Cambrian Period

The Cambrian Period lasted from 541 to 485 million years ago. At the beginning of this time period, the small unicellulars that represented most life on Earth became more complex and multicellular. They also diversified quite rapidly, bringing forth the first representatives of all modern animal phyla. Indeed, there is strong evidence that all animals evolved from a single common ancestor.

Life prospered in the oceans, but the land is thought to have been relatively barren, with nothing more complex than a microbial soil crust or biofilm. A few molluscs may have emerged to browse on that biofilm, but the continents were probably dry and rocky. The global supercontinent Pannotia had just broken up during the early part of the period, and the new continents were mostly flanked by shallow seas, which were relatively warm. Polar ice was absent for much of this period.

Most land masses were clustered in the Southern Hemisphere during this period, but were drifting north. During the early portion of the Cambrian, the supercontinent of Gondwana went through some large, high-velocity rotational movements.

Trilobites (I wrote about them in an earlier post) were rampant during the Cambrian period. Possibly this was because without any sea ice, the sea level was high, which meant large areas of the continents were flooded in warm shallow seas, which is ideal for sea live. But the sea levels did fluctuate somewhat, suggesting there were ‘ice ages’, possibly meaning pulses of expansion and contraction of a south polar ice cap. Although the beginning of the period was cold, the average temperature during the Cambrian was 7° Celsius warmer than today.

Even so, trilobites were not the dominant species, as was once thought. It seemed they were, because they had hard external shells that were easy to fossilize, much easier than the thin chitinous shells of other arthropods, and so trilobite fossils were much easier to find by today’s paleontologists.

The Cambrian period is often referred to as ‘the Cambrian Explosion’, indicating a huge increase in the variety and diversity of life forms. But it seems (to me) that it might be better to think of it as ‘the Period of Great Changes’. At the start of the Cambrian, new creatures with new behaviors and lifestyles destroyed the biofilm that covered the sea floor, so all the creatures (from the previous time period) who depended on that biofilm died out.

Around 515 million years ago, the number of species dying out was larger than the number of new species coming into existence. 500 million years ago, the oceans saw a big drop in the oxygen content, and at the same time, the level of toxic hydrogen sulfide increased. Either of these events alone could produce extinctions, so imagine what happened when they came in together.

Where would hydrogen sulfide have come from? There are a few ways nature makes it, including anerobic digestion by certain biofilms in the absence of oxygen. I can’t rule that one out, but I’m somewhat more inclined to ‘blame’ volcanoes, which also produce it, probably in larger quantities and certainly can do it in oceans. Also, the heat given off by the volcano(es) would tend to drive oxygen out of the water. So, was there a series of huge volcano events 500 million years ago? I don’t know. It seems possible.

And there we have the Cambrian period in a nutshell. No fascinating dinosaurs to study, but the thought of a spinning Gondwana certainly has my attention.

https://en.wikipedia.org/wiki/Cambrian

https://en.wikipedia.org/wiki/Hydrogen_sulfide

Boreal Forest

If you want to talk about a forest that is larger than the Amazon jungle, then you will probably talk about the Taiga, the Boreal Forest or the snow forest. They are all one thing, with different names used in different parts of the world. Some say it is one huge forest, stretching from Iceland through the Scandinavian countries, Russia, Mongolia, Alaska and Canada. It is a coniferous forest consisting mostly of pipes, spruces and larches. It covers 6.6 million square miles or 11.5% of the Earth’s land area.

The boreal forest has a subarctic climate, with a very large temperature range between seasons. Summers last 1-3 months, always less than 4 months, and any given 24 hour period during the summer will average 50 °F or less. In Siberia, the average temperature of the coldest winter month is between 21 and -58 °F. The ground being frozen for much of the year, or even permanently frozen, can restrict the growth of deep roots, thereby favoring shallow-rooted trees like the Siberian larch.

Despite these harsh condition, the plants in the boreal forest have a lower threshold to trigger growth, and thus they ‘wake up’ a little earlier than one would expect. Even so, the soil tends to be poor in nutrients. Fallen leaves and moss tend to sit on the soil for a long time in the cold climate, so their organic components are very slow to be added to the soil. Also, acids from the evergreen needles leach the soil, making it even less ‘appetizing’ for anything but lichens and some mosses. On the other hand, diversity of soil organisms is high, comparable to a tropical rainforest.

It seems surprising to me that in a world that is frozen most of the time, fire is one of the most important factors that shape the composition and development of boreal forest. Some members of the boreal forest won’t release their seeds until the pods have been exposed to fire, and I get that, but how does something covered in snow most of the time suddenly burst into flames? Obviously, there is something about the process that I don’t understand.

