Published: 3:52 AM GMT on دعيسوىكال شپږمه مياشت . 10, 2013
Not Like My Father’s
I want to continue in the personal and spontaneous spirit of the last blog. I heard a lecture recently talking about climate change and farming. The speaker made the comment that the climate was changing fast enough that a family farmer could not count on the weather being the same as his father’s.
Many of the discussions I have heard about farming and climate change start with a discussion of drought and that we expect more frequent and more severe droughts in the future. Flood is also mentioned, but anecdotally at least, we think of flood as more localized than drought. We also hear about warmer and earlier springs and, hence, longer growing seasons. This potential opportunity is muted by concerns that even if there is more precipitation that a warmer climate will cause more water stress for crops. In general, the farmer will have to manage more variable and more extreme weather.
We are already in a time of rapidly changing climate. The first decade of this century was the warmest recorded, and it has been many years since the monthly average of the Earth’s surface was cooler than the 20th century average. For the northern hemisphere, this warming has led to a lengthening of the growing season, as defined by frost-free days. Farmers have already adapted by planting earlier with seed developed to take advantage of these changes or to survive despite them. The last thirty years have also been a time when the rhythm of precipitation has changed. We see more precipitation in intense storms and changes in the seasonal cycle of the availability of fresh water.
I was recently on a telecon with some scientists from the Department of Agriculture. I learned that in recent years, heavy spring rains had been inhibiting spring planting. There have been problems with getting heavy equipment into the field. The amount of time when the soil moisture is right for both holding up the equipment and providing a good seedbed is becoming shorter (news link). The likelihood of seedlings being washed out by intense rains is increasing. Curiously to me, one response to this has been to build still bigger equipment so that more can be planted in the shorter amount of time that is available.
What I described in the previous paragraph is not something that is projected for the future; it is already happening (Impacts of Climate Change on Illinois Agriculture). Farmers and manufacturers see what is happening, and they adapt. This adaptation to perceived changes is real, costly and much more concrete than the abstract threats of more drought and more flood. Another real issue that we already respond to is the warm spell in spring that causes budburst of orchards, followed by a freeze that wipes out a crop.
Events such as the wet spring, budburst and crop loss, flooding out a crop are not new to farmers. What is new is how often such events are happening. It is also new that the places where the events are occurring are changing.
I grew up in the South of the United States, which is a four-season climate. I remember throughout my childhood peach crops that were wiped out by a late frost. In fact, almost every year there was concern in some part of the South of a swath of peaches being wiped out. And that is an interesting fact of climate variability and farming: There is almost always weather-related damage some place. In a country and rich as the United States, other regions of plenty mostly balance out these places of loss. It is this balance of agricultural plenty and loss that leads some to say that when viewed as a global or national market, agriculture is resilient to climate change.
If this collective agriculture is, in fact, resilient to climate change, this assumes either 1) the future climate is, on average, like our father’s climate or 2) we effectively adapt to climate as it changes. A confidence in agricultural resilience assumes that what resilience we have built in the past transfers into the future. Even if agriculture is collectively resilient, locally there is boom and bust.
In the South, precipitation is spread out across all of the seasons. Irrigated farming is the exception, not the rule. Southerners do not worry about water being stored in snow and dribbling out to use as it melted in the spring and the summer. As I have grown older and traveled and moved, I found out that much of the world does not have four seasons with rain spread throughout the year. Much of the world has a wet season and a dry season. Many parts of the world rely on water being stored as snow on high mountains, lasting into spring and melting to be used for agriculture in the warm season.
Scientists call being able to rely on having our father’s climate “stationarity.” If the climate were stationary, then in the future the averages and the extremes would be the same. To describe stationarity, scientists often use figures that describe the statistical distribution of “climate” or perhaps more correctly of temperature and precipitation. We talk about the average temperature increasing. We talk about average precipitation increasing or decreasing, depending on the region. We often talk about the “extremes,” especially extremely hot temperatures increasing. Precipitation extremes might increase either as prolonged drought or as intense rain and snowstorms. The changes in the statistical distribution of parameters that measure climate describe the lack of stationarity.
The normal ways that we talk about extremes do not always convey the way we are feeling climate change. The seasonality, the rhythm, the ebb and flow this is changing and felt in those muddy fields that preclude farm equipment and endanger planting. The change in seasonality is felt in intense winter snowstorms, followed by winter rains and early spring causing water to run through the ditches, rivers and reservoirs and to be unavailable for summer growing. The changes in seasonality are felt in an increasing number of early budbursts followed by the killing frost. This change in seasonality is as much a change in stationarity as any change in the average and mean temperature. In fact, the change of the rhythm of seasons can occur with very little change to the statistical description of averages and extremes. It might not even seem hotter.
How to cope with a climate that is not stationary is a major challenge for agriculture (and engineering). Deep within our planning for the future is the assumption that weather will remain the same – it will be like our father’s and mother’s weather. This is no longer the case.
Some good references:
Impacts of Climate Change on Illinois Agriculture
Farming Success in an Uncertain Future (Cornell)
Reinventing Farming for a Changing Climate (NPR)
Farm Level Adjustments to Climate Change (USDA)
Agricultural Adaptation to Climate Change and Adaptation to Climate Change in the Context of Multiple Risks both chapters in Climate Change in the Great Lakes Region (Dietz and Bidwell)
Barnett: Climate Change and Water and Snow Availability
Milly: Stationarity is Dead