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Freshwaters in New Zealand

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Freshwater ecosystems in New Zealand have been under considerable stress since European colonisation. In the past 150 years the draining of 90% of wetlands and the removal of a similar amount of indigenous vegetation has placed much strain on the health of freshwaters through the loss of the crucial hydrologic and biological functions performed by intact wetland and forest ecosystems. This loss has been exacerbated by the more recent intensification of farming with the concomitant addition of excess nutrients and sediment to water as well as the effects of urbanisation and introductions of exotic fish species. The cumulative impacts of all these changes can be seen with declining water chemistry measures and the biological status of freshwater ecosystems. The most obvious impacts are revealed by biological indicators with 68% of the native freshwater fish species listed as threatened, and 90% of lowland waterways failing bathing standards. Lowland lakes are under immense pressure; 44% of monitored lakes are eutrophic or worse and they are mostly the lowland lakes. The legislative response from central and local government to the obvious declines has failed to halt or even reduce the deterioration. In contrast, government initiatives to increase farming intensification mean there is little or no chance of improvement in the future for New Zealand freshwaters. Introduction Over the past century, New Zealand’s freshwater ecosystems have undergone significant and obvious deterioration, both chemically and ecologically. The decline is revealed in a multitude of ways, including severe reductions in biodiversity and aesthetic values corroborated by declining physicochemical measures taken at most lowland waterways (Larned et al. 2004). One of the starkest indications of the extent of the deterioration is the fact that New Zealand now has proportionally more threatened freshwater fish species than almost any country globally (Allibone et al. 2010; IUCN 2010). While in global terms the freshwater declines in New Zealand are relatively recent, they mirror declines worldwide where the symptoms and drivers of deterioration are similar but have occurred over much longer time periods. The primary driver of decline has been the unrestrained agricultural intensification (Williams 2004) with attendant increases in nutrient and sediment entering lakes, rivers and groundwater and to a lesser extent from the numerous impacts of urbanisation.
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