We still have a lot of river work to do

I’m continuing on from last week’s column on GWRC’s report Are we meeting our environmental outcomes on the Ka¯ piti Coast?

The Ka¯ piti Coast is full of seeming contradictions. It has a climate that is the envy of much of the rest of the region, yet is the most susceptible to climate change. Just over half of the catchment area remains virtually untouched, yet the coastal lowlands are almost 100 per cent modified. It contains two big, beautiful rivers that are surrounded by a number of small, degraded streams. It boasts long, pristine beaches but has one of the most degraded lakes in the country. It can experience very dry summers, but is prone to flooding at other times of the year.

Three key issues stood out in the report as requiring immediate attention.

Firstly, the impacts of climate change: under current predictions of sea level rise, parts of the Ka¯ piti Coast could be permanently inundated by the end of the century. But this is not the worst of it.

The biggest threat to the coast will be the combined effects of more intense storms, high tides and sea level rise. In the future, westerly storms coming from the Tasman Sea will get significantly worse, bringing heavier rain and stronger winds.

Further, the coastal dune systems, the first line of defence against coastal inundation, have been diminished by urban development and degraded by the invasion of exotic plant species.

Secondly, soil quality at market garden sites: excessive levels of phosphorus in soil are a region-wide problem and the Ka¯ piti Coast is no exception.

However, when it comes to market garden sites, the situation is a bit more severe. Over half the sites GWRC monitor have depleted levels of organic matter, which is essential for retaining moisture, nutrients and good soil structure. And nearly three quarters of the sites have low structural stability, meaning they are more prone to desiccation (becoming completely dried out), breakdown and erosion.

How’s this for a scary fact: soil is considered a non-renewable resource — once it has been destroyed, it is lost forever.

Thirdly, water quality, particularly small streams: all of the streams GWRC monitors on the Ka¯ piti Coast exhibit, without exception, poor water quality and degraded ecosystem health.

And let’s not forget Lake Waitawa (north of O¯ taki), which is also in poor condition and ranked 197th out of 259 lakes nationwide.

We cannot afford to be complacent about the O¯ taki and Waikanae rivers either. While they currently have very good water quality, they are both showing signs of degradation at their bottom ends.

Let’s not kid ourselves, we have a lot of work to do.