Randomized Controlled Trial of Bt Eggplant in Bangla: Bt brinjal raises yields by 51%, reduces pesticide costs by 37.5%, increases 128% net revenues, reduces pesticides toxicity above 70%

The Impacts of GM Foods: Results from a Randomized Controlled Trial of Bt Eggplant in Bangladesh. Akhter U. Ahmed  John Hoddinott  Naveen Abedin  Nusrat Hossain. American Journal of Agricultural Economics, November 13 2020. https://doi.org/10.1111/ajae.12162

Abstract: We implemented a cluster randomized controlled trial to assess the impact of genetically modified eggplant (Bt brinjal) in Bangladesh. Our two primary outcomes were changes in yield and in pesticide costs. Cultivation of Bt brinjal raises yields by 3,564 kg/ha. This statistically significant impact is equivalent to a 51% increase relative to the control group. There is a statistically significant fall in pesticide costs, 7,175 Taka per hectare (85 USD per ha), a 37.5% reduction. Yield increases arise because Bt farmers harvest more eggplant and because fewer fruits are discarded because they are damaged. Bt brinjal farmers sell more eggplant and receive a higher price for the output they sell while incurring lower input costs, resulting in a 128% increase in net revenues. Bt brinjal farmers used smaller quantities of pesticides and sprayed less frequently. Bt brinjal reduced the toxicity of pesticides as much as 76%. Farmers growing Bt brinjal and who had pre‐existing chronic conditions consistent with pesticide poisoning were 11.5% points less likely to report a symptom of pesticide poisoning and were less likely to incur cash medical expenses to treat these symptoms. Our results are robust to changes in model specification and adjustment for multiple hypothesis testing. We did not find evidence of heterogeneous effects by farmer age, schooling, or land cultivated. Bt brinjal is a publicly developed genetically modified organism that conveys significant productivity and income benefits while reducing the use of pesticides damaging to human and ecological health.

Limitations

We note three limitations associated with our analysis. First, our intervention consisted of a package of activities (most notably, training and a stipend) as well as the provision of seedlings, the latter randomized to be either Bt brinjal or the control variety, ISD‐006. Specifically, we note that farmers growing Bt brinjal received extensive training and support; the increase in yield relative to the control group might have been smaller in the absence of this support. That said, both the treatment and control groups received training on IPM; absent that training, the control group might have experienced even greater production losses due to pest infestations and might have spent even more money on pesticides. If this the case, our results underestimate the impact of Bt brinjal. Second, data on production, sales, and inputs as well as symptoms relating to pesticide poisoning are self‐reported. If respondents in the treatment group felt some social desirability bias to exaggerate their production success, or reductions in illness, this would upwardly bias our impact estimates. Third, we do not have direct measures of pesticide residues in soils; such information would provide a useful complement to our findings about the environmental benefits of Bt brinjal.

Summary and Conclusions

In Bangladesh, we implemented a cluster randomized controlled trial to assess the impact of Bt brinjal. Households in both treatment and control villages received a bundle of interventions including training, extension, an input package, and seedlings. Control villages received a conventional variety, ISD‐006. Treatment villages received Bt brinjal‐4, a variety that was genetically identical to ISD‐006 except for the addition of one gene (cry1Ac) that conveyed protection against the fruit and shoot borer pest.

Our two primary outcomes were changes in yield and in pesticide costs. We find that cultivation of Bt brinjal raises yields by 51% relative to the control group while reducing pesticide costs by 37.5%. These results are consistent with observational studies of yield and pesticide use summarized in Klümper and Qaim (2014), Zilberman, Holland, and Trilnick (2018), and other reviews noted in our introduction. Yield increases arise because Bt farmers harvest more eggplant and because less fruit is discarded post harvest. Compared to control farmers, Bt brinjal farmers both sell more eggplant and receive a higher price for the output. They incur lower input costs, resulting in a 128% increase in net revenues. Bt brinjal farmers used smaller quantities of pesticides and sprayed less frequently, and Bt brinjal reduced the toxicity of pesticides that were applied. Farmers growing Bt brinjal and who had pre‐existing chronic conditions were 11.5% points less likely to report a symptom of pesticide poisoning. Our results are robust to changes in model specification and adjustment for multiple hypothesis testing. We did not find evidence of heterogeneous effects by farmer age, schooling, or land cultivated.

We note three policy implications that follow from these results. They support the view that GMOs can contribute to the goal of increasing yields while reducing environmental stressors. They provide further justification for releasing Bt brinjal in countries such as India and the Philippines, where these varieties have been developed but not approved for cultivation due to public reservations about GMO foods. They point to the valuable role that public agencies can play in the dissemination of GMOs. The involvement of BARI and the Bangladesh Department of Agriculture in the development and support of Bt brinjal cultivation alleviates concerns raised by anti‐GMO activists regarding farmer sovereignty.

We have noted several limitations to our study. The most significant is the fact that Bt brinjal was provided as part of a package. Doing so allows us to better isolate the impact of Bt brinjal but raises concerns regarding external validity. Additional RCTs with a slimmer package would make it possible to assess whether this is a concern. Clinical measures of health and chemical measures of pesticide residues would strengthen our ability to assess impacts on health and the environment. Finally, our finding that consumers are willing to pay more for a GM crop is striking; further work understanding why would be of value. Such future work would further strengthen the results found here—that Bt brinjal, a publicly developed GMO, conveys significant productivity and income benefits to farmers while reducing the use of pesticides damaging to human and ecological health.