That the latest environmental report in lakes and rivers New Zealand reiterates grim news about the state of freshwater ecosystems, and warns that climate change will exacerbate existing threats.

Nearly all New Zealand rivers flowing through urban and agricultural areas (95-99%) carry pollution above water quality guidelines, while most of the country’s wetlands (90%) have been drained, and many freshwater fish species (76%) are threatened or at risk.

The most significant stresses on freshwater ecosystems fall into four problems:

NZ Ministry of Environment / Statistics, CC BY-SA

Climate change is receiving more attention than the previous assessment, reflecting the fact that glaciers are shrinking and the soil is drying up.

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What anchovies say about freshwater fish under pressure

The latest assessment is an update on a freshwater report in 2017 and comprehensive Aotearoa Environment 2019. It repeats the problem that we have seen before, but is starting to be implemented latest recommendations by the Parliamentary Commissioner for the Environment (PCE) asking for a stronger relationship between data and environmental management.

Biological impacts are at the forefront of this latest assessment. This shows that various freshwater organisms are at risk. Statistics for freshwater fish are the most concerning, with three quarters of the 51 native species already threatened or at risk of extinction.

This report uses certain native fish groups (angaanga, or galaxies) to connect the various impacts that humans have, in various habitats at various stages of life.

Angananga is better known as anchovy, a delicacy that is a mixture of juveniles from six different species captured when they migrated from the sea to the river.

Anchovy is considered a delicacy in New Zealand.

Angananga of various ages and species live in different habitats, so they can be used to represent the problems faced by various freshwater fishes throughout the ecosystem. The main stress factors include changing habitats, pollution and excess nutrients, use of water for irrigation and climate change.

Climate change is expected to exacerbate the pressure that exists on native organisms such as the face of angaanga and protect their habitat means understanding how much it will reduce water flow and create hotter and drier conditions.

Fill the gap in understanding

The use of organisms to assess environmental changes, including the effects of climate change, is a clear but important step. That makes it possible to consider climate change in a fulfilling way Environmental Reporting ActRequirements for reporting “collection of evidence”.

This latest report responds to PCE’s concerns about gaps in our knowledge, which were raised in Aotearoa Environmental Assessment 2019. The new strategy for filling large holes in our knowledge has three priorities: knowing and monitoring what we have, what we might lose, and where or how we can make a change.

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The report highlights that Mātauranga Māori, the process of using original knowledge about the environment, can fill some gaps in the data or add insight. Other methods and models, such as nutrition budget scenario, is also worth considering.

There is some good news too. Some pollution problems may be small or limited to very small areas. This includes some contaminants that emerge, such as fire retardant, which has been found in groundwater around the airport but is now banned or restricted.

The second good news is that new ways to study the environment can help fill large gaps. For example, lakes may be a more stable indicator of freshwater health than rivers and streams, but only 4% (around 150) of 3,820 New Zealand lakes are regularly monitored by regional councils.

For nearly 300 lakes, the report includes an index of plants that live in them, and more than 3,000 now have established methods for estimating lake water quality. More information is available, using the updated one estimation, satellite data for the past 20 years and sediment core to reconstruct environmental conditions for the past several hundred years.

Unfortunately, data from the lake confirms the general trend of freshwater decline, but at least various forms of supplementary information will help us better manage New Zealand’s freshwater ecosystems.

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