drought India 2005
© REUTERS/Jayanta DeyAn Indian farmer walks with his hungry cow through a parched paddy field in Agartala, capital city of India’s northeastern state of Tripura, March 10, 2005.
Who would have guessed that raising the cost of energy with regressive carbon taxes would harm a vital, low margin energy intensive economic activity?
Climate taxes on agriculture could lead to more food insecurity than climate change itself
  • Date:July 30, 2018
  • Source:International Institute for Applied Systems Analysis
  • Summary:New research has found that a single climate mitigation scheme applied to all sectors, such as a global carbon tax, could have a serious impact on agriculture and result in far more widespread hunger and food insecurity than the direct impacts of climate change. Smarter, inclusive policies are necessary instead.
New IIASA-led research has found that a single climate mitigation scheme applied to all sectors, such as a global carbon tax, could have a serious impact on agriculture and result in far more widespread hunger and food insecurity than the direct impacts of climate change. Smarter, inclusive policies are necessary instead.

This research, published in Nature Climate Change, is the first international study to compare across models the effects of climate change on agriculture with the costs and effects of mitigation policies, and look at subsequent effects on food security and the risk of hunger.

...

The researchers stress that their results should not be used to argue against greenhouse gas emissions reduction efforts. Climate mitigation efforts are vital. Instead, the research shows the importance of "smart," targeted policy design, particularly in agriculture. When designing climate mitigation policies, policymakers need to scrutinize other factors and development goals more closely, rather than focusing only on the goal of reducing emissions.

"The findings are important to help realize that agriculture should receive a very specific treatment when it comes to climate change policies," says Hasegawa. "Carbon pricing schemes will not bring any viable options for developing countries where there are highly vulnerable populations. Mitigation in agriculture should instead be integrated with development policies."
The abstract of the study;
Risk of increased food insecurity under stringent global climate change mitigation policy

Tomoko Hasegawa, Shinichiro Fujimori, Petr Havlík, Hugo Valin, Benjamin Leon Bodirsky, Jonathan C. Doelman, Thomas Fellmann, Page Kyle, Jason F. L. Koopman, Hermann Lotze-Campen, Daniel Mason-D'Croz, Yuki Ochi, Ignacio Pérez Domínguez, Elke Stehfest, Timothy B. Sulser, Andrzej Tabeau, Kiyoshi Takahashi, Jun'ya Takakura, Hans van Meijl, Willem-Jan van Zeist, Keith Wiebe & Peter Witzke

Food insecurity can be directly exacerbated by climate change due to crop-production-related impacts of warmer and drier conditions that are expected in important agricultural regions. However, efforts to mitigate climate change through comprehensive, economy-wide GHG emissions reductions may also negatively affect food security, due to indirect impacts on prices and supplies of key agricultural commodities. Here we conduct a multiple model assessment on the combined effects of climate change and climate mitigation efforts on agricultural commodity prices, dietary energy availability and the population at risk of hunger. A robust finding is that by 2050, stringent climate mitigation policy, if implemented evenly across all sectors and regions, would have a greater negative impact on global hunger and food consumption than the direct impacts of climate change. The negative impacts would be most prevalent in vulnerable, low-income regions such as sub-Saharan Africa and South Asia, where food security problems are already acute.
Sadly the full study is paywalled, but I think we get the idea.

Modern farming is energy intensive.

One easy example, production of Ammonia, a key ingredient in fertiliser, produces 1% of the world's greenhouse gas emissions. 80% of that ammonia ends up as fertiliser.

Production of Ammonia is sensitive to energy prices. A few months ago, Ammonia production in Europe was halted when global petroleum prices rose to a level which made production unprofitable.

There have been efforts to find a clean energy route to Ammonia production. To eliminate natural gas and CO2 emissions from the ammonia production cycle, you have to start by electrolysing water for hydrogen, itself an expensive process, before applying the extreme pressures and temperatures required to crack biologically inert nitrogen molecules and force the nitrogen to combine with hydrogen to form ammonia. The product is very expensive ammonia.

Raising the price of ammonia with carbon taxes, and passing costs on to farmers would be a gruesome balancing act between food affordability, farm productivity and ammonia production costs.

Affordable Ammonia is only one of the energy intensive inputs required to keep farms producing at a level which keeps food cheap.

I suspect there are many other essential economic activities which are also severely adversely affected by carbon taxes.