In my recent post Don’t mimic nature on the farm, improve it, I argued that we should cast aside the ideas of “balance of nature” and “nature knows best” in designing farming systems. There is no reason to “follow nature’s lead” if nature has not been optimized by any process that we know of, and therefore consists of mostly random mixes of species dictated primarily by natural disturbances. But if we don’t, what are we left with?
We are left with an agriculture based on human ingenuity, consisting of:
- Crop rotations; or better yet, dynamic crop sequences.
- Residue management and no-till planting to keep the soil covered and control erosion;
- Careful use of synthetic fertilizers in conjunction with organic fertilizers;
- Cover crop cocktails (This is where we can study unused and underused species to take advantage of “nature’s wisdom”. Precision crop planting in sequence with cover crops could potentially improve cover cropping benefits by allowing crop roots to advantageously colonize the root channels of the dead cover crops, i.e., sequential root channel colonization.);
- Genetically modified crops, including cover crops someday;
- Integrated pest management, including the use of improved pesticides.
All of these practices could be more widely used and more effectively applied.
What about those practices that are promoted because they mimic nature? Denison, in Darwinian Agriculture1, evaluates four of these nature-based practices: perennial grain crops, reliance on only local sources of nutrients, intercropping, and reliance on diversity to control pests. He then goes on to survey the evidence for each and gives his assessment. I’ve summarized Denison’s assessment here:
- Perennial grain crops – Perennials have their place, especially in feeding livestock, but due to low yields, “given the tradeoff between perenniality and seed production, emphasis on grain production may be misplaced.”
- Reliance on only local sources of nutrients – With regard to following nature, “local sourcing of nutrients in natural ecosystems is a constraint imposed by lack of external inputs, not an example of ‘nature’s wisdom’.” In other words, although it may be advised to use local sources of nutrients as much as possible, it should not be a constraint to us, just because it is a constraint of natural lands.
- Intercropping – There are errors commonly found in intercropping experiments, chiefly the failure to find or use the optimum density for the monocropped plots, an error which favors the intercropped plots. The design of these types of experiments is complex, but even in those carefully designed, “most intercrops yield more than the average of the two [or more] crops, but less than the best crop alone.” In this case, farmers will tend to grow the best crop. “Diversity may be there for a reason… but that does not mean that diversity is there for a purpose.”
- Reliance on diversity to control pests – We can compare diversity in space (the “balance of nature” that inspired intercropping) with diversity in time, or crop rotation (which has a long history of success and is not commonly found in nature). With intercropping, you expend the advantages of diversity (here, for pest control) the first year the intercrop is planted. What do you do for diversity the second year? On the other hand, with crop rotation, the whole system changes each year. The latter may work better than the former in the long run, but no research that has addressed this question. Nevertheless, there is no lasting solution to pests; “ongoing evolution [of pests] will tend to undermine all of our pest control measures, not just those based on toxic chemicals.” We cannot get off the pest control treadmill.
Although I think we would be better off without the “mimic nature” baggage, I am not saying that biodiversity is not important. We should incorporate more diversity in our cropping systems, not because nature is diverse, but so we can better use the properties and processes in individual plants. If it exists anywhere, the “genius” of nature is in individual species and not in the ecosystems. Right now, other than corn, soybeans, rice and wheat, we have not thoroughly explored the capabilities of many plants, domesticated or not.
Neither am I saying that interactions between species are not important. We should study intentional combinations of species, mixtures not found in nature, searching for simple, direct interactions between species that will give us our desired results. As Denison points out, we may gain more knowledge of individual species when they are studied in communities with other species – a job for agroecologists! However, if the idea that the sustainability of natural ecosystems depends on complexity is an illusion, agricultural systems should only be as complex as needed for our purposes, not more so.
Another benefit gained by casting aside “the romantic notions of a stable Eden”2 is that it should make us less susceptible to “silver bullet” solutions, wishful thinking and other such nonsense. In my experience, this is most needed in soil and pest management. There are no quick, easy, and cheap methods to improve soils. It takes bulk organic materials, either grown on-site (less expensive) or imported (more expensive). In the long-term, the nutrients that are harvested in the crop must be replaced; they cannot be produced by “better biology.” For insects, weeds, and disease, no amount of tweaking the system will make them go away.
