque pōhutukawa, effluent from a farm drains into the Waiheke Channel adjacent to the Te Matuku Marine Reserve. Stock roam freely through the waterway and the wetland above it. The smell, fortunately for the viewer, can only be imagined.
This is a compelling picture of run-off in the rural context, but the volume of material from major rural tributaries into the Firth of Thames, for instance, is orders of magnitude more concerning. Concentrations of nitrogen in the Firth have increased dramatically since the expansion and intensification of dairying began in 1998, as has phytoplankton and carbon dioxide. Oxygen depletion in the Firth is about four times worse than in the outer Gulf.
