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The Importance of the Riparian Margin

There has been a lot of publicity over the past few years about requirements for fencing off waterways and (ideally) planting this buffer in native plants. There are many different view points about whether this is a good thing or not but with an understanding of the importance of having this buffer between a waterway and agricultural or built-up land, the benefits are easy to see.

Recent video recorded by Adam examining the health of recent riparian restoration.

The riparian margin (the area of land beside a body of fresh water) interacts closely with the waterway itself in a multitude of ways and hence it doesn’t make sense to consider the two separately. The vegetation growing in this riparian zone performs a multitude of functions including providing shading, habitat for birds and insects, substrate for some native fish to lay eggs, filtration of water and pollutants and provision of woody debris into the stream itself. Fencing out stock is vital in ensuring that the vegetation remains healthy and able to perform these functions, as well as in protecting the stream banks from physical damage.

Shading of a waterway and of the smaller plant species near the water’s edge acts to control the temperature of the water and to keep it constant despite significant changes in the weather between seasons. This is vital in maintaining a healthy level of oxygen in the water which in turn keeps aquatic flora and fauna healthy and helps maintain water quality. Shade is also important in allowing koaro, inanga and kokopu species to breed because they lay eggs on bankside vegetation which need to stay cool and damp until they hatch.

Riparian vegetation is great at filtering the runoff coming from the land around it, removing pollutants and sediment so it doesn’t get into the stream. This is one of the major benefits in an intensive agricultural setting or a highly urban or industrialised environment and is one of the simpler ways of reducing our negative effects on our waterways. Having a decent planted buffer right along a stream or drainage channel can also reduce the severity of floods by slowing the water going into the stream and helping it to absorb into the ground rather than just rushing straight into the stream.

As plants establish they create strong, binding root systems that stabilize the stream banks preventing erosion and slumpage. This means that less sediment is carried away downstream to smother plants and animals in both freshwater and marine environments, but also that streams are much slower to eat away at the surrounding land – an important factor on productive land where every square meter plays its part in the farming system. An un-vegetated stream bank can fall away into the stream at a huge rate during yearly flood events, breaking fences, damaging infrastructure and creating safety issues due to instability.

Riparian connectivity to stream provide potential spawning opportunities

A planted buffer also creates places for native birds and insects to live as well as a corridor of habitat that allows them to move between different areas safely. The insects can also provide food for fish living in the stream and the woody debris falling into the stream provides food and habitat for fish and aquatic insects. The more species there are, the more robust and sustainable the system is and a healthy system provides less obvious benefits such as crop pollination, break down of organic waste and cleaner waterways for us all to enjoy.

So, whilst the initial work required may seem off-putting, the long-term benefits are substantial to both people and to wildlife. And the satisfaction of seeing the results of the work you’ve put in is fantastic! By making small changes we can create huge differences to the sustainability of our natural environment and ensure it remains a place that our friends and family can enjoy for generations to come.

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