The germination capacity of seeds varies over an 18.6 year cycle. Within this cycle, there are 7 years during which the cumulative phase reduces its efficiency, especially if the temperature is reduced. In this case, food crises and famines occur.

Correlation with the famine years.

A non exhaustive analysis of the famine years, on the basis of data published on Wikipedia, shows a correlation with the long viability cycle in seeds of about 18,6 years long, and the canonical seven years of lean times, when the range of the Moon declination, relative to the Equator, exceeds +/- 26 degrees.

A good correlation if you do not consider the famines due to wars, to inefficient income distribution, to exports from regions affected by food scarsity, as well those due to nonsensical policies.

Food crises as a result of senseless policies.

I recall here the food crisis provoked in Ukraine by Stalin (Holodomor 1932-1933) took place, within the 18.6 year cycle, in a period in which harvests are usually poor (lean period).

Instead, the food crisis of 1961 in China, a consequence of Mao's development plans, took place in a period when harvests should have been abundant (a period of fat cows).

Examples of food crises due to Nature.

I will mention just a few examples of food crises: the great famine of 1315-1322, and those when Louis xiv was king (little glaciation).

They occur:
(1) when the range of the Moon declination, with regard to the Equator keep itself above +/-26 degrees, and thus when there are short episodes of interaction (in the cumulative-dissipative cycle);
(2) and when the temperature is low during the cumulative phase, and so there are also few processes.
As a consequence, there are also few dissipative processes.

Closer to our times.

Less severe, but in a context of globalisation and speculation, one can mention the food scarsity, in particular during the years 2007 and 2008, if one refers to the prices. And whose end result was the so called “arab spring”, triggered by an event on december 2010, in a context of circumstances, gathered up during the preceding years.

Considering the future, the range of variation of the Moon declination, with regard to the Equator, will be more than +/-26 degrees, from september 2021 until april 2028.

All this will occur in a context of huge migratory movements, wars, crazy weather, sea levels rising, population explosion, the natural desire of men of improving their conditions. By contrast, the limits are not taken into account, until the moment everything bursts.