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How Much Did Crop Diversity Decline in the 20th Century?

It is generally assumed that crop diversity declined dramatically during the 20th century. This trend is blamed upon market pressures and the rise of corporate agriculture, among other things. But is the underlying assumption accurate? Paul Heald and Susannah Chapman of the University of Georgia (law and anthropology, respectively) suggest we may need to rethink what we think we know about vegetable crop diversity. In a new paper, "Crop Diversity Report Card for the Twentieth Century: Diversity Bust or Diversity Boom?", they present evidence that crop diversity has not declined meaningfully at all.

According to the conventional wisdom, the twentieth century was a disaster of monumental proportions for vegetable crop diversity. The conventional wisdom is wrong. Our study of 2004 commercial seed catalogs shows twice as many 1903 crop varieties surviving as previously reported in the iconic 1983 study on vegetable crop diversity. More important, we find that growers in 2004 had as many varieties to choose from (approximately 7100 varieties among 48 crops) as did their predecessors in 1903 (approximately 7262 varieties among the same 48 crops). In addition, we cast doubt on the number of distinct varieties actually available in 1903 by examining historical sources that expose the systematic practice of multiple naming. Finally, by looking more closely at the six biggest diversity winners of the twentieth century (tomatoes, peppers, lettuce, garden beans, squash, and garlic), we suggest that patent law is virtually irrelevant.
These results will be a surprise to many, but I think they are largely consistent with what economic theory would predict. While there are pressures toward greater commodification and standardization of agricultural goods, there are also pressures to satisfy the demands of niche producers and consumers. As our ability to modify crop varieties improved, and the costs of customization declined, desired crop varieties should proliferate.

These trends might not occur in tandem. That is, the pressure toward commodification to increase productivity and reduce costs may precede the pressure toward the development of specialty crops. If so, then one would expect to see an initial decline in crop diversity before an eventual increase. (Think of something like the agricultural equivalent of the "Environmental Kuznets Curve.") Some crop varieties are lost along the way, to be sure, but new varieties emerge as well, and I see no reason to presume that the older varieties are necessarily superior than the new ones. In many cases they will each have been the product of human design.

Consider this example. During the initial "Green Revolution" there was a decline in crop diversity as it was too costly to breed desired traits into all existing varieties of individual crops. Increased agricultural productivity came at the expense of local crop diversity. Over time, however, more advanced techniques make it much less expensive and time consuming to insert a desired characteristic into a given plant. This has enabled the insertion of desired traits into traditional local varieties, so that crop quality can be improved without sacrificing crop diversity. Somewhat ironically, some of the same groups that complain the most about the loss in crop diversity also oppose the technologies that can enable agriculture to meet more human needs without sacrificing it.

UPDATE: Study co-author Paul Heald adds some thoughts in the comments.

Curt Fischer:

[T]hey present evidence that crop diversity has not declined meaningfully at all.


Not really. They present evidence that vegetable crop diversity as measured by seed catalog listings has not declined.


It is generally assumed that crop diversity declined dramatically during the 20th century.


Zeroth, who is doing this general assuming?

First, acreage planted to vegetable crops is miniscule compared to acreage planted to grains.

Second, all agriculture is local. I take crop "diversity" to mean whether a given field is a monoculture, or is instead a mixture of several different species. Many others share my view, I think. Strain XYZ of lettuce growing next to strain ZYX of lettuce doesn't diversity make, at least in my book.

The reasons to hope for intra-species genetic diversity among the cultivars of a crop related to regionally varying presence of diseases, droughts, and other stresses. There are important reasons to cultivate diversity among crops, but it is important to realize that intra-species genetic diversity for a single type of crop is only one type of diversity.

Third, for some crops, like bananas, a decline in diversity over the 20th century is very well documented.
9.1.2009 3:52pm
Tracy Johnson (www):
I'm reminded of two apocryphal anecdotes:

1. An open market in South America will have umpteen potato varieties available, a U.S. supermarket will have two or three.

Thus confirming the hypothesis, however,

2. The Irish potato blight of the mid 1800's could have been prevented had the Irish cultivated more than one variety of potato.

Does this mean the hypothesis is not limited to the 20th century after all?

I'm also confronted in the market by new kinds of produce. Recently I bought some Pluot, apparently a hyprid of plum and apricot, developed during the 20th century.

What does this do to agricultural diversity?
9.1.2009 3:56pm
Tracy Johnson (www):
Confirm typo on "hybrid".
9.1.2009 3:57pm
Daniel San:
The report I hear most often concerning crop diversity is that there has been a tremendous shift toward corn. That corn is used in most prepared foods, is the preferred sweetener, and dominates our diets. This does not mean we do not have more varieties available, but that government policy has determined that corn must be abundant and cheap and that some of its key competitors must be expensive.
9.1.2009 3:57pm
einhverfr (mail) (www):
Certainly a trip to the grocery store doesn't show heirloom tomatoes for sale often if at all. Maybe one can find a few varieties of onions, etc.