Most boreal forest fires are either high-intensity crown fires or severe surface fires. These are large, often more than 10,000 hectares (a hectare is 100 acres) and sometimes more than 400,000 hectares. Different areas of the boreal forest burn at different lengths of time; drier areas might burn every 50 years, while wetter areas only burn every 200 to 300 years. And when an area burns, it could take decades, even a couple centuries to get back to ‘normal’. So all that carbon dioxide (a greenhouse gas) that is released into the air when those trees burn takes those same decades or centuries to be absorbed into the growing forest again.

This is particularly important now, when so much of the boreal forest is burning. Even Greenland - which doesn’t have any boreal forest, but does grow grasses and scrub brushes when enough ice melts to expose ground to seeds being blown around by winds - is on fire. Alaska and Canada are experiencing horrendous fires in their boreal forestland. In northern Siberia, one fire covered 7.9 million acres (over 3 million hectares), and that’s only one fire of 11 (or more) burning in Russia.

It’s been estimated that these fires dumped over 50 million tons of carbon into the atmosphere in June (2019), and they are still at it. 16 million adult trees burn in a day in Russia’s boreal forest fires. The Earth is not ready to absorb that much carbon. If we planted more trees - billions of them - it would help, but possibly not before the climate changes even more in response to that much carbon and carbon dioxide having been freed to begin with.

We really can’t sit around and wait any longer. We have to start facing this problem, and we have to do it NOW. The sky is falling, and doomsday is just around the corner.

https://www.dailykos.com/stories/2019/7/31/1875681/-Fire-at-the-top-of-the-world-Earth-s-largest-forest-is-burning-and-it-won-t-be-coming-back-soon

https://en.wikipedia.org/wiki/Taiga

OrganPipe Cactus fruit

I have often wondered what kind of food chain there would be in a desert that would allow people to live there. Oh, yes, I’ve heard about certain rats, rabbits, coyotes, snakes, lizards... But the fact is that as you go down the food chain to smaller and smaller creatures, eventually you have to get to plant-life. On Earth, it seems a pretty likely bet, anyway.

I am often disappointed by authors and filmmakers who forget there needs to be some kind of food chain. In my latest viewing of “Dune” - I can’t remember which version of it I was watching - it occurred to me that the people on the planet were apparently colonists, or descendents of colonists. There was much talk about the great worms, with no talk of what they ate. One assumes that there was a mouse species on the planet, but they might have come with the colonists. One assumes there are mice, because the nickname the common people adopt for Paul was the name of a species of mice who fight back. And in one scene, I saw at least 1 beautiful butterfly. Nowhere did I ever see any kind of plantlife out in the wild. So... what did the butterflies, the fierce mice, the worms and the people eat? I don’t know. I don’t remember anything like that being mentioned in the book, either. Sigh.

By comparison, Earth deserts are veritable hotbeds of life. So let’s take a look at another desert food source that I’ve heard about.

The organ-pipe cactus grows in the Sonoran Desert and Baja California. It has a very short trunk, from which dozens of stems grow, producing what one might think of as a bush. Its root system only reaches about 10 cm (4 inches) into the ground, but are sufficient for sucking up monsoon water when it occurs. Otherwise, the plant is pretty water-tight, with a water-proof skin and plenty of thorns to keep from getting eaten. An individual cactus can live 150 years, but doesn’t produce fruit until age 35. Probably because a good growing year will see it add a whopping 2.5 inches a year to its height.

In May and June, the organ-pipe cactus develops white/creamy flowers that only open at night and usually close back up by mid-morning. That doesn’t leave much time for day-time pollinators to get to it, but bats do the job just fine during the night.

Just before the rains come in July and August, the fruit ripens and splits open to reveal bright red flesh surrounding lots of seeds. Or maybe the fruit was red and the inner flesh was purple; I’ve seen it described both ways.

I didn’t find a lot of recipes for preparing organ-pipe cactus fruit. Apparently, you simply mash the fruit flesh and seeds into a sweet paste, which could be eaten as it was. Or you could dry it out to make a spreadable jelly. Another way would be to separate the seeds and place them in storage. Later, you could grind the seeds into a flour to make seed cakes. So, you could have your seed cakes and fruit jelly both!

en.wikipedia.org/wiki/Stenocereus_thurberi

www.nps.gov/orpi/learn/nature/organ-pipe-cactus.htm

http://www.ethnoherbalist.com/southern-california-native-plants-medicinal/pitaya-fruit/