Learning from History: The Importance of Genetic Diversity

“History doesn’t repeat itself, but it does rhyme” ~ Mark Twain

The Irish Potato Famine has gone down in history as one of the worst tragedies of the 19th century. In 1845, a fungal infestation, Phytophtthor infestans, reduced half of the potato crop in a single year into an inedible slime. In a very Biblical, Joseph and the Technicolor Dreamcoat fashion, the blight lasted for another seven years, ruining over three-quarters of the crop[1]. By the time the so-called Great Hunger ended in 1852, approximately one million Irish citizens had died from starvation and another million became refugees.

While Phytophtthor infestans is technically to blame, the root cause (at least from a biological standpoint), is actually a lack of genetic diversity. To accommodate the rapidly growing population, Irish farmers vegetatively propagated (a form of asexual reproduction made from cuttings) the “lumper” variety of potato. Since all the potatoes were clones, they were all genetically identical to one another, and therefore equally susceptible to any changes in the environment. Had greater variety of potatoes been planted in Ireland, Darwinian theory tells us that more of the crops would have been able to resist the blight. This could have reduced both the devastating impact and the length of time it persisted. As it was, however, the majority of the potato crop was decimated, along with the population so dependent on it.

Nearly 200 years later, and we still haven’t learned the lessons history taught us. The appeal of genetically identical crops for “big agriculture” includes scale (farmers can grow an extremely large yield without the need for seed) and efficiency (farmers have the ability to harvest all the crops at the exact same time). A third stated reason, strength, is much more nebulous, as what is considered strong today can just as easily be wiped out with the slightest change to its environment – whether the introduction of a new pest, a change in climate, or some other environmental factor.

Two examples in the 20th century illustrate this point:

  • In 1970, the Southern corn leaf blight decimated almost 70% of the corn population in the U.S. While this did not have devastating costs to human life, it is considered a larger financial catastrophe than the Irish potato famine, costing more than $6.5 Billion in today’s dollars.
  • Ten years later, the emergence of a new race of the insect grape phyllorexa, forced California vineyards to replant almost 2 million acres[2].

One of Southern Highlands Reserve’s ongoing projects is repopulating the red spruce forests. These forests have been threatened due to impacts from human activities, non‐native insects, and other natural factors such as insects, isolation, and climate. Today, these high elevation forests are still considered the second-most endangered ecosystem in the U.S. Dozens of birds, mammals, insects, and amphibians are dependent on these forests for their survival and are also endangered or threatened.

To find out more about SHR’s red spruce program or to donate to the cause, click here.

[1] Source:

[2] Source: University of Berkeley