The list of finely tuned characteristics of Earth’s ecosystem has grown longer—again. In recent articles I’ve reported on the delicate balance between too much and not enough earthquake and volcanic activity.1 I’ve also told how the quantity and intensity of cosmic rays must be balanced for production of sufficient H3+ in cold galactic gas clouds to provide for later formation of simple life molecules.2
To this not-yet-complete list3 we can now add two more characteristics: The amount of nitrogen and the amount of sulfur in Earth’s soil. These elements must be carefully balanced for survival of plant life on which animal life depends.
Three Canadian botanists and two American ecologists have identified five sets of organisms that factor into the nitrogen balance: 1) plants requiring a certain amount of nitrogen to survive, 2) decomposer microbes essential for soil renewal but competing with plants for nitrogen, 3) Mycorrhizal fungi, which funnel nitrogen to plants, 4) nitrifying microorganisms that draw their energy from the products of nitrogen mineralization, and 5) microfauna that graze on microbes and roots.4,5 The two teams’ studies revealed the delicacy and complexity of maintaining balance. For example, if too many decomposer microbes reside in a particular location, other plants will have too little nitrogen to survive. But if a location has too few of these microbes, soil decomposition will be insufficient for plants’ survival. Quantities of mycorrhizal fungi and nitrifying microorganisms must be balanced, too. While the fungi enrich the nitrogen supply, the nitrifying microorganisms deplete it.
The task of introducing plants on the third day now appears far more complex than we had imagined. Because these five sets of organisms work together to regulate nitrogen abundance, their introduction had to be carefully orchestrated to ensure their survival—and ours. If too much nitrogen is present in one location, decomposer microbes and nitrifying microorganisms will flourish there bringing the quantity of nitrogen available for plants down—but it must not come down too far. If too little nitrogen is present, mycorrhizal fungi will flourish, raising the quantity of nitrogen available for plants—but it must not rise too far.
As nitrogen in the soil rises, so do five environmental hazards: smog, acid rain, ozone destruction, greenhouse warming, and pH and nutrient imbalance in soils and waters. One study warns that human activities now deposit twice as much nitrogen into the soil as all natural processes combined and argues that we are now approaching the upper limit for plant survival.6 Movement toward either the upper or the lower limit of soil nitrogen threatens Earth’s biodiversity and biomass.
A recently published book, Laboratory Earth, reveals a similar delicacy in the sulfur balance.7 Without adequate sulfur in the soil, all plants will become deficient in certain proteins and die. But, too much soil sulfur is toxic to plants and raises the acidity of rain water, surface water, and the soil. Too much sulfur also disturbs the cycling of nitrogen.
For life to exist on Earth, the quantity of nitrogen and the quantity of sulfur in the soil must be fine-tuned. The manner in which nitrogen and sulfur move from the soil to life to water and to the atmosphere must also be fine-tuned, as must the rate at which this cycle progresses. At the risk of irritating readers with repetition, I’ll state once again that the more we learn about nature, the more evidence accumulates for design and implementation of that design by the biblical Creator.
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Facts & Faith, Second Quarter 1997 Issue