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'The Ugly Truth'

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Environmental impact of conventional and organic farming on the land used

Professor Jonathan Foley and Dr Hanna Tuomisto

On Thursday 18th October 2012 as part of Biology Week 2012 Professor Jonathan Foley and Dr Hanna Tuomisto answered your questions during a live online Q&A about the environmental impact of organic and conventional farming on the land used. Find out more about Hanna and Jon here. This discussion was also tweeted about under #landuse, view the storify here.

If you have a question on a plant science related issue then get in contact with our plant science panel via Twitter, @senseaboutsci using #plantsci, or email us at [email protected]. What topics are you interested in and what questions do you have?


1. "I know the yields are higher, but isn’t conventional farming reliant on agrochemicals and artificial inputs which negate soil fertility and pollute land, rivers and streams?"

JF: That's the general assumption. Organic systems typically use less chemicals and other inputs (but not always), which should be better for the environment overall, but often at the expense of lower yields (shown in a paper by Seufert et al. in Nature this year). In general, lower yields and lower environmental impacts characterize organic systems. And higher yields and higher environmental impacts for conventional. That's the supposed trade-off. But I am interested in blending the best of both worlds, and finding high yield / low impact agricultural solutions. I don't think that either organic or conventional are "better": they are different approaches to growing food, each with their pros and cons, and each representing a different trade-off. Why not take the best of both worlds?

HT: The optimal farming system would most likely be something between the current organic and conventional farming. Conventional farms can reduce the inputs by relying more on natural processes and using nutrient cycling and versatile crop rotations. A full ban of agrochemicals is not necessarily the optimal solution even in the terms of environmental impacts.

2. "If we want to increase yields doesn’t that mean we have to use a lot more pesticides?"

JF: Not necessarily. Pesticides are not always a key to increasing yields, especially if we manage pests with a more integrated approach, including organic and "integrated pest management" techniques. More diverse landscapes, and those with natural pest predators, can help control pests with much less insecticides. This can be done in any farming system - conventional or organic. I'm hopeful we can use these approaches on all farms, not just the organic ones."

HT: Not necessarily.Plant breeding may help to produce varieties that produce high yields without increasing the use of pesticides. Careful design of crop rotations can also prevent pest and weed problems.

Jonathon Harrington (email) 3. "Do pesticides used in organic farming have to go through the same rigorous testing procedures as those used on conventional systems?"

HT: All new pesticides have to go through the same testing procedures regardless of the farming system they are used in. Organic farming standards limit the use of pesticides, so most pesticides that are accepted in conventional farming are not accepted in organic farming.

@GIAradottir 4."What are the panelists views on land sharing vs land sparing. Which is preferable?" 

JF: Good question!  But I don't think it should be an either-or choice. Land sparing is probably the top priority overall, at the global scale, especially in critically endangered ecosystems like tropical rainforests. But I think land sharing should also be a priority for agricultural systems, where possible. And I don't believe it is a tradeoff, necessarily, if we can find highly productive agricultural systems that can do some degree of land sharing, while simultaneously sparing as much as possible for nature.

HT: The answer to this question depends on the aims. If the aim is to maximize the wildlife benefits, it depends on what type of wildlife/landscapes the society values. Land sparing may allow converting agricultural land to other uses such as forests, and therefore supports different species than land sharing would support.

@SLSingh 5. "Should we label organic food 'Warning, land-inefficient product, may cause damage to the environment'?" 

HT: Organic yields are generally lower than conventional yields. However, this is not always the case. In particular, legume crops have very similar yields in the two systems.

JF: A provocative question! The point here is that organic systems typically (shown in Seufert et al., Nature, 2012) have lower yields than conventional farms, and thereby need more land to produce the same food. However, this neglects the effects of the larger food system, for instance whether the crops are used for human consumption, animal feed, biofuels, etc, or how much of the food is wasted. Instead, I would like to see *all* food labelled with a measure of their *performance* - not whether the farm follows a particular ideological framework or not: How much land did it take to make these calories?  How much water?  How much carbon?  How many chemicals?  And then let people decide what's best.

6. "Please could you give your opinions on whether it is better to use less land to grow crops more intensively or more land less intensively?" 