A trip to the farmer's Market, OTOH....

So the fundamental questions will end up having to include:
1) How do we define diversity?
2) How do we measure it?

My entirely non-scientific survey of grocery stores and farmers markets suggest that while diversity of crops for small growers is going up or at least holding steady, diversity of crops for larger growers is declining.
9.1.2009 3:58pm
NCResident:
einhverfr:

Exactly what grocery stores are you shopping at that don't currently have heirloom vegetables? Large regional/nationwide grocery stores near me -- Harris Teeter, Krogers, Whole Foods -- certainly have a large selection of organic vegetables and heirloom tomatoes, etc. Once you get to the smaller vendors -- Bloom, Fresh Market, etc -- the selection is even greater. Even stores like Food Lion which typically have been more mass-market now are getting excellent produce sections as a way of targeting the Latino community in my area (varieties of cactus and peppers I've never heard of, yucca, etc)

By contrast, yes, the local Farmer's Markets DO have a great selection of heirloom tomatoes for instance, yet I've been somewhat interested to note that there seem to be few if any (I've never seen any) "family" lines that are unique to this area. Most of the varieties I see are famous mass-market heirlooms--Cherokee Purple, mortgage lifters, homestead, german johnson, etc.

I don't understand the stigma of hybridized vegetables. As far as I can tell most of the foodie snobs who are currently going nuts over heirloom tomatoes are the same people who never ever bought old hybrid tomatoes at roadside stands, and never went to farmers markets before they were hip, etc. Guess what--fresh, RIPE vegetables do taste better than artificially ripened / possibly refrigerated vegetables--that's true for hybrids AND heirlooms. The fact that ripe produce is now marketed as green, organic, and heirloom (and therefore anti-corporate, etc etc etc) is the icing on the cake.

Penn &Teller's Bullsht had a very funny (if not very scientific) episode on organic farming--including a blind taste test at a farmer's market--that was quite amusing.

A big "IMHO" of course...
9.1.2009 4:15pm
John Burgess (mail) (www):
As I recall it, complaints about commodification and lessing of varietals were lodged at seed companies such as Burpee's, alleged to have been buying up older varieties of flowers and vegetables in order to promote the sale of varieties on which they held patents.

Even if true, the explosion of the heirloom niche seems to have stopped it. My grocery stores, parts of national (and international) chains certainly offer a half-dozen varieties of, say, tomatoes, including heirloom varieties. If I want more, I can go to the weekly farmers' markets in the area.
9.1.2009 4:19pm
Brian K (mail):
As far as I can tell most of the foodie snobs who are currently going nuts over heirloom tomatoes are the same people who never ever bought old hybrid tomatoes at roadside stands, and never went to farmers markets before they were hip, etc.

you must not know many foodie snobs.
9.1.2009 4:28pm
Arturito:
IANAB (I'm not a botanist) but I seems to me that seed catalogs are a very poor proxy for biodiversity, even if we are only talking about cultivar diversity. Does anybody seriously think that in 1903 farmers from India, China, Africa, South America and Southern Europe bought their seeds from catalogs to the same extent that they do today? An increase in the thickness of a seed catalog could hide a ten-fold loss in actual cultivar diversity.
9.1.2009 4:28pm
Splunge:
I'm underwhelmed. What matters here -- the only reason to cherish "crop diversity" -- is the number of varieties with significant differences in their genome, giving them potentially significantly different resistance to disease, tolerance of growing condition variations, et cetera.

To be crude, 22 varieties of a hybrid tomato that vary in one or two genes can't possible be compared to 22 different wild varieties of, say, rye. It's apples to oranges, so to speak.

To actually compare species diversity it would be necessary to compare DNA homology, but that of course would be very expensive indeed, even if it could be done for the 1900 varieties.

In the absence of this quality of evidence, the scientific way to proceed is to admit we haven't a clue. There is no reliable answer to the question of whether "crop diversity" has in general increased or decreased over the past century.
9.1.2009 4:39pm
John Burgess (mail) (www):
I should also have mentioned that over the course of the year, there are at least four varieties of banana available in my grocery, beside the ubiquitous Cavendish.

There are also six or seven different plantains available if I want to look around.
9.1.2009 4:49pm
Occasional Lurker:
This is an odd piece by Prof. Adler, because it feels as though the important issues -- decline in diversity (real? not real?), and what that loss of diversity (if real) might mean -- end up getting lost in refuting "conventional wisdom."

I admit I know relatively little about the subject but an NPR show the other day made this thread a bit more interesting to me. Marketplace reported: "Take apples. Back in the pioneer days the U.S. had more than 7,000 named varieties. Today that number has fallen to around 300."

