Stream health little different

Researchers at the University of Otago have found that streams flowing through integrated sheep and beef farms are just as healthy as those flowing through organic farms.

The paper found conventional sheep and beef farms had the most negative impact on waterways, but the conditions of streams flowing through organic and integrated farms were similar.

Integrated farms aimed to reduce or eliminate the use of pesticides, used beneficial pest predators and encouraged environmentally responsible soil, water and energy management, researchers said in a statement.

The resulting paper, titled "Responses of stream macro-invertebrates and ecosystem function to conventional, integrated and organic farming", was recently published in the British Ecological Society's Journal of Applied Ecology.

The survey involved students and supervisors from the university's zoology department, its Centre for the Study of Agriculture, Food and Environment, the Agricultural Research Group on Sustainability and the National Institute of Water and Atmospheric Research (Niwa).

Research fellow Christoph Matthaei said the study focused on 15 streams, five each flowing through conventional, integrated, and organic non-intensive pasture-based sheep and beef farms near Amberley, Akaroa, Outram, Owaka and Gore.

Information was gathered on riparian management such as fencing, stock access, stock presence and regenerating woody and bank vegetation, which was determined as a percentage of bare ground, pasture, tussock, scrub and trees.

The different farm management styles were measured on how stream ecosystems functioned, water quality, biodiversity and the abundance of pollution-sensitive micro-invertebrate species, such as mayflies, stoneflies and caddis flies.

The assumption was that organic farming practices would have the least impact on streams, but Dr Matthaei said the research found integrated management had a similar effect.

While all the streams were polluted to some extent, those on conventional farms were most so, while those on integrated and organic farms had similar levels.

"Integrated and conventional farms received similar fertiliser and pesticide inputs, but nutrient and pesticide concentrations of integrated farm streams were generally low and more similar to organic than conventional farm streams," the authors said in their report.

"This may reflect greater care taken over the timing of inputs by farmers who follow integrated farming prescriptions."

However, all farm management was impacting on the health of streams, which were described as "moderately polluted", and the researchers recommended increased attention to fencing, riparian management and stream habitat.


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