There is growing scientific evidence that GE crops are harmful to biodiversity and the environment. Furthermore, once GE crops are released into the environment they cannot be recalled. As living organisms they can reproduce and pollute indefinitely.

The introduction of herbicide-tolerant GE crops to the US has resulted in a huge increase in both herbicide use, and the incidence of herbicide-resistant weeds.

Roundup, the herbicide sold by Monsanto in conjunction with its Roundup Ready GE crops, has been shown to be a potential endocrine disrupter — that is, it could interfere with our hormones. It is also toxic to certain wildlife, such as tadpoles.

The introduction of GE canola has been shown to have serious biodiversity impacts. For example, a UK government study found there were 24% fewer butterflies in the margins of GE canola fields because there were fewer weed flowers (and hence nectar) for them to feed on. In addition, there were fewer seeds for birds.

The use of Roundup on GE soy has also been shown to have an adverse impact on soil health, leading to reduced amounts of beneficial nitrogen-fixing bacteria in the soil.

Insect-resistant GE crops (termed Bt crops) have been shown to be toxic to “non-target” organisms (such as butterflies) and beneficial insects (such as green lacewings). They also threaten soil and water ecosystems, since many Bt crops secrete Bt toxins from the root into the soil. Agricultural wastes from Bt maize have been identified entering water courses.

Bt crops are intended to prevent the need for three applications of insecticide. Yet Bt maize varieties continuously release a toxin into the environment in quantities 3000–5000 times higher than the sprays used for non-GM farming.

In 1935, some 3000 imported cane toads were introduced in north Queensland to control native cane beetle populations. Today, cane toad numbers exceed 200 million, spreading into neighbouring states and threatening local biodiversity. We learnt an important lesson from this — playing around with natural ecosystems can have unpredictable effects which are extremely difficult to undo. This is just as true for the genetic engineering of crops.

In fact, the risks associated with GE crops may be greater – pollination through open air exacerbates the potential for contamination and hampers containment.

To date, no assessments of the environmental impacts of GE crops have been undertaken in Australia. However, one thing is certain – once harmful effects become apparent, it will already be too late.