Knowledge Gaps and Future Challenges

Our understanding of how crop yields will respond to rising atmospheric [CO2] and [O3] has improved substantially with the tremendous amount of research over the past four decades. However, a number of knowledge gaps and research challenges remain. FACE experiments have been restricted to temperate locations, with a limited selection of germplasm, which significantly restricts extrapolation of the results to global crop production estimates. Furthermore, FACE experiments have not investigated the interactive effects of simultaneous changes in [CO2], temperature, soil moisture and [O3] (Long et al. 2006). While technologically difficult, these experiments are not impossible. Infrared heater arrays (Kimball et al. 2008), passive infrared night-time warming and rain exclusion systems (Mikkelsen et al. 2008), and open-air O3 enrichment systems (Morgan et al. 2004; Karnosky et al. 2007) have been used to investigate interactive effects of [CO2] and other climate change factors. Apart from waiting 50-100 years to test model outputs, these experimental approaches remain the only way to test and constrain model projections of future food supply.

Adapting crops to elevated [CO2] remains a major challenge (Ainsworth et al. 2008a, b). Studies of wheat cultivars released throughout the twentieth century suggest that the sensitivity of yield to [CO2] has declined in more recently released cultivars (Ziska et al. 2004; Manderscheid and Weigel 1997). The relative sensitivity of wheat grain yield with a doubling of [CO2] concentration was strongly correlated with an increase in tiller production, leaf area, and subsequent panicle formation, and the ability to form new tillers was more limited in recent cultivars (Ziska et al. 2004). So, it seems that traditional breeding has not selected for [CO2] responsiveness, in fact, the opposite has occurred. Furthermore, breeding has not inadvertently selected for O3 tolerance (Fiscus et al. 2005). Thus, there is a need to understand the complex mechanisms of yield response to [CO2] and to use the genetic diversity available to improve responsiveness (Ainsworth et al. 2008a). With predictions that drought, high temperature stress and O3 pollution will increase throughout this century, causing damage to crop production and making the timing and application of nutrients, herbicides and pesticides more difficult (Porter and Semenov 2005; Tubiello et al. 2007b), maximizing crop response to elevated [CO2] is even more important.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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