Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Opinion piece: Protecting our waterways

Bill Lee

Bill Lee

Dr Bill Lee, an ecologist at Landcare Research, says a national riparian plan would have “major benefits” for our waterways.

New Zealand is a land of readily accessible waterways, with approximately 450,000 km of permanent rivers and streams crossing our country and about 1.75 km of flowing water in every square-kilometre of land. Water is vital for urban and agricultural development, recreation, and sustaining our biological and cultural heritage.

However, over the past decade intensification of land use and expanding urban areas have seriously channelised and degraded the quality of many waterways in lowland areas, to the extent that they are no longer fit for drinking, swimming or as sources of food. Consequently, their function to maintain the life and environment essential for human well-being in New Zealand and protect our international reputation for tourism and food safety is seriously compromised.

Rivers, streams, and wetlands are important natural ecosystems because they provide water for productive land use as well as help clean up the negative impacts of urban and rural activities, particularly pollutants that flow from the land.

Of particular importance is the vegetation along the riparian margin of waterways, which provide a vital role in this clean up. Sediment from erosion, unused added nutrients, toxins, and much more can be filtered, sequestered or transformed by habitats around waterways to create cleaner, wildlife-supporting habitats for us all. While, riparian margins play this important environmental role they also reduce space for productive uses.

Despite the apparent value of riparian buffers, riparian restoration programmes tend to be piecemeal reflecting individual industry or community actions. Our aim is to reverse this and provide the tools that allow the cumulative impact of riparian activities to be evaluated at scales that will provide enduring and substantial benefits from improved quality of waterways and associated riparian areas.

We are currently investigating costs and benefits of a national riparian network. This is to help promote discussions on-farm, within industry, across regions, and nationally of the value of having a riparian restoration network that effectively contributes to mitigating land use impacts while restoring freshwater habitats and the multiple services they provide.

To do this we are integrating databases on land use, farm profitability, and the environment with information on the mitigation and ecosystem service profiles of different types of riparian habitats in different environmental settings.By doing this at a national scale we are able to assess the net benefits of allowing these riparian habitats to recover or be restored.

Our initial analyses of a five metre riparian buffer along all waterways in the 17 million hectares of ‘productive’ land in New Zealand indicated major benefits. For example, diffuse source nutrient losses decreased by about 50 per cent, sediment decreased by more than 70 per cent, and net greenhouse gas (GHG) emissions from the agriculture and forestry sector fell by 25 per cent.

We are currently working on including opportunity costs, contributions to national biodiversity goals, the natural resilience of riparian habitats in different environments, and the possibility of passive versus active restoration programmes.

We have Predator Free New Zealand motivating the control of introduced feral pest mammals across New Zealand at unprecedented scales. A national riparian network and restoration programme is equally audacious but would deliver huge environmental gains while potentially still allowing headspace for some intensification of land use. This could be a key step to moving our national water targets from waterways for paddling to waterways for other more highly valued activities.

This project team comprises Dr Adam Daigneault, Dr Florian Eppink, Dr Norman Mason and Dr Suzie Greenhalgh.



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