I did not wake up this past Sunday (This was a few weeks ago now) morning thinking I would be writing an article this week about Joshua Tree's and the disaster they are speeding towards. I wasn't even planning on seeing them that day though they lay scattered in the area near where I live. I had zero intentions to ever write something on these trees, as they fall outside my fields of interest aka, wildlife. But it took two days and a thirty minute drive to change my mind.
I found my self in Joshua Tree National Park this past week. I had zero intentions of being there any time soon, but when you wife says lets go, you go. So six hours of driving later we arrived and were enjoying the whimsical shapes these trees make while setting up camp. The next day we set out to explore the park and show the kids the wonderful place that it was and see what we could see. As I drove around though, the little biology itch at the back of my head was scratching away at what I had heard about Joshua Tree's being petitioned under the endangered species act. Additionally, I had heard that these tree's were predicted to be extirpated from the park some time in the future, and Joshua Tree NP was just going to be a monument to once was.
But something wasn't jiving and I knew there must be fore to the story.
As we drove around I could see age classes of trees suggesting recruitment in some form going on. Additionally they seemed to distributed nicely in the park and there were lots of them. We also saw huge groves on our way through California so what's the big deal with these species going extinct and what is going on that's leading to this assertion? Then we decided to drive south and down hill within the park and the reality set in. As you descend down hill in all directions the Joshua tree's disappear. As you drive around the north end of the park you realize the trees are at the top of their elevation gradient and the "mountains" around only rise a few hundred feet above that in a few places.
Joshua Trees are on a peak in a sea of desert and were on their escalator to extinction, and they were near the top of the fall.
In the world of conservation biology, the escalator effect or escalator to extinction is not a new concept. If you do not follow this world though, this is a new idea. All around us we see mountains, hills valleys and so on. If you are a student of history you may have heard of Alexander von Humboldt who first described the idea of how plants and animals change with elevation thus they live in climate zones. This idea was revolutionary for its time and help establish some of the earliest foundations of ecology. Someone later on though picked up on this idea and made the connection to climate change and realized we had a problem.
The idea is as heat increases animals suitable for colder habitats have to move to higher elevation, and once they reach the top of the hill or mountain, there is no more room to go and thus they go extinct. If you are a pika, for example, you are very sensitive to temperature. If the temperatures rise just a few degrees, you can over heat and die. To get around this you can climb higher up the mountain. If there is no more mountain to climb though (i.e. you are at the top), you simply die. The end. Thus the elevator to extinction.
Joshua Trees seem to be facing that fate. When I got home I dug into the literature and found a few startling findings. First, many of the Joshua Trees within the park, the young, the old, are all clones. Very few new trees from sexual reproduction were occurring. Then I found out the symbiont, the Joshua Tree Yucca Moth, the one animal that actually pollinates the trees have mostly vanished from the park. Finally the distribution of the trees are slowly climbing up the hills, and are disappearing from the lowlands. The escalator was actively moving and it was restructuring the Joshua Tree forest this place is famous for.
If things continue as is, Joshua tree National Park might not have Joshua trees in it at all. It will be a monument to once was and a reminder to what we lost.
Reversing climate change is difficult. Individual actual rarely means much, and it is up to all of those who are in power to make a difference. I can educate, but CEO's can restructure their fleets of vehicles to electric. Governors can enact policies to use more renewable energies. We can all cut down on meats, and those who have the funds to switch to electrical systems can make a difference.