When discussing climate change, the scientific and policy communities generally differentiate between mitigation (reducing) of carbon/greenhouse gas emissions and adaptation to climate change. While there is certainly a causal linkage between these topics, this differentiation makes general sense in that taking action along either of these courses can take place independent of action along the other. In other words, as a society, we could choose to only concern ourselves with adapting to climate change without mitigating the greenhouse gas emissions that are forcing the changing climatic conditions (eventually we won’t have a choice whether we adapt). And, generally speaking, the scientific community usually considers the decision of whether we invest in a course of action that mitigates greenhouse gas emissions to be a societal decision (hopefully informed by science).
In a recent webinar where I presented the latest scientific information on the potential impacts of climate change on Pacific Northwest agriculture, a participant asked a very interesting question that I don’t recall ever hearing stated quite this way. The question had two parts. Part 1 essentially asked for my scientific opinion on whether the results I presented from our research were “good, bad or indifferent” with regard to the impact of climate change on PNW ag – which I’ve addressed on many occasions (there are likely to be some benefits to yield, increased incidence and severity of pest pressure, and many uncertainties regarding crop quality; see Climate FAQ 5 or webinar). Part 2 of the question was the really interesting aspect – essentially asking: given what we know scientifically about the impact of climate change on agriculture, how should farmers think about the topic of mitigating greenhouse gas emissions from agriculture? In other words, if climate change is going to benefit some areas of agriculture, are farmers off the hook for reducing greenhouse gas emissions?
It’s not often that I am completely caught off guard by a question, but I had never actually given any consideration to this specific nuance of the climate science debate. After a brief pause to gather my thoughts, I realized I do have a scientific opinion on this matter that might provide a slightly more rigorous contribution to the societal discussion of whether agriculture should take part in mitigating greenhouse gas emissions. My opinion is largely captured by the idea that our “scientific uncertainty” regarding climate impacts on agriculture actually supports the case that farmers should contribute to greenhouse gas mitigation as a measure of “risk management” for adapting to climate change.
At the risk of getting bogged down in defining scientific uncertainty, let me just say that what I mean by this is not the idea that we’re unsure whether climate change will impact agriculture, but rather that the range of possible scenarios and outcomes is large, precisely because there are a large number of variables (human and natural) that interact with each other.
For instance, we can’t be absolutely certain of a yield projection for 2050 without knowing exactly what the radiative forcing (the atmospheric energy balance that affecting global temperature) of the atmosphere will be – and that is based on emissions trends. So, instead of giving it our “best guess”, we provide a range of possible outcomes based on several possible emissions trends.
Many groups of scientists have provided ranges of projections for the critical variables affecting the climate, most notably the Intergovernmental Panel on Climate Change (IPCC). As agricultural scientists we also attempt to overlay ranges of variables that we think will affect how our regional agricultural system will respond to these stimuli (including impacts on trade, economic growth, water supply, etc.). All of these ranges are based on assumptions, many of which are made in close consultation with members of industry and government who are the ones who must make decisions on a day to day basis. I made this case in the webinar by demonstrating the significantly different yield results can be projected just by changing global climate models and emission scenarios used to drive the model.
Most of the agricultural projections we have modeled to date have been based on fairly modest projected changes when compared with the actual changes that are being measured. For instance, the 4th IPCC Assessment provided a range of possible emission scenarios based on assumptions of economic growth and policy implementation. After more than a decade of data collection, we know that the actual emissions trajectory is above the highest projected end of the range of the IPCC scenarios – meaning that the rate of change is accelerating faster than originally projected. Even in PNW agricultural situations where we are currently projecting short-term benefits, the longer-term picture is much more uncertain. Accelerating the rate of change means we’ll be dealing with the more severe end of the projections much more quickly than we expected, demanding that our adaptation strategies be accelerated as well.
So, what does this have to do with mitigating emissions from agriculture? We know that US agriculture is a relatively small part of the total emissions picture (~6% direct emissions) and yet it is more significant globally (ranging from ~10-35% depending on what is included in the study). Could mitigating ag emissions in the US actually make a difference to the climate in the absence of a comprehensive carbon strategy?
Agriculture is certainly not going to solve the global carbon problem alone (sorry, to those who think it can). However, getting serious about agricultural emissions could be a significant factor on the margins of keeping our global emissions trends within the range of currently available IPCC projections, making our agricultural projections to date much more likely to be within our ability to adapt. When you further consider that many of the agricultural mitigation strategies, like precision nitrogen use, reduced tillage, and manure digesters, are all key strategies for improving overall environmental and economic performance of our farms, it seems that there might actually be strong scientific justification for agricultural mitigation as an agricultural adaptation – or risk management – strategy. Accelerating these types of changes in the agricultural system could help us “buy time” for implementing a more comprehensive global carbon management strategy without leaving us completely subject to the whims of a changing climate.