There are those who will find this whole notion yet another example of arrogant man trying to control nature, and there are plenty of examples of where we have done a poor job at managing the Earth. However, we must realize that farming is controlling nature for our own purposes. We still need nature, and “wild” places, but unless critics can point to a mechanism by which natural ecosystems were consistently improved, we should not use them as blueprints for agriculture, nor should we assume that we cannot improve on them. There is no utopian state of nature, so we can stop trying to restore, recover, or regain any such state in agriculture. There is no way back, but there is a way forward.
1 Denison, R. F. (2012). Darwinian Agriculture: How Understanding Evolution Can Improve Agriculture. Princeton University Press. (Denison’s other main thesis in this book is that natural selection has left us few tradeoff-free opportunities for genetic improvement through genetic engineering. Full Disclosure – Denison served as my major professor in graduate school at UC-Davis. For more from Denison, view his Darwinian Agriculture blog.)
2 Marris, E. (2013). Rambunctious Garden: Saving Nature in a Post-Wild World. Bloomsbury Publishing USA.
Andrew, Please consider posting this on the linked in sustainable ag group. Then don ear protection and adjust your spam filters. Logic such as yours is not apprecited by many of the posters there. Enjoyed reading this.
You wanted proof of ecosystems being continuously improved? That’s impossible on a finite planet with finite resources. But nature did do a better job than humans could ever hope to. Nature turned this ball of dust into a variety of ecosystems until they reached near 100% solar energy efficiency. Humans, on the other hand, are turning this amazing creation of nature back into a ball of dust.
near 100% solar energy efficiency? That cannot be true. The first step in capturing solar energy is photosynthesis, which hovers around 3-6% efficiency. It’s funny that you mention this because I was just talking to a wheat scientist last week who is heading up a huge international project to improve the photosynthetic efficiency of wheat, which is sadly very low. Humans are going to improve upon nature to make plants more efficient than nature was able to do in 4.6 billion years. Of course, we’ve got a lot to learn, but don’t count us out!
Conveniently ignores the fact the humans are part of Nature (TM). Naturalistic Fallacy Fail.
Karl, you are right; “Actual solar energy conversion by photosynthesis and subsequent plant growth (biomass production) is much lower at around 2 – 4% for productive plant communities” (X-G Zhu et al., 2008).
On your other point of being able to improve photosynthesis in plants, Denison, in his book, has a lot to say on this which I did not cover in my posts. His argument here is that natural selection has already “tested” more options, for example with photosynthesis, than humans ever will, and that it is very unlikely that nature has missed simple, tradeoff-free improvements. In his chapter on this topic, he explains that there is an evolutionary explanation for the inefficiency of photosynthesis, one which he doubts we will overcome, at least without significant tradeoffs such as increased water use, and others. He then critiques recent claims that photosynthesis has been or will be improved through biotechnology.
I’ve often wondered why we draw the line at humans when we consider “nature”. Whether it is from an science based perspective or a religious perspective, counting humans out of nature is silly, in my opinion. From the science perspective, we evolved from nature. We may do some strange things but other animals do just as strange things although on a smaller scale (think termite towers). From a religious perspective, we were put her by god just as much as any other part of nature. So why do humans get cut out?
Ecosystems tend to have some key functional attributes that we’d be smart to mimic in agriculture. The three I tend to think of are:
1. Nutrient retention
3. High (net) productivity
From research on Biodiversity and Ecosystem Function it is clear that diversity plays a big role in creating these desired functions. Your piece is funny because it is framed as if you are dismissive of learning from ecosystem structure and then you come around to saying we need to use diversity on farms!
Jason, I agree that we should strive to improve some functions of agriculture, but not only because ecosystems have these functions, but because they serve our purposes. Ecosystems have good nutrient retention because they generally have low nutrient levels, and do not have a major part of their productivity being harvested and transported away every year. We could have an agriculture which mimicked this; stop adding nutrients, reduce our harvest, and yes we would improve nutrient retention, but we would also produce less food.
Also, the ecosystem structure which you equate with diversity is not the diversity that I am in favor of increasing. The “ecosystem structure” would have us planting many crops together. I am in favor of broadening the diversity of crops we do use, but one at a time in diverse rotations – not something you see in nature very often.
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