JF: I think we need to do a mixture of both. For example, let's have some intensive (high yields/small area) production of core staple crops (e.g. rice, wheat, maize), and maybe some low intensity but wide spread pockets of high nutrient crops (e.g. fruits and vegetables). There are trade-offs to both approaches, so I think we need to take advantage of both and use each where they are best suited.

HT: I would say that sustainable intensification might be the way forward. This would mean using practices that produce high yields while minimising the negative environmental impacts. Incentives should also be created for leaving some land aside for wildlife conservation purposes and carbon mitigation.

7. "Would reducing meat consumption ease pressure on land use?"

HT: Yes. For example, the production of 1kg of beef protein requires about 16 times more land than the production of 1kg of soy protein. Poultry and pork requires less land than beef but almost 4 times more than soybeans.

JF: Yes, in general, eating less meat would significantly ease the pressure on land use - especially if the meat is being produced in a grain-fed system. The efficiency of converting grain into animal products is very low: ranging from 40% for dairy, to 10% for chicken and pork, to only 3% for corn-fed beef. In other words, it takes about 33 calories of corn for cattle to make a single calorie of beef; the other 32 calories are lost. Reducing the amount of grain-fed beef, for example, would be tremendously useful in reducing the pressure on land use, especially in the United States. But not all meat is so inefficient: Grass-fed meat can be an efficient way to use land to produce food, particularly in less suitable areas."

8. "Is yield the priority, or should we be looking at ways of valuing and quantifying the biodiversity differences inherent with conventional and organic farming?"

HT: "Yield levels are also important when biodiversity issues are concerned. Lower yields mean that more agricultural land is needed to produce the same quantity of product so areas with natural vegetation may be converted for agricultural land. We need to look at the whole picture, and find ways to produce food that are good for the wildlife and environment."

@JustSayIt_MD 9. "Would love to know the stats on how many people you can feed if you grow food for people instead of growing it for animals"

JF: About 60% of the world's crop production is fed directly to people; about 35% is used to feed animals; and about 5% is used for biofuels. This varies a great deal from country to country, of course. In Asia and Africa, most of the crops are fed to people. In North America and Europe, more crops are fed to animals and used for biofuels. The 35% used for animals is used quite inefficiently, especially when using grains to feed cattle for beef production. If we rethink our diets and biofuel strategies, we could add another ~40% to the world's food supply immediately without growing another kilogram of crops. Diets matter *a lot*. Side note: See Foley et al. (2011) in Nature, or my article in Scientific American last year, to see more about this.

HT: Currently about 70% of the world's agricultural land is grassland. None of that is suitable for producing food directly for human consumption. Almost 10% of agricultural land is arable land used for feed production. It would take less than half of this land to produce the same amount of plant protein than is currently produced as livestock protein.

 ‏@plantscience 10. "What about 'well used' organic pesticides such as copper sulphate how are these assessed?" 

HT: Copper sulphate has been tested in exactly the same way as all other pesticides, and it is on the list of the accepted pesticides.

11. "Is the supply of inputs required to achieve higher yields non-organically sustainable? Indefinitely?"

JF: Good question. In the very long term, they are not sustainable. The energy resources (fossil fuels) and mineral nutrients (mainly phosphate rock) we currently depend on in industrial agriculture are ultimately limited on the planet - peak oil, peak phosphorus, and so on. However, technological innovation has a way of finding new ways to do old things; and I'm certain the renewable energy and mineral recycling technologies will find their way into agriculture in the coming years and decades, as these primary resources get too expensive. Furthermore, we can dramatically (and immediately) improve the energy and chemical intensity of agriculture, borrowing tricks from organic, and stretch out these resources.

12. "Are indirect land footprint issues considered in land use studies? i.e. organic systems additional nitrogen must either be grown in situ with leguminous crops – thereby forgoing a fruit or cereals harvest on the land for part of the time in rotation – or imported from elsewhere via animal manures."

JF: Generally, no, the ""indirect"" effects of how we farm are not fully considered by most studies. But we need to do this. The amount of land needed to produce the inputs used in organic or conventional agriculture (for manure, fertilizers, chemicals, energy, and water) are sometimes quite large. Right now, it's hard to know whether organic systems use more land than conventional when taking these issues into account. I suspect, however, that organic might use more land overall, but in a *far* less destructive way. (Hard to compare manure from pasture to phosphate mine!)  Apple and orange comparisons.

