Organic Food and Farming
Action plan area
Annex 3: Organic farming and the environment
Introduction
1. This paper was prepared by a Subgroup of the Action Plan for Organic Farming. Its purpose is to summarise the Subgroup's views of the likely comparative effects of organic and conventional farming on the environment.
General considerations
Assessing existing differences versus predicting future change
3. There are a number of reasons why future effects may be different from existing differences. These include:
Environmental impacts
4. Biodiversity: Comparative reviews of the evidence base have been conducted for MAFF, English Nature, The European Commission and the Soil Association. The general conclusion is that on average there is a positive benefit to wildlife conservation on organic farms. In most studies organic agriculture provides a conservation benefit, whereas there are few studies where a disbenefit is shown.
- Some of the potential causes for the biodiversity benefits of organic farming include: Organic standards require the sympathetic management of wildlife rich infrastructure features, such as hedges, and ditches. These features also play a role for the organic farmer, providing reservoirs for the predators of crop pests as part of the integrated pest control strategies practiced on organic farms.
- A higher proportion of organic lowland farms are in mixed farming.
- Use of synthetic fertilisers, agrochemicals and veterinary medicines is prohibited or much restricted, which removes direct and indirect problems for wildlife.
- Greater variety of crop structure because of more spring cropping in more varied rotations.
- Organic farms often use undersowing, such as with stubble turnips with the land then used for autumn grazing. This can produce attractive over-winter habitat for seed eating birds and helps boost populations of some farmland invertebrates.
- Existing unimproved grassland is protected under organic standards (although legislation on Environmental Impact Assessment gives protection to uncultivated land generally).
- Stocking densities are limited by productive capacity underpinned by the Organic Standards and so tend to be lower in organic systems. The lower density can be an advantage when grazing sensitive habitats. Different species of livestock are more often maintained on organic farms. This helps to control parasite burdens and has advantages in maintaining structurally diverse swards.
While some of these practices are used on some conventional farms it is only generally on organic farms where most of the relevant management is routinely and systematically carried out. Although, the evidence from several studies shows that birds do better on organic farms overall, there are some detrimental actions in organic farming, such as mechanical weeding or mulching operations taking place between April and July. If these practices were to intensify in the future they could reduce the overall benefits for ground-nesting birds. Both organic and conventional farms will perform better when under agri-environmental schemes.
5. Nitrate loss: Many organic systems operate at a lower level of nitrogen intensity than conventional systems, with nitrogen inputs from fixation by legumes, or from importation of animal feed onto the farm. MAFF research compared the losses reported in a study of 3 organic farms over a 3 year period with a database of losses from conventional farms within Nitrate Sensitive Areas over the same period. The more extreme NSA treatments (the use of cover crops and the conversion of land use to extensive grassland) were excluded from the comparison. The results showed that overall losses of nitrate from the organic systems studied were smaller than from the conventional systems when comparing all sites. They were similar to the conventional systems if grass sites receiving more than 200 kg/ha fertiliser N were excluded. The range of losses from site to site was large, which meant that the comparison between different systems was relatively insensitive. The variability indicates that there is considerable scope for further reduction in losses with both systems. Within organic systems, the greatest benefit would come from controlling losses during the transition from clover-grass ley to arable.
6. Phosphorus loss: The main loss pathway for phosphorus is by movement of soil particles. Leaching is a smaller and more site-limited effect. There are some additional "incidental" losses following the application of fertilisers or manures. There is no direct evidence of differences in phosphorus losses between organic and conventional agriculture. (See also comments on Soil Protection, below)
7. Pesticide pollution to water and air: Pesticide use in organic farming is very restricted. A small number of pesticides are approved for organic use (principally copper, sulphur, natural pyrethroids, and derris), but they tend to be used as a last resort and the last two are either only permitted for use in protected cropping or for a restricted range of horticultural crops. With the exception of sulphur on certain top fruit crops and pyrethroid sheep dip (which is used in the same way on both organic and conventional farms), the use of the restricted range of pesticides is very limited by comparison with conventional agriculture. In particular, organic farmers do not use herbicides, some of which (such as isoproturon) have presented particular water pollution problems. Pesticide pollution from organic farming will be far less common than pesticide pollution from conventional agriculture. These differences are likely to hold whether assessed per area, or per unit of food produced.
8. Energy efficiency: MAFF funded a desk-study on energy costs in organic systems.Organic systems had a lower energy input largely because of an absence of indirect energy inputs in the form of nitrogen fertiliser. The greater energy requirement for conventional crops holds on an area and yield related basis except in the case of organic carrots. Organic lowland livestock systems tend to have lower energy use than conventional. For extensive upland livestock systems, the energy uses are more similar, although on average organic production uses somewhat less. Some of the differences in energy ratio were large Organic arable production used 35% and organic dairy 74% less energy than conventional per unit of product.
