The Effects of Climate Change on Agriculture

Dr William L. Preston, Professor of Geography at CalPoly and author of Vanishing Landscape: Land and Life in the Tulare Lake Basin, discusses the effects of climate change on agriculture, as well as ways we can bolster crop resiliency and food security.

What effects of climate change on agriculture have we already witnessed?

“Agriculture has been, and is being, impacted by climate change.  Nearly every facet of climate fluctuation impacts agriculture.  Examples of factors are: length of growing season, temperature and precipitation, minimum and maximum temperatures, humidity, evapotranspiration, plant and animal growth and productivity, soil moisture, water availability, quantity, and quality etc.  The specific impacts of these and many more factors vary according to geography, cultural setting, and agronomic practices. “Although climate change may result in some advantages by offering opportunities for new crops in places that were unsuitable during previous climates, most of the consequences are negative, especially in developing societies.  The changes are occurring faster than we can adapt to them.  A good example of the challenge is that isotherms in the northern hemisphere are migrating northward at a rate of 35 miles a decade based on the last 30 years.  Agronomic adjustment will be challenging. “A rise in temperature of 1.8° F above the norm yields an approximate 10% fall in wheat, rice, and corn production.  More areas are experiencing soil moisture stress, which means more water is needed for crops.  Another related problem is that for every 1° F temperature rise, evaporation increases approximately 7%. The resulting stress on both soil moisture and available irrigation water is of great concern. Changing climate conditions also change the parameters of agricultural pests.  The outcome of these conditions has not been sufficiently studied to provide definitive regional evidence.”
U.S. Mid Western grain regions
Many areas have been experiencing increasing average temperatures and greater frequency and longevity of drought conditions.
This is presenting problems and challenges in some areas, especially in terms of grain production.  It is difficult to ascertain for certain, but this year’s drought that devastated the corn crop is probably in large measure a byproduct of climate change, and we can expect a greater frequency of these conditions.
Snow coverage in the Northern Hemisphere (on the Great Plains in particular) has been diminishing.  This trend will have consequences for wheat production.
Many areas in the Central Valley cannot grow certain fruits such as apples, cherries, and pears any more because these types of crops require a certain amount of winter chilling hours, and many localities no longer have enough.  The number of chill hours has declined as much as 30% since 1950.  In addition, milder winters have been connected to outbreaks of powdery mildew, brown leaf rust in barley and strip rust in cereal crops.
Irrigation consumes over 80% of the fresh water used in California.  Unfortunately, the snow pack has diminished by approximately 11% since 1970 and peak snowmelts are occurring over a week earlier.  This problem, in combination with factors such as warmer temperatures, will provide challenges in the quantity, timing, and quality of irrigation water.  California’s water infrastructure was designed to conform to a past climate and not the current climatic trends.
Northern Africa
The Sahel region in particular is being negatively impacted.  Owing primarily to climate change, the Monsoon summer rains are no longer reaching as far north as they once did and they also are dropping less precipitation in general (especially in the northern regions of the Sahel).  Most of agricultural land is not artificially irrigated, placing the populations in a very susceptible situation. Deterioration of production has contributed significantly to competition and conflicts over diminishing resources, such as in Darfur (part of the Sahel) in North Sudan.
I do not have the details of the impacts of growing climate instability in Asia.  However, the future is not promising.  A great deal of the irrigation water used by hundreds of millions of people in India, Pakistan, Bangladesh, and China depends upon glaciers in Tibet and the Himalayan Mountains.  These glaciers are diminishing.  What happens when they diminish even more and disappear altogether is frightening to contemplate.

What are we likely to see in the future?

“The future is difficult to crystal ball with ultimate confidence, owing to the tremendous complexity of the climate-Earth system.  However, computer modeling and observations reveal broad patterns and trajectories of change. For example: “Areas that are wet today will tend to get even wetter.  Precipitation will occur from storms that are larger and more intense, and vary more in terms of their timing and locations.  The type of precipitation will be skewed away from snow. “Growing seasons are and will continue to increase in time. “More threatening is that regions categorized as dry are currently expanding geographically, and will continue to expand and become drier. “The Intergovernmental Panel on Climate Change reported in 2007 that the spatial coverage of dry areas (as defined by the IPCC) has expanded by over 20% since 1980. “Agricultural regions around the world will be afflicted by new kinds of diseases and pests. “Glaciers and late season flow of rivers are shrinking and will continue to do so.”

  What can we do on a personal level to respond to a changing climate?

“Educate yourself and your community about the causes, consequences, and challenges presented by climate change. “Educate and support representatives who recognize its reality, immediacy, and challenges. “Learn about hazard management and help build resilient, self sufficient, and sustainable communities. “Protect wild lands that offer protection from some of the consequences of climate change (e.g., watershed protection etc.) and provide the material for adaptation (e.g., genetic diversity, soils that may not be in use now but may become ideal with changing growing conditions etc.). “Reduce material consumption to assist in reducing emission of greenhouse gases. “Stay positive and be courageous.  Climate change can be survived.”

How do we build resiliency into our food systems?

“We must learn from natural processes and human history. Ecological succession in nature demonstrates that generally the more diverse an environment is the more stable and resilient it becomes.  History tells us that human activities that are rather homogenous in their basic economic underpinnings are extremely vulnerable to environmental and cultural changes. “Examples are company towns and plantations that have folded owing to fluctuating markets, pricing of materials, energy availability, or executive decisions, etc.  If these locations also depend on outsiders for their sustenance, they are extremely susceptible and have little adaptive resilience in the face of change. Diverse economic pursuits that provide greater local self-sufficiency provide more hardiness and flexibility in adapting to changes of any kind. “Therefore, in order to build resiliency into our food systems the goal must be sustainability.  The guide is to nurture diversity in all respects (natural, cultural, domesticated species). “In summation, emphasize diversity, resilience, sustainability, and local endeavors.”

What kind of food systems work best in times of climate instability?

“Place emphasis on food systems that are community based, where consumers are intimately intertwined with food producers.  Ensure that food systems are diverse, sustainable, and rely much less on high energy and chemical inputs.  Anchor food systems in and on soils that are organically nurtured.  Indeed, the opposite of corporate farm soil that is often simply a sponge for chemicals. “The latter is unsustainable and soil ecosystems that have been rendered less diverse and are managed to meet the needs of only a few crops offer less potential for agronomic change as climate continues to change.  In essence, develop more organic food operations. “Endeavor to prioritize crops over traditional animal husbandry.  Integrate animals into sustainable systems where appropriate. “Food systems must be made more diverse, local, and organic.  The combination of peak oil and climate change rules out the future of 4,000-mile salad (really and metaphorically).  Smaller agricultural operations in a community’s hinterland that produce a wide variety of foods are important to stable resilient food supplies and communities.  Farmers that are knowledgeable about a variety of products are best able to adjust to changing growing conditions.  Urban gardens also enhance diversity and resiliency and should be integrated into local agricultural systems.  In order to achieve this, more energy efficient agriculture that depends less on expensive pesticides, herbicides, and fertilizers is required. “As rapidly as possible, reduce or eliminate reliance on distant corporate monoculture.  These kinds of operations, because they are monoculture, dependent upon high energy and chemical inputs and rely upon extensive distribution systems—are highly vulnerable to climate change (again, being exacerbated by peak oil).  They also are not invested in local communities, rather, they are focused on profits more than protecting or sustaining human health and the overall human condition.

“Do not wait for catastrophe to stimulate change in food systems.  Adaptive change is a process that requires time.  The time is now and we must get the future right.”

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