On the Ohio Investor Network, Paul Meagher has a good summary of my book's critique of biotechnology's exaggerated claims, from the perspective of a potential investor.
Recently in reviews Category
That's the title of a review article just published online by Science. Past and ongoing evolution have important implications for health, agriculture, and conservation of biodiversity, but communication among scientists applying evolutionary biology to different practical problems has been limited. That started to change in 2010, when a bunch of us (including most authors of today's paper) met on Heron Island, Australia, at the Applied Evolution Summit. Scott Carroll (UC Davis and Institute for Contemporary Evolution) had a lead role in both the meeting and the review article.
Evolutionary changes occur over generations, so crop pests and disease-causing pathogens with short generation times can evolve quickly, undermining our control measures. Species with longer generation times, including humans and some endangered species, evolve too slowly to keep pace with changes in their environments. For example, food preferences that evolved when meat and sugar were scarce may lead to unhealthy diet choices today.
Our paper discusses various ways to slow harmful evolution. Refuges not exposed to selection (e.g., by insecticides or fishing with nets) may slow evolution of insecticide-resistant pests or evolution of smaller fish. This approach partly depends on insect pests or fish from the refuges mating with individuals from outside. Refuges might be less effective for populations that reproduce asexually, such as bacteria or cancer cells.
To protect valued species that are evolving too slowly, we may be able to modify the environment to better match their inherited traits. Taxing unhealthy food might help, assuming we're sure which foods are unhealthy. For wild species, moving them to environments to which they're better adapted may work. Obsession with native species may blind us to the fact that their native range is now warmer than it was when they evolved. Unless we can reverse climate change, saving those species may require moving them (or allowing them to migrate) further from the equator or to a higher elevation.
Despite the authors' shared interests in evolution and in practical problems, applying insights from one field to another can be difficult. But I hope that this review will be helpful, both to practitioners and to students of evolution that have not yet narrowed their career options.
UPDATE: a Faculty of 1000 selection.
That's the title of a paper Toby Kiers and I just published in Philosophical Transactions of the Royal Society. We argue that:
"[despite] past selection for inclusive fitness (benefits to others, weighted by their relatedness)... [and despite some] evidence for kin recognition in plants and microbes... there is still ample opportunity for human-imposed selection to improve cooperation among crop plants and their symbionts"
Wednesday I'm off to the University of Illinois, where Michelle Wander and the Agroecology and Sustainable Agriculture program are using my book in a grad course on the Future of Agriculture.
Field Crops Research, a leading agricultural journal, has just published a review of Darwinian Agriculture by Jeffrey White. He suggests that there is "ample scope for debate and further research on speciﬁc propositions of Darwinian Agriculture." I agree and look forward to those debates. For example, I argued that perennial grain crops may never approach the yields of annual grains, because perenniality requires investing resources in over-wintering that could otherwise by used for grain. White agrees that this may be true in temperate climates, but maybe not in the tropics, if the "off-season" is short. He gives "perennially cropped sugarcane fields" as an example.
I agree that perennials can potentially capture a larger fraction of annual solar radiation, as I noted in the book. For example, a time-lapse movie of rice growth shows that this "annual crop" (which may be grown 2 or 3 times in a year) completely covers the ground only a small fraction of the time. Most of the time, sunlight is mainly hitting soil, evaporating water rather than powering photosynthesis. Perennials can use some of last-season's photosynthate to power rapid leaf growth, capturing a larger fraction of solar radiation sooner.
This isn't only true in the tropics. For example, the book cites a study showing that perennial Miscanthus can produce more biomass than corn. The photo below shows the Miscanthus plots Steve Hamilton showed me at Michigan State's Kellogg Biological Station, where I gave a talk earlier this month. But this Miscanthus doesn't produce any seed and I don't think sugarcane produces much.
What about perennial grasses that do produce significant amounts of grain? Sieglinde Snapp and colleagues at Kellogg Biological Station and The Land Institute have shown that perennial intermediate wheatgrass (kernza) can reduce nitrate concentrations in soil water much more than annual wheat, presumably reducing pollution of wells and rivers. But its first-year grain yield was only 112-157 kg/ha, versus 2807-3761 kg/ha for annual wheat. (Interestingly, the higher yields were with organic management.) Second year yields were 1390-1662 kg/ha for the perennial versus 4248-5017 for the annual. Unless the perennial really improves in subsequent years, the perennial would take more than three times as much land to produce the same amount of grain. I worry that the additional land will come from clearing forests or draining wetlands.
Janet Sprent, whose research I've admired for decades, reviewed my book in the Bulletin of the British Ecological Society. I couldn't find a web link to the review. She writes that "not all readers will agree with the arguments against these holy cows [perennial grain crops] but they deserve serious attention." Given our shared interest in nitrogen fixation, she was surprised by the lack of discussion of nitrogen-fixing cereals. But the book was already long enough to keep her "fully occupied on a 13 hour flight."
