As I mentioned the other day, there is a lot of frustration and denial on the part of farmers when it comes to nitrate pollution in the Central Valley. Recently, the UC Davis researchers who wrote the massive report on nitrates in groundwater held a public workshop to formally present their results. When pressed on the 96% figure for nitrate coming from agricultural sources, one of the scientists acknowledged that the figure may not be “precise”. Oh dear, you just admitted uncertainty – surely it only went downhill from there. Where were the error bars in the original study? If you admit uncertainty, then error bars at least constrain the uncertainty. An admission of imprecision suggests to the public that it all might be crap.
Turns out that the farmers may have some reasonable issues with the study methodology, partly because the study had to estimate nitrogen fertilizer application rates over the past ~60 years. Nitrogen prices have gone up significantly, which already presses farmers to be highly efficient in their applications. Plus there is more and more use of low-water irrigation (e.g., drip irrigation), which further decreases the rate of nitrogen leaching into the groundwater. The scale of the UC Davis study simply did not permit inclusion of these trends, which suggest that farmers are already mitigating the nitrogen issue as much as they can. Based on the above article, I doubt that the researchers satisfactorily explained why they conducted the study in the way that they did.
That said, legacy contamination is still an issue, and I don’t think there’s any way that fertilizer application was not the cause of the groundwater nitrate contamination. So who should pay to clean it up? I would still argue that nitrogen fertilizers and irrigation water are the easiest things to target, even if it is a burden on the farmers. The fees would provide a cost-benefit incentive for all farmers to engage low-water irrigation and efficient nitrogen use, plus there is some talk of using contaminated groundwater as irrigation water, letting the nitrates be consumed by crops. Think that’s unfair, farmers? Talk to the chemical industry about joint and several liability for Superfund sites under CERCLA…