GMO Debate

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•  Assessment of the potential risks and benefits associated with the genetic modification of crops

Genetically modified organisms (GMOs) are used in agriculture to improve crop yields and reduce farming costs

  • However the use of GM crops is a contentious issue, as economic benefits must be weighed against environmental risks

GM Crops and Human Health

  • GM crops can be used to improve human nutritional standards, by incorporating genes for certain proteins, vitamin or vaccines
  • Additionally, GM crops can be manufactured that lack common natural allergens or toxins
  • However, the inclusion or removal of certain genes could trigger unexpected adverse health reactions in some individuals
  • Currently, not all foods with GM components are labelled, making informed decisions of use difficult for consumers

GM Crops and Economic Consequences

  • GM crops can include genes to enable them to grow in a wider range of environments (e.g. drought / frost / salinity resistance)
  • GM crops can be manufactured to produce greater yields (crops can potentially grow larger and faster)
  • GM crops can include genes which slow the rate of spoiling, leading to longer shelf lives for GM foods
  • GM crops may possess resistance to certain viruses or produce toxins to pests (reducing need for the use of pesticides)
  • Herbicide resistant crops can be used to allow for the easier killing of weeds (which compete with crops for soil nutrients)
  • Overall, an improved yield, reduction in farming costs and ability to farm more land will provide an economic benefit to farmers
  • However, patent protection allows biotech companies to restrict the use of seeds and force farmers to pay high prices for use

GM Crops and Environmental Issues

  • The ability to farm a wider range of environments with GM crops will potentially reduce the need for associated deforestation
  • Also, the generation of pest-resistant crops means that less chemical insecticides will be released into the environment
  • However, GM crops could potentially reduce biodiversity in a region by competing with indigenous plant life
  • Furthermore, proteins or toxins produced by GM crops could negatively affect certain organisms within the ecosystem
  • Cross-pollination by GM crops could also result in the formation of herbicide-resistant weeds and grasses
  • GM crops with pest toxins could also accelerate the evolution of resistant pest species

Summary of Issues Associated with Genetically Modified Crops

GMO Arguments

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•  Analysis of data on risks to monarch butterflies of Bt crops

Bt corn is a genetically modified maize that incorporates an insecticide producing gene from the bacterium Bacillus thuringiensis

  • This insecticide is lethal to certain types of larvae, particularly the European corn borer which would otherwise eat the crop

Concerns have been raised that the spread of Bt corn may also be impacting the survival rates of monarch butterflies

  • While monarch butterfly larva feed exclusively on milkweed, wind-borne pollen from Bt corn may dust nearby milkweeds

Relationship between Bt Corn and the Monarch Butterfly

Bt corn

In 1999, a preliminary study was conducted investigating the association between exposure to Bt corn pollen and survivor rates among monarch caterpillars:

  • Monarch caterpillars were fed milkweed leaves that had been dusted with pollen from Bt corn (to simulate spread via wind)
  • Growth and mortality rates were compared against caterpillars fed on non-dusted leaves or leaves dusted with non-GM pollen
  • Caterpillars exposed to Bt pollen were found to have eaten less, grew more slowly and exhibited higher mortality rates

Effect of Bt Pollen on Survival Rates of Monarch Butterflies (Laboratory Conditions)

Bt graph 1

Some scientists suggested that these results may lack validity as they do not accurately reflect natural conditions:

  • There were higher amounts of Bt pollen on the leaves than would be found naturally (e.g. rain would diminish build up)
  • Larva were restricted in their diet (in the field, larva could feasibly avoid eating pollen dusted leaves)

A second study was conducted comparing the survivor rates of monarch butterflies based on proximity to Bt corn fields:

  • There was no significant increase in mortality when monarch larva were placed in or near an actual Bt corn field
  • From this it was concluded that exposure to Bt pollen poses no significant risk to monarch butterfly populations 

Effect of Bt Pollen on Survival Rates of Monarch Butterflies (Field Conditions)

Bt graph 2