High temperatures over several days or more for a crop such as corn (maize) can reduce the crop yield substantially. But new crop research reveals that it is not so much the heat and heat stress that impacts the plants, but water stress caused by increased evapo-transpiration through vapour pressure deficit (VPD) - the plants version of human sweating to cool down.
The new understanding comes from research and modelling by one of Australia's leading crop scientists, Professor Graeme Hammer, from the University of Queensland. Graeme has spent much of the last decade as professor in crop science at UQ's Queensland Alliance for Agriculture and Food Innovation (QAAFI) developing increasingly sophisticated computer models to predict the growth and yield of agricultural crops. Lead author for the study was David Lobell, an Assistant Professor in Environmental Earth System Science and Associate Director of the Center on Food Security and the Environment at Stanford University.
The widespread and persistent drought in the US during 2011-2012 has expanded according to the US Drought Monitor as reported on Climate Central. Are we starting to see the signs of a megadrought in the US southwest? Are human influences such as climate change contributing to or causing this widespread extreme weather event?
As of 18 September 2012, 64.82 percent of the contiguous U.S. has been declared as suffering from at least moderate drought - a new record. Extreme drought occurs across 20.74 percent, while the most severe category has ravaged 6.26 per cent of the land. And the seasonal outlook provided by NOAA provides little happy news predicting the drought will persist till the end of the year.
The drought is the worst to occurr since the dustbowl years of the 1930s and comes as North America experiences well above normal temperatures over spring and summer breaking many temperature records with the first half of 2012 being the hottest on record for the United States. July 2012 was the hottest month on record for the continental United States. But Australia and a few other places had abnormally cool month so putting the chill on a hot July for a global record.
Do you fancy a bit of chocolate every now and then? Perhaps a hot cup of drinking chocolate and milk before going to bed? or a few small pieces of a bar of chocolate while watching TV? Maybe a fancy imported Swiss or Belgium chocolate with coffee and liquers at the end of a dinner party? or maybe some cool chocolate icecream on a hot summer's day? This could all become a thing of the past as chocolate becomes an extreme luxury item due to global warming.
Most western people have a bit of a sweet tooth and enjoy the pleasure of indulging in chocolate, either in small amounts, or sometimes less moderate binges. For dentists it provides a continuing customer base. I admit it, I am partial to the odd bit of chocolate. So I am dismayed with the latest reports that climate change will decimate cocoa farming and chocolate production with the decline noticeable as soon as 2030 with a major impact by 2050. The price of chocolate is also escalating as western taste for this luscious indulgence spreads to more people in developing countries.
For the USA the 'normal climate' just got warmer. Every decade the National Oceanic and Atmospheric Administration (NOAA) updates a range of climate measures averaged over the previous 30 years. These measures are called the climate normals.
From July 2011 the latest climate normals will be for the 30 years from 1981 to 2010. Climate measures for the 1970s has been dropped and the first decade of the 21st century, the hottest on record has been added. This has resulted in both maximum temperatures and minimum temperatures being about 0.5F warmer on average in the new normals. "The climate of the 2000s is about 1.5 degree F warmer than the 1970s, so we would expect the updated 30-year normals to be warmer,” said Thomas R. Karl, L.H.D., National Climate Data Centre director.
Caption: Comparing average temperatures year round, every state experienced warmer temperatures in 1981–2010 compared to 1971–2000. Image by NOAA.
Crop yields are under threat from rising carbon dioxide emissions with climate change, according to new scientific research. In a new study published in Science on wheat and the mustard plant Arabidopsis at the University of California at Davis, scientists found that increasing atmospheric carbon dioxide interferes with plants' ability to convert nitrate into protein resulting in lower nutritional yield.
This has implications for global food production, food nutritional quality and food security. It effects not only humans but the animal ecosystems dependant on current plant physiologies.
"Our findings suggest that scientists cannot examine the response of crops to global climate change simply in terms of rising carbon dioxide levels or higher temperatures," said lead author Arnold Bloom, a professor in UC Davis' Department of Plant Sciences.
"Instead, we must consider shifts in plant nitrogen use that will alter food quality and even pest control, as lower protein levels in plants will force both people and pests to consume more plant material to meet their nutritional requirements," Bloom said.
