Politicians are focusing on water quality issues ahead of this year’s election, recognising this is a major concern for New Zealanders. There has been a lot of talk about planting more riparian margins, but very little discussion about the time and cost involved in the ongoing weed control and maintenance of these margins. I asked Rob and Jan Fryer, of FuturEcology, about the reasons why landowners resist riparian planting and how councils can help to resolve these issues.

This is part one of a two-part series of articles to be published on this website. The second article provides practical advice on choosing the best plants for your site and establishing a weed control regime. Click here to access the second article.

Stock exclusion is now becoming a legislative requirement, with staged dates for when it takes effect for different stock types. What are the implications for landowners, both in terms of time and money?

Farmers and other landowners benefit from seeing riparian management (including fencing, planting and weed control) as a business expense that can be outsourced if they lack the time to do it themselves.

Particularly in the dairy industry, time to do the work is a big factor. Often it’s not a problem to carry out planting in winter, but maintenance is needed in the spring and autumn. This job is likely to drop well down the priority list when calving and milking are underway.

It’s really important not to underestimate the work required because fencing off land without maintaining riparian margins is a bad idea — leading to creeks overgrown with blackberry and old man’s beard.

Of the landowners you work with, what are their concerns about planted riparian margins?

There is resistance. Landowners ask why would I fence off this area and have to do all this weed control, especially when they can point to local examples of weed infestation. It’s a hard sell!

One of the biggest issues with stock exclusion or regeneration of riparian margins is the transition of “clean” country to weed corridors. No landowner likes to be a party to this, especially if they have worked hard to keep their property clean of damaging weeds. There could be some shading from exotic weeds along the margins. However, a margin dominated by a small number of exotic weeds will actually reduce biodiversity and do little in terms of filtration of sediments compared to a well-constructed and well maintained riparian planting.

Other concerns are around fencing and flooding issues, for rivers and streams that flood frequently. These are quite valid concerns, although they are not insurmountable if the right approach is taken.

Forestry and subdivision in headwaters are causing silt build up. In a more natural environment you wouldn’t get that level of silt. This means downstream river beds are getting shallower, and therefore flooding more.

To manage this issue, people need advice on the right shrubs to plant and the right fence to use (eg a two wire electric fence).

How can councils help to address these concerns?

In some districts, councils have assisted through the provision of plants or contributions towards plant costs for riparian plantings. More focus on the numbers of plants that have survived after three years (rather than the number initially planted) would be helpful. This could involve assistance with maintenance in the first year because this is the critical time.

How big a threat are weeds for New Zealand’s biodiversity?

Not enough public money is being put into managing weed threats to our biodiversity. New Zealand’s Predator Free 2050 goal really needs to include weeds.

It’s a massive problem that decision makers have to think hard about. For example, QEII covenants are great, but slow destruction can occur over the long term, as no weed control leads to exotic weeds infestation.

We believe that councils in particular are either unaware or ignoring the issues of riparian maintenance that are becoming more of a problem year by year. A handful of weeds get the headlines such as wilding conifers in our iconic high country yet all around us is the ticking time bomb of exotic species (including Sycamore) that have the potential to totally dominate our ecosystems.