9. Soil protection: There is little UK evidence on the relative benefits of organic or conventional systems for soil protection. Such studies as have been done and those from other countries tend to show benefits for organic systems. Organic farmers pay particular attention to their soils, and it is a fundamental tenet of organic farming to operate a sound rotational system to "feed the soil" to maintain organic matter content and to keep it in good condition. However the return of organic matter may not be much different to a high yielding conventional system. The control of weeds by cultivation, which is more frequent in organic systems, may increase infiltration of rainwater which would reduce run-off and soil loss, or it may result in greater oxidation of soil organic matter and greater risk of soil loss by wind and water erosion. Studies into the microbial response of soils to organic management indicate there are benefits in many but not all situations and not always in all the attributes measured. The absence of soluble nutrients, most pesticides and reduced use of veterinary medicines such as antibiotics and ivermectins can be expected to benefit soil organisms.
10. Carbon dioxide: Net emissions of carbon dioxide from agriculture depend upon use of fossil fuel and the amount of carbon sequestration in soil organic matter. Emission from fossil fuel use will be lower on a per area and a per yield basis, reflecting the greater energy efficiency of organic agriculture noted above. There is insufficient evidence on whether there is a significant difference in the amounts of carbon sequestered in soils.
11. Ammonia: Ammonia is mainly lost from the surface of manures, either from animal buildings or hardstandings, which are soiled by manures, or during storage and handling. Manures produced in organic systems often have a lower concentration of nitrogen than do conventionally produced manures. Organic systems encourage the composting of manures, which leads to a relatively high loss of ammonia, although this will reduce the amount emitted when the compost is subsequently spread. Given the constraints on housing and stocking rate it is not possible to have intensive pig and poultry organic units, which are a major source of ammonia from conventional systems. Organic pigs and poultry will have similar losses to conventional outdoor units. It seems likely that on balance there is little difference between organic and conventional systems in the amount of ammonia which is lost from the system per unit of yield, but it is likely that emissions are lower per unit area. Given that nitrogen is more valuable to organic systems than it is to conventional systems (which can purchase nitrogen fertiliser at about 30p per kilogram), there should be a greater incentive for organic farmers to control ammonia losses in the future.
12. Nitrous Oxide: Nitrous oxide is emitted from manures and from soils. Emission tends to occur intermittently when there is a combination of the appropriate conditions. Within conventional agriculture, the main risks arise from manures and from the waterlogging of soils by heavy rainfall following fertiliser application. Within organic farming the risks are likely to come from manures and from waterlogging of soils where there is a legume crop. In the absence of direct measurement, it is not possible to assess whether there is any difference in risk from organic or conventional production.
13. Methane: About 75% of methane on farms is emitted directly from ruminant animals (chiefly cattle and sheep). There have been no direct comparisons of methane generation between organic and conventional production. Different types of fodder will generate different amounts of methane, with higher rates released from diets which are high in roughage relative to diets high in starch. This will tend to result in higher emissions from organic systems, as organic diets tend to be high in roughage and low in concentrates. Methane emission per unit of livestock product decreases as the intensity of animal production increases (two cows producing 5,000l of milk will generate more methane than one cow producing 10,000l of milk). On average, production intensity is lower in organic than conventional systems, so methane generation from organic farms is likely to be greater per unit of food produced. Because of the lower stocking densities, it maybe similar on an area basis.
14 Controlled Wastes: Waste is generally lower in organic farming since the system relies less on external inputs. Packaging materials for agrochemicals, veterinary medicine, animal feed, and fertilisers should all be lower on organic holdings. There is also little need for disposal of pesticide washings on organic systems.
15. Human Pathogens: Pathogenic organisms from livestock can contaminate surface waters used for drinking, bathing or irrigation. There is no reliable information on any differences in the incidence of zoonoses between organic and conventional farms although there is on-going research. Studies have shown that composting manures and treating slurries as encouraged under organic standards decrease the survival of any pathogenic organisms but stacking or long term storage can also be beneficial. The methods of handling manures between farming systems may not be sufficiently different to produce a consistent effect and therefore information on the incidence the organisms is needed before any conclusions can be drawn.
Conclusion
16. The analysis can be summarised as follows:
|
Biodiversity |
On average organic is better |
|
Nutrient pollution to water |
Available information is limited, but losses of nitrate from organic systems are similar on an area basis to losses from conventional systems subject to limits on quantity and timing of fertiliser and manures. |
|
Pesticide pollution |
Organic is better |
|
Energy efficiency |
Organic is usually better |
|
Soil protection |
On balance organic has benefits for soil organisms although little difference has been shown for physical effects |
|
Carbon dioxide |
Organic is better because of reduced energy use |
|
Ammonia |
Little difference per unit yield, but probably lower emissions from organic per unit area |
|
Nitrous oxide |
Insufficient information |
|
Methane |
Conventional is probably better per unit of output, but may be similar on an area basis |
|
Controlled Wastes |
Organic is better |
|
Pathogens |
No information - subject to ongoing research |
17. In all cases (apart perhaps from pesticide pollution), it is important to recognise that the differences relate to an average farm. Individual farm management and farmer motivation will have a significant effect on environmental impacts regardless of the farming system.
Organic Action Plan, Environment Subgroup
July 2002
Members of the Subgroup:
Peter Costigan (Chair) (Defra)
Ian Alexander (English Nature)
Gundula Meziani (Soil Association)
Bruce Pearce (Elm Farm Research
Centre)
Rob Robinson (Environment Agency)
Roger Unwin (Defra)
Richard Winspear & Hannah Bartram
(RSPB)
Page published: 26 November 2003