@Gramlin 13. "Should we be recycling human dung into our food chain?"

JF: Hmm. There would be some pluses and minuses to this strategy. On one hand, recycling nutrients from human waste would be a great way to close part of the nitrogen and phosphorus cycles of agriculture and the food system. In fact, this is what a lot of countries do, using "night soil". Parts of China have been doing this for thousands of years. However, there are some obvious downsides to this strategy in terms of sanitation and human health. Overall, I think it should be done, but only if we can do it safely.

HF: In terms of improving the efficiency of nutrient use, it would be beneficial to return the nutrients from human communities back to the fields as fertilizer. However, various contaminants in sewage sludge currently restrict this possibility in many areas.

14. "Conventional farming requires artificial nitrogen production, and this process has a substantial impact on greenhouse gas emissions. Is it possible to quantify this as an impact of conventional farming practises compared with organic farms, which presumably have to transport in nitrogen (in the form of manure), potentially over large distances?"

HT: The studies show that greenhouse gas emissions of organic and conventional farming are quite similar when compared per unit of product. The emissions related to production of agricultural inputs, such as fertilisers and pesticides, are higher in conventional farming, but organic farming has higher fuel use at the farm.

@BruceWoodacre 15. What "environment" would the UK have without farming? (serious Q - no "natural" environment in the UK, all created by agriculture)

HT: If land in the UK was left unmanaged for a long period of time, the natural vegetation in most parts would probably be forest.         

@RebeccaNesbit 16. "Could you explain exactly what land sharing is and what the benefits are?" 

JF: Land sharing"" and "Land sparing" are used to describe how we might farm to best benefit the environment (especially in terms of biodiversity and wildlife). "Land sharing" usually means farming in a low-intensity, environmentally "friendly" way to allow more wildlife and biodiversity on the farm itself.  Such farms might have lower yields, take up more land, but they "share" land with nature. On the other hand, "land sparing" strategies rely on high intensity, high yield agriculture in small, focused areas to produce food (even without being wildlife friendly) on smaller areas, "sparing" land elsewhere for nature.

Mimi Tanimoto 17. (email) "What are the relative pros and cons of monoculture vs polyculture?"

JF: Monocultures are easier to farm with big machines, which saves on labor costs and infrastructure. In other words, it's cheaper to farm with industrialized methods. However, polycultures are far, far better for the environment overall; and polycultures are also more resilient to climatic disturbances, pests, diseases and so on.  So overall, I think polycultures are significantly better for improving the sustainability of agriculture - and monocultures are a "house of cards": all monocultures fail, given enough time.

18. "Is organic farming better for local wildlife?"

JF: Almost certainly. One of the best things about organic farms is that they use far less chemical inputs - especially different biocides to control pests and disease - that can inadvertently harm wildlife. Furthermore, organic farms are typically much more diverse than conventional farms (especially big monocultures of corn and soybeans), which provides more suitable habitat and better conditions for local wildlife.A farm doesn't have to be organic, however, to get many of these benefits.  Many conventional farms can do this too, by cutting back on pesticides and having more diverse landscape mixes. I would like to see more hybrid organic-conventional approaches used, instead of a fierce battle between the two. Why not blend the best of both approaches?

HT: Most studies have found higher abundance and richness of wild animal and plant species on organic than conventional farms. The benefits of organic farming are larger in intensively managed landscapes than in diverse landscapes with many landscape features. It is still unclear whether conventional farming with specific practices for biodiversity conservation can provide higher benefits than organic farming.

@CarbonTiptoes 19. "How can farmers help bees?" 

JF: Use less pesticide. Grow more diverse crops. Leave some land for flowers and other forms of natural vegetation.  

HT: Farmers can help bees by reducing the use of insecticides and herbicides, and by leaving non-cropped areas for natural vegetation where bees can nest.

@Drystonesonnet 20. "Every year RSPB complains that bird numbers on UK farms are still dropping. Most farmers in England & Wales signed up to ag/env schemes. Is this a failure of policy?" 

