|MadSci Network: Agricultural Sciences|
All I can give you to answer this question is personal experience. I know of no scientific studies. First and foremost, big farming is big time destructive. On big farms large tractors and huge plows and combines cause 'collateral' damage. From here on out, I will no longer refer to this death as collateral - it is military speak for people killed when bombs and bullets go astray and I do not like it (Okay, no more politics). I think it might be best to compare implements rather than farming systems (conventional versus organic). Almost all farmers use plows. These plows come in a variety of shapes and sizes and can go down to a wide range of depths. Things that live in the ground do not fare well when the plow comes through; mice voles, moles, earthworms, etc. all will suffer immediately, but that is only the beginning of the story. Plowing speeds up the breakdown of organic matter that many insects, bacteria, etc live off of. Repeated plowing will reduce levels of organic matter to levels were very little animal life is supported. A comparison of a field that has seen frequent plowing with one that is farmed without tilling will give you an indication of the amount of life that is affected by plowing. In the Palouse region of the Pacific Northwest one of the major problems faced by no-till farmers was the huge increase in the rodent populations, which had a fair impact on the grain being grown. Hawk, owl, coyote, and snake populations will increase to match the rodent populations, but it takes time for these carnivores to catch up. And of course if a disease should run through the rodent population, many of these predators will starve. We always had trouble with hungry coyotes and pet cats and dogs. I guess this is the part where we all sing "The Circle of Life." Planting equipment is usually pulled by tractors and comes in all kinds of sizes. However, I would guess that most things can go deep enough, fly high enough, or are small enough to not be killed. As far as those bugs that get under the tires, well, tractors are very heavy as a rule. Harvest equipment is fairly large when one thinks of combines for corn, wheat and soybeans. Most big animals get away and do, but every once and a while you hear of an animal that got caught. Over a 12-year period in eastern WA, I once heard about a young deer and a combine. As big as these machines are, they do not deal well with large things going through them and the deer stopped work for hours. As a secondary teacher in ID very many years ago, I drove grain truck to supplement my income (and it was great pay compared to my school salary I might add). I hauled wheat, grass seed and lentils. I was always amazed at the number of insects that would come out of the combine and into the truck. I was also amazed at how many survived their trip through the heart of the machine. These grains are not cleaned in a tooth brush and water sense. They fall though sieves and get blown around straw, chaff, insect parts and soil are mostly removed. But I digress. The harvest does kill a few things, mostly insects and things that happen to get under a wheel. Let's look at the big picture. Before farming in North America there were huge tracts of undisturbed land. There was a huge variety of habitats and lots of animals of all sorts that occupied these habitats. Once farming began, the natural habitat was destroyed and the variety of animals declined, as they had no place to live. It could be argued that almost all of this land was farmed organically to begin with and there were farm and field boarders where some animals could survive. The bigger farms one sees today have continued to reduce the diversity of the landscape and animal populations and the sheer variety of these animals has continued to decline. Deer and rodents have, by and large, done very well but they are the exception. I have spent days conducting research in wheat fields and only seen the occasional vole and hawk and seen the odd insect (grasshoppers and aphids mostly). When I hiked in the nearby mountains where farming is not allowed, there were animals of all sorts and types everywhere I looked. Farming of any sort is tough on the environment. Most wild animals do not do well on farms and move away or die. The actual act of farming does kill animals, but except for plowing the carnage is not that great.
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