I wish it was so easy!
Boy, it is getting warmer on this blue marble floating in space. During the women’s soccer (or football) championships in France, they were complaining about record temperatures in Europe, and by this weekend, our temperatures are going to reach close to 100 degrees Fahrenheit, or 37.8 Celsius. As I write this (July 17, 2019), there was a news flash that Miami recorded the warmest low temperature early in the morning (84 Fahrenheit or 28.9 C).
Thank goodness, nature is still able to cope with these extremes in our area. Where we live we have had approximately 6 inches (150 mm) more rain than average by this time of the year. At least there should be enough water in the deeper layers of the soil for at least the trees and other deeper rooting plants, but I may have to supplement the shallow rooted plants.
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| Our ferns underneath the dogwood in our yard. These ferns were dug up (saved) by my wife at a construction site she was permitting. These ferns would have been destroyed if she had not dug them up. Now they are protected by our gargoyle and thanking us for our effort. This is an example of plants that need supplemental watering because they don't root very deeply. |
One way plants deal with the excessive heat is through evaporative cooling. Plants sweat, just as we do. Except with plants, we call it evapotranspiration. With us, sweating is an active thing, or at least with me it is. I actually get really wet when it is hot outside, and that is a great way of cooling, albeit somewhat embarrassing in public at times. Plants do not get wet, but they open their stomata (small mouth like openings) on their leaves and water evaporates though it, thus cooling the warming leaves. Most plant leaves are also very thin and small, which keeps them close to the air temperature prevents them from heating up in the direct sun light (like your car) and burning up. Pine needles are very good at this, which is why they grow throughout the southeast US. However, different plants have different ways of doing this. Some of you may have heard of quaking aspen; leaves from these trees start to shake (or quake) when the get too hot and they cool down that way. Cacti in the desert have a lot of water in their flesh that helps them in heating up very slowly. Moreover, the spines of cacti serve as suntan lotion and absorb radiation. The saguaro cacti also have fins that serve as cooling fins on the sides that are not hit by the sun.
These are what we biologists call some of the different strategies that plants use to deal with heat stress. However, plants can only adapt or strategize that much! Eventually it gets too hot! In the tropics, some plants have adapted to that as well. They drop their leaves and go dormant, just like our trees do in winter when it gets too cold. However, there has to be enough water in the soil and they have to have stored enough energy to grow back when the temperatures get more hospitable, otherwise, they die. They usually grow back in the rainy season. Finally, here we have not even talked about how increased temperatures may also cause an increase in pests and diseases. You get the message.
So, what is going to happen to the natural world or plants in our times of climate change? Alternatively, am I allowed to call it global warming, which is what it is? I frame this question this way, remembering that every time I mentioned global warming 10 or even 5 years ago in my workshops, I had students either rolling their eyes writing terrible reviews of my classes. There were at least one or two students that complained how I was “pushing my liberal agenda.” So I changed my tune and called it climate change and the complaints lessened over time. Guess what? Nowadays, I can talk about global warming again!
For someone like me, who grows bonsai, life becomes more challenging. We use a much more porous growth medium that does not hold water. This means that we may need to water two times per day. Then those small pots can warm up very quickly and cook the roots, or at least give a leg up to mold and diseases. As you can see, it can be a challenge.
For nature, it is another thing. I am only briefly going to write about plants and forest today and actually, we are not completely sure, but we can make a very solid educated guess. Plants in the northern hemisphere that live on the southern margins are going to have a challenge. What I mean is that they are already being challenged by the heat and cannot handle it much hotter. They will eventually disappear from the heat. This could be because they can no longer produce any viable seed, or because they simply die from heat stress. Somehow, nature will need to replace them and the problem is that native plants cannot move north fast enough to fill in the spots that have been opened up. These spots are often filled by invasive alien species. It is expected that invasive alien species will be able to take over larger tracks of land. The problem is these plants are often not very nutritious for local wildlife and insects.
So what can we do about global warming, that is in addition to being political active and voting? The New York Times published an article not so long ago where they estimated that the planet has room for about 2.5 billion acres of forest that can be planted. While this will help in removing some carbon and reducing global warming somewhat, it is not enough. Can you imagine planting a forest of this size? So what can we do? Well, we can plant trees around our homes. If you are a loyal reader, you know I have been on a crusade against folks who cut trees around their home as soon as they move into our neighborhood. Trees are so much more efficient in fixing carbon than lawn. In addition, they modify the climate around your home. There is another interesting article about all this in a recent New York Times. So yes, in addition to growing my miniature trees, I also grow large trees in my small yard, although this makes it often difficult for me to find it difficult to find a sunny spot for my miniature trees.
