There’s a new book coming out soon that should be of
interest to many readers of this blog. It’s written by Tony Fischer, Derek
Byerlee, and Greg Edmeades, and called “Crop yields and global food security: will
yield increases continue to feed the world?” At 550 pages, it’s not a quick
read, but I found it incredibly well done and worthwhile. I’m not sure yet when
the public release will be, but I’m told it will be a free download in early
2014 at the Australian Centre for International Agricultural Research website.
The book starts by
laying out the premise that, in order to achieve improvements in global food
security without massive land use change, yields of major crops need to
increase about 1.3% of current levels per year for the next 20 years. They
explain very clearly how they arrive at this number given trends in demand, with
a nice comparison with other estimates. The rest of the book is then roughly in
two parts. First is a detailed tour of the worlds cropping system to assess the
progress over the last 20 years, and second is a discussion of the prospects for
and changes needed to achieve the target yield gains.
For some, the scope
of the book may be too narrow, and the authors fully recognize that yield
progress is not alone enough to achieve food security. But for me, the depth is
a welcome change from a lot of more superficial studies of yield changes around
the world. These are three men who understand the different aspects of agriculture
better than just about anyone.
The book is not just
a review of available information; the first part presents a lot of new
analysis as well. Tony Fischer has dug into the available data on farm and
experimental plot yields in each region, with his keen eye for what constitutes
a credible study or yield potential estimate (think Warren Buffet reading a financial
prospectus). This effort results in an estimate of yield potential and yield
gap (the difference between potential and farm yields) by mega-environment and
their linear rate of change for the past 20 years. The authors then express all
trends as a percentage of trend yield in 2010, which makes it much easier to
compare estimates from various studies that often report in kg/ha or
bushels/acre or some other unit.
There are lots of
insights in the book, but here is a sample of three that seemed noteworthy:
- Yield potential continues to exhibit significant progress for all major crops in nearly all of their mega-environments. This is counter to many claims of stagnating progress in yield potential.
- Yield gaps for all major crops are declining at the global scale, and these trends can account for roughly half of farm yield increases globally since 1990. But there’s a lot of variation. I thought it interesting, for example, that maize gaps are declining much faster in regions that have adopted GM varieties (US, Brazil, Argentina) than regions that haven’t (Europe, China). Of course, this is just a simple correlation, and the authors don’t attempt to explain any differences in yield gap trends.
- Yield gaps for soy and wheat are both quite small at the global level. Soy in particular has narrowed yield gaps very quickly, and in all major producers it is now at ~30%, which is the lower limit of what is deemed economically feasible with today’s technology. One implication of this is that yield potential increases in soy are especially important. Another is that yield growth in soy could be set to slow, even as demand continues to rise the most of any major crop, setting up a scenario for even more rapid soy area expansion.
Any of these three points
could have made for an important paper on their own, and there are others in
the book as well. But to keep this post at least slightly shorter than the
actual book, I won’t go on about the details. One more general point, though. The last few years of high food prices
has brought a flurry of interest to the type of material covered in this book.
For those of us who think issues of food production are important in the
long-term, this is generally a welcome change. But one downside is that the
attention attracts all sorts of characters who like to write and say things to
get attention, but don’t really know much about agriculture or food security.
Sometimes they oversimplify or exaggerate. Sometimes they claim as new
something that was known long ago. This book is a good example of the complete opposite of that –
three very knowledgeable and insightful people homing in on the critical
questions and taking an unbiased look at the evidence.
(The downside is that it is definitely not a light and
breezy read. I assigned parts of it to my undergrad class, and they commented
on how technical and ”dense” it was. For those looking for a lighter read, I am
nearly done with Howard Buffet’s “40 Chances”. I was really impressed with that
one as well – lots of interesting anecdotes and lessons from his journeys
around the world to understand food security. It’s encouraging that a major
philanthropist has such a good grasp of the issues and possible solutions.)
Gene modification seems to play important roles in both increasing yield potential and decreasing yield gap. If soybeans yield potential is boosted mainly by gene modification, then there will be yield gap in soybeans just as the yield gap in maize, because regions such as Europe and China are reluctant to adopt GM varieties. Will these regions be forced to adopt GM varieties in the end? My second question is: To what percentages of the yield growth (1.3% per year) can be contributed by increase in yield potential and decrease in yield gap respectively?
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