Maybe that's bad science too, I don't know.

http://marketplace.publicradio.org/
display/web/2009/08/25/pm-seed-savers
9.1.2009 5:05pm
NCResident:
you must not know many foodie snobs.

If only. As with religion, converts frequently have the most zeal.
9.1.2009 5:51pm
einhverfr (mail) (www):
NCResident:

I live in Washington State. While stores that cater to foodie snobs (Whole Foods, Puget Consumers Coop, etc) tend to have heirloom tomatoes, more mainstream supermarkets (Safeway, Albertsons, Red Apple Markets) don't generally. Given that the latter outnumber the former by at least an order of magnitude that doesn't suggest to me that larger growers are in fact growing heirloom crops.

On the other hand, my first job was at a roadside stand. I would still note that most roadside stands have more variety than most supermarkets. Being where I was, I learned a lot about apple varieties (but we don't have any apples as good as the russet apples I remember as a kid).
9.1.2009 6:16pm
Brian K (mail):
If only. As with religion, converts frequently have the most zeal.

a simple yes would have sufficed.
9.1.2009 6:23pm
Richard Gould-Saltman (mail):
Comparing apples, oranges, and fancy tomatoes.

Seed catalogs have, going back more than a century, included a bunch of "sport", exotic" or "hobbyist" varieties defveloped by and for those folks who, when they weren't putting in, or harvesting, several hundred acres of corn, or soy, or silage crops (milo, etc.) were competing to produce, e.g., the "completely seed-free watermelon", purple [beans/peppers/carrots/tomatoes] "world's most productive tomato plant", "world's biggest pumpkin", and "the pepper which looks most like a penis" (not makin' that last one up, either, though they tended not to be shown at County Fairs).

I've always enjoyed seed catalogs. There's something so undeniably optimistic about copy which suggests that your world will be virtually transformed if you spend $1.50 for a packet of tomato seeds which will yield the biggest, sweetest, most nutritious, most wilt-and-fungus-free tomatoes you have ever known!

Recently, there's been an upsurge in the demand for such things, and for heirloom fruits and veges for city-folk, due to foodie-ism.

This frankly has very little impact on the percentage of all US tons of corn or wheat or soy which are all of one variety, (or of a very closely related set of patented hybrids), the number of acres of grafted (identical) navel and Valencia orange trees, the percentage of commercially farmed acres of bananas in South and Central America which are in Standard Cavendish, as opposed to anything else etc.
9.1.2009 7:16pm
MCM (mail):
Our study of 2004 commercial seed catalogs shows twice as many 1903 crop varieties surviving as previously reported in the iconic 1983 study on vegetable crop diversity. More important, we find that growers in 2004 had as many varieties to choose from (approximately 7100 varieties among 48 crops) as did their predecessors in 1903 (approximately 7262 varieties among the same 48 crops).


How does this tell you a damn thing about crop diversity? So some entrepreneurs came with thousands of new varieties of seeds. What does that tell you about what farmers are actually growing? What does that tell you about what people are buying and eating? Absolutely nothing. Even if there were a million more types of "tomatoes, peppers, lettuce, garden beans, squash, and garlic" seeds available, how many more of those will I actually see in my local supermarket?

This is an incredibly weak piece, Adler.
9.1.2009 7:48pm
Richard Gould-Saltman (mail):
BTW, I gotta ask, 'cause I don't know: back when I was an undergrad at Ohio State, I surely wouldn't have gone to anyone in the law school or the Anthro department for this data, or a meaningful analysis of it; I would have gone directly to the Botany Dept. and Ag School, without "passing Go or collecting $200". Does U Georgia NOT have an Ag School?
9.1.2009 8:41pm
NCResident:
Brian K: a simple yes would have sufficed.

Yes what? Sorry, don't get what you're trying to say.
9.1.2009 8:47pm
Steve2:
Richard Gould-Saltman, the University [sic] of Georgia does indeed have a College of Agriculture and Environmental Sciences. Among other things, they're a major source of applied sciences research in... grass. Specifically Bermuda Grass - they've developed a number of commercially important cultivars.
9.1.2009 10:19pm
Randy R. (mail):
" While there are pressures toward greater commodification and standardization of agricultural goods, there are also pressures to satisfy the demands of niche producers and consumers."

So, in other words, if it weren't for us liberal hippie types and the food snobs, you know, the ones who are a niche marker and make demands for something other than the Big Boy Tomato, there would be no diversity at all.

Score one for us!
9.2.2009 12:32am
DBennett (mail):
Curt is the only one who's nailed it: "all agriculture is local".

Let's use a real-world example. I'm writing from a farming community in Northern California. Across the street there are 6,000 acres of sunflowers. Nothing else. Just sunflowers. Now, driving by, you can tell that each 200-acre-or-so field has a different variety of sunflowers: some are tall, some short, etc. Does this mean that we have a diverse crop here?