I probably could have lumped nitrogen-fixing cereals with C4 rice: both are big enough changes that we can't assume they have already been "tested and rejected by natural selection", but both may be "beyond anything humans today could design and implement from scratch." I may have to modify the latter statement for C4 rice after seeing what progress they've made at the International Rice Research Institute, next month, although copying other C4 plants isn't the same as designing a new photosynthetic system "from scratch." Making nitrogen-fixing cereals might be even more difficult, however, as I have discussed on my other blog.
Chris Smaje, a regular commenter here, reviewed my book for Permaculture Magazine (link to docx file here) and separately on this blog, Small Farm Future. Both reviews are examples of the kind of thoughtful discussion I hoped to generate with the book. He wrote:
"I suspect that it's ultimately impossible to create any kind of agriculture that can usefully be regarded as 'natural', but the further we depart from it the more we're flying blind..."Similarly, I wrote (p. 74):
"the more we depart from nature, the more we enter unexplored territory, with possible unknown risks."Still, the quantitative comparisons in Chapter 6 are consistent with my theoretical argument that it may be possible to improve on the overall organization of natural ecosystems. For example, crop rotation may be a good idea, even though natural ecosystems rarely have such dramatic changes in plant species from one year to the next. In contrast, Chapter 5 argues that making simple, tradeoff-free improvements in individual-plant traits like drought resistance will be much harder, even with biotechnology. This is because natural selection has tested individual traits competitively against alternatives, over millennia. Meanwhile, no natural process has consistently improved overall ecosystem organization on that time scale -- see previous post.
The first review is in Evolution, and written by Duur Aanen, from the University of Wageningen. He's best known for his research on "agriculture" by nonhuman species, particularly fungus-growing termites, including mechanisms that limit the evolutionary success of "cheater" strains of fungi. I also liked his recent commentary on weeding vs. intercropping in the algal gardens of damselfish.
Professor Aanen's review summarizes and apparently accepts the main arguments in my book, only faulting me for not citing recent work by Piter Bijma, relevant to my suggestion that improving the collective performance of fields and flocks will often require reversing the effects of past individual selection. Looks like his work might stretch my math ability and that of some of my readers.
The second review is by Peter Thrall, of CSIRO, and published in Evolutionary Applications. He has published extensively on coevolution of legumes and rhizobia and on the application of evolutionary principles to agriculture.
This review is more critical, though constructive. Thrall doesn't seem to disagree so much with my scientific hypotheses as with my characterizations of the views of others. Maybe he's right that "the world has moved on", both in rejecting natural ecosystems as a model for agriculture to copy, and in the tendency of biotechnologists to ignore tradeoffs. I hope I gave enough examples of promising work by agroecologists (such as Jacob Weiner) and biotechnologists to make it clear that the habits of mind I criticize are not universal. I agree that agronomists often think about tradeoffs and whole-crop performance and credited Colin Donald, an Australian agronomist, as a key source of my ideas.
Thrall is more optimistic about developing C4 rice than I was in the book, but maybe I'll change my views after visiting the International Rice Research Institute in March.
He writes that "there is a bibliography, but individual statements are not consistently referenced." That was my main objection to Diamond's otherwise excellent Collapse, so I tried to provide specific references for points that I thought might be controversial, except for those that were clearly matters of personal opinion. Apparently I missed some. In closing, he writes:
"I don't agree with everything in it, and there are many other topics that could have been included, but it has certainly got me thinking, and that is really all one can ask of a book such as this."
That was my intent. If disagreements with my book inspire more smart people to work at the interface of evolution and agriculture, it will have served its purpose.
Frankfurter Allgemeine Zeitung (19 December 2012) liked my book, as near as I can tell with my rusty German.
So did The Biologist.
I couldn't find web links for these.
Allison Snow, whose publications have included some of the best work on gene flow from transgenic crops to weeds, has reviewed Darwinian Agriculture in the journal, Science. My main goal in writing the book was to increase the sophistication of public discourse on agriculture, so I was pleased by her suggestion that "the book is perfect for discussion-based seminar courses." She also wrote that "Denison comes across as part genius and part dreamer." Maybe, but I'm not the only one.
See also the two-part review by Jeremy Cherfas on the always-interesting Agricultural Biodiversity Weblog. His review was also quite positive, but I need to consider and respond to his suggestion that I've underestimated the potential of varietal mixtures.
Similarly, Timothy Crews, of the Land Institute sent a couple of journal articles they've written about tradeoffs in perennial grain crops, which I should have cited and discussed. I plan to do that here, when I can find the time.
As of today, there are no customer reviews on Amazon in the US, but there's one on Amazon UK.
I'm still waiting for the first negative review. No hurry, I guess.