The Crass Practicality: We EAT biodiversity

We have discussed the consequences of environmental richness or monotony for lemmings and proposed that it is analogous to the human need for diverse biological resources. Today we address the area in which the application of this principle has the biggest consequences: Agriculture.

The long view of monocultures:

Eleven thousand years ago, absolutely no one grew their own food. Instead they lived off of wild game, fish, and plants. Today only a tiny handful of people continue to live this way. Instead we live off of food that we cultivate deliberately or that someone else cultivates for us. Indeed, by the time everyone in this room is dead, there will probably be no primarily hunting and gathering cultures left. Their members will have dispersed and been assimilated by agricultural cultures.

Why did this change occur? After all, humans had done nicely as hunter/gatherers for many millenia. When you think about it in depth, this is really a restatement of Yali's question.

Traditionally, members of agricultural cultures would have answered that it was because of the inherent superiority of their life style, citing:

A synthesis of current anthropological, archeological, and historical data that suggests something more complex happened.

Origins of Agriculture: Advantages of the hunter-gatherer life:

Advantages of food production:

Agriculture, thus, not only has immediate benefits, cultures that adopt it soon find that they can't back away from it without: In short, they have been thrust from the Garden of Eden and are stuck with a back-breaking life style that will leave them stunted and feeble as individuals but highly competative as societies.

When farmers and hunter-gatherers meet:

Such interactions aren't necessarily hostile. Indeed, cooperative arrangements based on division of labor can include:

So why do the non-agriculturalists always seem to disappear? When agriculturalists interact with their neighbors, they have certain advantages, regardless of their intentions:

Agriculturalists, who already had a population density advantage, will find themselves facing fewer and fewer hunter-gatherers because crowd diseases will kill more of them proportionally.

By this means a world of tall healthy hunter-gatherers was gradually replaced by one of little, sickly, but fecund agricultural monoculturists who did well in good times and whose societies collapsed in bad ones.

Global economy and health:

All of this had changed by the dawn of the industrial age, when conditions combined to increase human health. (Stature, at right, is a good first-order proxy.)


However the incentives of industrial farming have brought the monoculture back in a new form.

Human agriculture and habitat diversity.

  • The effect of agriculture on world habitats also creates a dichotomy between a varied mosaic of different crops and varieties on a local scale - "patchy agricultural environments" and monoculture agriculture, based on the industrial scale cultivation of a single crop. Consider the US situation in the early 1990s (Union of Concerned Scientists Background Paper 2001):
  • Monocultures have some awesome advantages, especially in the near term:

    But it has its down-side:

    But all of this is minor compared to the long term threat: The day may come when the pests evolve faster than our ability to cope with them. There have been foreshadowings:

    Thus, the human situation - dependance on an agricultural monoculture - mirrors that of the tundra lemmings - dependance on a natural monoculture, just on a longer time scale. Our monoculture is productive now, but the development of agricultural technologies must be in a constant race with:

    if disaster is to be forestalled. The worst-case scenario is a full-blown human boom and crash cycle (of which we are now in the boom). We have discussed smaller scale versions of these, but there is something distancing about the fact the our examples, Easter Island, the Norse, and the classic Maya were pre-industrial societies. Consider an industrial-age example:


  • The Irish Potato Famine (1845-1851): A perfect storm of rational people following their self-interest in a land governed by institutions that couldn't adapt to a novel threat.

    Just IMAGINE a similar blight today effecting rice in mainland Asia.


    Is there a more fail-safe approach? In hindsight, the environmental mistakes we have reviewed are understandable:

    Ireland's mistake is especially telling: It was to become dependant on a potato monoculture. You can hardly blame them. In near-term costs and benefits, it was the rational course. No one anticipated the sudden appearance of an alien plant pathogen. But by their fruits we shall know them.

    The more we limit the diversity of the biological resources (crops) on which we depend, the more we set ourselves up for lemming-like boom and crash cycles. The alternative is deliberately to hedge our bets by cultivating a much wider range of crops than we think we need. In some ways, America is moving in this direction with:

    It's a beginning. But where do these foods come from? Natural Biodiversity. There are conceivably many more useful food crops waiting to be domesticated. Indeed, we already know of some food sources that have been left alone because they are economically infeasible now but might become feasible in the future - oak trees (right).


    I began with the fates of lemmings in natural environments of variable diversity as a metaphor for the prospects of human society in unnatural agricultural environments, then gave anecdotes about human survivability. Can we put any of this on a more concrete footing?

    Yes, we can.

    Biological productivity as a function of diversity: In recent years, mathematical ecosystem models have become more sophisticated. Models of Loreau et. al. (2001) indicated that although stable environments at equilibrium may be most productive when dominated by a small number of species, the situation changed radically when environments were variable. In such cases, habitats with greater diversity were better able to cope with change without reducing productivity. This was true even though there was some element of chance regarding which species would ultimately become dominant. Thus, diversity is an asset to productivity in changing ecosystems.

    The coming food crisis: Currently there are roughly 7.1 billion humans. By 2050 there are expected to be nine billion, leading us to fear a future food crisis. Such fears are not new. In the 1970s (when Merck was you age) similar fears were being allayed by the green revolution in agricultural technologies whcih greatly increased productivity, especially in Asia. The differences between then and now:

    As a consequence, agricultural scientists are stepping up efforts to develop and deliver appropriate technologies such as:


    We may need to modify cultural approaches to food, including:

    Whatever the details, the general principles of our attitude toward biodiversity should be clear: