Comments on: Meta-analyzing diversity

By: Ecoagriculture reviewed, again

Ecoagriculture reviewed, again — Wed, 22 Jun 2011 08:59:40 +0000

[...] a recent meta-analysis that there are recognizable socioeconomic patterns to the distribution of infraspecific crop diversity on farm. A study has just been published which suggests that the number of species cultivated by a [...]

By: The debunking of the genetic erosion meta-narrative continues

The debunking of the genetic erosion meta-narrative continues — Mon, 10 Jan 2011 12:49:15 +0000

[...] supports the strategy used by a recent meta-analysis of on-farm data which used the named landrace as the unit of study. It looks like an effective monitoring system [...]

By: More on meta-analyzing diversity at Agricultural Biodiversity Weblog

More on meta-analyzing diversity at Agricultural Biodiversity Weblog — Wed, 16 Apr 2008 14:01:38 +0000

[...] may remember a post a few days ago summarizing something of a milestone paper by Bioversity scientists and partners which analyzed ten years’ worth of data on the diversity of 27 crops on farms in 8 countries [...]

By: Jacob

Jacob — Wed, 16 Apr 2008 05:47:43 +0000

I don’t understand this long-term insurance explanation of the difference between the evenness/richness relations of staples and non-staples.

I would expect that farmers grow varieties for the market or bulk consumption in large quantities while planting speciality varieties of these same crops in small quantities, just for direct needs or petty trade (like non-staples).

Wouldn’t that be a more obvious explanation for the observed pattern?

Speciality varieties of staple crops defy the distinction between staples and non-staples.

By: Jeremy

Jeremy — Mon, 14 Apr 2008 13:49:50 +0000

@Toby

I’m not sure how you intend to use evenness as a measure of diversity, when the paper suggests that there are at least two different kinds of relationship.

For staples, evenness is low for a given level of richness, suggesting that farmers are growing a little of the “extra” varieties as insurance for the future.

For non-staples, evenness is higher for a given level of richness, suggesting that farmers are growing all the varieties in the quantities they need for some immediate use or purpose.

So what is the nature of the “close relationship between … richness measures (varietal diversity) and eveness” that will be so illuminating across crops, countries and regions? Is it the same for each crop species?

By: Luigi

Luigi — Mon, 14 Apr 2008 13:20:06 +0000

Thanks, Toby. There's more on the richness-evenness relationship in the Bioversity press release on this important paper.

By: Toby Hodgkin

Toby Hodgkin — Mon, 14 Apr 2008 12:43:30 +0000

Thanks, Luigi, for your thoughtful comments. Perhaps another point that could be made is that the Jarvis et al. data on crop diversity from these 8 countries and 27 crops shows that there is a close relationship between their richness measures (varietal diversity) and eveness – particularly for farm level analyses. This may be worth following up as we look for indicators of diversity on farm that could be used nationally or globally – we may be able to explore how measures of eveness might be used to provide such indicators.

By: Luigi

Luigi — Fri, 11 Apr 2008 19:09:27 +0000

Yes, this paper did not look at intercropping, but I’m sure the project generated plenty of data on inter-specific diversity, and no doubt in time there will be a meta-analysis of that too. Regarding your request for input, if you’d like to write a paragraph or two of background, we could publish it as a regular post for more visibility.

By: Ford Denison

Ford Denison — Thu, 10 Apr 2008 23:57:39 +0000

Aside from an obscure reference to “crop complexes” in a table caption, I couldn’t find anything in the paper on intercropping. Also, they say that “community richness (omitting cassava) is 8-fold that of farm richness.” So there may be high diversity at the landscape scale, moderate diversity within farms, but not necessarily much diversity at the scale of meters. One question I will be exploring in Darwinian Agriculture, and which I would welcome input on, is how the benefits from a given level of diversity depend on the spatial and temporal patterns in which it is deployed.