Pesticides & Fertilizers
Organic farming is thought to mean that no toxic chemicals are sprayed onto plants or injected into animals. However in reality what it means is that no synthetic chemicals are used prior-to, or during the growing of the produce. This is an important distinction because there are a wide range of toxic substances which can be derived from 'natural' sources which are used as pesticides in organic farming.
So the question becomes which is better - natural pesticides or synthetic pesticides? Natural pesticides are typically more water soluble meaning they wash
away more quickly requiring them to be sprayed more often than synthetic
pesticides, they are also often less potent meaning larger quantities
must be applied to get the same effect. So large-scale organic farming actually uses more pesticides than large-scale conventional farming.
But its not just the quantity of pesticide that is important it is also the health and environmental impacts of the pesticides. Studies have found that natural pesticides have just as many health-concerns as synthetics. Likewise organic pesticides also have off-target effect (kills organisms other than the intended target) but unlike synthetic pesticides they cannot be chemically modified to reduce these effects. Indeed some Canadian scientists found in a head-to-head comparison of
pesticides to control aphids that the organic pesticides were worse for
the environment than the synthetic one.
One of the most common natural pesticide is pyrethrin which is purified from chrysanthamums. It is primarily used as an insecticide against flying insects and sprayed onto fields by plane or helicopter. It is also highly toxic to fish when it runs off agricultural fields into streams and rivers. It only lasts a couple of days when exposed to direct sunlight but can last upto months in soil/river sediments. At high doses it is a neuro-toxin attacking nerves and the brain; it is also carcinogenic.
Another frequently used natural pesticide is rotenone, another insecticide which is so toxic to fish it is also used as a piscicide in fish management. It is also slighly toxic to birds, but has only acute irritant effects on mammals. Rotenone is obtained from the stems and seeds of several plant species and lasts about a week in the environment being quickly broken down by sunlight and heat. Also when used in combination with pyrethrin, rotenone is toxic to bees.
In addition to pesticides, a key ingredient in intensive agriculture is fertilizer. Again organic produce uses fertilizers just as much as conventional agriculture but uses manure instead of synthetic fertilizer. There are two differences of note between manure and synthetic fertilizer: synthetic fertilizer contains phosphorus obtained through strip-mining whereas manure contains much higher levels of bacteria and pathogens. Conventional agriculture can and does use manure as well (since it is cheaper than synthetics) but also use synthetic chemicals and/or radiation to sterilize it before application to the fields. Thus it is more important to remember to wash organic produce before eating it than conventionally growth produce. Similarly both organic and conventional farming contribute equally to eutrophication - the pollution of water systems by excess nutrients from fertilizer run-off and sewage - and the dead-zones of low oxygen which result.
Yields & Land-use
Most of the damage currently being done to the environment by agriculture is not through the use of pesticides & fertlizers, rather it is the destruction of natural habitats to convert them into agricultural fields. Deforestation, which is a major source of CO2 and a contributing factor to the majority of species facing extinction, is mainly caused by the expansion of agricultural lands.
To reduce the need to expand agricultural lands it is crucial to maximize the yield (food/area) of current croplands if we are going to feed the estimated 10 billion people who will be living on this planet by the end of the century. Organic farming simply does not produce as much food as conventional farming (no more than 80% of yields from conventional farming). A 20% increase in the area currently used for agriculture would simply be catastrophic for the planet (we already use 35% of the ice-free land surface for farming) - and for some crops impossible because already 90% of usable land is being used. Indeed, Australia is already farming in semi-arid lands previous considered unsuitable for agriculture.
Thus for that reason organic farming is considered worse for the environment than conventional farming and can only be considered sustainable if combined with near complete veganism to drastically reduce the demand for meat, dairy, and eggs.
Organic vs GMO
Finally, a notable restriction on organic farming is the complete exclusion of genetically modified organisms (GMO). This will further hamper attempts to increase yields by preventing the insertion of resistance genes against pest, and even genes improving resistance to droughts and floods which will become more common in the future due to climate change (a threat recently outlined in the IPCC report). Furthermore this restriction is completely irrational because many GMOs simply incorporate the ability to produce the same natural pesticides organic farmers are happy to spray onto their plant into the plant itself. Eg. Organic farming allows the spraying of Bt toxin onto corn but not the growing of Bt-corn (Bt is an insecticide produced by bacteria). GMOs which produce their own pesticides reduce the amount entering the wider environment because smaller quantities will be grown just in the leaves of the plant rather than spraying the entire countryside with it.
The best hope for the future is to combine crop-rotation and soil-promoting techniques from organic farming with genetic engineering and the most efficient/least harmful pesticides, so that we can continue to feed the growing population in a changing climate while minimizing deforestation and ecological side-effects.
