Slipping away: follow-up

More from the interview with Chris Phillips (4 minute free preview, 13 minute read for paid subscribers)

The following is a lightly-edited transcript from my discussion with Chris Phillips about erosion. There was so much more than made it to the article, and it was a fascinating journey into an aspect of our landscape that we often don’t think about.

As always, I started at the beginning, asking questions about how he first became interested in the subject.

Me: can you tell me about when you first became interested in science?

Chris: Well, I suppose at school, and that’s a long, long time ago. In my school, I went to Marlborough Boy’s College. You either went down an arts route or a science route and I went down a science route, although I was frustrated at the time because after School Cert I couldn’t pursue geography which I really liked. I had to go down a more traditional science and applied maths route. I went to university to study mineral technology but ended up doing geology and physical geography, realising after reflection that I really didn’t want to become a mining engineer.

I like the observational side of geography and landscapes, and essentially that’s kind of how my career has evolved. I did a degree in geology and physical geography, I then went and did a Master’s in earth science at Waikato, did a Master’s thesis on sedimentation in Lake Matahina which is a hydroelectric lake.

I finished that then got a role in the Protection Division of Forest Research Institute of the Forest Service. My work focused on geomorphology, geological mapping on the east coast to develop terrain assessments for protection and production forests at the time. After a couple of years doing that, based in Gisborne, I got promoted to a scientist or junior scientist in those days. Then about four years in I got offered the opportunity to do a PhD. I went to Lincoln to the Agriculture Engineering department which later became the Natural Resources Engineering department and did my PhD, studying the rheological behaviour of debris flows [I learned a new word here – rheology is the study of how things flow]. While I was there, the Forest Service ceased to exist, in 1987, but we were grandparented into subsequent organisations, MAF, MoF and eventually Landcare Research.

I consider myself more of a generalist earth scientist rather than a specialist, such as an engineering geologist. Over the years I’ve worked acrossa broad range of things. I’ve been in and out of science management as well, managing teams of people, managing portfolios of projects and all that kind of stuff.

Me: When did you first become aware of erosion as a problem?

Chris: probably right back at school in geography, not that I really can remember too much about those days. In my 7^th Form yearbook I put down something like the career I wanted to pursue was in soil conservation, but the likely outcome was grave digger. I guess soil conservation was always in the back of my mind and the reason why you have soil conservation is because you have erosion.

Me: So how big a problem is erosion in New Zealand? Are we particularly bad internationally?

Chris: Yes and no. There are parts of New Zealand which have been rated as some of the most erosion prone, that is, they deliver the most amount of sediment to the oceans. The east coast region on the North Island is one of those. It’s been put up there alongside the Yellow River in China. I’m not up to date with who is in the top ten these days, but New Zealand is known as an erosion-prone place. It’s because of all those factors – its uplift, its tectonic setting, its climatic weather setting and then the human interactions over the last couple of centuries.

Me: So I’m making a bit of a list here but rainfall, slope….

Chris: Rainfall, slope, vegetation cover, geology – the type of rocks, the rate of tectonic uplift, also the geology. The geology not only includes the rock type but also how much faulting, folding and shearing has taken an intact piece of rock and scrunched it up to make it more prone to those agents of erosion like wind, frost and rain, and gravity.

Me: So if you’re studying erosion, what are the important questions you’re looking at?

Chris: The loss of topsoil is important for people growing things. We need soil to grow things in, and if we don’t have it, we can’t use it. If we lose it, soil takes quite a long time to build back up. So that’s one thing.

The second thing which has been driving a lot of interest in research is sediment. The product of erosion is sediment – soils turn into to sediment. The four key water quality contaminants in New Zealand are nitrate (or nitrogen), phosphorus, E.coli and sediment. Sediment has got quite a strong connection or correlation with E.coli and phosphorus. Phosphorous is bound to sediment and also if you get fine sediment, you’ve often also got high concentrations of E.coli particularly if there are lots of animals in and around areas that are eroding or supplying sediment. Nitrogen has got nothing to do with sediment so lets forget that one (though it still is a key contaminant in water), but the other three are connected. Usually it’s phosphorus and sediment, less so about E.coli.

