Living with a changing climate
Land sediment delivered to the sea in storms such as last week’s can have a detrimental impact on seafloor animals, says NIWA Strategy Manager – Coasts and Estuaries, Dr Drew Lohrer.
Surf clams and other shellfish, primary producers like kelp and microalgae, and potentially the birds, fish and mammals feeding on them can all be affected.
“The runoff from land during flood events often contains rubbish including non-degradable plastics, faecal coliform and other microbes and pathogens that can make us sick, and woody debris that can be unsightly and hazardous to navigation,” says Dr Lohrer.
“Although we cannot directly control the weather, we can take steps to curtail the runoff of pollutants into our waterways and can make our catchments less prone to erosion by improving our land use practices.”
The He Awa Ora, He Tai Ora, Healthy Rivers, Living Sea Education Trust has seen first-hand the impact on marine ecosystems of such floods.
The trust delivers marine and freshwater outdoor education programmes at Te Tapuwae o Rongokako Marine Reserve
“After a heavy rainfall event the water clarity is much lower and the sediment that settles on the reef can impact the habitat for a lot of marine life,” said trust project manager and tutor Amy-Rose Hardy.
“Where we snorkel on the reef at the marine reserve, the Pouawa River leads out near the southern boundary, so whatever is happening upstream is impacting this marine area and affecting this ecosystem.
“Our reserve is unique and has eight different habitat types where the sediment settling among the reef is ultimately destroying some of these habitats for specific marine species.
“We have schools booked to snorkel on the reef next week (if conditions improve and are aligned with our health and safety protocols), so it will be interesting to see if there are any noticeable impacts at this site.
“This creates an additional component to our education programmes, where we can teach tamariki about the importance of protecting and restoring all our natural environments, from the maunga to the moana.”
Trust chair Murray Palmer said the sediment and debris carried in the rivers during high floods has a huge impact on marine life.
“In rural areas, floodwater carries fine mud, woody debris, dumped material and animal faeces; and in urban areas, there are these materials plus sewage overflows and storm water. This contamination can become a danger to all forms of life in the sea and along the coast.
“Apart from direct contamination, the level of biological oxygen demand increases and the availability of excess nutrients can fuel algal blooming.”
Mr Palmer said it was important for authorities and the communities to look at both deforestation and reforestation in a more “intelligent” way to help prevent further damage.
“Clear felling of trees in large areas of steep land inevitably impacts on flood flows. When there are multi-tiered forests growing in such areas, they can absorb a lot of water and release it slowly, as opposed to bare land which allows water to run straight off carrying debris and soil.
“We saw it happen devastatingly during the last flood (June 2021).
“Not only that, a lot of our cities, infrastructure and homes have been placed on flood plains and in coastal environments which are typically vulnerable environments. Climate change and sea levels rising, and warming, are associated with worsening weather events.”
Reforestation of perennial native forests in steep land to protect waterways was the first step to prevent harm to rivers and marine life, Mr Palmer said.
Doing this would mean rain would fall on the canopy, not directly on the ground. As well, restoring wetlands throughout a catchment would further help intercept flood flows throughout the river system.
“On a long-term scale, the reduction of carbon dioxide and other greenhouse gas emissions is expected to help reduce the likelihood of extreme climate events.”
The Government was focused on making changes to address this issue with changes to the emissions trading scheme, potential emissions disincentives and the Three Waters reform programme, Mr Palmer said.
“However, local authorities have a huge part to play in managing the social, ecological, cultural and economic effects of extreme events because they control where infrastructure and land development are sited, and how land and water is managed.
“As a community we have a lot to think about in terms of where we place our structures and production landscapes.
“These are hard questions and will need serious consideration.
“Avoidance of natural hazard zones is key.
“The good news is that retirement from these zones may help restore their natural hazard mitigation functions and, as with coastal wetlands, some of the most productive ecosystems known.”
Climate Change Minister and Green Party co-leader James Shaw says the kind of weather events happening on the East Coast were a direct effect of climate change.
“We have always had floods and storms but now, the frequency and severity of such events has increased. This year’s flooding was worse than last year’s and last year’s was worse than the year before.
“This pattern is occurring in other parts of the country, like in Westport. We have had two major ‘one in 100-year’ events in the past year.”
Mr Shaw said sea levels were definitely rising and Aotearoa New Zealand was only just starting to see the impact.
“I think because we have always had such dramatic weather events, we don’t notice storms or coastal erosion easily — we have lived with these things. Now, people are noticing the effects which have worsened over time.
“Coastal towns, communities and marae are starting to be inundated more frequently than in the past.
“It is quite concerning because we know there are 70,000 houses around the country that are in low-lying areas and are exposed to the risk from sea-level rise in the coming decade.
“There are houses on flood plains all over the country; roads, commercial buildings and airports which are built in areas prone to not just coastal erosion, but also river plain flooding.
“On one side it’s billions of dollars worth of property at risk, and on the other these are our homes, our cultural link and our communities at risk.”
Mr Shaw said to deal with this issue, for the first time, in August this year, the Government would be publishing the Climate Change Adaptation Plan and next year, a Climate Change Adaptation Act would be introduced to Parliament.
“In the short term, we could provide good information and data to enable local communities to look at it and discuss what they can do to help build more resilience.
“While the Government is producing a national adaptation plan for the whole country, we do want to provide a framework, data, tools and information to local communities and iwi, for them to be able to make their own adaptation plan.”
NIWA coastal and estuarine physical processes scientist Dr Christo Rautenbach says researchers are doing their best to quantify changes to the climate using sophisticated models to predict future scenarios.
“These include sea level rise,” he said.
“What I can say is that sea level rise will make most problems worse in the future, for example, coastal nuisance flooding will most likely become more and more frequent until it becomes commonplace and eventually unsustainable for certain land areas.
“Hence why we are planning to adapt, retreat/restore or abandon certain areas.
“Unfortunately there is also not a
one-size-fits-all and the climate change-related research has to be accompanied with detailed regional and district planning
(a co-designed approach).
“Numerous councils around the country are pro-actively doing exactly that, which is awesome to see and to be part of.
“Together with this, short-term forecasting is also crucial to help emergency response agencies react in a timely manner.”