April 9, 2011. One of the principles that I try to follow in my job is that I don’t change the message depending on the audience; maybe change the emphasis or they way I tell it, but I aim not to change the fundamentals. With this in mind I found myself recently sitting in a small community hall in the middle of the farmland that forms the catchment of the Waituna Lagoon, to the east of Invercargill.
There were some of the local dairy farmers there to talk about the lagoon. They were the good ones who were trying to make a difference. They were there to tell me about all the ways they were trying to improve their practices on their family farms to cut nutrient flows into the lagoon. Which is a good thing.
So it was with heavy heart that I felt obliged to tell them that it was hard to see how the lagoon could be cleaned up without cutting the number of dairy cows in the catchment. Not something that they wanted to hear – those cows are their livelihood. But we need to cut the amount of nitrogen leaching through the system by maybe 50% and, even with the best of practices, that will be difficult with the current number of dairy cows in the system.
Some of the members of the Landcare group were there too. Their problem was that there were so many corporate dairy farms, with itinerant farm managers and workers passing through. Just when they had managed to train up one manager about the impact of the dairy herds on the lagoon, they would move on to be replaced by another with the sole focus of increasing production. I have written before about the issues of corporate dairying in Southland and transient workforces.
Waituna lagoon is part of the Awarua wetland, one of the largest wetlands in the country and recognised as a Ramsar site – we have signed an international treaty promising to protect it. But Waituna lagoon is in a critical state. It is an ecological system that could die in the near future if something doesn’t change.
Sometimes systems have a linear response to more pollution – a bit more pollution causes a bit more decline; but sometimes it’s a non-linear response – a bit more pollution causes total collapse. This second scenario is what we are looking at with Waituna.
Coastal lakes like Waituna often have relatively clear freshwater because the freshwater plants, Ruppia in this case, on the bed of the lake hold the sediment and nutrients in place. By holding the sediment in place the water stays clear of mud so the sunlight can reach the ruppia; and by holding the nutrients in place, there aren’t nutrient-fed algal blooms, so again the sunlight can get to the ruppia. A virtuous feedback loop.
The ruppia is the home of the invertebrates, the ruppia and the invertebrates feed the fish; and they all feed the birds. Waituna is one of the strongholds of the endangered giant kokopu, one of our wonderful native fish, and dozens of migratory bird species.
If the ruppia die off then the nutrients and sediment are released from the bottom and the lake can flip from one state to an entirely different state. It can rapidly become muddy, deoxygenated and full of algae and nutrients.
One of the things that can kill the ruppia is if there is too much nitrogen and phosphorous in the water, leading to algal growth in the water which blocks out the sunlight to the ruppia and they die. Or if too much sediment enters the system it can smother the ruppia. This is precisely the problem we have now.
Something similar happened to lake Ellesmere/Te Waihora after its native freshwater vegetation was weakened by nutrient and sediment inflows, (and partially replaced by exotics), and then the remaining weakened seabed grasses were ripped up by the Wahine storm. The release of sediment and nutrients meant the grasses couldn’t re-establish, so the system flipped and now it’s toxic pea soup – still ecologically significant but very degraded.
I started the day meeting with DoC, Environment Southland (ES) and local Maori from the Awarua Runanga of Ngai Tahu. We met at a café on the site of an old lignite mine – the Lignite Pit Cafe (they had done ecological restoration which we didn’t get a chance to look at). We had regional council staff, DoC staff, scientists, greenies, mana whenua – it was great and one of my favourite situations. As a result of funding that the Green Party got out of the last government, they have been able to employ scientists to understand what’s going on with the lagoon, and also to pay for around 50kms of fencing in the catchment.
They explained that, after putting together the science from ES and DoC, they realised that they had an emergency and they risked losing the lagoon forever if they don’t take urgent action. They are currently working with all the farms in the catchment to stop another big influx of nutrients this winter to avoid sending it over the edge.
They are trying to manage the opening of the lagoon to the ocean – they hope by releasing the nutrient rich water they can stave off the flip. But as they do so they lower the level of the lagoon exposing the ruppia beds and they die back, and the introduction of salt from the ocean makes it difficult for the ruppia to reproduce. It is desperate emergency management stuff.
One of the remarkable aspects is that the regional council, after having opposed attempts to save the rivers and lakes in Southland before, have finally realised they have a problem (a change in Chair seems to have helped). Ali Timm, the Chair, said on March 15:
Even if there is 100 percent compliance with every condition on every consented activity and 100 percent adoption of best management practices by everyone in the Waituna catchment, the science is telling us that these on their own will not be enough to prevent the lagoon from flipping.
Most people don’t realise that only 10% of the nitrogen coming off a dairy farm is related to the effluent coming out of the dairy shed – most of the nitrogen comes through urine, faeces and fertiliser in the field, and that’s unregulated. So simply following the conditions of a resource consent, on dairy shed effluent, won’t be enough.
After a long discussion of the science of declining ruppia and spiking phosporous, we heard from mana whenua about the value of the lagoon and wetlands to them, and their sense of impending loss.
Then we headed down to the lagoon itself to get on the water. We passed numerous large corporate dairy farms on the way. There was a strong breeze on the lagoon and only me, Dave and Vicki (local Greens), and Maurice from Fish and Game went out on the water. We paddled onto the little lagoon as the waves on the big one were too choppy. It was beautiful out there and still looked pretty good to the uninformed eye. The farmland wasn’t far away.
After we pulled out we bumped into a couple of old guys in a boat from old local families who were taking manuka branches out to their maimai for the duck shooting season. They told me in no uncertain terms that my job was to save the lagoon! I hope they voted Green.
This lagoon needs emergency intervention if it is to survive.