Author: Luigi Guarino

Posted on

More messing about with Droppr

I continued my exploration of IFPRI’s wonderful Droppr software by looking at its future climate tool. You click on a spot on the Earth and it tells you how total precipitation and average temperature will change, for each month of the year. Again, I did it for the mother-in-law’s farm, and this is the result:

Looks pretty bad, at least for temperature. Although of course, for maize at least, which is the main food crop in that area, what you really want to know is peak, rather than average, temperatures. That’s according to a study by David Lobell and Marianne Bänziger we nibbled a few days back, and which recently got a big write up in The Economist:

Days above 30°C are particularly damaging. In otherwise normal conditions, every day the temperature is over this threshold diminishes yields by at least 1%. Moreover, days where the temperature exceeds 32°C do twice the harm of those at 31°C. And during a drought, things are worse still. Then, yields take a hit of 1.7% per day over 30°C.

Posted on

Featured: SPAM

Glenn enlists Churchill in rebuking Luigi for being too hard on his IFPRI friends about SPAM:

SPAM is for broad scale analysis. It is like what Churchill said about democracy, god-awful, but much better than anything else.

What do you think? Does he protest too much?

Posted on

Ground-truthing SPAM

Jeff Horwich has an interesting post over at HarvestChoice Labs looking at the effect of the tsunami on agriculture in northern Japan. He used the Droppr tool, which combines Google Maps with lots of other data, in this particular case the world-wide crop distribution data from the Spatial Production Allocation Model (SPAM). In SPAM

…tabular crop production statistics are blended judiciously with an array of other secondary data to assess the production of specific crops within individual ‘pixels’ – typically 25–100 square kilometers in size. The information utilized includes crop production statistics, farming system characteristics, satellite-derived land cover data, biophysical crop suitability assessments, and population density.

Intrigued, I decided to do a little lighthearted ground-truthing of the SPAM data. I only looked at one location, I admit, but what I found was a bit disappointing. I zoomed in on the location of the mother-in-law’s farm in the Limuru highlands (-1° 4′ 39.60″, +36° 40′ 44.80″). Here’s what the place looks like.

This is the view from space, courtesy of Google Earth. 1

Now, according to the SPAM methodology that’s a cropping intensity of 0.59%, with the main crops being sorghum, sweet potato/yam, groundnut, banana/plantain, potato, coffee and sugarcane.

Jeff very niftily embedded both a map and a spreadsheet of the production data for the main crops in his post, but I wasn’t able to work out how to do that. So you’ll have to make do with this wholly inadequate screengrab, I’m afraid.

What my mother-in-law and her neighbours actually grow is maize, beans, potato and tea, tea and tea. A pretty different set of agrobiodiversity to what SPAM thinks. And I think she would be surprised at the low value of cropping intensity. This is a very high-potential area.

Anyway, that’s only one data point. It would be interesting to know from the SPAM guys if there’s a more systematic attempt going on to check on, and refine, the results of the model.

Posted on

Dams, lying links, and databases

A post on e-agriculture about information resources related to water in agriculture allows me to update, on the occasion of World Water Day, a piece we had here some years back. The links in that old post of ours no longer point to the things they used to, but if readers are still interested in that African dams database they can now find it elsewhere. Alas, I couldn’t get the Google Earth file to work, but if you do the work-around from the Excel file you get the map below. I’ll reiterate my original questions, to which I have no better answer now than four years ago, alas:

I would guess that the effect of dams and new irrigation schemes on local wild biodiversity is usually negative, but is that necessarily always the case also for agro-biodiversity? I suspect so, but is there a possibility that at least sometimes existing crop genetic diversity is simply displaced a bit geographically or ecologically within the same general area and augmented by new crop genetic diversity adapted to the new conditions?