Emma Marris and I shared the stage at a recent event at Washington State University, organized by Andy McGuire. Emma argued that "hands off wilderness" and "preserving natural ecosystems in their 'pristine' state are incompatible. If keeping species from going extinct is more important than keeping them where they were in 1491 (or earlier, presumably, outside the Americas), then we should bet-hedge with a variety of approaches to conservation. Watch for her upcoming op-ed.
Just Royal Society publications, unfortunately, but now's your chance to get three papers I published with Toby Kiers over the years:
...or some of those other Royal Society papers you've been craving.
In Darwinian Agriculture, I argued that accepting tradeoffs rejected by past natural selection is key to past and near-future crop improvement, whereas novel phenotypes never tested by natural selection may eventually make major contributions. In this post, I will briefly discuss two recent papers relevant to this hypothesis.
Lee DeHaan and David Van Tassel published "Useful insights from evolutionary biology for developing perennial grain crops", in American Journal of Botany, while Lin et al. published "A faster Rubisco with potential to increase photosynthesis in crops" in Nature.
Perennial plants often develop more extensive root systems than annuals, reducing the risk of erosion. Well-managed perennial forages (pastures and hay fields) are arguably our most-sustainable agricultural system, supplying milk, meat, wool, and leather, and often getting most of their nitrogen from symbiotic rhizobia bacteria (the main focus of my own research) rather than external inputs.
The Land Institute, where DeHaan and Van Tassel work, has been attempting to develop perennial grain crops. I have argued that greater investment of photosynthate or nitrogen in roots will usually leave less of these limiting resources for grain (seeds). All else being equal, DeHaan and Van Tassel apparently agree:
"where annual crops can use a similar amount of water, light, and nutrients as the perennials... annuals will indeed have greater yield potential"But they have argued (and I agree, on p. 97 of my book) that perennials may sometimes capture more of these resources than annuals can. The last chapter of my book, on diversity and bet hedging, therefore included perennial grains as an example of high-risk approaches deserving some funding.
The potential of perennials to photosynthesize more months per year than annuals also implies using water more months per year, but their superior root systems can sometimes help water soak into the soil rather than being lost to runoff.
Actual results so far are somewhat discouraging, however. DeHaan and Van Tassel cite a paper by Culman et al., which found greater above-ground biomass in a perennial grass, kernza, relative to wheat. So it might be a better forage than wheat, but its grain yield (with moderate fertilizer) was only 4% that of wheat in year 1 and 39% in year 2. So it would take about 5 acres of kernza to produce as much grain as 1 acre of wheat. Where are those extra 4 acres (and the water to irrigate them) going to come from? Or can we realistically expect significant yield increases without losing the benefits of perenniality?
I have argued that while some tradeoffs (e.g., root vs. grain) constrain crop improvement, other tradeoffs can represent opportunities. For example, the fastest versions of the key photosynthetic enzyme work best at CO2 concentrations greater than atmospheric. Lin et al. transferred genes for one of these enzymes from cyanobacteria into tobacco. The resulting plants grew more slowly than unmodified tobacco, even at 9000 ppm CO2 (atmospheric is now 400 ppm). So this looks like a step in the wrong direction, but it's only a first step. The cyanobacterial enzyme works well in cyanobacteria because they also have a CO2-concentrating mechanism. Some plants, including corn, have different CO2-concentrating mechanisms. See "The evolutionary ecology of C4 plants" for an interesting discussion of how these mechanisms evolved in plants. If someone could combine the faster cyanobacterial enzyme with a plant or cyanobacterial concentrating mechanism, they might achieve significantly greater photosynthesis.
That could take a decade or more, but it's worth noting that perennial grains have been a significant focus of the Land Institute for most of their 38-year history.
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.
Both talks are part of symposia with other interesting speakers.
August 18: Student Organic Seed Symposium, NY Finger Lakes Region
October 28: minisymposium (with Emma Marris, author of "Rambunctious Garden: Saving Nature in a Post-Wild World") on "Saving Nature and Improving Agriculture: Where does Nature's Wisdom Lie?" Washington State University, Pullman
I have two invited reviews due this summer, building on the theme from my book, that past natural selection improved trees (and the wild ancestors of our crops) much more than it has improved the overall organization of forests (and other natural ecosystems):
In Global Food Security, Andy McGuire and I will ask, "What can agriculture learn from nature?" If natural selection or some other process had consistently improved the overall organization of natural ecosystems, then agriculture might benefit from copying that organization. If every natural ecosystem had some process that adjusted the relative abundance of species to maximize ecosystem-level productivity and/or stability, then we could (for example) try to match the ratio of grasses and legumes in our pastures to those in nearby grazed meadows. I expect to argue, however, that nothing has consistently improved natural-ecosystem organization, so mindless mimicry of natural ecosystems is unlikely to improve agriculture. The wild ancestors of key crops grew naturally as monocultures, but that doesn't necessarily mean polyculture wouldn't be better. It's still worth studying how natural-ecosystem organization affects productivity and stability, and thinking about which features of natural ecosystems might be worth copying.
In "Evolutionary tradeoffs as crop-improvement opportunities", intended for Field Crops Research , I will argue that past natural selection has been improving individually-beneficial plant traits like drought tolerance for millions of years, leaving few simple, tradeoff-free options for further improvement. Accepting tradeoffs rejected by past natural selection has been key to past crop improvement and that is probably still true.
For a preview, see my discussions with farmer/blogger Chris Smaje and soybean-breeder Clem Weidenbenner in the comments for this post on Small Farm Future.
Chris argues that rotating annual crops with pasture is copying nature. I don't see any close analogs to such rotations in nature, so disagree. The pasture phase might benefit from copying some aspects of natural grazing systems, though.
Clem has various examples of plant breeding improving crops in ways that natural selection hasn't. I agree, but would any of those changes have improved individual-plant fitness in nature? If not, what are the prospects for improving traits like stress tolerance, which would (if tradeoff-free) have improved individual fitness?
Increasing or decreasing oil content beyond its natural range would presumably decrease fitness, even though it may be useful to us. Clem mentions range expansion of crops, which could show that humans can improve traits like cold tolerance in ways that past natural selection on the crop's wild ancestors didn't. I need to read more about this, but I find it interesting that high-altitude maize picked up cold-tolerance genes from teosinte, not the other way around.
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.
My paper titled Increasing cooperation among plants, symbionts, and farmers is key to past and future progress in agriculture is now available on-line at the Journal of Bioeconomics, if your library has the right kind of subscription. Otherwise, they want $40 to download the paper. It would be cheaper to buy a hardbound copy of my book. The paper has some new material that's not in the book, of course, but the book is still probably a better deal. Does anyone pay that much to download one paper?
I'm in Saskatoon to give a department seminar and speak at a student-organized symposium. I'll add a web link if I find one, but here's last year's, where Wes Jackson spoke. That could have been an interesting debate.