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Rough Science 3 New Zealand: Ellen McCallie's diary: Shakers

Updated Tuesday, 27th February 2007

Ellen McCallie's diary about the challenge for the Shakers programme, from the BBC/OU series Rough Science 3

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Day 10 – earthquakes

This was a great day. If every day were like this, I would do television forever. Challenges were given and I ended up needing to determine when the last major earthquake in this area occurred. This seemed impossible until we got a look into the equipment box – tree corers. That’s a major clue.

For at least the last 15 years, New Zealand scientists have been worried about their forests. In any given forest here, most all of the canopy trees – the trees that “reach the sky” – are old and about the same age. This is unusual. Most of the time you find trees of all different ages making up the canopy. Thus, a mature forest in the US can have canopy trees from 50 to several hundred years old. That doesn’t seem to happen here. First, the common tree species are long-lived (500 to 1000 years old) conifers. Second, they don’t survive well as saplings in the understory waiting for a mature tree to die, so they sprout, grow for a while and then die waiting to get enough light to become canopy trees. But why are the canopy trees in an area all about the same age?

Scientists worried for a while that New Zealand forests must be dying – that all the forests were made of old trees that weren’t regenerating. Then someone started aging the trees. Most of the trees in a stand were about the same age, given or take 50 years. And the dates at which these tree stands began corresponded to several years after major earthquakes in New Zealand. Viola! It isn’t that the forests are dying out, but that earthquakes are major factors in shaping forests here.

Basically, New Zealand earthquakes are big, and they cause massive landslides that can wipe out entire areas, especially when combined with raging rivers. So, the rock and gravel carried down by rivers after massive earthquakes decimate previous forest, covering it with gravel and rock. It is in this new substrate, “soil”, that new trees start to grow, all at approximately the same time – soon after the earthquake.

If we can figure out the age of these trees, we’ll know the approximate date of the last big earthquake. We are looking for the absolute oldest tree in order to be the most accurate.

In picture-perfect weather, Kate and I went helicopter hiking, as they call it around here, to find a piece of land out of a big river’s normal flood plain, but within range of a mighty river carrying earthquake landslide wash. We found such a place, and was it exquisite. I’d never been in such a wet, mossy, old conifer forest before. Kate joined us for half of the day. She and I took tree cores.

I came bouncing back to our base, pleased as pie and ready to count rings. This will be really tough as slow growing trees have narrow growth rings, which makes them really difficult to count. At least I am working with plant material - beautiful, interesting plant material. The question remains, did I get all the way to the center of the trees?

Day 11 earthquakes

Another good day. Kathy went tree coring with me this morning, which was really good, especially when it came to removing stuck cores. The whole lot of us has arm-wrestled before. Kathy beat everyone but one of the cameraman, quite impressive. Between the two of us, we almost pulled the cores out of the trees.

Drew had fun taking footage. He just kept the camera going with a smile on his face.

This type of forest is quite rare, even in New Zealand, as most of it has been cut for agricultural (ranching) land. The interesting bit is that if there is another earthquake in the next hundred years or more, most of the paddock/grazing land in this entire area is likely to be under gravel and rock anyway. Hopefully, there will be enough seed stock for colonization to begin from scratch again. I wonder what birds do in an earthquake…

I couldn’t believe how little time it took to sand and count yesterday’s cores. We have decent equipment this year. It makes all the difference. A day like today also emphasizes that this is a team project. We are all working to show how science is done, that it is an active process of experimentation, not a recipe in a book. I think this program is doing this well – and easily. Oh, what a joy!

Another nice piece is that email and phone contact is readily accessible. I’m not much for the phone, even at home. It is nice to pop out an email to family in the evening if we get home before the place shuts. I’ve found out that my mom has taken to my little dog, which is really comforting as my parents are keeping little Abby for six weeks. I didn’t want her to drive them crazy. Another wonderful thing is that it has rained in St. Louis, so my yard, which I planted in mostly native prairie and wildflowers with the neighborhood kids and advice from Shaw Nature Reserve, is dripping with blossoms. It has turned out to be an amazing first year garden. I never expected this much growth. I hope the kids who helped collect seed and plants are happy about it too.

Day 12 earthquakes


It’s too amazing to be true, but it is! Our estimate of the date of the earthquake based on the tree cores was off by only eight years – 1725 v 1717. Before anyone says "this is beginner's luck", let’s talk about the “repeatability” of science.

When scientists report their findings in journals, they state their methodology so that others can check their results. In other words, we’ve just further substantiated that 1) the forest we were in appears to be, based on our limited six core sample, even aged – all the trees were between 246 and 277 years old, and 2) the trees in this forest began colonizing the area in about 1725. Thus, we’ve just substantiated that the data and the results that the first group got are actually reasonable.

Now, I cannot prove or substantiate that an earthquake actually caused the forest on that patch of land to be decimated so this next bunch of trees could colonize the area and grow into the forest that is there today. We do, however, know that the Maori people did not have a common practice of clear-cutting forest. We also know that there are many forests in this area that are basically the same age as this one. Few natural phenomena can cause such catastrophic disruption besides earthquakes, volcanoes and hurricanes. Windstorms and floods are more isolated and usually don’t affect entire regions. So, I feel like we’ve just won big on a TV game show. Hooray for trees!

Plus, the production team just won’t stop talking about the beauty of the forest. Some of them call it fairyland, some call it the green cathedral, and all of them want to go back. Hoorah! People value things they love and find appealing. That’s what’s going to keep the forests alive, healthy, and functioning for us as well as the rest of the planet.





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