I only have one way to describe this paper: Garbage In, Garbage Out.
9.2.2009 1:15am
padraic2112 (mail) (www):
I'm less than underwhelmed.

A working copy (unpublished and hence not peer reviewed) can always be a diamond in the rough, this doesn't look to be the case here.

As has been pointed out, seed catalogs are a bad proxy for biodiversity, for much the same reason an ammunition catalog would be a bad proxy to determine the diversity of the U.S. Army's supply of firearms.

The conclusion is certainly grossly unwarranted given both the question posited and the methodology used.
9.2.2009 1:46am
TokyoTom (mail):
Jon, doesn`t a seed catalog simply measure varieties of seeds available, not relative acreage planted?

Is`t it possible (even likely) that we are seeing both a trend toward reliance on monocultures of the highest-yielding / most easily marketed varieties, even as we see niche producers and consumers maintaining a demand for heirloom varieties?
9.2.2009 3:56am
Paul Heald (mail):
Thanks for the comments folks! Here are some thoughts in reply:

1. We do not purport to measure diversity in terms of acreage or shelf space in supermarkets. It is clear that monoculture predominates in both those markets. We wanted to start a debate on what counts as diversity, and I think we have succeeded. It is critical, however, to remember that the major goal of diversity is preserving genes that can be used to improve crops in the future and to deal with disasters caused by monocultures. One does not need massive plantings in terms of acreage to preserve diversity for its primary purpose of crop improvement. The "niche" markets criticized in the comments do that much at least.

2. Yes, varietal diversity is a proxy for genetic diversity, but it's a decent proxy and our study is far more accurate than the only prior one, the 1983 study that compared the 1903 catalog inventory to holdings in the National Seed Storage Lab.

3. Yes, UGA has an Ag School and a Botany Department, but neither ours, nor any other, has been willing to challenge the conventional wisdom so firmly established by the 1983 study. Susannah is an ethnobotanist by the way, whose primary work so far has been about apples. In any event, this study is not rocket science--it requires no special PhD level skills. I would trust almost anyone on this list serve to do what we did accurately.

4. There are no hybrids in our study.

5. Yes, "hippies" and "food snobs" play big role here, but not as big as immigrants from SE Asia and Central and South America who bring their varieties with them. Just because these folks are not firms, does not mean that they don't nuture a true market. Jonathan's best point was to describe this as a happy UofC econ story. There is nothing more disturbing than telling people with little faith in markets that they've created a nice efficient one with huge benefits!
9.2.2009 10:05am
Curt Fischer:
Paul Heald: We do not purport to measure diversity in terms of acreage or shelf space in supermarkets.

Why are the first sentences of your paper "According to the conventional wisdom, the twentieth century was a disaster of monumental proportions for vegetable crop diversity. The conventional wisdom is wrong."

Since acreage planted and shelf space in supermarkets are well-understood and important types of diversity, you should change the first sentences of your paper to better reflect the paper's content.


We wanted to start a debate on what counts as diversity, and I think we have succeeded.


Yes, you have succeeded - a debate has begun. Does this mean that you chose seed catalog listings as a metric of diversity soley to be provocative - to start the debate? If so, your contention that "the conventional wisdom is wrong" is not supported by anything in your paper.

If not - if you really think seed catalog listings are a useful and informative metric of diversity - one would think that your goal would be to end, rather than start, any debates.
9.2.2009 12:49pm
Soronel Haetir (mail):
Curt Fischer,

As far as I can tell seed catalog listings were chosen because that was the metric used by the prior study. If that prior study was incorrect about the availability of diversity then the entire conversation is far more open. When holding such debates it is often the case that you do not choose the ground the fight takes place on.
9.2.2009 9:59pm
Randy R. (mail):
Paul: "It is critical, however, to remember that the major goal of diversity is preserving genes that can be used to improve crops in the future and to deal with disasters caused by monocultures. One does not need massive plantings in terms of acreage to preserve diversity for its primary purpose of crop improvement."

thanks for the feedback. However, I notice a disconnect in your two sentences above. One very obvious and worrisome disaster caused by monoculture is having a vast amount of food supply destroyed by a bug, fungus, or something else that it is susceptible to. IF that were the case, a small sampling of diverse crops would not be able to replenish what was lost in a short time.

We would actually benefit from having massive planting of diverse crops now, before any disaster occurs, precisely so that we have enough of something to feed the population.
9.3.2009 12:17am
Sammy Finkelman (mail):
t would be interersting to compare 1983 seed catalogs to 1903 and 2004. Otherwise maybe the conclusion could be that there's less diversity (or was less diversity) in a seed bank than in a seed catalog.
9.6.2009 3:00pm

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