Blooming among thorns
Conservation progress in Rodrigues (4 minute preview, 8 minute read)
I’m in the last stages of trying to draft an academic paper on decision-making for managing pests, and it’s doing my head in. I’ve been working on an apparently simple piece of work– asking people about what makes good or bad decision-making when it comes to managing pests in New Zealand. I’ve used what I learned to put together some simple guidance, and my main interest now is getting the information into the hands and heads of people who work on pests.
To get it published in an international journal, however, I’ve got to put it into a wider context. This has had me reading hundreds of academic papers, some of them scientific papers about pests, some of them social science – what people think about pests – and some of them getting into unfamiliar fields like psychology, economics and philosophy. My brain is full. I’m now close to having a decent draft but it has been a struggle.
Among the papers I discovered, but probably won’t use, is one which looks at the reasoning people use to decide if pest management is necessary. As someone who has worked on this issue, I like to think that we make decisions based on good evidence and defensible values, such as when we know that a particular plant or animal which isn’t native to New Zealand causes harm to native or other valued species.
It turns out, however, that even experts are influenced by how attractive they think that a plant or animal is, according to one of the papers I found. A plant with pretty flowers doesn’t seem like such an urgent priority for control, even if it’s spreading through natural landscapes and harming native species. An unappealing plant, however, seems as if it might be a problem, even if it actually isn’t.
When I remember Île aux Cocos, a small island on the edge of the Rodrigues lagoon, my most vivid memory is my first encounter with a couple of particularly unappealing plants. I assumed they were invasive, but I later learned that in fact they were native. They showed me that I’m not immune to the biases reported in the paper I mentioned above.
Île aux Cocos is a 15 hectare island on the Rodrigues lagoon, which makes it a little more than half the size of Matiu/ Somes Island in Wellington Harbour. It’s a very different type of island from Rodrigues itself, which is volcanic and at least 2.5 million (possibly up to 10 million) years old. Île aux Cocos is a sand cay (sometimes spelled key), a type of island which forms on coral reefs, like many of the islands in the Maldives. It will have formed long after the main island of Rodrigues, although I haven’t been able to find out how old it is.
Île aux Cocos is important for seabirds. Several species breed there and migratory species, including the ruddy turnstone, stop over. I spent a couple of hours looking at the plants growing there and had memorable encounters with plants known as grey nicker and devil’s horse-whip. Just from the name, I’m sure you can tell that encountering devil’s horse-whip is going to be unpleasant. Grey nicker, however, sounds more innocuous. I can assure you though, it’s not.
Grey nicker is a shrub which is native to tropical coastal regions around the world. The reason that it’s native to so many areas is that the seeds float (the seeds are also the part of the plant that is grey). It is actually quite common for coastal plants to have very wide distributions. Many of the coastal plants I learned to identify in Mauritius and Rodrigues also turned out to be native to various Pacific Islands and the Maldives, as I learned when I visited there. In flower, grey nicker is not completely unattractive, since it has fragrant yellow flowers, but the whole plants is covered with vicious spines. I was supposed to collect specimens of the plants I found, but wasn’t prepared for something so spiny and ended up with a lot of scratches.
When I finally had my specimen, I looked down at my legs to discover that my trousers were covered with spiny seeds. I’d stepped into a patch of nondescript plants which grew around thigh-high. What I hadn’t noticed were the seed heads. These were long stems held above the leaves and covered with the seeds. Brush against them, and the seeds immediately detach from the stem and attach to whatever has touched them – in this case, me. It’s a very effective way for plants to move around. New Zealand’s native piripiri or bidibids have the same habit, as does hooksedge, which once spread around the forest by attaching to the feathers of moa, kiwi and other ground-dwelling birds.
Devil’s horsewhip, like grey nicker, turned out to be native to Rodrigues. The seeds don’t float, but they must have dispersed around the Indian Ocean attached to migratory birds. At the time I first encountered it, though, I assumed it was invasive.
The lagoon on which Île aux Cocos sits is broad and shallow – so shallow that boats are simply punted about with long poles, like the punts which once carried cargo on the River Thames. I spent a bit of time snorkelling on the lagoon, and it seemed to be mainly around waist deep. However, I snorkelled in an area where the edge of the lagoon is only a couple of hundred metres from the shore. On the western side of the island, the edge of the lagoon is kilometres from the shore.
