Enough of carbon talks. Heres a new element with potential
biology, chapter 23, Nitrogen fixing, notes: This element is essential to life and is the building block of proteins. Photosynthesis and plant growth is impossible without it. The element is nitrogen. Although the Earths atmosphere is an abundant source, it cannot be used by plants until it is fixed. This means converting gaseous nitrogen into forms usable by living organisms. Usually cooperative bacteria that live in soils or in harmony with plants do the fixing. Life would not be possible if the nitrogen cycle was disrupted.
The part that any chapter is yet to include: global warming can disrupt the nitrogen cycle. Warmer climates could lead to loss of nitrogen from desert soils in the form of gas. Desert plants already have limited supply of nitrogen. Desert ecology would be doomed.
Over the years scientists observed that nitrogen losses from arid zones could not be accounted for just by the biological mechanism of nitrogen gas production. For exampl e, about one to three kilogrammes of nitrogen gas is lost per hectare of land per year in the northern Mojave Desert in the US. The biological mechanism would imply release of trace amounts of nitrogen gas by the microbes in the desert soil during nitrogen fixing.
Ecologist Jed Sparks and evolutionary biologist Carmody McCalley from Cornell University in usa tried to trace the ways in which nitrogen is disappearing. They covered small patches of soil in the Mojave Desert with sealed containers to measure nitrogen gases that escape desert soils. At 40 to 50C rapid increases in gases coming out of the soil was found. Any place that gets hot and dry in all parts of the world might exhibit this pattern, concluded Sparks.
The team warned that some climate models predict more summer rainfall for desert areas and the water, when combined with heat, would greatly increase nitrogen losses. The study was published by Science on November 6. Deserts account for 40 per cent of the Earths surface. Arid and semiarid lands are the most likely areas for new human settlements.
The story of the escaped nitrogen takes a worse turn when it combines with the nitrogen pollutants released by human activities. The lower atmosphere replete with the pollutants is a second layer of ozone which does not protect from UV rays. It increases the greenhouse effect warming the planet.
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