Reflecting on invasive species
By: Rafa Contreras-Rangel
After being away from the workplace for two weeks, I’ve been at a loss as to what to write for this month’s blog. I usually write about the kind of work my crew and I have been doing lately, but seeing as how we haven’t worked in a while, my options were limited. Today, as I was pondering what to write for this blog while cutting down a tree for our project, I noticed that the tree I was cutting was a green ash. It was then when it hit me that what I wanted to write for this week’s blog is invasive species.
You might be wondering why I decided to write about invasive species since, after all, the green ash is native to Minnesota. The key to my epiphany did not come from the fact of seeing an ash tree, it came for the reason why I was cutting it down. The ash tree was dying.
Before I go on, I would like to explain what an invasive species is for the readers that might not know. By definition, an invasive species is a species that does not belong. That means that an invasive species is any species that does not belong to the local ecosystem, it can be a plant, animal, or even a fungus. An invasive species also generally displaces a native species, disrupting the local ecosystem, and in worst case scenario, could lead to the extinction of native species.
Now that I got that out of the way, we’ll go back to my story. So why was this ash tree dying? There is this tiny beetle, called the emerald ash borer, that lays its eggs in the bark crevices of ash trees. Once the beetle eggs hatch, the larvae feed on the tissue under the bark, creating crevices that disrupt the nutrient and water transport of the tree, eventually killing it. Now generally the ash tree’s ancestor would have had millions of years to coevolve with the beetle and build up its defenses to survive its attack. Unfortunately, it just so happens that this beetle is native to Asia and was probably brought over here in shipping crates. While the modern ash tree has developed defenses to fight off its native predators over millions of years, it is virtually defenseless against this new parasite.
So why doesn’t the ash tree evolve or adapt a way to fight off this new predator? The answer to that questions is time. In order to evolve, the surviving parents have to pass on their genes to their offspring. The current belief is that the beetle came from Asia in the 1990s, and studies have shown the beetles kills its host within ten years. Ash trees do not reach seeding age until they’re ten years old, which means almost all ash trees will be killed before they can pass on their genes to the next generation.
Before I came to work for the conservation corps, I lived in Michigan. I also did conservation work there, and I remember hearing people talk about ash trees all the time but I never actually got to see one. I later learned from my crew leader that the fallen logs we usually cut up were all dead ash trees. If you ever visit Michigan you will see these dead trees everywhere, and you probably won’t see any live ones. It was sad to think about. Knowing that these trees had just been there not too long ago, and now they were all gone. At the time I was sad because I thought I would never get to see these ash trees that everyone but me seemed to know. That all changed once I moved to Minnesota.
I was so happy when I went out on my first buckthorn removal project with the Corps because I finally got to see what a live ash tree actually looked like. And not only were the trees alive, they all seemed to be thriving. This was during the spring, and now on this summer day I have gone back to another buckthorn removal project. Unfortunately, this time I did not experience happiness once I got to the project site. Most, if not all, of the ash trees on this site were half dead, with leaves on only the topmost part of the tree. It felt as if I was stepping back in time, and I was now witnessing what had happened in Michigan right before I moved.
Think about it. Here in Minnesota we all know ash trees. But if the same thing that happened in Michigan is happening here, they will not be around much longer. This means that any friends that visit from the south will never get to see it. Your kids might not get to know what an ash tree is or what it looks like. These people will be just as I was when I was in Michigan. They will hear about it all the time from people like us that have seen it before, but will always wonder just what kind of tree it was.
I know that my blog is turning out to be a bit more depressing than usual, so I want you to know that all’s not lost. There are many teams out there trying their best to slow and stop the spread of emerald ash borer. Trees are being monitored in order to remove any new infestation. Insecticides are being developed and used to kill the beetles with the hope of slowing their spread. And most important of all, in my opinion, is that biological control, in the form of parasitic wasps, has been deployed since 2007. Biological control is the use of another organism to combat the spread of invasive species. These organisms are usually the natural predator from the native ecosystem of the invasive species. While this may sound scary at first, since this sounds like yet another invasive species is being introduced, these organisms are generally harmless to the rest of the ecosystem since they only target the invasive species. Many years of study goes into biological control before it’s approved for release.
By this point you’re probably thinking invasive species could be one of the worst things that could have happened to our local ecosystems. But is that really the way we should be looking at invasive species? I used to think yes, but after learning more about invasive species and how they got here, I have changed my stance. Yes, invasive species are bad to native ecosystems and it is one of the biggest threats that my generation will have to face in the coming years. But invasive species are not here because they are evil and want to take over the world. If you are familiar with invasive plants, you’ll have to agree that invasive plants tend to be quite beautiful. Now why is that? Could it be, perhaps, because people that left their country decided to bring the most beautiful plants to not be homesick? I don’t know if that’s true, but it is a good question to think about. What I am trying to get at is that invasive species did not bring themselves here, we brought them here. An invasive species is not good or evil, all it is trying to do is survive, and it just so happens that the new ecosystem it was placed in by humans is perfect for it to thrive.
So next time you go out to your local forest or lake do not get angry or discouraged when you see it overrun with invasives. They are not evil; they are just making the best out of the situation they got put into. Instead, think about ways that you can alleviate the problem we created. Maybe you could check your shoes or boat before leaving to not spread their seeds any further. Maybe you can learn to identify them better to make sure they’re not growing in the garden by your driveway, that way you can avoid accidentally spreading their seeds everywhere you drive. Just remember that there is always something you can do to alleviate the problems we created. The little things you do are the ones that matter the most. You do not need to be in cutting edge research to make a difference.