Thursday, 25 July 2019 09:55

How do riparian strips fare long term?

Written by  Bert Quin, managing director of Quin Environmentals.
What management needs to be done to ensure riparian strips do not become overloaded and therefore useless? What management needs to be done to ensure riparian strips do not become overloaded and therefore useless?

Could our riparian systems become overloaded and therefore useless? 

Riparian strips are correctly promoted as useful tools for reducing environmental pollution, especially for their ability to filter out faecal bacteria and sediment before these enter streams. But there is much more to it, writes Bert Quin.

Many frequently made claims for the ability of riparian strips to improve water quality are based on very short-term studies only. This is particularly true of phosphorus (P) and nitrogen (N) removal. 

Unfortunately, we are now in the days of emphasis on short-term, quick-results trials that lend themselves to publication in many different journals to ensure more cash from equally short-sighted funding organisations and companies with vested interests.

In-depth studies of the longer-term change in effectiveness of riparian strips, development of optimum management plans for them and how to pay for these, are few and far between. 

Instead of long-term trials of actual riparian strips, where cause and effect can be clearly assessed, we just monitor river and lake water quality. Reductions in levels are presented by fertiliser industry funded scientists as ‘proof’ that the ‘mitigations’ the authors and funders of the research are promoting are the cause of the reductions. And they are implied to be a permanent fix and supposedly safe for continuing application of high rates of the fertiliser N and soluble P. 

Nothing could be further from the truth. 

Entry of the ‘big four’ (ie calcium, magnesium, phosphorous and boron) into riparian strips certainly results in less loss direct into the waterways they border. But we have to keep in mind that the quantities of the ‘big four’ being released from intensively grazed pastures are massively greater – typically by one to two orders of magnitude -- than those that enter water from native vegetation.

So the two most important questions should be, what management needs to be done to ensure riparian strips do not become overloaded and therefore useless, and, who should pay for this management?

A promising sign of increasing understanding is a recent article in Dairy News (June 25), sourced from the Waikato Regional Council publication ‘The condition of rural water and soil in Waikato region’. The article repeats the WRC’s advice that riparian strips and drains must be ‘very well maintained’ to be environmentally effective, but neither get into the detail and long-term costs. But the magazine article is poorly headed ‘Plants, fencing keeps nasties out of water’. A far more relevant title would have been ‘Riparian strips and drains must be well maintained to be effective’. 

The article states, “In ideal conditions, fenced grass riparian strips can reduce sediment entry to streams by 80%, dissolved P by at least 50% and nitrate-N by at least 60%”. It doesn’t define ‘ideal conditions’ or make any comment on how quickly the P and N loss reductions can diminish.

Let’s look at the effect of different losses, short and long-term, and consider the two ‘elephants in the room’ -- the continuing overuse of fertiliser N and soluble P fertilisers.

To be continued in Dairy News, August 6.

• Bert Quin is the managing director of Quin Environmentals.

More like this

Dark ages

OPINION: Before we all let The Green Party have at it with their 'bold' emissions reduction plan, the Hound thought it wise to run the numbers through the old Casio.

Govt limits forestry conversions

Farmers have welcomed the Government’s move designed to limit farm to forestry conversions entering the Emissions Trading Scheme (ETS).

Faulty models used to measure emissions

OPINION: If you have kept your finger on the emissions pulse, none of the below information will be a surprise to you. However, if you are a farmer that has not been following New Zealand’s ruminant methane issue then you may be in for a nasty shock.

ETS logic - stranger than fiction

OPINION: Over the last two weeks we have seen a Bill pass through the house that removes the ETS backstop from agriculture emissions, and once again we heard some strange logic being presented.

Featured

Editorial: KiwiSaver to the rescue?

OPINION: Farmers are rightly urging the Government to relax the rules around KiwiSaver and allow young farmers to use their savings towards purchasing either a house, cows or a farm.

DairyNZ Farmers Forum underway

Over 300 farmers and rural professionals have gathered in Hamilton for the first DairyNZ Farmers Forum for this year.

National

Top ag scientist to advise PM

A highly experienced agricultural scientist with specialist knowledge of the dairy sector is the Prime Minister's new Chief Science Advisor.

Machinery & Products

Hose runner saves time and effort

Rakaia-based equipment manufacturer Pluck’s Engineering will soon start production of a new machine designed to simplify the deployment and retrieval…

» Latest Print Issues Online

Milking It

Genuine Hipkins

OPINION: At the recent NZ Dairy Industry Awards, opposition leader Chris Hipkins made a surprise appearance.

Unserious greens

OPINION: The Greens aren't serious people when it comes to the economy, so let's not spend too much on their…

» Connect with Dairy News

» eNewsletter

Subscribe to our weekly newsletter