Week 12 - Increasing Yields, Selective Breeding, Controlling Pests and Environmental Management

As the human population continues to grow, we continue to use technology and science to help us produce more food. We create large continuous fields of the same kinds of food called Monocultures. Wheat, canola, oats and barley grow for endless kilometres on the open prairie. What are the positive and negative effects of this type of farming?

In order to protect crops and increase yield, farmers and foresters will use any number of methods. Each of these methods will have consequences that can be both detrimental and advantageous to the grower. Sometimes, we do something to fix a problem and find that we have accidentally created a whole new problem. In coming up with solutions, we must look at the whole picture.

In 1939, the chemical DDT was discovered to be a powerful insecticide. From that time until 1960, it was extensively used to prevent disease and increase crop yield, by killing insects. However, in the 1950s, scientists began to notice that some birds of prey were decreasing in numbers. Upon closer examination, they found that DDT builds up in the fatty tissue of the birds that eat these insects. Through experimentation, scientists found out that DDT interfered with the ability of mother birds to provide enough calcium to harden the shells of their eggs. Therefore, the bird numbers were decreasing because their young would not survive. In some places around the world today, DDT is still being used. What effect would this have on Canada? What effect does this have on the global food chain?

Herbicides are chemicals that kill targeted plants considered to be pests by man. Man considers weeds to be competitors for their main crop. They take valuable nutrients and water from the soil, and they compete for sunlight with the desired crop, thus reducing yield. For instance, the common dandelion stores nutrients in its roots through the summer so that in early spring it can get a strong start before the competitors. Its broad leaves allow dandelions to shade out many of the plants they grow with. They are able to create seeds all summer long, each flower creating hundreds of seeds which are carried a long distance by the wind. They are adapted to all kinds of soil, including those with poor nutrients. They are even well adapted to lawns that are frequently mowed. To top this all off, dandelions also release a chemical agent to slow down the growth of grass and other plants nearby. Herbicide and fertilizer combinations such as "Weed and Feed" are used by consumers to not only make the grass on a lawn healthier, but also to kill the weeds.

An insecticides is also a chemical control, but meant to kill insects instead of plants. Unfortunately, insecticides can also kill helpful insects, such as those that pollinate crops. Some insects are food for other animals. By using insecticides, these animals will have less food, or will be harmed by eating poisoned insects, or drinking water that has been contaminated by insecticides.

One of the issues with using chemical control pesticides is the ability for insects and weeds to become resistant to the chemicals. In other words, as insects reproduce very quickly, they can often rapidly adapt to the new challenges in their environment. So let's take a field, and say that we spray it and 99% of the insects die, but 1% do not. This 1% will reproduce, and the next time a chemical is sprayed, their offspring will have a higher chance of surviving. Scientists have discovered that as pesticide use increases, the number of insect species resistant to pesticides increases as well. Food producers should be aware of this, and only use pesticides when absolutely necessary. The only way to deal with resistant insects is to use higher doses of the chemical, or develop new pesticides. One of the major human concerns with pesticides is whether or not they are still in our food when we buy them at the grocery store. Some have thought that pesticides may be linked to cancer. We have a delicate sustainability issue. Do we attempt to produce food with chemical controls that have high yields and can feed the world's population, but risk the side effects of ingesting pesticides. Just as in the example of the birds of prey and DDT, how much bioaccumulation of chemicals can the human body sustain without there being any harmful effects?

Just as we worry about pesticides bioaccumulating in our bodies, we have to worry about what happens to pesticides as some of them wash off plants and leave residue in the soil and water. If the pesticide doesn't easily decompose, it can build up, making the soil potentially toxic and the water undrinkable.

Farmers who chose to run organic food productions must pass strict inspections in order to be certified as organic. Producing without chemicals can be very expensive and requires much extra monitoring and lots of extra work. Nonetheless, organic growers can demand higher prices for their produce, and their land has less chance of residue buildup. Consumers who buy organic foods will pay a little bit more for their food, but have less worry about bioaccumulation of chemicals.