As climate change intensifies, careful management of nitrogen fertilization by farmers will become critical to reduce losses in crop productivity and quality, according to the research.
The concentration of carbon dioxide in Earth's atmosphere has increased by 39 percent since 1800, and on current projections will increase by an additional 40 to 140 percent by the end of the century.
Plants require nitrogen, mostly in the form of nitrates in the soil, to survive and grow. Research has shown that when atmospheric carbon dioxide concentrations increase by 50 percent, the nitrogen status of plants declines significantly.
"This indicates that as atmospheric carbon dioxide concentrations rise and nitrate assimilation in plant tissues diminishes, crops will become depleted in organic nitrogen compounds, including protein, and food quality will suffer," Bloom said. "Increasing nitrogen fertilization might compensate for slower nitrate assimilation rates, but this might not be economically or environmentally feasible."
"One fear is insect outbreaks will become more extensive, because the insects will have to eat more to meet nutritional needs." Arnold Bloom told the ABC. (Listen to a popdcast interview with Arnold Bloom)
A study at the University of Illinois found that in a soybean field subjected to higher concentrations of carbon dioxide, the plant leaves were more prone to attack from beetles.
As plants absorb more carbon dioxide, levels of plant nutrition will go down and for some toxin levels will go up. So crops will have less nutritional yield which will mean humans or other animals will need to eat more to get the same level of nutrition. Plants will put more energy into defensive systems such as phenols or cyanide compounds.
Dr Ros Gleadow told a recent ABC Catalyst program "Leaves of plants grown at elevated carbon dioxide have a lot less protein. Wheat, barley, rice, all of those in probably only 50 to 60 years time will have 15 to 20% less protein in them than they do now." she said, "In about 50 years time or even 100 years time eucalyptus leaves will have trouble supporting arboreal herbivores like koalas because the phenolic concentration will be too high and the protein level too low."
Bad news for the Koala, one of Australia's iconic creatures, facing extinction from climate change.
Cassava is one of the world's staple food crops because of the plant's drought tolerance. However increased CO2 will stimulate more cyanogen compounds in the plant. Dr Ros Gleadow told Catalyst "We grew cassava at three different concentrations of carbon dioxide. Today's air, one and a half times the amount of carbon dioxide and twice the carbon dioxide of today. And we found that cyanogen concentration in the leaves increased."
Cyanide poisoning from Cassava produces a serious paralytic disease known as Konza, which was first diagnosed in 1981 in Mozambique. Simple methods have been devised to treat the cassava root to allow enzymes to eliminate some of the cyanide as hydrogen cyanide gas, making the tuber relatively safe to eat after processing.
Dr Ros Gleadow outlined that in high carbon dioxide environment the yield from the tuber is also reduced, "The plants actually made less tubers when we grew them at elevated carbon dioxide." she said, "It is all very highly balanced in plants, the ratio of the proteins and the toxins. When you grow plants at elevated carbon dioxide the plants are more efficient so they can grow really well. And at the same time allocate more of their resources to defence."
You can watch the whole segment from Catalyst - Toxic Crops - on the ABC website or download for later viewing.
While carbon dioxide is increasing, there will also be effects from changes in rainfall and water, changes in temperature, which will effect crops. Corn, soybeans and cotton are the largest three crops by production value in the US which will be affected by extreme heat. Above a certain threhold - 29 degrees - crop yields decline rapidly with the effects being described as 'damaging large' by a report by Agricultural Economists published in August in the Proceedings of the National Academy of Sciences.
We appear to be in for a period of declining crop yield as well as nutritional yield due to climate change which will challenge feeding the world's still growing population.
Takver is a citizen journalist from Melbourne who has been writing on Climate Change issues and protests including Rising Sea Level, Ocean acidification, Environmental and social Impacts since 2004.
Higher temperatures caused by the changing climate are likely to have a devastating effect on crop yields. Corn, soybeans and cotton are the largest three crops by production value in the US which will be affected by extreme heat. Above a certain threhold - 29 degrees - damaging effects have been described as 'damaging large' by a report by Agricultural Economists published in August in the Proceedings of the National Academy of Sciences.
