What is the phenomenon of population regulation? What does it have in an ecosystem?

When the population growth is completed, its number begins to fluctuate around some more or less constant value. Often, these fluctuations are caused by seasonal or annual changes in living conditions (for example, changes in temperature, humidity, food supply). Sometimes they can be considered as random.
In some populations, fluctuations in numbers are cyclical in nature.
The most famous examples of cyclic fluctuations include fluctuations in the numbers of some species of mammals. For example, cycles of three- and four-year periodicity are characteristic of many mouse-like rodents (field mice, lemmings) and their predators (polar owl, arctic fox).
The most famous example of cyclical fluctuations in the number of insects is the periodic outbreaks in the locusts. Information about the invasion of wandering locusts dates back to ancient times. Locusts live in deserts and low-water areas. Over the years, it does not migrate, does not harm crops and does not particularly attract attention. However, from time to time the density of locust populations reaches monstrous proportions. Under the influence of crowding, insects undergo a number of changes in their appearance (for example, they develop longer wings) and begin to fly into agricultural areas, eating everything in its path. The reasons for such population explosions are apparently due to the instability of environmental conditions.

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