So, it’s a water quality contaminant and it can affect ecosystems in aquatic environments, whether that’s in the freshwater or coastal environment. It makes the water turbid and fish can’t see, so they can’t catch their prey, so it has an ecosystem impact. Also the sediment, when it settles out and deposits on the stream or sea bed, it smothers the invertebrates and insects which the fish eat, which also is a problem.

So sediment is a contaminant from both those points of view. In the National Policy Statement for Freshwater Management, water clarity is a metric that is used to rate or describe the state of New Zealand’s freshwaters. There are a whole lot of catchments around the country which don’t meet the bottom-line standard and so there will have to be quite a lot of soil conservation effort required to reduce the amount of sediment and improve water clarity to meet the minimum standards.

Those are basically the two reasons why scientists study erosion in New Zealand. Soil is what has built our civilisations, we need it for growing food and so it’s a food security thing if we don’t have soil. Then the other one is the impacts on the aquatic and receiving environments.

Me: can I just ask a slightly random question. What’s the most interesting place erosion has taken you?

Chris: Probably in Iran because we don’t see bad lands here. Bad lands are a particular style of erosion. You see them in Spain and all sorts of other places.

Assessing surface erosion treatments, Iran (image credit: Chris Phillips)

Me: I’ve seen them in America, they’re amazing. [and you know that was just the excuse I needed to share one of my bad lands photos with you.]

Utah badlands (image credit: Melanie Newfield)

Chris: I was there [in Iran] on an FAO job in the 90s. Also China, in a place called Jiang Jia Gully which is where debris flows, channelised debris flows occur on a scale which is way bigger than we’re likely to see in New Zealand. The Chinese professor at the debris flow observation station could hear the claps of thunder up in the mountains and then looked at his watch and said “debris flow in 37 minutes” and sure enough, bingo, there you go. Because they’d been observing these things over many, many years they understood the link between rainfall in the mountains and the occurrence of debris flows in the channel. The landscape was very steep, it was shattered and it rained a lot and they just knew what would happen.

Jiang Jia Gully, China (image credit: Chris Phillips)

Debris flow surge, Jiang Jia Gully (image credit: Chris Phillips)

Me: I think we touched on this already but are some areas particularly bad for erosion?

Chris: Yes, erosion is not the same everywhere, it relates to all those different factors. We also talk about sediment yield as a proxy for how much erosion is occuring in a catchment. This is the total amount of sediment that goes past a point in the catchment. It’s measured in tonnes per square kilometre per year. That is the way you compare different catchments or different regions of New Zealand in terms of their erosion.

And so places like the East Coast have very high sediment yields and places like the McKenzie Country or parts of Otago or Southland, have lower sediment yields.The reason is because of the combination of all those factors – steepness, geology, rainfall, vegetation cover, etc. And just while I remember it, the other important thing is that erosion and sediment yield are not the same even though we tend to use the terms interchangeably. So you can have high erosion rates which aren’t reflected in the amount of sediment that gets exported out of a catchment, i.e., the material is deposited not far from where it was eroded and may not reach the stream network to be transported away. You can have erosion as a scientist would measure it at source, which is the dislocation of particles from here to there, but if it doesn’t reach a stream it may not really matter to what gets exported from a catchment.

Well, it matters at the point where it was eroded from. Often what we see is quite a bit of redistribution happening on a slope or something like that. It doesn’t necessarily mean that if you have high erosion you have high sediment yield there but often those two things are connected. Many soil conservation measures aim to prevent erosion from occuring in the first place or intercept sediment, thus reducing the amount getting into streams.

Me: I’m not super familiar with the whole East Coast but I remember going up on the east coast of the Wairarapa and driving on some roads up there. There was stuff across the road all the time. Is their soil particularly soft or their rock?