HT: Agriculture is not the only reason for bird losses. Climate change and expansion of urban areas and transportation infrastructure have an impact on birds too. RSPB tests the impacts of different agri-environmental scheme practices on birds, and advises farmers to choose the most cost-efficient options for conserving birds. 

Darby Springs Farm (email) 21. "How do we optimize farming systems that provide ecosystem services as well as food yield?"

JF: I wish I knew the answer to this one!  Sadly, the problem is one of today's economic frameworks: people only get paid for commodities,not for ecosystem services farms may provide such as maintaining clean water, stable soils, healthy wildlife, and productive pollinating insects. But if we can find ways to pay farmers to produce food *and* ecosystem services, which we all benefit from, then we can see tremendous opportunities for agriculture to work more closely with the environment.  This is beginning to happen with ""water funds"" in Latin America, and carbon markets elsewhere, but this needs to be dramatically increased worldwide.

HT: The best approach might be to utilise both natural processes and modern technologies. The farming systems would be something between current organic and conventional farming. The practices could include the use of versatile crop rotations, recycling of nutrients and preventative pest and weed control. Conventional pesticides and fertilizer could be used if necessary.

22. "Has there been a carbon footprint comparison between conventional and organic farming techniques for different crop types?"

JF: Probably, but to be honest, I'm not sure I'd believe them as they depend on a lot of assumptions. But in terms of greenhouse gas emissions, the BIG issues aren't whether things are farmed organically or conventionally, or whether they're local or not. The BIG emissions from agriculture stem from three things: deforestation (mainly for soy and beef in the Amazon, or oil palm and timber in Indonesia), methane (from rice fields and cattle), and nitrous oxide (from overfertilized fields, whether conventional or organic). These three things are more than 90% of global agricultural emissions. The differences between organic and conventional, or local and distant, don't really make a big difference globally. Small potatoes (no pun intended) by comparison.If you want to lower greenhouse gas emissions from agriculture focus on deforestation, reducing methane (from cattle, then rice) and the over use of fertilizers and manure; eat less meat and avoid things linked to deforestation.

23. "Regardless of the debate on how food is grown, isn’t the real issue about reducing food waste? If less food was grown there would be less waste."

JF: Very good point!  When we waste 30-40% of the world's food (in poor countries and rich countries alike), we can certainly improve the availability of food in the world by reducing waste. Compare this to the 20% improvement in global crop yields we've seen in the last 20 years, from billions of dollars invested in plant breeding, GMOs, technology, etc. I think reducing food waste, and rethinking some aspects of our diets and biofuel policies, is the best possible way to improve food supplies around the world.  And yet it's the solution that gets the least attention (and funding). We need to address this.

HT: Reducing food waste would help to reduce the environmental impacts of food production too. In the developed world households waste about 25% of the food they buy. Increasing the public awareness of the negative impacts of food wasting might help to alleviate the problem.

@plantscience 24. "How can we best promote the uptake of mixed and integrated farming systems?" 

JF: First of all, we need to realize that polarized "us versus them" debates in agriculture are harmful, and distract us from solving bigger food and environment problems. The debates about organic and GM crops are something of a sideshow anyway, since only 1% of the world's food is certified organic, and only 10% is GM. So 90% of the world's food is *neither* organic nor GM. Let's focus on solving the bigger problems, like how we can get more healthy food with less environmental and social harm across *all* of our agricultural systems.  And let's shift our approach of labelling with arbitrary names (e.g. "organic" or "local") to labels that indicate performance (e.g. what nutrition is being delivered, and how many resources/what environmental impact it took to produce it?)

@TheVeganSociety 25. "Of all greenhouse gas emissions globally caused by the UK, what's the likely range for the fraction due to farming?‏"

HT: Agriculture accounts for 8.5% of the UK greenhouse gas emissions. The whole UK food system has been estimated to account for about 20% ofthe UK emissions, and when the emissions related to changing the use of land are included the contribution would be about 30%.



Our Q&As answer the questions people put, which may mean that some parts of a subject are covered well and others not. If there is an issue that you think is not tackled, you are welcome to send a follow up question to our plant science panel