December 2020

I have commented that there is no such thing as disaster in nature, only change. Many changes run in cycles, just like the daily cycle of night, dawn, morning, afternoon, evening and the yearly cycle of winter, spring, summer and autumn (fall). Incidentally, although fall is used in the USA instead of autumn, it is actually an ancient English word commonly used up to the 17th century when it was largely replaced by the Latin word autumn(us). The climate is also changing.

There is also the carbon cycle, water cycle and of course life cycle of every organism that lives. Diseases also tend to go in cycles, and there is a commonly quoted cycle of rabbits and myxomatosis caused by the rabbit myxoma virus. Rabbits control this disease by changing their behaviour. As the population of rabbits breeding underground in warm burrow nurseries increases, the transmission of myxoma virus by the secondary host, which is the rabbit flea, increases. This causes many rabbits to die. Then, those rabbits that breed above ground under bushes, as some do, are more likely to survive because the (cold blooded) fleas are more likely to die of cold during frosts. These rabbits then increase in number but sometimes produce offspring that resume the underground breeding strategy in order to avoid predators such as foxes. This allows the myxoma virus to increase again and so on.

Similarly, there is a well-known cycle of Arctic foxes and Arctic hare numbers. As the hare numbers increase, so fox numbers increase until too many survive to be supported by the over hunted hares and many foxes die of starvation, allowing the hares to increase again and so on.

These population cycles, regulated by climate, disease or predation control the numbers of animals that we see around us. There is no reason to suppose that the same cannot happen among humans. It was predicted by Thomas Robert Malthus (1766 – 1834). We are unlikely to be controlled by predators because we are the planet’s top predator, but we have less control over climate and microbes. In the end, each living thing dies, which is sad for those around it, but then there is room for others to be born, providing joy for those around the birth event.