Chris: The mudstones and sandstones of most of the North Island hill country, so pretty much up through the Wairarapa, Manawatu, out towards the upper Whanganui, up through northern Hawkes Bay up into the east coast of the North Island and some little bits and pieces up around the Waikato, it’s basically a similar rock type and it largely behaves all the same. So yeah, it’s what we would call typical North Island hill country, sheep and beef farming, which is now being you know, changed to carbon farming in many places or it’s been under plantation for a while. In those big storms it largely responds as we’ve seen on the TV in recent storms such as Cyclone Gabrielle, with many landslides across the rural landscape and also a lot of sediment deposition in the downstream floodplains and valley bottoms.

Me: do you see those as among our most urgent problems?

Chris: personally I think erosion and sediment is one of our key issues because it impacts quite a lot of stuff. But I think we just have to understand that erosion is a natural process. There are some things we can do to help manage it, we will not prevent it at all because it can’t be prevented in all cases. But we can try and reduce the amount of erosion in some places better than in other places. Perhaps in some areas, we’ve gone over a tipping point and the situation is probably a bit irretrievable. It will end up being nature through long, long periods of time that will end up having to kind of deal with the situation.

But it very much depends on whether we are trying to utilise the land and the landscape, the whenua, for productive purposes or not which determines how important these things are. Taking a much wider view, more holistic and more integrated view of catchments or landscapes – it’s really the only way we can kind of deal with a lot of this stuff. There’s no point trying to improve the water quality of a lowland stream if you’ve got erosion carrying on up the catchment. The idea is that everything really needs to be put into a broad context and awareness raised of the connections in the landscape, i.e., everything is connected so actions in one place have consequences in another.

Me: we’re not really planning where our forests are for particular purposes terribly well at the moment are we?

Chris:  In general terms we did plan and put many of those erosion prone areas into plantation forests, mainly radiata. At the time, this was a sensible idea and I would argue that it was the best solution. In hindsight, we probably should have taken the smaller paint brush out but it was more expedient to convert large areas from grass to forest.

But we do need to be thinking more of that. We need something more akin to the European situation of forests being multipurpose – they’re there for hazard mitigation but they’re also there for production. They are managed on a closed-canopy, single tree extraction basis, in areas where the natural hazard is high. They do that because in part these forests are subsidised by local or federal governments, so that the foresters don’t necessarily need to be extracting all the value from the trees. They tend to be 150 years before they’re harvested, so it’s a different forestry system to the steepland plantation radiata forests we have in New Zealand.

I would expect that with time we will probably mature in our view of the way in which we utilise our landscapes. I think we are still very much thinking in a resource-taking mindset, rather than working more in harmony with our physical landscapes. I was pleased that the report that came out from the Ministerial inquiry, From Outrage to Optimism, talks about future landscapes having a much finer mosaic of land use. Ultimately that’s where we need to go.

The way it’s been done in recent decades, it’s at too coarse a scale. It needs a finer scale of resolution of the landscape to inform where certain things should or shouldn’t be done. The current erosion susceptibility classification in the National Environmental Standard for Plantation Forestry, the policy instrument that determines what planning restrictions relate to a particular class of land, is too coarse. That is something that myself and others have been saying to MPI for quite some time and they probably acknowledge this.

It comes through in the inquiry. What is needed is that people make decisions on the ground at a scale which is there in front of them. They don’t make decisions based on hundreds of hectares. We’ve got to get a bit more sympathetic with the landscape we’re working in and that means a much finer scale of resolution of a) understanding and b) management.

We’ve gone around our landscapes with four-inch paintbrushes. What we need to do now is take a very fine paintbrush and look at our landscapes closely, which is a blessing and curse. New Zealand spatially has very diverse landscapes, you don’t need to go very far for things to change. The geology changes, the climate changes, the soils change, the vegetation patterns change. We can’t sit in a car and drive 100km and it’s the same stuff everywhere, we don’t have that (unlike some countries). The diversity of our landscapes means we need to have a the diversity of land use that sits within those landscapes. I’ve always believed that.