Wednesday, July 27, 2011

How Can Crops Be Adapted to Climate Change?

wikipedia: sunflowers

Earlier, this month, I published the post titled "CSSA's Crop Adaptation to Climate Change Report." James Giese, Director of Science Communications for the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, dropped by and left a comment under the post directing us toward more CSSA publications.

Today, I'd like to feature one of them, "Crop Adaptation to Climate Change," a summarized version of the CSSA policy statement. CSSA is an international scientific society comprised of 6,000+ members with its headquarters in Madison, WI.

To follow, I've chosen excerpts which, in the first part discuss Climate Change factors having known impacts upon plants and crop production. Then, in the solutions part, I chose the "Develop New Crops" portion, which includes the exciting topic of perennial grains. We also need to continually test the seeds that we have saved and find which ones are most resilient as conditions change. This means growing older crops which somehow became abandoned in this age of scarce seed diversity.
Bye, bye monoculture grains and back to a more balanced and diverse food shed approach to feeding the world.

The hope would be to take the best of all crops, seeds, systems, and agronomy knowledge that we've acquired during man's agrarian timeline to date and apply what makes the most sense to each unique regional set of circumstances. This would help humans mitigate the challenges facing agriculture caused by Climate Change.

There are many hopeful solutions. Our industrialized Ag system is based upon expensive annual inputs and CC means more frequent crop failures. I expect workable solutions will dictate fewer of these costly inputs, requiring more sustainable practices in combination with science-provided intensification. Most likely, it will also lead to more of us working to produce our food than the 2% currently in the U.S. We live in interesting and rather exciting times for agriculture!


"The goal is to produce higher yields with reduced greenhouse gas emissions per unit of production and to conserve and enrich the organic content of soils, and to promote efficient water use, and ecosystem integrity."

How Will Climate Change Affect Cropping Systems?

Beyond its direct effects on weather, climate change will increase both abiotic stresses, such as drought, and biotic stresses, such as pest pressure, on agricultural systems. Of greatest concern and largely unknown are the influences that interactions among different types of stresses will have on crops.

Drought is expected to limit the productivity of more than half of the earth’s arable land in the next 50 years, and competition for water between urban and agricultural areas will compound the problem. While the use of brackish and saline water could also help alleviate the world’s water problems, this option is only possible with the development of salt-tolerant crops or management practices that alleviate salt stress. As a result, to limit the impact of drought, there is an urgent need for crop varieties and cropping systems that conserve water and retain yield during periods of water scarcity.

Developing these crops is difficult, however, because of the interplay of crop response systems to drought at the genomic, metabolic, biochemical, and physiological levels. To make drought-tolerant varieties available to farmers, interdisciplinary teams of scientists working at the cellular, plant, and field scales must work together to discover ways to manipulate these complex, multi-level processes and improve crop response.

Temperature influences the growth and development of all crops, shaping potential yield throughout the growing season. Current temperatures in the American Midwest are optimum for production, while southern U.S. temperatures already exceed the optimum. Temperature events higher than normal are expected to reduce cereal and grain legume yields.

Elevated temperatures are known to shorten the grain-filling period, for example, and to reduce pollen viability and weight gain in grain. Moreover, elevated temperature changes can result in warmer, less severe winters, which sometimes allow diseases and pests to survive and overwinter, increasing the likelihood of reduced yield the next cropping season. For all of these reasons, adapting crops and cropping systems to new seasonal fluctuations and temperatures will require region-specific strategies.

Carbon dioxide (CO2) is fundamental to crop carbohydrate production (important for crop productivity and yield) and overall plant metabolism. It is also plays an important role in climate change. Atmospheric CO2 concentrations have risen dramatically over the past 200 years and may reach 450–1000 ╬╝mol by the end of this century, according to the Intergovernmental Panel on Climate Change.

Rising CO2 levels will likely boost the overall productivity of many crops, although important tropical grasses like maize, sugarcane, and sorghum and some cellulosic biofuel crops don’t respond as well to elevated CO2 levels. Increases in productivity could be offset, though, by pressures such as insect and fungal pests, ozone, and more variable precipitation, although the degree to which this occurs will depend on the physiology and biochemistry of each crop.

Ozone, an important greenhouse gas and agricultural pollutant, continues to increase because of fossil fuel combustion. Crops take ozone into their leaves during photosynthesis, where the gas lowers photosynthetic rates and accelerates leaf death, affecting crop maturity and productivity. Present-day global yield losses due to ozone are estimated at approximately 10% for wheat and soybean and 3–5% for rice and maize.

Biological stresses on cropping systems include weeds, insects, viruses, bacteria, and fungi. Temperature is considered the most important factor in determining how insects affect crop production and yield, and some populations of insect species, such as flea beetles, are showing signs of overwintering because of warmer winter temperatures. Viral, bacterial, and fungal pathogens also respond greatly to temperature as well as to humidity and rainfall. Thus, as the growing season lengthens and winters moderate due to climate change, pressures from plant, microbial, and insect pests are expected to rise due to an increased capacity for overwintering, greater movement of organisms, and expanded adaptation zones.

The climate has always been in a state of flux, but the current rate of change is much faster, and the range of weather variables much broader than ever seen before in modern agriculture. Today, two primary approaches for adapting crops to these conditions exist: (i) improving existing crop cultivars and developing new crops and (ii) devising new cropping systems and methods for managing crops in the field.


wikipedia: wild rice

Develop new crops.

New crops will likely play a key role in maintaining and increasing agricultural production. Domestication began only 5,000 to 12,000 years ago for our oldest crops such as maize, wheat, potatoes, and sorghum while blueberries and wild rice were domesticated more recently. Development and domestication of crops has enabled us to modify them to optimize yield and nutritional qualities.

Today, some scientists are crossing perennial relatives of crops such as maize, millet, rice, sorghum, sunflower, and wheat with their annual, domesticated counterparts for use in developing perennial grain crops. Additionally, a growing interest in bioenergy has also encouraged the domestication and breeding of C4 grasses, including switchgrass, and miscanthus. Domestication and breeding of new crops is a long-term solution, requiring many years of effort before formal testing can be performed.

[Written by C. Gala Bijl, senior science policy associate for ASA, CSSA, and SSSA, and M. Fisher, lead writer for CSA News magazine]