Sustainable Agriculture Literature Review - Boulder County

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The unintended effects of genetically engineered crops on non-target organisms could
affect future biodiversity. For example, Bacillus thuringiensis (Bt), a pesticidal property
found in some varieties of genetically engineered (GE) crops, may negatively affect
populations of butterflies and moths. 660 A laboratory study found that pollen from Bt corn
caused high mortality rates in monarch butterfly caterpillars. Even though monarch
butterfly caterpillars do not consume corn, they consume milkweed plants, which can
contain Bt pollen that drifted from a neighboring farm. The results of the current studies
are still being debated, and there is no agreement about the potential risk on non-target
organisms. 661
Genetically engineered crops may put pollinators at risk, and many crops depend on
insects for pollination. Pollinators are both ‘managed’ species, such as honey bees, and
wild species of bees, flies, beetles, and other insects. Only studies on managed species
have been performed. There are two ways that GE crops can impact pollinators, either
directly posing a hazard to the pollinator, or indirectly by changing its habitat. Bt crops
have insecticidal proteins, which are more likely to affect pollinators directly. The
experiments conducted on honey bees and bumblebees have shown no adverse affects
of Bt crops. The results of studies on the effects of new insecticidal GE crops on nontarget
organisms currently under development have not been released. 662
Soil Microbial Communities
The majority of biodiversity in agricultural systems resides in the soil. Interactions among
the soil biota have large effects on the quality of crops, the incidence of soil-born plant
and animal pests and diseases, and the beneficial organisms that help cycle nutrients or
act as predators for unwanted pest species. 663 The available evidence suggests that soil
biota biodiversity provides multiple benefits to agricultural production including: (1)
conferring disease suppressiveness, (2) providing resistance and resilience against
disturbance and stress, and (3) increasing nutrient and water use efficiency. The extent
to which these benefits are provided by soil biota is the source of debate as a range of
field conditions can affect the value of benefits. Efforts to quantify the impact
economically of both direct impacts (organisms themselves and metabolic products) as
well as indirect impacts (the long-term outcome of their activities), have estimated that
664, 665
soil biodiversity provides services valued at over $1.5 trillion dollars.
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