Climatic Change and Agriculture

Current State of Climate Change:

Projection of surface temperature
(IPCC Summary 2007)

 After Industrial Revolution, global atmospheric green house gases significantly increased. Especially carbon dioxide is the most abundant and important green house gases of all that has been produced by human forces. From the 280ppm, which was pre-industrial level of atmospheric CO2,  the level has increased up to 379 ppm in 2005. Compared to the amount of natural increase of CO2(180ppm-300ppm) over the last 6.5 millions years, the increase that humans have made in this short period time looks very threatening(9).
 Increased green house gases led to an increased amount of aerosols which traps more solar energy around the Earth space. As a result, temperature in some regions on the earth has increased almost 2-3 Celsius in last 100 years, and it is projected to increased more dramatically(1).


Climate Change Impact and Agriculture in Danger:

 Climatic warming caused increase in temperature and decrease in precipitation. Increased temperature with decreased precipitation may cause droughts in arid zones, reducing the plant cover and vegetation, which further lead to severe droughts by increasing albedo and decreasing evapotranspiration. Decrease in vegetative area meaning smaller agricultural land will result in feminine and diseases associated with malnutrition among people(3).

 While increased temperature affects agriculture through reduction in vegetative area, increased atmospheric CO2 threatens agriculture by affecting plants' physiological responses. Because plants use CO2 as energy source, we might expect the plants' biomass to constantly increase. However, what we actually see from the results of experiments is decreased photosynthetic rate of the plants and assimilation of CO2 in plants(10). More importantly, because less photorespiration is processed at higher CO2 and low oxygen environment, rate of nitrogen uptake of plants also decreases(2,18). Nitrogen is necessary fertilizer for plants to grow healthy and improve the quality of their seed, fruit and leaves. With low nitrogen uptake, plants will have poor quality as food sources(13,18). Wheat, rice and potatoes which takes big parts of human diets will reduce its protein quality by 10 percent(2). World population will have to suffer poorer nutrition.

nitrogen assimilation in both C3 and C4 plants
decrease along with increase in pCO2
(Bloom 2009)

plants' biomass eventually decrease 
with overloaded CO2 level
(Dukes et al. 2005; Korner 2006;
 Rasse et al. 2005; Kimball et al. 2007)

    Climate warming will also induce rapid pest dispersion on agricultural crops. With increased temperature, warmer winters will allow rapid insects and pests outbreaks, especially at mid- and high latitude areas. According to Curran et al.2008, the plant fossil records showed specifically high abundance of damages from insects at the time of thermal maximum. Curran explains this discovery with increased temperature favoring insects reproduction and with high CO2 limiting nitrogen assimilation in plants pushing herbivore insects to have more consumption to make up the poor nutrition(4). This might happen in our future with increasing temperature and increasing atmospheric CO2.

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