After my intro to volunteering last time, I thought I’d cover one of the major control projects I’ve been doing whilst at the Mareeba Wetlands. Although the land is pretty much left to do its own thing here (some areas are grazed by cattle, but most aren’t) there is one area of habitat management in which people must intervene: invasive species.
Of course for most of the major examples of invasive species decimating local wildlife, we turn to Australia. Rabbits, foxes, and cane toads are three of the most common examples of introduced species munching their way through the native wildlife, and in the case of cane toads, being eaten and highly poisonous helps them to make sure the food web is utterly nackered. Ironically, the other major invasive species massacre example I could think of was the brown tree snake eating its way through the island of Guam… a snake which is native to Australia (I saw one the other day, more on that in another post… if I remember).
Indeed some visitors to the Wetland last week came from Guam, and their young children apparently referred to every bird as a chicken, a small chicken, or a bit chicken, because they simply hadn’t seen other birds, because the Brown Tree Snake has eaten them all.
Anyway, today’s post is about none of those. It’s about a plant called Lantana. Lantana has pretty yellow and red flowers, is really easy to grow, and takes very little looking after, therefore wealthy gentlemen loved to have it in their gardens. Unfortunately, it turns out that Lantana is very quick to spread over here (birds love the seeds, and it establishes very quickly), the leaves are ludicrously poisonous to most animals, and it burns at a very high temperature. This is a problem in a country where the wildlife has evolved to survive (and often require) regular burning from natural forest fires. If the temperature of those fires increases, the gum trees can no longer survive it, so they die out , and then plants which are quick to colonise take over… plants like Lantana.
To kill off this beasty isn’t too easy either. The “quick and easy” way, is to pull the plant out, root and all, and leave the root to cook in the sun. Unfortunately however, you can only do this when the plant is quite young. Once it gets too large the roots are too deep/wide and brute force (without the assistance of a quad bike) isn’t enough. At present there is no species specific herbicide for Lantana, and so a liberal spraying of herbicide won’t help (or will kill everything and cost a lot). Instead you have to take the personal approach, with a cane knife. By cutting down all of the branches to the root, you can use specific application of a generic herbicide, spray it into the cut stems, and it will then be taken down into the root, and kill the whole plant without massacring every other plant in the neighbourhood. However, if you don’t cut off and spray every single stem, the plant will simply re-grow from the uncut/unsprayed section. Similarly, when pulling plants out, if you don’t get every connected root out of the ground, the plant will continue to grow. On the plus side, once you get the hang of it (and have a sharp knife), felling the stems is quite simple (the right angle of approach and the right force will see you slice through even the thickest stems in a couple of swings) and so you can kill many plants in a morning… which is just as well, as they seem to be springing up everywhere!
Unfortunately, this is a tale with a sad end to it. As with so many invasive species issues, we’re fighting a losing battle. The plant is stupendously wide spread, you see it all along the road on the way from Cairns to Mareeba, and that’s just a single transect through the land (though admittedly perhaps less managed than much of the surrounding area). Though I could cut down hundreds of them, there are thousands more which will spread seeds right back here in the next year, and then the whole problem begins again. The issue is similar to that of Himalayan Balsam in the UK, with two major differences. The first is that Balsam only grows along river banks, so is relatively confined, you know where to find it at least. The second is that the UK is a fraction of the size of Queensland, and we find it near impossible to keep on top of the balsam there. While balsam can be steadily tackled by large teams of volunteers working from upstream to downstream in river catchments (the seeds largely spread down the course of rivers), keeping on top of Lantana here would require thousands of full time workers out killing it, and even then, you always miss some, and they could spring up anywhere. Even if there were thousands of people out killing Lantana full time, it’s just one of a vast array of invasive species over here, each with it’s own unique horrendous impacts. I fear that in this world where sustainability is the current keyword, eventually we may need to look at our management of invasive species and ask “is this sustainable?” (or even “are we having any discernable impact?”). The answer in many cases I fear, is no. But that then leads to the question “can we allow our native species to be out competed by invasive species? How much diversity, how many processes, how much natural heritage can we afford to lose to invasive species?
I fear Lantana is a species which is here to stay, and each year cattle station owners (cattle station = Australian cattle ranch) will kill the individuals on their property because it is necessary to keep their cattle alive, but other than that it will simply spread.
What a depressing end to a post. I’ll try to make the next one a bit more joyful.
Until next time