When the political fog descends and obfuscates an issue such as water quality, the truth and clarity can remain hard to find. It is as though the authorities have decided that no further available evidence or action is required — so the fog remains.
Rural New Zealand has been found guilty of being the main cause of water pollution. The debate has been closed and laid at the feet of fertiliser and livestock.
Yes, nitrates are a real issue especially where tile drains exist. Nitrates have also been carbon dated at about 100 years of age — well before irrigation and dairying.
The public also need to be aware that a crop of potatoes uses twice as much nitrogen fertiliser as a dairy farmer.
The reasons for poor water quality have been widely known within the science community, yet one particular reason has been ignored by local and central government.
It is inconceivable that authorities from ministries to regional councils do not know of the destructive capacities of rotting leaf litter from the willow trees, deeply lining the riparian margins of too many of our rivers and lakes.
Willow trees can line both banks of a river for which everybody and nobody is responsible. These trees continue to be ignored, as the blame for water quality and quantity has been preset.
Few would complain about a managed single line of willows on one side of a river to protect from riverbank erosion but all too often the willows are anything from a couple of metres to 20 or so metres deep and on both banks.
It has been well established in environmental literature that a mature willow tree can consume 400 litres of water a day during summer, which is of course when water demand is at an absolute premium with competing interests all stating their use is of the highest use possible.
The problems really start when autumn arrives and willow leaves turn to beautiful calming shades of golden hues. All the while — the poets’ collective souls wax lyrically about the shaded colours to gladden the hearts of all who gaze upon their occasional beauty.
Little thought is given to the next biological stage and state of water quality as a result.
Enter the science guys. In moderate leaf litter falls, the willow can supply and support what they call detrital food webs and microbial food webs.
However, where excessive inputs from where wall-to-wall willows exist far beyond the riparian zone (Lindis and Manuherikia rivers) then water quality falls and algae blooms can occur, and not a dairy or beef cow in sight.
Nobody has ever asked for a wide public discussion so as to ask the pertinent questions around environmental health of a water body. Questions as to whether the correct indexes are used for the opposing interests to debate along with the need to fully understand factual data so the problems can become workable solutions all can live with.
To suggest the only outcome possible is the environmental bottom line is simplistic. Willow leaf litter breaks down and releases nitrogen and phosphorus into the water body leading to localised oxygen depletion which in turn impacts on fish and invertebrates.
This process has long been blamed on use of artificial fertiliser. Only highly specialised isotope techniques can determine the truth of the source of the enrichment.
A NZ Geographic article entitled ‘‘Our Deeply Toxic Relationship with Willows’’ has highlighted willows have fundamentally altered our river systems by creating slow, shaded and organic-rich environments.
Good outcomes really do depend on informed questions and indexes being used to promote solutions. It will start with the truth being told about the toxic role of willows.
Removal on an industrial scale and financed by us all — local and central government — is vital. Ngāi Tahu should also contribute due to their interest and claims of ownership in and of fresh water. This interest must include the riparian margins.
If nature and the environment need a true champion, then its first lieutenant is clearly the people who can make the difference and not those who wrongly appoint blame and demand compliance from afar.
Perhaps the divide is now far too wide along with opinions from all sides being too entrenched.
Curiously, Environment Canterbury (ECan) has apparently sprayed willows on the main stem of Ahuriri River to great effect along with genuine environmental resilience — the Rangitata, Rakia, Ashburton and the Waimakariri rivers have also been sprayed so why not Otago?
• Gerrard Eckhoff is a former Otago regional councillor and Act New Zealand MP.
