1. Is GM Safe?
The question "is GM food safe" is a meaningless question. Each genentic modification will have it's own impact on the species in question and also on the whole environment around it - the effects is far too complex for us to be able to predict so we will only know the full effects over time. Some modifications might well turn out to be fine, especially those that could have been achieved using selective breeding over a longer time frame. The most extreme modifications are clearly not safe and might have a catastrophic impact on the environment.
2. Who Controls GM?
Large companies invest a lot of money into genetic modifications and as a business it's important for them to make a profit. To prevent competitors using their research they apply for a patent on their modification. Once a farmer goes down the GM route they may find they are locked into buying certain fertilizers or pest control chemicals from the same company in order to get the best from their new crop. Or the supplier of GM will tie them into a contract. Some farmers have been treatened with legal action when the genetic pattern is identified on their land. There are also concerns about the fertility of some GM pigs, no-one is sure whether this is to make sure that the farmer always has to buy from the GM company.
3. Genetic Modification vs Selective Breeding
Some GM supports compare GM to an accelerated form of selected breeding. For a long time man has picked the best individuals, whether it be pigs, cows, wheat or corn and bred them together. Over a relatively long period certain characteristics can be developed such as beef cows with less fat or corn plants with shorter stalks. However, each generation of selected breeding is exposed to the effects of nature and so there is time to observe any undesirable side effects. With genetic modifications we can leap forward by adding genetic patterns from alien species. We will always run the risk of accidentally releasing a modification that has disasterous consequences - we are not always as smart as we think we are!
4. Better Safe than Sorry
Once the genie is out of the bottle it's not going to be easy to every put it back. Time and again mankind has created problems by introducing non-native species, whether it be rats in the Galapagos, rabbits in Australia or Japanese knotweed in the UK.
5. Agriculture in the Ecosystem
In the densely populated UK the vast majority of our land is used for agriculture. This means that our farms and plantation forests are very important to our ecosystem. If GM were successful in elimating weeds (a weed is just a plant growing in the wrong place) and pests (just another species trying to survive) then all the creatures up the food chain will decline. Everyone likes to see butterflys but the caterpillers are not so popular and caterpillers often need weeds such as nettles - unfortunately you can't have one without the other. Of course, it is incredibly important that we produce enough food for the UK to be reasonably independant on basic foods but we must take our fair share and allow nature her fair share too.
6. GM Can't Eradicate Hunger; Education Can
GM supporters point to the need to increase food production to feed the Third World. Two problems with GM as a solution to this; firstly there is already enough food grown worldwide it just a question of getting it in the right place without destroying local markets, secondly GM technology is expensive and very high tech. We can not solve the food problems of the Third World by getting them addicted to technology that has to be purchased from us. Education is the key; through education farmers can find their own solutions using more traditional approaches, education also has a very significant effect on population so we can avoid the vicious cycle of more food leading directly to an increased population, leading to demand for more food - especially if this food can only be grown using western technology. This will inevitably lead to disaster.